Another "Suggest" AQA exam question walk through
Example 2: Q3 Paper 2 2023
This next question is more complex, and there are two ‘suggest’ questions.
But first - I always recommend you don’t read the actual questions until you’ve looked at the background information, graph etc. Doing this will help you avoid getting overwhelmed and jumping to mistaken conclusions (which is very common in exam situations!).
So let’s keep the questions for later. First make sense of this:
Here is another example of a “Suggest” question from a past paper.
Find the main “Suggest” article and first example question here
Example 2: Q3 Paper 2 2023
This next question is more complex, and there are two ‘suggest’ questions.
But first - I always recommend you don’t read the actual questions until you’ve looked at the background information, graph etc. Doing this will help you avoid getting overwhelmed and jumping to mistaken conclusions (which is very common in exam situations!).
So let’s keep the questions for later. First make sense of this:
1. Don’t panic!
This question is going to challenge your working memory by throwing lots of information at you all at once. Tackle it bit by bit to make sense of what’s going on.
2. Use your knowledge to make sense of the background information:
There are tomatoes, a “mycorrhizal species’, and different water conditions.
You know that mycorrhizae are fungi (3.5.4)
You know that plants need the correct amount of water in order to grow (GCSE)
You can understand the experiment – including identifying the independent, dependent, and controlled variables. (8.3)
You can understand the data – what is the graph is showing? (6.4)
Top tip: Write “IV” and “DV” on the paper to identify the Independent and Dependent variables.
Water availability = IV
Whether mycorrhizae were added to the soil = IV
The mean mass of tomatoes = DV
…. What is the graph showing?
· The pair of bars on the left of the graph compare the yield of tomatoes from plants grown in conditions of water shortage.
o The bar on the far left is for plants grown in soil that did not have mycorrhize added. The other is for plants in soil that did have mycorrhizae added.
o The results show a significant difference between the yield of tomatoes for these two groups of plants. The plants with mycorrhizae yielded more tomatos.
· The pair of bars on the right compare plants that did not experience water shortage.
o Again, the bar on the left is without mycorrhizae, and that on the right is with mycorrhizae.
o The results show no significant difference between the yield of tomatoes from these two groups of plants.
Got that? Ok now you’re ready to look at the questions. How would you approach these?
3. Answer questions in order:
The first part of the question (not shown) is about phosphorous cycles, so you will already be thinking about content from 3.5.4 (Nutrient Cycles).
4. Check the Command Word:
‘Suggest’.
5. Understand the question:
These questions are quite straightforward.
6. Think about relevant information from the spec
You know that mycorrhizae facilitate the uptake of water and inorganic ions by plants. (3.5.4)
You know that there are a variety of living organisms in soil, and that these are in competition (3.7.4)
ou have identified the fertiliser concentration as a controlled variable (8.3)
7. How many marks are there available?
Each question has two reasons for two marks; one mark per reason. Make them good ones!
8. So, what are your answers?
There are a variety of different ways to get the marks, allowing you to play to your strengths. Give it a go before looking at the makr scheme below.
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Q3 Paper 2 2023 Q3.3 – mark scheme
Did you get the marks?
Paper 2 2023 Q3.3 – example answers
Good answer examples, which would win marks:
✅ to ensure that there are no other fungi growing in the soil
✅ to remove any seeds in the soil so that other plants don’t grow and consume the nutrients and water
✅ to ensure that there are no pathogens in the soil that can infect the tomato plants
Poor answers that would not get the mark – can you identify where they’ve gone wrong?
❌ To remove harmful bacteria
❌ To kill everything living in the soil so it doesn’t interfere with the experiment
❌ to make sure that conditions are ideal for growing tomato plants
Q3 Paper 2 2023 Q3.4 - markscheme
Paper 2 2023 Q3.4 – example answers
Good answer examples, which would win marks:
✅ The investigation is on the effect of water shortage so the concentration of fertiliser should be a control variable
✅ The concentration of fertiliser will affect the growth of the plant so the recommended amount should be used to get the best crop
✅ Fertilisers can affect the water potential of the soil which may impact how water is absorbed by the roots
Poor answers that would not get the mark – can you identify where they’ve gone wrong?
❌ Without fertiliser the tomatoes won’t grow
❌ So that the soil doesn’t affect the size of the tomatoes
❌ So that the tomatoes can be compare
Article by Natalie Vlachakis (an ex-teacher who also worked for AQA) & Jenny Shipway
How to answer "Suggest" questions in AQA A level Biology
Command words are important! Step by step guide to how to approach and answer “Suggest” questions for top marks in AQA A level Biology.
Article by Natalie Vlachakis (an ex-teacher who also worked for AQA) & Jenny Shipway
Command Words: What do you Suggest?
There are many ways that examiners can ask an A-level Biology question. They might ask you to describe the structure of DNA. Or to explain the importance of the xylem being kept open as a continuous tube.
In exam questions, words like ‘describe’, ‘explain’ (and ‘suggest’) are known as command words. Always pay attention to command words because they tell you what type of knowledge or skill is being tested, and how you should approach the question.
So - when you get a question that asks you to ‘suggest’ something, what exactly does it want from you?
‘Suggest’ Questions
‘Suggest’ questions are usually asking you to use your biology knowledge and understanding to make sense of, and build upon, information about an unfamiliar organism and/or experiment.
Using unfamiliar contexts is a way for examiners to check that you really understand the content; rather than just having memorised set phrases and information.
You aren’t expected to already know the answer, or even be absolutely 100% certain that you’re correct. You just need to come up with something that would make sense biologically, and is likely to be true.
Example Exam Question
Q6 Paper 1 2023
The question:
How to approach this question:
1. Don’t panic!
A question about historical classification of bacteria?! That topic is not in the spec!! Don’t panic – all the information you need about any off-spec topic will be provided in the question.
This example question is going to test your knowledge of classification, bacteria and microscopy (all from the spec), and – most crucially - your ability to apply that knowledge in an unfamiliar context.
2. Use your knowledge to make sense of the background information:
You know that bacteria are uni-cellular organisms. Your knowledge of bacterial structure will allow you to understand the description of how bacteria appear under the microscope. You know what a flagellum is. (3.2.1.2)
You know how ‘species’ and ‘genus’ are used in classification (3.4.5)
Your knowledge and experience of microscopy will allow you to understand the description of the limitations of optical microscopes. (3.2.1.3)
3. Answer questions in order
Answering question 6.2 (‘consider’ = ‘review and respond’) first will help you. This question gets you thinking in more detail about things that will help you answer 06.3.
4. Check the Command Word:
Question 6.3 asks you to ‘suggest’. So you know that you should use your existing knowledge/skills to make sense of, and build upon, the information given. You don’t need to know the exact answer for sure, but you need to give a biologically reasonable answer.
5. Understand the question:
The question asks “why” the species have been renamed.
Why might someone rename a species? – because they were misclassified before
Why might they have been misclassified before? – because of the limitations as in your answer to 6.2
Something has changed in recent years that has made it possible to classify these bacteria more accurately than before. What might this be?
6. Think about relevant information from the spec
What have you learned that is related to this question?
Phylogenetic classification (3.4.5)
Methods of studying cells (3.2.1.3)
7. How many marks are there available?
There is only one mark available – you can do this! But if possible, try to include more than one thing that might get a mark, so if one fails you are still ok.
8. So, what’s your answer?
Give it a go before looking at the markscheme below. Remember you need to use specific, technical language to win marks.
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Q6 Paper 1 2023 6.3 - mark scheme
A range of answers are acceptable for this 1 mark. How did you do?
