2. Cell Membranes

Question 1

What are 2 functions of the cell-surface membrane?

Answer 1

• It allows different conditions to be established inside and outside of a cell
• It controls the movement of substances in and out of the cell

Question 2

Describe the position of the phospholipids in the phospholipid bilayer:

Answer 2

The hydrophilic heads of both layers point to the outside of the cell surface membrane, while the hydrophobic tails point inwards.

Question 3

What are the 3 functions of the phospholipids in the membrane?

Answer 3

• Allow lipid soluble substances to enter and leave the cell
• Prevent water soluble substances entering and leaving the cell
• Make the membrane flexible and self-sealing

Question 4

Where are proteins found in the cell membrane?

Answer 4

They are interspersed throughout the cell surface membrane. They are also embedded into the phospholipid bilayer.

Question 5

What are the two main ways that proteins are embedded into the phospholipid bilayer?

Answer 5

1. Some proteins occur in the surface of the bilayer and never extend completely across it
2. Other proteins completely span the phospholipid bilayer from one side to the other

Question 6

What is the purpose of the proteins that just occur in the surface of the bilayer?

Answer 6

They act either to give mechanical support, or in conjunction with glycolipids, as cell receptors for molecules such as hormones.

Question 7

What is the purpose of the proteins that span the entirety of the bilayer?

Answer 7

Some are protein channels, which form water-filled tubes to allow water-soluble ions to