Question

24 the structure of membranes key idea: plasma membranes are composed of a lipid bilayer with proteins moving freely within it. the fluid mosaic model of membrane structure glycolipid fatty acid tail is hydrophobic (repelled by water) water molecules pass between the phospholipid molecules by osmosis. lipid soluble molecules, e.g. gases and steroids, can move through the membrane by diffusion. attached carbohydrate phosphate head is hydrophilic (attracted to water) carrier protein co₂ phospholipids naturally form a bilayer with the hydrophobic parts pointing away from the water. channel protein cholesterol is a packing molecule and is important in cell membrane fluidity. glycoprotein cell interior the fluid - mosaic model of membrane structure (above) describes a phospholipid bilayer with proteins of different types moving freely within it. the double layer of lipids is quite fluid. it is a dynamic structure and is actively involved in cellular activities. 1. list the important components of the plasma membrane: 2. identify which kind of molecule on the diagram: (a) can move through the plasma membrane by diffusion: (b) forms a channel through the membrane: 3. list the types of proteins pictured in the diagram: 4. (a) on the diagram (right) label the hydrophobic and hydrophilic ends of the phospholipid. (b) which end is attracted to water?

Explanation:

1. Based on the fluid - mosaic model and the diagram, the components are phospholipids, proteins (channel and carrier), glycolipids, glycoproteins, cholesterol.
2. (a) Lipid - soluble molecules like gases and steroids can diffuse through the plasma membrane. (b) Channel proteins form channels through the membrane.
3. The proteins are channel proteins, carrier proteins, and glycoproteins.
4. (a) The fatty - acid tail is the hydrophobic end and the phosphate head is the hydrophilic end. (b) The hydrophilic end (phosphate head) is attracted to water.

Answer:

1. Phospholipids, proteins (channel and carrier), glycolipids, glycoproteins, cholesterol.
2. (a) Lipid - soluble molecules (gases and steroids). (b) Channel proteins.
3. Channel proteins, carrier proteins, glycoproteins.
4. (a) Hydrophobic end: fatty - acid tail; Hydrophilic end: phosphate head. (b) The hydrophilic end (phosphate head).