Cell membrane structureAQA A-Level Biology: Mind map

Exam questions on Cell membrane structure

1. A technician cut equal-sized discs from a beetroot with a cork borer and then rinsed them in distilled water before starting an experiment on membrane permeability.
   The technician placed other discs in ethanol. Explain why the solution around these discs became redder than the solution around discs in water.2 marks
2. Phospholipid molecules have a hydrophilic head containing a phosphate group and two hydrophobic fatty acid tails. A cell-surface membrane has an aqueous solution on both sides: tissue fluid outside the cell and cytoplasm inside it.
   Explain why sodium ions cannot easily diffuse through the middle of the membrane.2 marks
3. The cell-surface membrane of a liver cell contains phospholipids, cholesterol, proteins and short carbohydrate chains. In 1972 Singer and Nicolson proposed the fluid-mosaic model of membrane structure.
   Describe the arrangement of the phospholipids, proteins and carbohydrates in this membrane.3 marks