Cell Membranes

Question 1

Where are plasma membranes found?

Answer 1

Cells, organelles and vesicles

Question 2

What are the functions of a plasma membrane?

Answer 2

• form a barrier between 2 environments
• control exchange of substances between environments
• allows different conditions to be established and maintained

Question 3

What is the difference between a plasma membrane and a cell surface membrane?

Answer 3

A cell surface membrane envelopes the cytoplasm of a cell
Plasma membrane can be found anywhere

Question 4

What is the cell surface membrane made from?

Answer 4

Phospholipids

Question 5

What is the structure of a phospholipid?

Answer 5

Hydrophilic head:
Phosphate with phosphoester bond
Hydrophobic tail:
Glycerol wire ester bond
Attached to 2 fatty acids

Question 6

What is the fluid mosaic model?

Answer 6

Molecules within the phospholipid bilayer fit like a mosaic and are free to move within the layer

Question 7

What does the fluidity of the bilayer depend upon?

Answer 7

Temperature and presence of cholersterol molecules

Question 8

Phospholipid

Answer 8

• arranged in bilayer
• hydrophilic head points out
• hydrophobic tail faces in
• form total waterproof barrier around the cell/organelle/vacuole

Question 9

Extrinsic protein

Answer 9

• proteins on the outside of the cell
• receptors
• enzymes

Question 10

Intrinsic protein

Answer 10

• proteins that goes all the way through the bilayer
• allows water soluble molecules to pass into or out of cell
• channel proteins or
• molecules can entry by facilitated diffusion

Question 11

Glycoprotein

Answer 11

• protein with carbohydrate chain coming off of it
• recognition of self
• helps cell stick to each other to form tissues

Question 12

Glycolipid

Answer 12

• carbohydrate chain attached to phospholipid molecules
• self recognition
• maintains stability of cell membrane

Question 13

Cholesterol

Answer 13

• molecule sits within the phospholipid bilayer
• bind to tails of phospholipids, causing them to pack more closely together- restricts movements (less fluid more rigid)
• maintain integrity and fluidity of cell membrane (shape)

Question 14

What molecules can pass through the phospholipid bilayer?

Answer 14

Small molecules e.g. oxygen and carbon dioxide
And lipid soluble molecules

Question 15

What properties should a drug have to enter a cell quickly?

Answer 15

Small molecules and lipid soluble