2.5 Biological Membranes

Question 1

What are phospholipids and what are there structure

Answer 1

• Make up the majority of the plasma membrane
• Have polar heads and non polar tails

Heads= Hydrophyllic
Tails = Hydrophobic

One side of tail= Saturated and straight
Other side= Unsaturated and with a kink which increases fluidity

Question 2

What is the effect of temperature on membrane fluidity?

Answer 2

High temp= More fluid ~ Particles vibrate and move more

Question 3

What is the purpose of cholesterol in phospholipid bilayer?

Answer 3

Helps stabilise molecule
Not as much of a set temperature
Low temps- Keeps it fluid
High temps- Stops it getting too fluid

Question 4

Why are there saturated and unsaturated fatty acids?

Answer 4

Produce a more fluid membrane

Question 5

What are Glycoproteins and what are there function?

Answer 5

• Embedded in the cell surface membrane with attached carbohydrates
• Role in cell adhesion as well as receptors for chemical signals

Question 6

What are glycolipids and what are there function?

Answer 6

Similar to glycoproteins with attached carbohydrate chains
Work as cell markers and can be identified as the immune system

Question 7

What are channel proteins?

Answer 7

Provide a hydrophyllic channel that enables passive movement of membranes

Question 8

What are Carrier proteins?

Answer 8

Often involves the shape of proteins changing
Used in both diffusion and active transport

Question 9

What is a colorimeter?

Answer 9

A machine which measures the transmitted light
The result is a measure of light that is absorbed by the mixture in A.U

Question 10

What effects membrane permeability?

Answer 10

Temperature- Increased kinetic energy
Solvents- Organic solvents are usually less polar. This can disrupt/dissolve membranes

Question 11

What is water potential?

Answer 11

The pressure exerted by water molecules as they collide with a membrane or container
Measured in kPa
0 kPa is pure water

Question 12

What is the definition of Osmosis?

Answer 12

Diffusion of water from an area of higher water potential to an area of lower water potential through a partially permeable membrane

Question 13

What are the features of a hypotonic cell?

Answer 13

Closer to 0 water potential sonnet movement is into cell
Cell takes in too much water and bursts (lysis)

Question 14

What are the features of a normal red blood cell in relation to water potential?

Answer 14

WP outside and inside are at equilibrium

Question 15

What are the features of a hypertonic cell?

Answer 15

Lower WP outside the cell
Water moves out
It becomes shrivelled and crenated

Question 16

What are the features of a turgid plant cell?

Answer 16

Higher wp outside so water goes in
Protoplast pushed against cell wall
Cell is turgid

Question 17

What are the features of a flaccid cell?

Answer 17

WP at equilibrium.
Protoplast begins to pull away from cell wall
Making it flaccid

Question 18

What are the features of a plasmolised cell?

Answer 18

Wp is higher inside plant so water exits
Protoplast completely pulls away from cell wall
Plasmolised

Question 19

What is Facilitated diffusion and what are the two types?

Answer 19

-Used for small ions and polar molecules-Diffuse through aquaporins
- Large molecules bind to carrier proteins (too large to diffuse down aquaporins)
- specific to different molecules

Question 20

What is endocytosis?

Answer 20

When large volumes of stuff enter the cell
A section of membrane enclosed the particle and brings them in via vesicle
Phagocytosis = solids
Pinocytisis =liquids
ATP is needed

Question 21

What is exocytosis?

Answer 21

Large volumes going out
A vesicle is moved to the membrane (ATP needed)
Cell surface membrane and vesicles fuse
Contents are released