Q6 Paper 1 2023 6.3 – example answers
Successful answer that would win marks:
✅ “Different species will have different DNA sequences so by using genome sequencing they can identify different species”
✅ “Comparing the base sequences of mRNA from the different bacteria will show how similar they are to one another so whether or not they are the same species”
✅ “Electron microscopes have better resolution that optical microscopes so scientists can see the arrangement of the flagella in more detail”
Poor answers that would not get the mark – can you identify where they’ve gone wrong?
❌ “They can identify phylogeny better now, by looking at the DNA”
❌ “They can see more detail with microscopes now so there are fewer mistakes”
❌ “Advanced techniques allow more accurate determination of phylogeny“
A final thought:
The word ‘Suggest’ can be used in different types of questions (e.g. “Suggest two reasons why … ”, “Suggest how … ”) . But the word ‘Suggest’ always invites you to think about the problem in your own way - to use the information in the question with your biology knowledge to come up with your best possible answer.
Want more? Find another “Suggest” exam question walk-through here
AQA Paper 3 Extended Essay: picking topic areas, past paper titles, and examiners’ guidance
Past paper essay titles and topic areas for A level Biology paper 3, with tips and guidance for how to select the best topic areas for your essay.
Just want the titles? Jump here.
It can be hard to pick which topics you want to write about in your essay. The article below provides examples and tips to help you through this process. For a full overview of the Extended Essay, go to this previous blog post.
Background
The AQA Paper 3 Extended Essay is a 25-mark synoptic essay that appears at the end of Paper 3. You need to write an essay using one of the provided titles.
E.g.: “Write an essay on using DNA in science and technology”, or “Write an essay on the importance of membranes in the functioning of cells”.
There are different ways you can approach your essay, but to win marks you need to:
Present examples from different topic areas (numbered parts) of the specification
Link these topic areas to the main theme
Present the information at A-level standard, using correct terminology
Avoid irrelevant topics, irrelevant information, or factual errors
How Many Topic Areas Do I Need?
AQA say “several”, and suggest a minimum of 4. I would suggest you choose 5 or 6 from the specification. You need to spend a similar amount of time on each one.
Off-spec topics: to score 24-25/25, you would need to include a topic outside the A-level specification. But I always recommend students stay within spec. You don’t need to score so high to get an A* overall (aiming for 18/25 is fine!), and many students attempting off-spec topics fail due to lack of depth and scientific terminology. Using something you heard on a podcast isn’t enough; you need to present it at A-level standard or above.
Example Essay Title and possible Topic Areas
The examiners give feedback after the exams explaining which topic areas they consider appropriate for each title. It’s worth looking at some examples to get an idea of how it works. Here’s one to start:
Example extended essay title:
Write an essay on the importance of membranes in the functioning of cells
Possible topic areas:
• 3.1.3 Lipids (phospholipids)
• 3.2.1.1 Structure of eukaryotic cells
• 3.2.1.2 Structure of prokaryotic cells
• 3.2.2 All cells arise from other cells (nuclear membrane breakdown in mitosis)
• 3.2.3 Transport across cell membranes
• 3.2.4 Cell recognition and the immune system
• 3.3.1 Surface area to volume ratio
• 3.3.2 Gas exchange
• 3.3.3 Digestion and absorption
• 3.4.2 DNA and protein synthesis
• 3.5.1 Photosynthesis
• 3.5.2 Respiration
• 3.6.1.2 Receptors
• 3.6.2.1 Nerve impulses
• 3.6.2.2 Synaptic transmission
• 3.6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors
• 3.6.4.2 Control of blood glucose concentration
• 3.6.4.3 Control of blood water potential
• 3.8.2.2 Regulation of transcription and translation
Having a lot of choice is great as you can pick areas where you are strong. But remember to spread your choice through the whole specification - avoid picking similar/neighbouring sub-sections.
Can you work out how each of the above topics areas could relate to the theme? How are they important? It’s crucial to approach each area with the theme in mind, rather than just writing about that topic area in general. Larger topics may include irrelevant information that you need to avoid.
But you don’t need to link the topics to each other (even though it might sound like that on the marking information). You need only to link them to the main theme.
How to think of potential Topic Areas
It can be difficult to think broadly under exam pressure, so here’s a trick I suggest students try:
Think your way through the Kingdoms of Life. Can you think of illustrative examples from each Kingdom? (Ok, maybe not protists.)
Think your way through different scales. From single molecules → macromolecule → organelle → cells → tissue → organ → organ system → individual → populations → community → ecosystem.
Scribble down all the ideas you can think of for the essay titles, then see which list looks most likely and focus on picking from that.
By choosing topics with a variety of Kingdoms and Scales, you can get both breadth and depth into your selection. You want to pick topic areas that are as spread out as possible in the specification. Just make sure they will all serve the essay title!
Practice with Past Papers
Practice choosing topics! Just reading the list won’t help you - it’ll just make you think it’s easier than it is. Your titles will be different to these, so remembering doesn’t help either. You need to practice the process to acquire this skill.
Look at each title, write a list of potential topics, and then check these against the examiners’ lists shown below. Do this a few times and you will start getting a feel for how to think your way through the spec.
For each topic, think about what information would be relevant to the title, and why the topic is important to the theme. You will need to write about both of these to get the marks.
Recent Past Paper Essay topics:
Phosphorus-containing substances and their importance in biological systems.
The mechanisms and importance of transport within organisms.
The importance of interactions between organisms and their environment.
The importance of shapes fitting together in cells and organisms.
How bacteria can affect the lives of humans and other organisms.
A cycle is a biological pathway or process in which the end product of one cycle becomes the starting point for the next cycle. Write an essay on cycles in biology.
Carbon dioxide may affect organisms directly or indirectly. Write an essay to describe and explain these effects.
Polymers have different structures. They also have different functions. Write an essay to describe how the structures of different polymers are related to their functions.
Using DNA in science and technology.
The importance of membranes in the functioning of cells.
More AQA Paper 3 Extended Essay Titles here
Examiners’ expected topic areas:
Below are the same essay questions numbered in the same way. Each has a list of topic areas that examiners considered it appropriate to use. Remember your chosen topic areas should be from very different parts of the specification, not all from the same section.
Phosphorus-containing substances and their importance in biological systems.
3.1.3 Lipids
3.1.5.1 Structure of DNA and RNA
3.1.5.2 DNA replication
3.1.6 ATP
3.1.8 Inorganic ions
3.2.1.1 Structure of eukaryotic cells
3.2.2 All cells arise from other cells
3.2.3 Transport across cell membranes
3.3.3 Digestion and absorption
3.4.1 DNA, genes and chromosomes
3.4.2 DNA and protein synthesis
3.4.3 Genetic diversity can arise as a result of mutation or during meiosis
3.4.4 Genetic diversity and adaptation
3.4.7 Investigating diversity
3.5.1 Photosynthesis
3.5.2 Respiration
3.5.4 Nutrient cycles
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.2 Control of blood glucose concentration (cyclic AMP)
3.6.4.3 Control of blood water potential
3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins
3.8.2.1 Most of a cell’s DNA is not translated
3.8.2.2 Regulation of transcription and translation
3.8.3 Using genome projects
3.8.4.1 Recombinant DNA technologyThe mechanisms and importance of transport within organisms.
3.1.3 Phospholipids
3.1.4 Proteins
3.1.6 ATP
3.1.7 Water
3.2.1.1 Structure of eukaryotic cells
3.2.2 All cells arise from other cells
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.1 Surface area to volume ratio
3.3.2 Gas exchange
3.3.3 Digestion and absorption
3.3.4.1 Mass transport in animals
3.3.4.2 Mass transport in plants
3.4.2 DNA and protein synthesis
3.4.3 Genetic diversity can arise as a result of mutation or during meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.1 Survival and response (IAA)
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.1 Principles of homeostasis and negative feedback
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of interactions between organisms and their environment.
