Cell Membranes

Question 1

Function of membranes: permeable?

Answer 1

Controls what enters and leaves the cells

Question 2

Function of membranes: separate compartment from cytoplasm?

Answer 2

Specific metabolic reactions can take place within them

Question 3

Function of membranes: internal transport system?

Answer 3

E.g. endoplasmic reticulum

Question 4

Function of membranes: isolation?

Answer 4

Isolate enzymes that might damage cells e.g. lysosomes

Question 5

Function of membranes: surface?

Answer 5

Provide surface on which reactions can occur e.g protein synthesis

Question 6

What are membranes made out of?

Answer 6

Phospholipids- arranged in a bilayer

Question 7

What molecules can easily pass through the membrane?

Answer 7

Small, uncharged, non-polar molecules

Question 8

Why are membranes referred to as a fluid mosaic model?

Answer 8

Fluid- not fixed movement
Mosaic- mixed pattern

Question 9

Functions of phospholipids: permeability?

Answer 9

Form water impermeable barrier to polar substances- makes it selectively permeable

Question 10

Functions of phospholipids: permeable to allow what molecules through?

Answer 10

Non-polar molecules

Question 11

Functions of phospholipids: different concentrations?

Answer 11

Allows cell to maintain different concentrations either side

Question 12

Functions of phospholipids: fluid?

Answer 12

Makes membrane fluid to fuse with other membranes/make vesicles

Question 13

Why is a cell membrane referred to as a fluid mosaic model?

Answer 13

Fluid- not fixed movement
Mosaic- mixed pattern

Question 14

What happens if there is too little/too much cholesterol?

Answer 14

Too much = too rigid
None = too fluid

Question 15

What is the structure of cholesterol?

Answer 15

Hydrophobic tails
Hydrophilic heads

Question 16

Where do the cholesterol molecules fit?

Answer 16

Between the phospholipid bilayer - orientated the same way
Head out, tail in

Question 17

Is cholesterol hydrophobic or hydrophilic?

Answer 17

Hydrophobic to prevent the loss of water

Question 18

Is cholesterol hydrophobic or hydrophilic?

Answer 18

Hydrophobic

Question 19

Function of cholesterol: movement?

Answer 19

Reduce movement of other molecules

Question 20

Function of cholesterol: fluidity?

Answer 20

Makes the membrane less fluid at high temperatures

Question 21

Function of cholesterol: tissues?

Answer 21

Helps cells attach to one another and form tissues

Question 22

Function of cholesterol: strength?

Answer 22

Adds strength to the molecule

Question 23

Where do proteins span across?

Answer 23

The whole membrane

Question 24

What do proteins help the cell do?

Answer 24

Stuck together

Question 25

What does intrinsic mean?

Answer 25

Inside the bilayer

Question 26

What does extrinsic mean?

Answer 26

Outside the bilayer

Question 27

What is a glycolipid?

Answer 27

A carbohydrate covalently bonded to a lipid

Question 28

What does a glycolipid act as?

Answer 28

A cell-surface receptor

Question 29

What does a glycolipid add?

Answer 29

Stability

Question 30

Are glycoproteins extrinsic or intrinsic?

Answer 30

Extrinsic- they are on the outer surface of the cell membrane with carbohydrate chains attached

Question 31

What are glycoproteins?

Answer 31

Cell- surface receptors- specifically for hormones and neurotransmitters

Question 32

Where are the carbohydrate chains found in the glycoproteins?

Answer 32

Found on the outer phospholipid monolayer- the carbohydrate chains also project out into fluid in the cell