Cell Membranes

Question 1

What are cell membranes primarily made of?

Answer 1

Cell membranes are primarily made of lipids, with proteins and some proteins having carbohydrates attached.

Example: Phospholipids

Question 2

What makes lipids hydrophobic?

Answer 2

Lipids are almost exclusively made of hydrocarbons, with non-polar bonds that make them hydrophobic.

Example: Fats

Question 3

What are the main functions of lipids?

Answer 3

Lipids store energy, are structural components of cell membranes (as phospholipids), function as pigments, act as hormones (steroids), provide insulation (blubber), and repel water (cuticle on leaves).

Example: Steroids

Question 4

What are triglycerides composed of?

Answer 4

Triglycerides consist of one glycerol molecule attached to three fatty acids.

Example: Fats

Question 5

How do saturated and unsaturated fatty acids differ?

Answer 5

Saturated fatty acids have no double bonds, making them straight and tightly packed. Unsaturated fatty acids have one or more double bonds, making them kinked and preventing tight packing.

Example: Olive oil vs butter

Question 6

What determines the fluidity of lipids?

Answer 6

The degree of fatty acid saturation determines lipid fluidity. Saturated fats are less fluid, while unsaturated fats are more fluid.

Example: Solid vs liquid fats

Question 7

What are phospholipids, and what is their role in membranes?

Answer 7

Phospholipids are the main component of biological membranes, with a hydrophilic phosphate head and hydrophobic fatty acid tails, forming a bilayer in aqueous environments.

Example: Cell membranes

Question 8

What is the fluid mosaic model?

Answer 8

The fluid mosaic model describes the cell membrane structure, where lipids form the membrane’s integrity and proteins ‘float’ within the phospholipid bilayer.

Example: Cell membrane structure

Question 9

How does cholesterol affect animal cell membranes?

Answer 9

Cholesterol makes up to 1/4 of the lipids in animal cells, making the membrane more structurally sound, especially since animal cells lack cell walls.

Example: Animal cells

Question 10

What factors affect membrane fluidity?

Answer 10

1. Temperature: Fluidity decreases as temperature drops.
2. Lipid Composition: Cholesterol and long-chain saturated fatty acids reduce fluidity.

Example: Cold temperatures

Question 11

What are the three types of membrane proteins?

Answer 11

1. Peripheral membrane proteins: Located on the surface.
2. Integral membrane proteins: Embedded in the membrane.
3. Anchored proteins: Attached to the membrane via a lipid anchor.

Example: Protein types in membranes