the fluid mosaic model

Question 1

What is the membrane structure composed of?

Answer 1

Lipids, proteins and carbohydrates

Question 2

What type of lipid is the structure made of?

Answer 2

Phospholipids

Question 3

What is a phospholipid?

Answer 3

A type of lipid (a glycerol molecule) with a phosphate group attached to it and two fatty acid tails

Question 4

What is the fluid Mosaic model?

Answer 4

A form of the cell surface membrane, composed of two layers of fatty acids and phosphate groups assembled into opposing sheets

Question 5

What do the phospholipid molecules form?

Answer 5

A flexible, thin, continuous double layer (bilayer)

Question 6

Why is this arrangement fluid?

Answer 6

The phospholipids are constantly moving

Question 7

What is the structure of the phospholipid molecule?

Answer 7

They have a hydrophilic head and a hydrophobic tail

Question 8

What is the structure of the head of a phospholipid molecule?

Answer 8

The head contains a phosphate group and because its hydrophilic it attracts water and is polar

Question 9

What is the structure of the tail of a phospholipid molecule? And what do the tails form?

Answer 9

The tail is made of two fatty acids and because its hydrophobic it will repel water and is non-polar. The tails form fatty acid chains

Question 10

Which way do the hydrophilic heads face in the bilayer?

Answer 10

The hydrophilic heads face out towards the water on either side of the membrane

Question 11

Which way do the hydrophobic tails face in the bilayer

Answer 11

The hydrophobic tales are on the inside making the centre of the bilayer hydrophobic

Question 12

Why don’t membranes allow water soluble substances through it?

Answer 12

Because the centre of the bilayer is hydrophobic meaning that water-soluble substances like ions will be repelled

Question 13

Why does the fluid music structure reference mosaics?

Answer 13

Because protein molecules are scattered through the bilayer like tiles in a mosaic

Question 14

Are the proteins scattered throughout the bilayer stationary?

Answer 14

No, because phospholipid bilayer is fluid the proteins can move around within it. They can slide around the membrane very quickly and collide with each other, but can never flip from one side to the other

Question 15

What are the 6 types of protein?

Answer 15

Integral proteins, peripheral proteins, transport proteins, receptor proteins, recognition proteins and structural proteins

Question 16

What do integral/ channel proteins do?

What do they form?

Answer 16

They span from one side of the phospholipid bilayer to the other
They form protein tunnels that allow specific molecules to pass through the cell membrane, often acting as cell receptors

Question 17

What do peripheral proteins do?

Answer 17

These sit on one of the surfaces and form a temporary bond with the cell membrane allowing them to detach and reattach at specific times with specific signals and

Question 18

What do peripheral proteins allow the cell to do?

Answer 18

Coordinate and communicate using a network of proteins and reactions

Question 19

What do integral proteins allow the cell to do?

Answer 19

Channelling and transporting molecules across the membrane

Question 20

What are recognition proteins ?

Answer 20

Often glycoproteins embedded in the cell membrane which allow cells to communicate with others

Question 21

What is an example of recognition protein?

Answer 21

The A and B antigens on red blood cell membrane

Question 22

What do the transport proteins do?

Where does the transport take place?

Answer 22

Allow the transport of most small molecules across the membrane
It takes place through it integral proteins which provide hydrophilic channels for the passage of ions and polar molecules?

Question 23

What examples of transport do transport protein allow?

Answer 23

Facilitated diffusion and active transport

Question 24

What are receptor proteins?

Answer 24

Proteins that are on the outside surface of the cell membranes and have a specific binding site where hormones or other chemicals combined to form a hormone receptor complex

Question 25

What does the hormone receptor complex trigger?

Answer 25

It triggers other events in the cell membrane or inside the cell

Question 26

What are structural proteins?

What are they attached to?

Answer 26

Structural proteins are on the inside surface of the cell membrane and are attached to the cytoskeleton

Question 27

What do the structural proteins do?

Answer 27

They are involved in maintaining the cell shape or in changing the cells shape for motility.

Question 28

Can structural proteins be on the outside surface of the cell membrane?

Answer 28

Yes, they can be used on the outside surface in cell adhesion which is sticking cells together temporarily or permanently

Question 29

What is a glycoprotein?

Answer 29

A type of protein that has a polysaccharide (carbohydrate) chain attached to it

Question 30

What is a glycolipid?

Answer 30

A type of lipid that has a polysaccharide (carbohydrate) chain attached to it

Question 31

What do the fatty acid chains do?

Answer 31

They link together to stabilise and strengthen the membrane

Question 32

What is cholesterol?

What is their structure?

Answer 32

A type of lipid that is present in the membrane. It fits in between the phospholipids, forming bonds between them. This makes the cell membranes more rigid and can regulate its fluidity
They have hydrophilic head some hydrophobic tails

Question 33

Where are the carbohydrates found in the cell membrane?

What do they form?

Answer 33

On the outer surface of all eukaryotic cells attached to the membrane proteins or sometimes to the phospholipids
On the surface, they form glycolipids

Question 34

What is the outer layer of the structure called?

Answer 34

The extrinsic layer

Question 35

What is the inner layer of the structure called?

Answer 35

The intrinsic layer

Question 36

How does the saturation of the tales influence on the fluidity?

Answer 36

The more unsaturated they are, the more fluid the membrane because spent tales fits together more loosely

Question 37

What do glycolipids do?

Answer 37

they keep the membrane stable by forming hydrogen bonds with the water molecules outside the cell

Question 38

what types of molecules can pass directly through the cell membrane?

Answer 38

small
uncharged
oxygen
carbon dioxide

Question 39

how does the ability to recognise the cell by the membrane help the immune system? (2 things)

Answer 39

white blood cells wont attack them if they are identified as out own cells
they can be identified as foreign bodies

Question 40

how does the bilayer help the cell?

Answer 40

creates a barrier between the external and internal environment and maintains them

Question 41

what will too much cholesterol in the membrane do?

Answer 41

Too much cholesterol will make the membrane too rigid/less fluid and make exchange less efficient.

Question 42

what will too little cholesterol in the membrane do?

Answer 42

Too little cholesterol will mean that the membrane is too fluid and breaks up/doesn’t provide necessary
structure

Question 43

why does the bilayer form?

Answer 43

lipids cause water so arrange into a cage like structure, so forming a bilayer will reduce this effect

Question 44

at high temps, how does cholesterol affect membrane fluidity?

Answer 44

decreases it

Question 45

at low temps, how does cholesterol affect membrane fluidity?

Answer 45

increases it