OCR A-Level Biology Questions And Verified Answers With Complete Answers| Graded A|

OCR A-Level Biology Questions And Verified Answers With Complete Answers| Graded A| What is the MAIN role of membranes and what are the other roles? Correct Answer -COMPARTMENTALISATION -site of chemical reactions -cell signalling -cell adhesion How do cell membranes compartmentalise? Correct Answer Membranes are hydrophobic layers that separate different regions of substances dissolved in water. This hydrophobic layer acts as a barrier preventing the movement of hydrophilic molecules from one region to another. It keeps one compartment separate from another. What are the 3 examples of membrane compartmentalisation? Correct Answer -separate contents of the cell from the environment -separate different areas of the cell from each other (organelles) -separate different areas within organelles How are cell membranes sites of chemical reactions? Correct Answer Some enzymes or electron carriers involved in aerobic respiration or photosynthesis have to be in particular positions relative to each other in order to work. Being membrane bound allows these organelles to be maintained. What is cell signalling and how are cell membranes involved in cell signalling? Correct Answer Cell signalling is where one cell releases a chemical which causes a response in another cell. Glycoproteins are often the receptors on cells that detect the presence of the chemical and cause changes to the cell. What is cell adhesion and how are cell membranes involved in cell adhesion? Correct Answer The binding of a cell to a particular surface or substrate particularly the extracellular matrix of another cell. Some types of glycoproteins perform this role. What are the 5 components of membranes? Correct Answer -phospholipids