Cell Surface Membrane

Question 1

What does the cell surface membrane control?

Answer 1

The exchange of materials between the internal cell environment and the external cell environment

Question 2

How permeable is the cell surface membrane?

Answer 2

Partially permeable

Question 3

What is the cell surface membrane formed from?

Answer 3

A phospholipid bilayer

Question 4

What is the cell surface membrane made up of?

Answer 4

Hydrophilic head- glycerol and phosphate groups (polar)
Hydrophobic tails- 2 fatty acid chains (non-polar)

Question 5

What do hydrophobic tails act as?

Answer 5

A barrier to soluble substances- ensures that water soluble molecules (sugars, amino acids and proteins) cannot leak out of the cell

Question 6

The hydrophobic tails also allow what else to not get in?

Answer 6

Unwanted water-soluble molecules

Question 7

The hydrophilic heads and hydrophobic tails can be chemically modified to act as?

Answer 7

Signallling molecules- by moving within the bilayer to activate other molecules e.g. enzymes

Question 8

How can they also be chemically modified?

Answer 8

By being hydrolysed- which releases smaller water soluble molecules that bind to specific receptors in the cytoplasm

Question 9

What do proteins do in the cell surface membrane?

Answer 9

Transport proteins create hydrophilic channels to allow ions and polar molecules to travel through the membrane

Question 10

What do transport proteins also allow the cell to do?

Answer 10

Allows the cell to control what leaves and enters the cell

Question 11

What are the 2 types of proteins?

Answer 11

Channel (pore) proteins
Carrier proteins

Question 12

Each protein is specific to what?

Answer 12

A particular ion/molecule

Question 13

What does cholesterol do in the membrane?

Answer 13

Regulates the fluidity of the membrane

Question 14

Where do cholesterol molecules sit between and what does this prevent?

Answer 14

Sit between the phospholipids- prevents them from packing too closely together when temperatures are low- prevents membranes from freezing

Question 15

What do glycolipids and glycoproteins contain?

Answer 15

Carbohydrate chains that exist on he surface of the cell- known as receptor molecules

Question 16

What do receptor cells bind with?

Answer 16

Certain substances at the cell’s surface

Question 17

What are the 3 types of receptors?

Answer 17

Signalling and neurotransmitters
Endocytesis receptors
Cell adhesion and stabilisation as carbon can form hydrogen bonds with the H20

Question 18

What does cholesterol prevent?

Answer 18

Water and dissolved ions leaking out of the cell

Question 19

What do the peripheral proteins provide?

Answer 19

mechanical support- they are connected to proteins or lipids to make glycoproteins and glycolipids
Cell recognition

Question 20

What do integral proteins do?

Answer 20

Protein carriers or channel proteins involved in the transport of molecules across the membrane

Question 21

What do protein channels form?

Answer 21

Tubes that fill with water to enable water-soluble ions to diffuse

Question 22

What do carrier proteins do?

Answer 22

Bind with other proteins adn larger molecules (glucose/amino acids) and change shape to transport them to the other side of the membrane

Question 23

What time of molecules pass through the membrane?

Answer 23

Lipid soluble substances- hormones
Small molecules- CO2, O2

Question 24

What molecules cant pass through the membrane?

Answer 24

water soluble (polar) substances
Large molecules

Question 25

How can temperature affect the fluidity of membranes?

Answer 25

High temperatures cause molecules to vibrate more

Question 26

How can cholesterol content affect the fluidity of the membrane?

Answer 26

Cholesterol increases the fluidity

Question 27

How can the length of the fatty acid chains affect the fluidity of membranes?

Answer 27

Longer fatty acid tail length causes lesser fluidity- more rigidity

Question 28

Function of cell-surface membrane?

Answer 28

Acts as a barrier and actively controls what moves in and out of the cell