AQA A Level Biology 4/5/6 mark questions (2024) (Certified Answers)

Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5) 1 (Simple / facilitated) diffusion from high to low concentration / down concentration gradient; 2 Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer; OR Large / polar / water-soluble molecules go through proteins; 3 Water moves by osmosis / from high water potential to low water potential / from less to more negative water potential; 4 Active transport is movement from low to high concentration / against concentration gradient; 5 Active transport / facilitated diffusion involves proteins/carriers; 6 Active transport requires energy / ATP; 7 Ref. to Na+ / glucose co-transport; Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. (5) 1 Many alveoli / alveoli walls folded provide a large surface area; 2 Many capillaries provide a large surface area; 3 (So) fast diffusion; ________________________________________________ 4 Alveoli or capillary walls / epithelium / lining are thin / short distance between alveoli and blood; 5 Flattened / squamous epithelium; 6 (So) short diffusion distance / pathway; 7 (So) fast diffusion; ________________________________________________ 8 Ventilation / circulation; 9 Maintains a diffusion / concentration gradient; 10 (So) fast diffusion; Scientists believe that it may be possible to develop vaccines that make use of microfold cells. Explain how this sort of vaccine would lead to a person developing immunity to the pathogen (5) 1.Vaccine contains antigen/ dead pathogen