Plasma Membrane Worksheet Answers

1. The two most important functions of the plasma membrane are two of:

1. The plasma membrane defines and encloses the cell;

2. It is the boundary between intra and extracellular fluid;

3. It is selectively permeable i.e. it maintains homeostasis.

2. The best definition of Homeostasis is:

a) Keeping a constant temperature inside a cell or organism despite external changes.

b) Keeping constant conditions within a cell or organism despite external changes.

c) Keeping a constant pH inside a cell or organism despite external changes.

d) Keeping constant conditions outside a cell or organism despite internal changes.

3. The two most abundant molecules in the plasma membrane are:

1. Proteins

2. Phospholipids (or fats or lipids)

4. This is true of the structure of the plasma membrane:

a) It is a double layer of protein molecules with phospholipid molecules randomly dotted through it

b) It is single layer of phospholipid molecules

c) It is a double layer of phospholipid molecules with protein molecules dotted in it.

d) It is single layer of protein molecules with phospholipids dotted in it.

5. Add the following labels to the diagram of the plasma membrane shown below.

protein molecules; protein channel; double layer of phospholipid molecules

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