3.1.2 Carbohydrates (the relationship of structure to function of glycogen, starch and cellulose in animal cells and plant cells)
3.1.4.2 Many proteins are enzymes (enzyme inhibitors)
3.1.7 Water
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.1 Surface area to volume ratio
3.3.2 Gas exchange
3.3.3 Digestion and absorption
3.3.4.1 Mass transport in animals
3.3.4.2 Mass transport in plants
3.4.4 Genetic diversity and adaptation
3.4.5 Species and taxonomy (courtship)
3.4.6 Biodiversity within a community
3.5.1 Photosynthesis
3.5.3 Energy and ecosystems
3.5.4 Nutrient cycles
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission (effects of drugs)
3.6.4.1 Principles of homeostasis and negative feedback
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.7.1 Inheritance
3.7.3 Evolution may lead to speciation
3.7.4 Populations in ecosystems
3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins
3.8.2.1 Most of a cell’s DNA is not translated
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of shapes fitting together in cells and organisms.
Proteins & Enzymes
3.1.2 Enzyme properties and digestion
3.1.2 Protein structure
3.1.3 Plasma membrane structure and cell transport
3.1.6 Antigens, antibodies, B cells & T cells
3.1.6 VaccinesNucleic Acids
3.2.2 Structure of DNA
3.2.2 DNA Replication (not PCR)
3.5.7 Transcription & translation
3.5.8 Transcriptional factors, oestrogen, siRNA
3.5.8 Restriction enzymesPhysiology
3.2.4 Haemoglobin
3.5.2 Action potentials & synaptic transmission
3.5.3 Muscle contraction
3.5.4 Control of blood glucose concentrationHow bacteria can affect the lives of humans and other organisms.
Bacteria & Disease
3.1.1 Pathogens
3.2.10 Resistance to antibioticsEcological Importance
3.4.6 Nitrogen cycle
3.4.6 EutrophicationMaking Use of Bacteria
3.5.8 Use of bacterial enzymes e.g. restriction endonuclease, DNA polymerase for PCR
3.5.8 Use of bacterial plasmids e.g. in vivo gene cloning, genetically-modified crops, gene therapy
3.5.8 Use of bacteria to produce useful chemicalsA cycle is a biological pathway or process in which the end product of one cycle becomes the starting point for the next cycle. Write an essay on cycles in biology.
Ecological cycles
4.6 Nutrient cyclesBiochemical cycles
1.2 Enzyme action
4.2 Synthesis of ATP from ADP
4.3 Light-independent reaction
4.4 The Krebs cyclePhysiological and genetic cycles
1.4 The mechanism of breathing
1.5 The cardiac cycle
2.5 The cell cycle
5.3 Muscle contractionCarbon dioxide may affect organisms directly or indirectly. Write an essay to describe and explain these effects.
Carbon dioxide affects the physiology of organisms
1.4 Pulmonary ventilation and the mechanism of breathing
4.3 Light-independent reaction of photosynthesis. Limiting factors
5.1 Role of chemoreceptors in controlling heart rateThe direct effects of increasing carbon dioxide concentration
4.6 Respiration, photosynthesis and human activity giving rise to short-term fluctuations and long-term change. Yield of crop plantsIndirect effects of increasing carbon dioxide concentration
4.6 Distribution of animals and plants
1.2 Effect of temperature on enzymesPolymers have different structures. They also have different functions. Write an essay to describe how the structures of different polymers are related to their functions.
3.1.1 Monomers and polymers
3.1.2 Carbohydrates
3.1.4 Proteins
3.1.5 Nucleic acids
3.2.3 transport across membranes
3.2.4 Cell recognition and the immune system
3.3.3 Digestion and absorption
3.4.1 DNA, genes and chromosomesUsing DNA in science and technology.
DNA and classification
2.2 Structure of DNA
2.3 Differences in DNA lead to genetic diversity
2.9 Comparison of DNA base sequencesGenetic engineering and making useful substances
2.5 Plasmids
5.8 The use of recombinant DNA to produce transformed organisms that benefit humansOther uses of DNA
2.5 Cell cycle and treatment of cancer
5.8 Gene therapy; Medical diagnosis and the treatment of human disease; The use of DNA probes to screen patients for clinically important genes.The importance of membranes in the functioning of cells.
3.1.3 Lipids (phospholipids)
3.2.1.1 Structure of eukaryotic cells
3.2.1.2 Structure of prokaryotic cells
3.2.2 All cells arise from other cells (nuclear membrane breakdown in mitosis)
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.1 Surface area to volume ratio
3.3.2 Gas exchange
3.3.3 Digestion and absorption
3.4.2 DNA and protein synthesis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.2 Receptors
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.8.2.2 Regulation of transcription and translation
More AQA Paper 3 Extended Essay Titles
More past paper essay titles for A level Biology paper 3, with lists of appropriate topic areas for each
There is a full overview of the AQA Paper 3 Extended Essay here
The ten most-recent Essay titles are found there, or in the blog article AQA Paper 3 Extended Essay: picking topic areas, past paper titles, and examiners’ guidance
This article has a list of more (older) titles with lists of appropriate topic areas for you to use when practicing selecting appropriate topics and/or writing essays.
Don’t just read the topic area lists! You need to train your brain to be able to think through the specification and make appropriate links so that you can do this for any essay titles that come up.
Write an essay on:
The many different types of relationships and interactions between organisms.
The membranes of different types of cells and how they are involved in many different functions.
The importance of ions in biology.
How energy is transferred within and between organisms.
How cells and organisms carry out exchanges with their external environment
to maintain their internal environment.
The importance to humans of the control of growth, reproduction and development of organisms, including themselves.
The importance of responses to changes in the internal and external environment of an organism.
The ways in which water and the regulation of water content are important to organisms.
The control of processes in cells and the importance of these controls.
The importance of receptors in living organisms.
The importance of movement in living organisms.
The importance of diffusion in organisms.
The importance of nucleotides, molecules derived from nucleotides and nucleic acids in keeping organisms alive.
The importance of nitrogen-containing substances in biological systems.
The importance of interactions between cells and between organisms.
The importance of complementary shapes of molecules in organisms.
The importance of the control of movement in cells and organisms.
The importance of bonds and bonding in organisms.
The importance of DNA as an information-carrying molecule and its use in gene technologies.
The causes and importance of variation and diversity in organisms.
The functions of enzymes and their importance in organisms.
The uses and importance of ATP in organisms.
The importance of ions in metabolic processes.
The importance of cycles in biology.
The many different types of relationships and interactions between organisms.
1.P Pathogens and effects on host.
2.T Taxonomy.
2.C Classification and evolution.
2.I Inheritance and evolution.
2.Gc Genetic code, universal.
2.B Behaviour.
2.Ev Populations and evolution, variation between individuals within a species.
3.BP Relationships within ecosystems − eg predator / prey.
3.E Energy transfer in ecosystems.
3.N Nutrient cycles, the organisms involved.
3.S Succession, biodiversity, species and individuals in a community.
4.H Human impacts on the environment and its effect on relationships between organisms − including farming.
4.Gt Gene technology and GMO and selective breeding.
