plasma membrane

Question 1

What is an integral protein?

Answer 1

any protein that goes through the phospholipid bilayer

Question 2

Where are Peripheral Protein found?

Answer 2

They are found on either side of the membrane (outside or inside), but they do not ever go through (they are only attached to one side)

Question 3

Carbohydrate Chains

Answer 3

These are sugar molecules that are attached to one another

Question 4

What is the structure of a phospholipid?

Answer 4

It is made out of phosphorous and lipids
Head contains a phosphate group (Hydrophilic)
Tails are the lipids (fatty acids) (Hydrophobic)

Question 5

Definition of Amphipathic

Answer 5

(when part of the molecule is attracted to water (hydrophilic) and another part is not attracted to water (Hydrophobic).

Question 6

List 4 functions of membrane proteins

Answer 6

Channels – some proteins have a pore/channel that allows the passive transport (no energy required) of substances between the inside and outside of the cell.

Carriers – these proteins bind to substances on one side of the membrane and then change shape to transport them to the other side. Carrier proteins that use energy to change shape are termed protein pumps.

Recognition – certain proteins help the cell in differentiating between self and non-self cells (important in triggering an immune response).

Receptors – these proteins usually span the whole membrane to relay information from the inside or outside of the cell.

Question 7

What is Cholesterol?

Answer 7

Cholesterol is a steroid made up of a non-polar part comprising four ring structures, a hydrocarbon tail, and a polar hydroxyl group (hydrophilic).
(amphipathic molecule)

Question 8

How does cholesterol affect the permeability of mammalian membranes to some solutes.

Answer 8

The presence of cholesterol in the membrane restricts the movement of phospholipids and other molecules, thus reducing membrane fluidity. But, at low temperatures, it also disrupts the regular packing of the hydrocarbon tails of phospholipid molecules, which prevents the solidification of the membrane. This enables the membrane to stay more fluid at lower temperatures, allowing the membrane to function properly. Additionally, it reduces membrane permeability to hydrophilic molecules and ions such as sodium and hydrogen.

Question 9

Describe the Davson–Danielli model

Answer 9

It comprises a lipid bilayer sandwiched between two protein layers on either side of the membrane.