Lipids & Membranes

Question 1

What is an advantage of a fluid membrane?

Answer 1

Proteins can communicate much faster with each other

Question 2

What is a property of carbohydrate chains for cell-cell signalling?

Answer 2

They are hydrophobic

Question 3

What membrane is the only one to contain carbohydrates?

Answer 3

Plasma membrane

Question 4

How much of cholesterol is made in the diet?

Answer 4

10%

Question 5

Give 5 examples of proteins in membranes

Answer 5

• Structural
• Receptors
• Ion Channels
• Transporters
• Enzymes

Question 6

What are the 3 types of membrane protein and give info on each?

Answer 6

Integral (intrinsic) - embedded in the lipid membrane and span the entire membrane. they form either alpha helices or beta strands.

Anchored proteins which are covalently bound fatty acids. They allow fluidity of the membrane.

Peripheral (extrinsic) proteins which are attached to membrane surface by ionic interactions with integral proteins or with the polar head of phospholipids.

Question 7

Lipids are — in water, — in fat and organic solvents

Answer 7

Insoluble, soluble

Question 8

What are examples of a polar head on phospholipids?

Answer 8

choline, ethanolamine, inositol

Question 9

Why are phospholipids amphiphatic?

Answer 9

They have a hydrophilic head and hydrophobic tails.

Question 10

What bond holds a fatty acid chain to a glycerol molecule?

Answer 10

An ester bond

Question 11

In a fatty acid, what does (x:y) stand for?

Answer 11

x = number of carbons in chain
y = number of double bonds

Question 12

Draw the cholesterol molecule

Answer 12

Look up

Question 13

What does the polar head of the cholesterol bind to?

Answer 13

The head of the phospholipid

Question 14

What is meant by the lipid bilayer being asymmetrical?

Answer 14

The two halves have a different lipid composition.

Question 15

What is the definition of fluidity?

Answer 15

The ease at which lipid molecules move about in the plane of the bilayer (regulates movement of proteins, signalling and exocytosis)

Question 16

What things regulate the fluidity of the membrane?

Answer 16

• Fatty acids determined by the chain length and saturation degree. Short chain fatty acids reduce the tendency of hydrocarbon interacting and increases fluidity and kinks in unsaturated fatty acids lead to less stable van der waals interactions and hence increases fluidity.
• High cholesterol content resists the random movement of polar heads and decreases fluidity.

Question 17

Why is increased cholesterol content of red blood cells associated with liver disease?

Answer 17

The fluidity of the membrane is decreased and this alters cell shape and impairs oxygen transport.