The Structure and Function of Membranes

Question 1

Name the three roles of the plasma membrane

Answer 1

1. A permeable barrier protecting the cell’s contents from it’s external environment/ the organelle’s contents from the cytoplasm
2. Site of chemical reactions
3. Site of cell signaling

Question 2

What does the plasma membrane separate?

Answer 2

The cell’s contents from the external environment

Question 3

What does an organelle’s membrane separate?

Answer 3

The organelle’s contents from the cytoplasm

and/OR

It separates the contnents within the organelle from eachother

Question 4

Explain why the structure of the phospholipid bilayer is called the Fluid-Mosaic model?

Answer 4

The phosolipids are free to move in the layer relative to eachother, this gives the membrane flexibility

Proteins are embedded in the cell membrane and these proteins vary in size, shape and position like in a mosaic

Question 5

What is the name of the model for the structure of the cell membrane?

Answer 5

The fluid-mosaic model

Question 6

What are the roles of cholesterol in the cell membrane

Answer 6

1. Makes the cell membrane more stable
2. Controls the fluidity of the cell membrane

Question 7

Name the two different types of protein in the cell membrane

Answer 7

Intrinsc protein

Extrinsic protein

Question 8

Name the two types of intrinsic protein

Answer 8

Channel protein

Carrier protein

Question 9

What type of molecules can diffuse straight through the phospholipid bilayer?

Answer 9

Fat soluble molecules and small hydrophobic molecules

also water because it is a small molecule

Question 10

What do channel proteins contain which allow polar molecules and ions to diffuse through?

Answer 10

Water

Question 11

What is a channel protein?

Answer 11

A pore in the cell membrane which allows polar molecules and ions to diffuse through

Question 12

What is the function of a carrier protein?

Answer 12

They change shape to allow specific molecules through the phospholipid bilayer

remember, the carriers are the ones that CHANGE SHAPE and CARRY the molecules through the bilayer

Question 13

Give three different functions of extrinsic proteins

Answer 13

1. Give structure the the cell membrane
2. Act as enzymes
3. Act as membrane-bound receptors

Question 14

What is a glycoprotein?

Answer 14

A carbohydrate chain attatched to a protein in the phospholipid bilayer

Question 15

Give the functions of glycoproteins

Answer 15

1. Allow cells to attatch to eachother to form tissues (adhesion)
2. Act as receptors for chemical signals

Question 16

What is a glycolipid?

Answer 16

A carbohydrate chain attatched to a phospholipid

Question 17

What is the function of the glycolipids

Answer 17

They are cell markers/antigens which allow cells in the immune system to recognise them as self/non-self

Question 18

What is the role of a membrane-bound receptor?

Answer 18

A site where hormones and drugs can bind