Components Of Cell Membranes

Question 1

Phospholipid’s head is hydro….and the tail is hydro….?

Answer 1

• The head is hydrophilic - it attracts water
• The tail is hydrophobic - it repels water

Question 2

How does phospholipids form a barrier to dissolved substances?

Answer 2

• The molecules automatically arrange themselves into a bilayer - the heads face out towards the water on either side of the membrane.

Question 3

How does cholesterol molecules fit between phospholipids?

Answer 3

• They bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together.
• This makes the membrane less fluid and more rigid.

Question 4

What are the functions of channel proteins and carrier proteins in the cell membrane?

Answer 4

• Channel proteins form channels in the membrane - these allow small or charged particles through.

• Carrier proteins transport molecules and ions across the membrane by active transport and facilitated diffusion.

Question 5

What are glycoproteins and glycolipids?

Answer 5

• Glycoproteins are proteins that have a polysaccharide chain attached.
• Glycolipids are lipids that have a polysaccharide chain attached.

Question 6

What are the functions of glycoproteins and glycolipids in the cell membrane?

Answer 6

• They stabilise the membrane by forming hydrogen bonds with surrounding water molecules.

• They’re sites where drugs, hormones and antibodies bind.

• They act as receptors for cell signaling.

• They’re also antigens.

Question 7

Describe the fluid mosaic structure of a cell membrane.

Answer 7

• Phospholipid molecules form a bilayer.

• This bilayer is ‘fluid’ because the phospholipids are constantly moving.

• Cholesterol molecules are present within the bilayer.

• Protein molecules are scattered through the bilayer, like tiles in a mosaic.