This free quiz has 11 real AQA A-level Biology exam questions on cell structure and microscopy (24 marks, about 30 minutes). It marks itself: tick-box, table and calculation questions are marked for you, and for written answers you check your work against the real AQA mark scheme.
What the quiz covers (AQA 3.2.1)
the structure of viruses, and why they are described as acellular and non-living
features of prokaryotic cells
comparing a bacterium with an HIV particle
matching parts of a plant cell to their descriptions
the functions of mitochondria and the Golgi apparatus
why electron microscopes give higher resolution than optical microscopes
calculating actual size from magnification, and choosing between optical, SEM and TEM
using cell fractionation and ultracentrifugation to isolate mitochondria (4 marks)
How to use it
Write each answer in full before you open the mark scheme, then tick only the points you really made. For the calculation, convert mm to µm before you divide by the magnification. In the cell fractionation answer, name every property of the solution and say exactly what you spin and at what speed.
Where students lose marks (from AQA examiners’ reports and mark schemes)
Each point below is followed by wording that gained marks.
Energy is released, not made. Many students wrote that mitochondria “produce energy” or “create energy”, called them “the powerhouse of the cell”, or wrote about “energy for respiration”.
✔ Gains credit: the mitochondrion is the site of aerobic respiration, where ATP is made and energy is released.
Vesicles and secretion. Answers often said Golgi vesicles carry proteins “to where they are needed” or “out of the cell”, which lacked detail. Some confused exocytosis with endocytosis.
✔ Gains credit: the Golgi apparatus modifies and packages proteins, and vesicles move them to the cell-surface membrane and fuse with it (exocytosis).
Electron wavelength. Many students wrote about the microscope itself, such as “the electron microscope has a shorter wavelength”, which was rejected. Some confused resolution with magnification.
✔ Gains credit: electrons have a shorter wavelength than light, so an electron microscope gives a higher resolution.
SEM and TEM images. Many students said an SEM image is 3D but didn't say a TEM image is 2D, so only 13% gained both marks. Others mixed the two up and said a TEM gives 3-D images.
✔ Gains credit: an SEM shows a 3D surface because electrons bounce off the specimen, whereas a TEM shows a 2D image of internal structures because electrons pass through it.
Converting mm to µm. Unit conversion was the main problem in size calculations, for example turning 46 mm into 4600 µm. A small number divided the real size by the image size.
✔ Gains credit: measure the image, convert mm to µm by multiplying by 1000, then divide by the magnification.
Cold, buffered, isotonic. Students often gave only part of this point, or wrote about “damage to cells” rather than organelles. Terms such as turgid, plasmolysed or crenation were rejected, and “buffering prevents damage to organelles” was too vague.
✔ Gains credit: an ice-cold solution reduces enzyme activity, a buffer stops proteins denaturing, and the same water potential prevents osmosis so organelles don't burst or shrink.
Low speed, then supernatant. Many left out “low speed” for the first spin, or wrote “centrifuge it again” without saying it was the supernatant. Some described the pellet forming at the top of the tube.
✔ Gains credit: homogenise and filter, centrifuge at low speed so the heaviest organelles such as nuclei form the pellet, then spin the supernatant at a higher speed.
Keep practising
The other AQA 3.2 self-marking quizzes: Mitosis · Membrane transport · Immune system
Topic 3.1 quizzes start with carbohydrates
The AQA topic index
weekly AQA group classes: Year 12 on Tuesdays at 5.15pm, Year 13 on Wednesdays or Thursdays at 6.30pm
Questions © AQA, from past A-level and AS Biology papers, with their mark schemes and examiners’ reports.