Chapter 6: 6.1 Membrane Structure and Composition

Question 1

Phospholipids are the primary component of…

Answer 1

Cell membranes

Question 2

Phospholipids are ———–

Answer 2

Amphipathic

Question 3

Describe:

Phospholipid Structure

Answer 3

• A hydrophobic tail (the fatty acid side chains)
• A polar head (consisting of the negatively charged phosphate group)

Question 4

What is the difference between saturated vs. unsaturated fatty acids?

Answer 4

Saturated:
* Do not contain any double bonds (fully saturated with hydrogens)

Unsaturated:
* Contain one or more double bonds

Question 5

True or False:

The plasma membrane is fluid

Answer 5

True

Question 6

What determines the degree of fluidity of the membrane?

Answer 6

Depends on the type of lipids making up the membrane

Question 7

What factors affect plasma membrane fluidity?

Answer 7

• Temperature
• Tail length
• Degree of unsaturation
• Cholesterol

Question 8

How does temperature affect membrane fluidity?

Answer 8

At higher temperatures, membrane has more fluidity than at lower temperatures

Question 9

How does tail length affect membrane fluidity?

Answer 9

Longer fatty acid tails = More intermolecular interactions between phospholipids = Less fluidity

Question 10

How does degree of unsaturation affect membrane fluidity?

Answer 10

If the fatty acids are unsaturated:
* Double bonds create “kinks”
* Pushes adjacent phospholipids further apart
* Increased spacing = Reduced intermolecular interactions = Increased fluidity

Question 11

How does cholesterol affect membrane fluidity?

Answer 11

Depending on temperature:
* High temperature: Cholesterol presence decreases fluidity
* Low temperature: Cholesterol presence increases fluidity

Question 12

What is the difference between Integral Membrane Proteins vs. Peripheral Membrane Proteins?

Answer 12

Integral Membrane Proteins:
* Permanently associated with the membrane
* Usually span the membrane (transmembrane proteins)

Peripheral Membrane Proteins:
* Temporarily associated with the membrane through weak non-covalent interactions

Question 13

Define:

Lipid rafts

Answer 13

Clusters of a specific lipid bound to the plasma membrane (e.g. cholesterol)

Question 14

True or False:

Carbohydrates do not accumulate on the surface of a cell

Answer 14

False, sugar resides can accumulate on surface and act as receptors

Question 15

What are glycoproteins?

Answer 15

Carbohydrates bound to proteins embedded in the membrane

Question 16

What are glycolipids?

Answer 16

Sugars (carbohydrates) bound to lipid directly

Question 17

True or False:

The membrane is made up of lipids

Answer 17

False, it is made up of lipids but also proteins

Question 18

What are integral membrane proteins?

Answer 18

The proteins that are permanently bound into the membrane

Question 19

What are peripheral membrane proteins?

Answer 19

Proteins that are transiently or indirectly bound to the membrane

Question 20

What functions could membrane proteins have?

Answer 20

• Transport
• Catalytic reactions (enzymes)
• Anchors
• Receptors