Module 2 Section 5 - Cell Membranes

Question 1

What do membranes control

Answer 1

Membranes control what passes through them

Question 2

What are membranes at the surface of the cell

Answer 2

They are barriers between the cell and its environment

Question 3

What does the membranes at the surface of cells control

Answer 3

Controls which substances enter and leave the cell

Question 4

What is said about the permeability of membranes on the surface of the cell

Answer 4

They are partially permeable - they let some molecules through but others not

Question 5

How would substances typically move across membranes at the surface of cells

Answer 5

Diffusion
Osmosis
Active transport

Question 6

What do membranes on the surface of the cell allow

Answer 6

Recognition by other cells
Cell communication

Question 7

What are membranes within cells

Answer 7

The membranes around organelle divide the cell into different compartments. Making functions more efficient.

Question 8

What can membrane within cells form

Answer 8

Vesicles to transport substances between different areas of the cell

Question 9

What do membranes within cells control

Answer 9

Which substances enter and leave the organelle, they are also partially permeable

Question 10

Can you find membranes within organelles

Answer 10

Yes - these act as barriers between the membrane contents and the rest of the organelle

Question 11

Membranes within cells can be the site of what

Answer 11

Site of chemical reactions

Question 12

Cell membranes have a

Answer 12

Fluid mosaic structure

Question 13

What are all membranes composed of

Answer 13

Lipids (mainly phospholipids), proteins and carbohydrates (usually attached to protein or lipids)

Question 14

In 1972 what was suggested to describe the arrangement of molecules in the membrane

Answer 14

The fluid mosaic model

Question 15

In the fluid mosaic model what forms a continuous double layer (bilayer)

Answer 15

Phospholipid molecules

Question 16

Why is the phospholipid bilayer fluid

Answer 16

Because the phospholipids are always moving

Question 17

What is present within the bilayer

Answer 17

Cholesterol

Question 18

What is scattered throughout the bilayer

Answer 18

Protein molecules

Question 19

What are glycoproteins

Answer 19

Some proteins that have a polysaccharide chain attached to it

Question 20

What are glycolipids

Answer 20

lipids that also have a polysaccharide chain attached to it

Question 21

What are the different components of the cell membrane

Answer 21

Phospholipid
Cholesterol
Proteins
Glycolipids
Glycoproteins

Question 22

Phospholipid molecules have a

Answer 22

Head and tail

Question 23

The Phospholipid head is

Answer 23

Hydrophilic - attracts water

Question 24

The phospholipid tail is

Answer 24

Hydrophobic - repels water

Question 25

How are the phospholipid molecules arranged

Answer 25

They automatically arrange themselves into a bilayer - head face out towards the water on either side of the membrane

Question 26

The centre of the bilayer is

Answer 26

Hydrophobic meaning the membrane doesn’t allow water soluble substances through it

Question 27

What does cholesterol give to a cell membrane

Answer 27

Gives the membrane stability

Question 28

What is cholesterol

Answer 28

A type of lipid

Question 29

Is cholesterol present in all membranes

Answer 29

Yes

Question 30

Where does cholesterol fit in

Answer 30

Cholesterol molecules fit in between the phospholipids, they bind to the hydrophobic tails causing them to pack more closely meaning the membrane is less fluid and more rigid

Question 31

What do proteins control in the cell

Answer 31

Proteins control what enters and exits the cell

Question 32

Some protein form what in the membrane

Answer 32

channels in the membrane which allow small or charged particles through

Question 33

Other proteins (carrier proteins) transport what

Answer 33

Molecules and ions across the membrane by active transport and facilitated diffusion

Question 34

Proteins can acts as

Answer 34

Receptors for molecules in cell signalling, when a molecule binds to the protein a chemical reaction is triggered inside the cell

Question 35

What do glycolipids and glycoproteins do for the cell

Answer 35

Act as receptors for messenger molecules

Question 36

How do glycolipids and glycoproteins stabilise the cell

Answer 36

They form hydrogen bonds with surrounding water moelcules

Question 37

Glycolipids and glycoproteins are sites where what bind

Answer 37

Drugs Hormones Antibodies

Question 38

Glycolipids and glycoproteins are also what

Answer 38

Antigens

Question 39

Cell signalling is..

Answer 39

How cells communicate with each other

Question 40

How do cells communicate with each other

Answer 40

Messenger molecules

Question 41

Describe the three steps a messenger molecule makes to communicate with other cells

Answer 41

-one cell releases a messenger molecule -this molecule travels to another cell -the messenger molecule is detected by the cell because it binds to a receptor on its cell membrane

Question 42

What plays an important role in cell signalling

Answer 42

Cell membrane receptors

Question 43

What act as receptors for messenger molecules

Answer 43

Proteins in the cell membranes (membrane-bound receptors)

Question 44

What is specific about receptor proteins

Answer 44

Their shape

Question 45

What can bind to the receptor proteins

Answer 45

Only messenger molecules with a complementary shape can bind to them

Question 46

Different cells have different….

Answer 46

Types of receptors - they respond to different messenger molecules

Question 47

What is a cell that responds to a particular messenger molecule called

Answer 47

Target cell

Question 48

How do many drugs work

Answer 48

By binding to the receptors in cell membranes, they either trigger a response or block the receptor and prevent it from working

Question 49

How can you investigate the permeability of a membrane

Answer 49

Beetroot cells contain a coloured pigment that leaks out - the higher the permeability the more pigment leaks out.

Question 50

What affects the permeability of a membrane

Answer 50

Temperature Solvent type Solvent concentration

Question 51

What happens to the permeability of a membrane if the temperature is below 0°c

Answer 51

-The phospholipid pack more closely due to not much energy and the membrane becomes rigid -The channel and carrier proteins in the membrane deform **increasing the permeability** -Ice crystals may form and pierce the membrane further increasing the permeability.

Question 52

What happens to the permeability of a membrane if the temperature is between 0°c - 45°c

Answer 52

Phospholipids aren’t as packed because they can move around - the membrane is partially permeable. As the temperature increases the phospholipids move more because they have more energy and this increases permeability

Question 53

What happens to the permeability of a membrane if the temperature is above 45°c

Answer 53

The phospholipids start to melt and membrane becomes more permeable. The water inside the cell expands putting pressure on the membrane and channel and carrier proteins deform so they can’t control what enters and exits the cell which increases permeability.

Question 54

What happens to the permeability of a membrane if you surround it in a solvent

Answer 54

A solvent such as ethanol increases membrane permeability of the cell membrane

Question 55

Why does surrounding the cells in a solvent increase membrane permeability

Answer 55

This is because solvents dissolve the lipids in a cell membrane so the membrane loses its structure

Question 56

What happens to the permeability of a membrane if you increase the concentration of the solvent

Answer 56

The permeability of the membrane will increase