4.Ar Antibiotic resistance.The membranes of different types of cells and how they are involved in many different functions.
1.M Membrane function as selectively permeable barrier.
1.T Transport mechanisms across membranes.
1.CT Absorption and co-transport of sodium ions and glucose.
2.P Photosynthesis, chloroplast, thylakoids.
2.R Respiration, mitochondrion and cristae.
2.Ps Protein secretion, RER, SER and Golgi.
3.A Surface receptors / antigen and immune response.
3.CD Cell division.
3.B Vertical and horizontal transmission − membranes and bacteria.
3.Pc Pacinian corpuscle.
4.Tr Tropisms − movement of IAA.
4.N Nerve impulses / action potentials.
4.S Synaptic transmission.
4.Mc Muscle contraction, calcium ion movement / storage.
4.H Hormones - eg Blood glucose regulation − insulin and glucagon.
4.O Osmosis, including water movement in plants.
Breadth, one mark for use of an example from each of the following approaches: 1. Membranes − basic functions 2. Organelle membranes 3. Cell surface membranes 4. Processes − eg protein secretion, synaptic transmission, cell divisionThe importance of ions in biology.
3.1.3. and 3.2.2. Phosphate in structure of phospholipids, structure of membranes, nucleotides, DNA and RNA
3.1.3 Water potentials and osmosis, chloride ions and cholera; Co-transport involving sodium ions
3.2.4. Haemoglobin and iron
3.2.7. Passage of water through plants, symplast and root pressure
3.4.1. ATP and ADP
3.4.3 Protons in photosynthesis, including reduced NADP and phosphorylated intermediates
3.4.4. Protons in respiration, reduced NADS and FAD and phosphorylated intermediates; Glycolysis and lactate
3.4.5. Use of (NPK) fertilisers
3.4.6. Nitrogen cycle
3.5.1. Chemoreceptors, heart rate and Pacinian function
3.5.2. Nerve impulses and synapses
3.5.3. Calcium ions and muscle contraction, and phosphate from ATP
3.5.8. Genetic fingerprinting, electrophoresisHow energy is transferred within and between organisms.
Photosynthesis
Energy transfer through ecosystems
Food production
Digestion (as in fuel)
Absorption (by cells)
Mass transport
Respiration
ATP
Stimuli and responses
Muscle contraction
Nerve impulsesHow cells and organisms carry out exchanges with their external environment to maintain their internal environment.
Homeostasis (concept of)
Digestion and absorption
Cells
Lung function
Gas exchange
Passage of water through plant
Nutrient cycles
Response to stimuli
Neurones
Temperature control
Tissue fluid and its formation
Control of blood glucose concentration
Negative feedback
Gene expressionThe importance to humans of the control of growth, reproduction and development of organisms, including themselves.
3.1.1. Pathogens (and invasion of human tissues)
3.2.10 Antibiotic resistance − control of bacterial growth
3.1.3. Cholera
3.1.6. Immune response and vaccination (to control growth of pathogens)
3.2.11. Human influence on biodiversity
3.4.1. Human populations
3.4.5. Humans and farming practices
3.2.3 selective breeding
3.4.6. Use of fertilisers and pesticides
3.4.7. Succession − control of
3.4.8. Genetics − prediction of inherited conditions
3.5.7. Control of gene expression − stem cells
3.5.7. Regulation of gene expression − prevention, treatment and cure of cancer
3.2.5 Mitosis and cancer
3.5.8 Gene cloning and transfer
3.5.8 Gene therapyThe importance of responses to changes in the internal and external environment of an organism.
3.1.3. Transport in and out of cells (of specific substances)
3.1.6. Immune response
3.2.4. Haemoglobin
3.2.7. Transpiration − response to environmental factors − gas exchange in plants
3.2.9. Behaviour
3.2.10. Adaptation and selection
3.4.8. Changes in populations − selection pressures
3.5.1. Responses to stimuli − plants and tropisms − control of heart rate
3.5.1. Taxes and kineses
3.5.1. Receptors
3.5.2. Control of Heart Rate
3.5.1 and 2 Simple reflexes and neurones and synapses
3.5.2 and 5.4 Hormones and responses
3.5.2 Chemical mediators
3.5.4 Homeostasis − response to changes in internal environments
3.5.5 Feedback
3.5.7 Gene expression as part of responseThe ways in which water and the regulation of water content are important to organisms.
3.1.1 Monomers and polymers – carbohydrates – lipids – proteins
3.1.7 Water
3.2.3 Transport across membranes – osmosis – water potentials
3.3.2 Gas exchange – plants
3.3.2 Gas exchange – fish
3.3.2 Gas exchange – insects
3.3.4.1 Mass transport in animals - blood – circulation
3.3.4.1 Mass transport in animals – tissue fluid and formation
3.3.4.2 Mass transport in plants – transpiration stream
3.3.4.2 Mass transport in plants – translocation
3.5.1 Photosynthesis
3.5.4 Nutrient cycles – leaching and eutrophication
3.6.1 Growth responses in plants
3.6.4 Homeostasis
3.6.4.3 Control of blood and water potentialThe control of processes in cells and the importance of these controls.
3.1.3. and 3.2.4. Organelles and processes
3.1.3. Transport across membranes
3.1.3. Cholera
3.1.5. Immune response
3.2.2. Meiosis
3.2.5. Mitosis and cell cycle and DNA replication
3.2.7. Passage of water through plant
3.4.2. ATP
3.4.3. Photosynthesis
3.4.3. Respiration
3.2.10. Antibiotics and genetic variation
3.4.8. Inheritance
3.5.1. Receptors
3.5.2. Nerve impulses and synapses
3.2.7. Passage of water through plant
3.5.3. Muscle contraction
3.5.4. Control of blood glucose concentration – hormones – plant growth substances
3.2.6. Cell differentiation
3.5.6. Polypeptide synthesis and gene mutations
3.5.7. Gene expression
3.5.8. Gene therapyThe importance of receptors in living organisms.
3.1.4.2 Enzymes
3.2.1.2 Structure of prokaryotic cells and of viruses
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.4.1 Mass transport in animals
3.4.2 DNA and protein synthesis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.1 Principles of homeostasis
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of movement in living organisms.
3.1.4.2 Enzyme-catalysed reactions
3.1.5.2 DNA replication
3.1.6 ATP
3.2.2 Cell division
3.2.3 Transport across membranes
3.2.4 Immune response
3.2.2 Gas exchange
3.3.3 Digestion and absorption
3.3.4.1, 4.2 Mass transport
3.4.2 DNA and protein synthesis
3.4.3 Meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synapses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscle
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.7.3 Evolution (population isolation and movement between)
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of diffusion in organisms.
3.1.7 and 3.1.8 water and inorganic ions
3.2.3 transport across membranes
3.3.2 gas exchange
3.3.3 digestion and absorption
3.3.4.1 mass transport in animals
3.3.4.2 mass transport in plants
3.4.2 DNA and protein synthesis
3.5.1 photosynthesis
3.5.2 respiration
3.5.4 nutrient cycles
3.6.1.1 plant responses to stimuli
3.6.1.2 receptors
3.6.2.1 nerve impulses
3.6.2.2 synaptic transmission
3.6.3 muscle contraction
3.6.4.1 and 4.2 control of blood glucose concentration
3.6.4.3 control of blood water potentialThe importance of nucleotides, molecules derived from nucleotides and nucleic acids in keeping organisms alive.
