Structure of cell membranes

Question 1

Plasma membranes are vital structures found in all cells. Why?

Answer 1

• Forms a boundary between cell cytoplasm and the exernal environment
• Allows different conditions in and outside of the cell
• Controls the movement of substances in and out of the cell

Question 2

What components make up a cell membrane?

Answer 2

• Phospholipids bilayer
• Glycoproteins
• Glycolipids
• Extrinsic proteins
• Intrinsic proteins
• Cholesterol

Described as fluid-mosaic model due to mixture & movement of components

Question 3

Describe the structure of a phospholipid bilayer

Answer 3

Phospholipids arrange into a bilayer so that the hydrophilic heads face outwards and hydrophobic tails face inwards

Question 4

Describe the function of a phospholipid bilayer

Answer 4

Creates a hydrophobic center in the bilayer so that water-soluble substances cannot pass through

Question 5

Describe the structure of a glycoprotein / glycolipid

Answer 5

Short carbohydrate chain attachted to a intrinsic protein or a lipid

Question 6

Describe the functions of glycoproteins / glycolipids

Answer 6

• Cell adhesion
• Cell recognition
• Cell signalling

Question 7

Where are extrinsic proteins found?

Answer 7

Embedded in the cell membrane but doesn’t extend completely across

Question 8

State the function of extrinsic proteins

Answer 8

• Provides support
• Cell recognition as receptors when connected to proteins/lipids

Question 9

Where are intrinsic proteins found?

Answer 9

Emedded in the cell membrane where they span across from one side of bilayer to the other

Question 10

What are the two types of intrinsic proteins?

Answer 10

• Protein channels
• Carrier proteins

Question 11

Describe the function of protein channels

Answer 11

Enables water-soluble ions to diffuse in and out of the cell by forming tubes that fill with water

Question 12

Describe the function of carrier proteins

Answer 12

Transports larger molecules in and out of the cell by binding to them and changing shape

Question 13

Describe the structure of cholesterol

Answer 13

Cholesterol molecules have a hydrophilic and hydrophobic region
Hydrophobic region binds to fatty acid tails causing them to pack closely together

Question 14

Describe the function of cholesterol in cell membranes

Answer 14

• Provides stability
• Reduces the fluidity of the membrane