Respiration Photosynthesis and AS knowledge - a terrific synoptic A-level Biology question

One from the OCR Unifying concepts paper, combines respiration and photosynthesis.

(a) think photolysis and Oxygen accepting electrons ...

(b) is about phosphorylation and diffusion gradients

(c) is about the nature of passive transport and using proteins

(d) is about endosymbionts and prokaryotes

pdf question here and markscheme here