3.1.6 ATP
3.1.4.2 Enzymes – ATP, phosphorylation and activation energy
3.1.5 Nucleic acids – information carrying molecules
3.2.2 Mitosis
3.2.3 Transport across membranes – active transport and co-transport
3.3.3 Absorption
3.4.1 DNA, genes and chromosomes
3.4.2 DNA and protein synthesis – ribosomes as nucleic acids – mRNA, tRNA – etc.
3.4.3 Genetic diversity – mutations
3.4. Meiosis
3.4.4 Diversity and adaptation
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.2 Nerve impulses
3.6.3 Muscle contraction
3.6.4.2 Control of blood glucose – second messenger and cAMP
3.6.4.3 Control of blood water potential
3.8.1 Control of gene expression – Mutations
3.8.2 Gene expression
3.8.2.2 Regulation transcription and translationThe importance of nitrogen-containing substances in biological systems.
3.1.4 and 3.1.4.2 proteins and enzymes
3.1.5 nucleic acids
3.1.5.2 DNA replication
3.1.6 ATP
3.2.1.1 ribosomes
3.2.2 cell division
3.2.3 transport across membranes
3.2.4 immune response
3.3.3 digestion and absorption
3.3.4.1 haemoglobin
3.4.1 genes and chromosomes
3.4.2 protein synthesis
3.4.3 mutation
3.4.7 investigating diversity
3.5.1 photosynthesis
3.5.2 respiration
3.5.4 nitrogen cycle
3.6.2 nervous coordination
3.6.3 muscles
3.6.4.2 control of blood glucose (and peptide / protein hormones)
3.7.1 inheritance
3.8.1 alteration of DNA sequences
3.8.2.2 regulation of transcription and translationThe importance of interactions between cells and between organisms.
3.2.1.2 Viruses
3.2.4 Cell recognition, immune system, HIV
3.3.2 Gas exchange
3.3.4.1 Mass transport in animals
3.3.4.2 Mass transport in plants
3.4.4 Genetic diversity and adaptation
3.4.5 Species and taxonomy (courtship behaviour)
3.4.6 Biodiversity within a community
3.5.3 Energy and ecosystems
3.5.4 Nutrient cycles
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles are stimulated
3.6.4.2 Control of blood glucose
3.6.4.3 Control of blood water potential
3.7.1 Inheritance
3.7.2 Populations in ecosystems
3.7.3 Evolution and speciation
3.7.4 Populations in ecosystems
3.8.2.3 Gene expression and cancerThe importance of complementary shapes of molecules in organisms.
3.1.4.2 Many proteins are enzymes
3.1.5.1 Structure of DNA and RNA
3.1.5.2 DNA replication
3.1.6 ATP
3.2.2 All cells arise from other cells
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.3 Digestion and absorption
3.4.1 DNA, genes and chromosomes
3.4.2 DNA and protein synthesis
3.4.3 Genetic diversity can arise as a result of mutation or during meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.2 Receptors
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of the control of movement in cells and organisms.
3.1.4.2 Enzymes and control of action
3.1.5.2 DNA replication
3.2.2 Mitosis, binary fission
3.2.3 Transport across membranes
3.2.4 Cell recognition and the immune system
3.3.2 Gas exchange
3.3.3 Digestion and absorption
3.3.4.1 Mass transport in animals
3.3.4.2 Mass transport in plants
3.4.2 DNA and protein synthesis
3.4.3 Meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nervous impulses
3.6.2.2 Synaptic transmission
3.6.3 Muscle contraction
3.6.4.2 Control of blood glucose
3.6.4.3 Control of blood water potential
3.7.1 Inheritance
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancerThe importance of bonds and bonding in organisms.
3.1.1 Monomers and polymers
3.1.2 Carbohydrates
3.1.3 Lipids
3.1.4.1 General properties of proteins
3.1.4.2 Many proteins are enzymes
3.1.5.1 Structure of DNA and RNA
3.1.5.2 DNA replication
3.1.6 ATP
3.1.7 Water – cohesion
3.2.2 Mitosis
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.3 Digestion and absorption
3.3.4.1 Mass transport in animals – haemoglobin
3.3.4.2 Mass transport in plants
3.4.2 DNA and protein synthesis
3.4.3 Mutation and meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.5.4 Nutrient cycles
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.8.1 Mutations
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancer
3.8.4.1 Recombinant DNA technologyThe importance of DNA as an information-carrying molecule and its use in gene technologies.
3.1.5.1 Structure of DNA
3.1.5.2 DNA replication
3.2.1.1 DNA in mitochondria (and chloroplasts)
3.2.1.2 Prokaryotic DNA
3.2.2 DNA replication in interphase and binary fission
3.4.1 DNA, genes and chromosomes
3.4.2 DNA and protein synthesis
3.4.3 Genetic diversity and meiosis
3.4.4 Genetic diversity and adaptation
3.4.7 Investigating diversity
3.7.1 Inheritance
3.7.3 Evolution may lead to speciation
3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins
3.8.2.1 Most of a cell’s DNA is not translated
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancer
3.8.3 Using genome projects
3.8.4.1 Recombinant DNA technology
3.8.4.2 Differences in DNA between individuals of the same species can be exploited for identification and diagnosis of heritable conditions
