(a)[5]
Use a label line together with the correct letter to identify each of the following on Fig. 1.1. P: protein for active uptake of potassium ions Q: protein for facilitated diffusion of polar molecules R: receptor site for a hormone S: hydrophilic heads of phospholipids on the internal surface of the membrane T: molecule that modifies the fluidity of the membrane
(b)[3]
Some cells take in bacteria by endocytosis. Explain how endocytosis happens at a cell surface membrane.