Lesson 3 - Membranes

Question 1

What are the six functions of biological membranes?

Answer 1

1. Define cell boundary.
2. Define enclose compartments.
3. Control movement of material into and out of cell / organelles.
4. Allow response to external stimuli.
5. Enable interactions between cells.
6. Provide scaffold for biochemical activities.

Question 2

What is the trilaminar structure?

Answer 2

The trilaminar stucture is a lipid bilayer; which is then made up of phospholipids with proteins embedded in or associated with the layer.

Question 3

Explain the components of the Fluid Mosaic Model of Biological Membranes.

Answer 3

The fluid explains components are mobile. The mosaic explains diverse ‘particle’ like proteins, carbohydrates, and cholesterol which penetrate the lipid layer; these components can interact.

Question 4

True or False: the hydrophilic phospholipid head groups are part of the outer / exterior leaflet.

Answer 4

True!

Question 5

True or False: Hydrophobic fatty acyl side chains are part of the inner / cytosolic leaflet.

Answer 5

True!

Question 6

What are the two main components of a Phospholipid?

Answer 6

1. They contain two non-polar fatty acyl molecules (“fatty acid chains”).
2. They contain a polar head group linked by a phosphate residue.

Question 7

True or False: Phospholipids are NOT amphipathic.

Answer 7

False. Phospholipids contain both hydrophilic and hydrophobic parts. Thus meaning they are amphipathic!

Question 8

How does synthesis occur in a pre-existing membrane?

Answer 8

Synthesis occurs in a multistep process at the interface of the cytosol and outer endoplasmic reticulum membrane.

Question 9

What are the three classes of membrane proteins?

Answer 9

1. Integral
2. Peripheral
3. Lipid-Anchored

Question 10

Define location and function of integral membrane proteins.

Answer 10

Integral membrane proteins span the lipid bilayer. These membrane proteins surround cells and organelles, which play critical roles in moving molecules across them and the transduction of energy and signals.

Question 11

Define peripheral membrane proteins.

Answer 11

Peripheral membrane proteins are associated with the surface of the lipid bilayer. These protein are found temporarily attached to the cell or mitochondrial membrane. Their function is to support, communicate, enzyme and molecule transfer in the cell.

Question 12

Define lipid-anchored proteins.

Answer 12

Lipid-anchored proteins attach to a lipid in the bilayer. Lipid-anchored proteins insert and assume a place in the bilayer structure alongside similar fatty acid tails.

Question 13

What are the three different transmembrane protein functions?

Answer 13

1. Transport of nutrients and ions.
2. Cell-cell communication (gap junction)
3. Attachment.

Question 14

What is the difference between lipid movement between leaflets and laterally in a leaflet?

Answer 14

Lipids move easier and quicker laterally within a leaflet while lipids movement between leaflets is difficult and slow.