3.8.4.3 Genetic fingerprintingThe causes and importance of variation and diversity in organisms.
3.1.4.1 Proteins have a variety of functions in all living organisms
3.2.4 Effect of antigen variability on disease and disease prevention
3.4.3 Genetic diversity from mutation
3.4.3 Genetic diversity from meiosis
3.4.4 Genetic diversity and adaptation
3.4.5 Courtship behaviour
3.4.6 Biodiversity within a community
3.4.7 Investigating diversity
3.5.3 Energy and ecosystems – farming practices
3.6.3 Slow and fast twitch muscles
3.7.1 Inheritance
3.7.2 Populations
3.7.3 Evolution leading to speciation
3.7.4 Populations in ecosystems
3.8.1 Alteration of base sequences
3.8.2.2 Regulation of transcription and translation
3.8.2.3 Gene expression and cancer
3.8.4.1 Recombinant DNA technology
3.8.4.2 Identification of heritable conditions
3.8.4.3 Genetic fingerprintingThe functions of enzymes and their importance in organisms.
3.1.4.2 Many proteins are enzymes
3.1.5.2 DNA replication
3.1.6 ATP
3.2.4 Cell recognition and the immune system (lysozyme)
3.3.3 Digestion and absorption
3.4.2 DNA and protein synthesis
3.4.4 Genetic diversity and adaptation (penicillinase in bacteria)
3.5.1 Photosynthesis
3.5.2 Respiration
3.5.4 Nutrient cycles
3.6.2.2 Synaptic transmission
3.6.3 Muscles
3.6.4.2 Control of blood glucose
3.8.4.1 Recombinant DNA technology
3.8.4.3 DNA fingerprintingThe uses and importance of ATP in organisms.
3.1.5.2 DNA replication
3.1.6 ATP
3.2.2 All cells arise from other cells (mitosis)
3.2.3 Active transport
3.3.3 Digestion and absorption − co-transport
3.3.4.2 Mass transport in plants
3.4.2 DNA and protein synthesis
3.4.3 Meiosis
3.5.1 Photosynthesis
3.5.2 Respiration
3.5.4 Nutrient cycles − nitrogen fixation3.6.2.1 Nerve impulses − resting potential
3.6.2.2 Synaptic transmission
3.6.3 Myofibril/muscle contraction
3.6.4.2 Control of blood glucose concentration (2nd messenger model)
3.6.4.3 Control of blood water potentialThe importance of ions in metabolic processes.
3.1.4.2 Many proteins are enzymes (H and denaturation)
3.1.5.2 DNA replication
3.1.6 ATP
3.1.8 Inorganic ions
3.2.3 Transport across cell membranes
3.3.3 Digestion and absorption
3.3.4.1 Mass transport in animals
3.3.4.2 Mass transport in plants
3.4.2 DNA and protein synthesis
3.5.1 Photosynthesis
3.5.2 Respiration
3.5.4 Nutrient cycles
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors
3.6.4.3 Control of blood water potential
3.8.4.3 Genetic fingerprintingThe importance of cycles in biology.
3.1.1 Monomers and polymers
3.1.4.2 Many proteins are enzymes
3.1.5.2 DNA replication
3.1.6 ATP
3.2.2 All cells arise from other cells
3.3.2 Gas exchange – mechanism of breathing
3.3.4.1 Cardiac cycle and blood circulation and 3.6.1.3 Control of heart rate
3.4.3 Meiosis
3.5.1 Photosynthesis – light independent reaction
3.5.2 Respiration – Krebs cycle and electron transport chain
3.5.4 Nutrient cycles
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Muscle contraction
3.6.4.1 Negative feedback
3.6.4.2 Control of blood glucose concentration
3.6.4.3 Control of blood water potential
3.7.4 Populations in ecosystems – predation
3.8.4.1 Recombinant DNA technology – PCR
AS Level Biology OCR A H020/01 Breadth in biology - June 2024 Self Marking Quiz
Self marking quiz for revision of OCR A Breadth in Biology - June 2024
Practising recall is so important for retention and learning. Try this quiz without books first !
Try this quiz - if you found it useful then please ❤️ (at the bottom of the page) and share, you can follow me on instagram - alevelbiologytutor
A Level Biology OCR A H420/02 Biological Diversity - June 2024 Self Marking Quiz
Self marking quiz for revision of OCR A Level Biology A Biological Diversity H420/02 - June 2024
Practising recall is so important for retention and learning. Try this quiz without books first !
A Level Biology OCR A H420/01 Biological Processes - June 2024 Self Marking Quiz
Self marking quiz for revision of OCR A Level Biology A Biological Processes H420 01 - June 2024
Practising recall is so important for retention and learning. Try this quiz without books first !
How to approach and answer AQA A-level Biology Questions that need you to interpret Graphs- lots of AQA past paper questions
How to approach and answer A-level Biology Questions that need you to Analyse Figures, Tables and Images - lots of example past paper questions with the markschemes
Magical top tip: DO NOT LOOK at the question first - LOOK at the data first
This simple trick can transform how easily you will be able to answer graph questions
ALWAYS LOOK AT THE DATA FIRST
Look closely at the graph or table
Graphs - look very carefully at the axes - have they plotted rate or time, mass/volume or concentration ? Often students assume enzyme graphs have rate on the y axis - sometimes they don’t !
Table - is the IV in the first column ? What are the units of the DV ? Has a mean been calculated ? Is the data in each row consistent ?
are there range/SD bars on the graph ? remember this indicates the variation in the data that was used to calculate the mean
do the range bars or standard deviation bars overlap ?,
If the Standard deviations (+or- 2 SD overlap then the DIFFERENCE between the MEANS is due to chance - the differnce between the means is not statistically significant).
In a table what range is in the replicates when you compare to the mean ?
what trends can you observe ?
then think about what principle of biology is being shown by the the trends, for instance - enzymes and substrate concentration or mitosis and distance from the root tip
How would you explain the highest value, the lowest value, the point at which the line crosses the x axis, how would you explain the largest range, how would you change the method to reduce the spread in the data ?
Have a look at these 20 excellent recent graph interpretation AQA Questions
An old collection of OCR maths-heavy questions for extra practice
Y12 and Y13 AQA small group weekly class information
A Level Biology OCR A H420/02 Biological Diversity - June 2023 Self Marking Quiz
Self marking quiz for revision of OCR A Level Biology A Biological Diversity H420/02 - June 2023
Practising recall is so important for retention and learning. Try this quiz without books first !
A Level Biology OCR A H420/01 Biological Processes - June 2023 Self Marking Quiz
Self marking quiz for revision of OCR A Level Biology A Biological Processes H420 01 - June 2023
Practising recall is so important for retention and learning. Try this quiz without books first !
AS Level Biology OCR A H020/01 Breadth in biology - June 2023 Self Marking Quiz
Self marking quiz for revision of OCR A Breadth in Biology - June 2023
Practising recall is so important for retention and learning. Try this quiz without books first !
Try this quiz - if you found it useful then please ❤️ (at the bottom of the page) and share, you can follow me on instagram - alevelbiologytutor
Group tutoring topics and Y13 & Y12 OCR A and AQA small group information
How to Approach A level Biology Graph and Table Questions: Tips and Exam Question Pack
Get top marks when analysing figures, tables and images by avoiding common mistakes that students make
This article contains key vocabulary, a strategy for how to approach questions for success, a multichoice quiz with answers, and a big pack of past paper exam questions
Don’t panic, it’s only a graph
The single best exam tip for graphs and tables exam questions is to start by looking at the graph or chart itself. DO NOT LOOK AT THE QUESTIONS FIRST! This single thing will help you avoid the most common mistakes that students make.
But you also need to know what you’re doing. Which means you’ll need to be confident with these terms:
Background Knowledge / Vocabulary:
Independent Variable: The variable that you purposefully set to different values during the experiment
Dependent Variable: The variable that you measure during the experiment, which is unknown until it is measured
Replicate: Experimental data is often replicated - the same data point is recorded multiple times for the same conditions
Accuracy / Precision: Accuracy is how close the replicated values are to the correct value, and precision is how close they are to each other. If there is an unknown problem with the experiment, results can be very precise but have very low accuracy.
Range / Standard Deviation: The amount of variation in the data. A large range or standard deviation means that the replicated data had a broad range of results. A small range or standard deviation means they were much more similar in value. Range / Standard deviation is therefore a measure of precision.
Trend: What is the general relationship between the dependent and independent variables? When the experimenter increased the independent variable, what happened to the dependent variable? What shape is the graph?
How to Approach the Question:
1. Look at the graph or chart first!
Too many students look at the question first, get confused or panicky about what it is asking, and form preconceptions about what data they need. This then means they are then unable to look at the data clearly, and miss the information they actually need. Looking at the graph or chart first both makes the data easier to understand, and makes it easier to work out what the question is asking.
Trust me, this is a major factor in student success. If you only take away one thing from this article, always look at the graph or chart first.
2. Don’t panic if it’s about something totally unfamiliar
Students can get very thrown if the question is about an organism or molecule that they have never heard of before (the exam boards do this a lot). This sudden panic makes it hard to think clearly.
Remember - if you have covered all the course material, even if the question is about something weird and new then all the information you need will be in the data. The things that look scary are just surface details. If the question was “Fred gave James two apples, how many apples does James have” you wouldn’t need to know who these people were to answer the question.
But don’t just dive in to the details of the data …
What’s going on here?
3. Understand the format
Don’t waste time looking at the actual dots or numbers until you understand how the data has been presented. Check every aspect methodically. It’s too easy to make assumptions based on previous graph/table formats you have seen - this one might be different!
Look at the headings / axis labels and units. What is the data showing?
Identify the independent variable and the dependent variable. If possible, it’s helpful to label them “IV” and “DV”.
What type of data is shown? Is it averages? Does it include a Range or Standard Deviation?
