AQA A LEVEL BIOLOGY PAPER 1 QUESTIONS AND CORRECT ANSWERS UPDATED 2022.

AQA A LEVEL BIOLOGY PAPER 1 QUESTIONS AND CORRECT ANSWERS UPDATED 2022. AQA A LEVEL BIOLOGY Paper 1 2022 1. What is the function of the cell membrane?: To control what enters and leaves the cell, acts as a barrier between the cell and its environment. 2. What structural feature of the cell membrane allows substances to enter/leave?: Partially permeable 3. What is the fluid mosaic model?: States that a membrane is a fluid structure (because phospholipids are constantly moving) with a "mosaic" of various proteins embedded in it 4. Describe the structure and function of phospholipids.: Hydrophilic head and hydrophobic tail, arranged in a bilayer (heads face outwards, tails face inwards). Lipid-soluble substances only allowed to pass through. 5. What is the function of cholesterol in the CSM?: Make phospholipids pack more closely together, restricting the movement of the phospholipids, making the membrane less fluid/more rigid. 6. What is simple diffusion?: The (passive) movement of particles from an area of high concentration to an area of low concentration. 7. What is facilitated diffusion?: The passive movement of a large/charged particle down its concentration gradient through a carrier/channel protein. 8. What is the process of facilitated diffusion using a carrier protein?: Large molecule binds to a carrier protein in membrane. Protein changes shape. Protein releases the large molecule on the opposite side of the membrane. 9. What is the process of facilitated diffusion using a channel protein?: Channel proteins form pores in membrane. Charged particles can diffuse down their concentration gradients to the opposite side of the membrane. 10. What are the factors affecting simple diffusion?: Concentration gradient, thickness of exchange surface and surface area. 11. What are the factors affecting facilitated diffusion?: Number of transport proteins and strength of gradient. 12. What is osmosis?: Diffusion of water through a partially permeable membrane from an area of high water potential to an area of lower water potential. 13. What are the factors affecting osmosis?: Water potential gradient. Thickness of exchange surface. Surface area of exchange surface.