Graphs: Check the axis labels. Have they plotted rate or time, mass/volume or concentration? Often students assume enzyme graphs have rate on the y axis - but sometimes they don’t!
Tables: Check: is the Independent Variable in the first column? Is the data in each row consistent?
4. Look at the data
Now you understand its context, look at the actual dots or lines or numbers. Check:
Does the Range overwhelm differences in values: Do the range bars or standard deviation bars overlap? If they do, then there is significant overlap between the populations of replicated results that were used to calculated the average values.
Unspecified Ranges: If there are replicates but no range bars or standard deviation has been calculated, how broad does the range look when you compare the replicated data values to their mean?
Trends: What trends can you observe? Then think about what principle of biology is being shown by the the trends.
Now think about what it all actually means:
Values: How would you explain the highest value, the lowest value, the point at which the line crosses the x axis,
Range: How would you explain the largest range? How would you change the method to reduce the spread in the data?
5. Ok - NOW look at the actual questions
Try to see past the detail. How does this data/question relate to things you have studied?
Your working memory can easily get overloaded with details, making it hard to think. If the examiners have introduced a new organism, its name won’t be important. What might be important is the environment in which it lives, or its interactions with other organisms. You know what data you have, and what the questions are, so pick out what actually matters here. Is this a question about enyme reaction rates? Or about surface area to volume ratio?
This is why it’s useful to look at the data first - you will be able to look at it with a clear eye, making it easier to pick out how it’s relevant to the material you have studied.
6. Give the required information
Avoid the common mistakes that lose students marks:
If they say you should use the data, you must either quote it, or show how you have used in in a calculation
Refer to the axis/data labels wherever possible. Don’t say “the graph goes up”, do say “the saturation of haemoglobin increases”
A-Level Biology Past Paper Graphs and Charts Exam Questions:
Got all that? Ok! Here are some questions for you to practice.
And remember - don’t read the questions until after you have made sense of the graph or chart.
If you’re looking for more maths-heavy questions to practice, here is an older but popular set from OCR.
If this post has been helpful, please like ❤️ below and share with your friends.
This article was written by Dr Jenny Shipway with guidance and editing from Tom. Tom has over 26 years experience specialising in A level Biology teaching and tuition, and has helped many students achieve top grades in the subject.
Transport in Animals: Haemoglobin, Oxygen Dissociation Curves, and the Bohr Effect
Haemoglobin, Oxygen Dissociation Curves, and the Bohr Effect
Red blood cells stuffed full of haemoglobin. Their bright red colour tells us their haemoglobin is in the form of oxyhaemoglobin, with bound oxygen.
This article includes an explanation of the topic followed by a short multiple-choice quiz with answers, and a collection of past-paper A-level exam questions for you to try.
Single-celled organisms absorb oxygen directly from their surroundings for use in aerobic respiration. But animals have cells buried deep within their bodies, far from the outside world. For this reason, the ability to transport essential substances like oxygen, and to remove waste products like carbon dioxide, is crucial for all animals.
This A-level Biology topic is challenging, but it’s really important to build an understanding of the mechanisms behind these processes. You’ll need to understand exchange and transport, and get to grips with the role of haemoglobin in transporting oxygen and carbon dioxide. And you really will need to understand it properly - as with most A-level topics, memorisation is not enough.
The really clever bit about oxygen transport in animals is the way that cooperative binding affects haemoglobin’s oxygen dissociation curve. Master that and you’ll be well on your way to getting full marks in this topic.
Vocabulary (for reference, don’t worry if you don’t know all these yet!):
Partial Pressure: The pressure exerted by one particular gas in a mixture.
Haemoglobin: A protein found in red blood cells. Able to bind oxygen, carbon dioxide, and other ligands.
Oxyhaemoglobin: Haemoglobin bound to oxygen, as occurs during oxygen transport.
Carbaminohemoglobin: Haemoglobin bound to carbon dioxide, as occurs during carbon dioxide transport. Yes it has a funny name! Be careful not to confuse it with carboxyhaemoglobin, which is hemoglobin bound with carbon monoxide.
Haemoglobinic Acid: Haemoglobin bound to a proton, as occurs during carbon dioxide transport.
Cooperative Binding: The phenomenon where the first oxygen molecule to bind to one of haemoglobin’s binding sites increases the affinity of the remaining binding sites for oxygen. And the first to release makes it easier for the others to release.
Carbonic Anhydrase: An enzyme that catalyses the reversible conversion of carbon dioxide and water into carbonic acid.
HCO3–: The bicarbonate ion, one of the ways in which carbon dioxide is transported in the blood.
Chloride Shift: The movement of chloride ions into red blood cells as bicarbonate ions move out, maintaining electrical neutrality during the transport of carbon dioxide.
Oxygen Dissociation Curve: A curve on a graph that shows how saturated with oxygen haemoglobin is at different partial pressures of oxygen. It curves because of the effect of cooperative binding. The position of the curve is affected by pH.
Partial Pressure:
None of this will make any sense if you don’t understand what partial pressure is, so that’s a good place to start. Partial pressure is the pressure exerted by one particular gas in a mixture. You can increase the partial pressure of oxygen molecules (O2) in air by either having greater overall air pressure, or by a larger proportion of the air being oxygen.
The percentage of Oxygen in the air is the same on Everest as at sea level.
When you ascend Everest, the percentage of oxygen in the air does not fall, but the air pressure does. And so the partial pressure of oxygen in your alveoli falls.
When you re-breathe the same air, the air pressure does not fall, but the percentage of oxygen in the air does. And so the partial pressure of oxygen in your alveoli falls.
Gases still have partial pressures when they are in solution. The partial pressure of carbon dioxide is really high in an unopened can of coke. And the partial pressure of oxygen in your body fluids must be carefully regulated if your cells are to survive.
Remember that oxygen is the final electron acceptor in oxidative phosphorylation on the inner mitochondrial membrane, where it becomes water (H2O). Respiration therefore removes oxygen molecules (O2) from the body, lowering its partial pressure. The harder a tissue works, the more ATP will be produced from aerobic respiration, and the more oxygen atoms will be moved from O2 into H2O.
Respiration therefore lowers the partial pressure of oxygen (O2) in the tissues. Especially in energy-hungry tissues like muscle.
The partial pressure of carbon dioxide (CO2) also changes in the body. Respiration produces carbon dioxide by decarboxylation of pyruvate in the link reaction and citrate (etc) in Krebs cycle. As the partial pressure of oxygen falls, that of carbon dioxide increases. It’s not the same oxygen atom (remember the one from O2 ended up in H20), but the two processes are closely connected.
Respiration therefore increases the partial pressure of carbon dioxide in the tissues. Especially in energy-hungry tissues like muscle.
This is why animals need a system to support gas transport - it is necessary to move oxygen in to the tissues from the outside world, and to move carbon dioxide out of the tissues to excrete it out of the body.
Haemoglobin’s role:
Haemoglobin plays a pivotal role in transporting oxygen and carbon dioxide in the bloodstream. Haemoglobin is a protein containing four polypeptide chains, each of which provides a binding site that can bind reversibly with oxygen or protons (and some other things too). The timing of its binding and release of its ligands depends on various factors:
Haemoglobin - there are four polypeptide chains, here two are shown in green, and two in red (apologies to anyone who is colour-blind, I didn’t make this graphic). Each polypeptide chain is folded to create a subunit of the protein, and each subunit provides a binding site which can bind one Oxygen molecule.
Oxygen Binding: When oxygen levels are high, haemoglobin binds with oxygen molecules, forming oxyhaemoglobin. This happens in the lungs, where blood is brought close to the surface of the alveoli. Oxyhaemoglobin is bright red; this is what gives blood its red colour.
Cooperative Binding: When the first oxygen molecule binds, haemoglobin changes shape in a way that increases the affinity of its remaining binding sites for oxygen. This results in a rapid increase in oxygen saturation once the first oxygen molecule binds to haemoglobin. There is a similar effect on release of oxygen - releasing one oxygen makes it easier for the others to be released.
Carbon Dioxide Binding: Haemoglobin binds a small percentage of the carbon dioxide produced by the body tissues to help transport it back to the lungs. Haemoglobin bound to carbon dioxide is called carbaminohemoglobin, and is a dark maroon colour. It is not blue!
Carbon Dioxide transport:
About 30% of the carbon dioxide produced by body tissues gets directly bound by haemoglobin for transport. A lot more - about 70% - travels in the blood plasma. This is possible because of the action of the enzyme Carbonic Anhydrase.
Carbonic Anhydrase: Inside the red blood cell, the enzyme carbonic anhydrase catalyses the reversible conversion of carbon dioxide and water into carbonic acid. This acid then dissociates into bicarbonate ions (HCO3-) and protons (H+).
Haemoglobinic Acid: The positively-charged protons from the dissociated carbonic acid bind to the haemoglobin to form haemoglobinic acid. This keeps these positive charges inside the red blood cell.
Chloride Shift: In contrast, the negatively-charged bicarbonate ions are free to diffuse out of the red blood cell into the blood plasma. To maintain electrical neutrality, chloride ions (Cl-) diffuse into the red blood cell. This is known as the chloride shift.
Cooperative Binding and the Oxygen Dissociation Curve:
The much-feared oxygen dissociation curve. The really interesting thing is that it is not a straight line. You need to know why not, and why this is crucial for oxygen delivery to the body tissues.
The Oxygen Dissociation Curve is a graph plotting the partial pressure of oxygen (how much oxygen there is in the environment) against how saturated the haemoglobin is with oxygen.
The graph is always drawn with the partial pressure of oxygen on the X-axis, showing low oxygen to the left, and high oxygen to the right. Oxygen binding is plotted against the Y-axis, with the curve plotted higher at partial pressures where the haemoglobin is more saturated with oxygen.
Take a little while to work out exactly what the graph is showing, as it can be a bit confusing at first.
As you might expect, when there is more oxygen around, more oxygen gets bound. But it’s not quite as simple as that.
The sigmoid shape of the oxygen dissociation curve shows why haemoglobin is so ideally suited to its role in oxygen transport. The shape of the curve is explained by haemoglobin’s remarkable property of cooperative binding.
Haemoglobin has four tertiary domains, each with its own binding site. So it can carry four oxygen molecules. The really clever bit is that when the first oxygen molecule binds, this causes a change of shape in the protein that increases the affinity of the other three binding sites for oxygen. This increased affinity increases their chances of binding oxygen too. This all has the effect that once just one oxygen has bound, the haemoglobin’s binding sites are quickly saturated. And the opposite happens when oxygen dissociates - the dissociation of the first oxygen reduces the affinity of the other binding sites.
The way in which one binding event encourages others is called Cooperative Binding. This ‘all or nothing’ tendency affects the shape of haemoglobin’s oxygen dissociation curve by squashing it down at the bottom and up at the top, creating its famous sigmoid shape.
The sigmoid shape of the oxygen dissociation curve is crucial for efficient oxygen delivery to tissues. At low oxygen concentrations (e.g., in tissues with high metabolic activity), haemoglobin exhibits low affinity for oxygen, allowing it to release oxygen to respiring cells. Conversely, at high oxygen concentrations (e.g., in the lungs), haemoglobin exhibits high affinity for oxygen, facilitating its uptake from the lungs.
The Bohr Effect: Carbon Dioxide and the Oxygen Dissociation Curve
Notice that the right-shifted, red curve is lower than the blue one. This tells us that at high CO2, haemoglobin has LESS affinity for oxygen. (The colours don’t mean anything.)
Haemoglobin’s oxygen dissociation curve isn’t fixed in place. It can move to different positions depending on the pH.
The pH in the red blood cell is affected by the partial pressure of carbon dioxide (remember how it behaves during transport?). High levels of carbon dioxide indicate that the body is active and needs more oxygen.
Active muscles also produce lactic acid through anaerobic respiration, which further reduces the pH.
A low (acidic) pH has the effect of moving the oxygen dissociation curve to the right. This means that any any given partial pressure of oxygen, this high-CO2, right-shifted curve is lower than before.
It’s not enormously intuitive, but you can see this clearly if you draw a line vertically up through the graph at a chosen partial pressure of oxygen. Look at where it meets each curve. It will hit the right-shifted curve before it hits the original curve, because the right-shifted, high-CO2 curve will have lower oxygen saturation at this (or any) patial pressure.
That means that at any partial pressure of oxygen, the high-CO2 haemoglobin has a lower affinity for oxygen than before, and is more likely to release its oxygen into the tissues.
Reducing haemoglobin’s affinity for oxygen at high partial pressures of carbon dioxide helps it release oxygen in the active tissues that need it most.
Fetal Haemoglobin and Myoglobin
Haemoglobin sometimes needs to pass its oxygen to other, similar oxygen-binding molecules. It needs to pass it to myoglobin for oxygen storage in muscles, and to fetal haemoglobin to pass oxygen to the growing foetus.
These similar-but-different molecules have their own oxygen dissociation curves. If oxygen is to be passed to them, they must have a higher affinity for oxygen than normal haemoglobin. And this is what is seen. When you look at their curves, they are left-shifted with respect to haemoglobin. Draw a line up from any chosen partial pressure of oxygen, and it will hit the curve for normal haemoglobin first, because the fetal haemoglobin or myoglobin will have higher oxygen saturation.
This means that at any partial pressure of oxygen, they have a higher affinity for oxygen, and are able to bind oxygen that has been released by the normal haemoglobin.
Multiple Choice Questions (answers below):
What is the primary function of haemoglobin in the bloodstream?
a) Transporting nutrients
b) Transporting oxygen
c) Transporting waste products
d) Transporting hormonesWhich enzyme catalyzes the reversible conversion of carbon dioxide and water into carbonic acid?
a) Carbon dioxide synthase
b) Carbonic anhydrase
c) Haemoglobinase
d) Bicarbonate dehydrogenaseWhich acid is formed when haemoglobin binds with a proton?
a) Carbonic acid
b) Haemoglobinic acid
c) Hydrochloric acid
d) Sulfuric acidWhich ions move into red blood cells when bicarbonate ions diffuse out?
a) Sodium
b) Potassium
c) Chloride
d) HydrogenWhat effect does an increase in carbon dioxide concentration have on the oxygen dissociation curve?
a) It shifts the curve to the left
b) It shifts the curve to the right
c) It has no effect on the curve
d) It decreases the steepness of the curve
Multiple Choice: answers
1. Answer: b) Transporting oxygen
2. Answer: b) Carbonic anhydrase
3. Answer: b) Haemoglobinic acid
4. Answer: c) Chloride
5. Answer: b) It shifts the curve to the right
How did you do?
These questions were just a quick test to see if you can remember some of the key points. If you struggled a bit then go back and review the content. But also check that you really understand what’s going on with this topic. The exam board will intentionally phrase the questions to make it as difficult as possible for anyone to answer by having just memorised key facts.
When you’re ready, try some real exam questions:
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This article was written by Dr Jenny Shipway in collaboration with Tom
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