Transport Across Membranes 3.2

Question 1

What is glycerol?

Answer 1

An alcohol with three carbon atoms, each linked to an OH group.

Question 2

What are the main groups of lipids?

Answer 2

Triglycerides and phospholipids.

Question 3

What is the R group on a fatty acid?

Answer 3

A variable hydrocarbon tail.

Question 4

What are the two kinds of fatty acid?

Answer 4

Saturated and unsaturated.

Question 5

What does a cell surface membrane form?

Answer 5

A semi-permeable boundary between the cell cytoplasm and the external environment.

Question 6

What happens if you shake phospholipids in water?

Answer 6

They arrange themselves to become micelles.

Question 7

What does the fluid mosaic model describe?

Answer 7

The arrangement of molecules within the phospholipid bilayer.

Question 8

What is the function of cholesterol?

Answer 8

It helps to maintain the cell membranes shape and stabilityby restricting the movement of phospholipids.

Question 9

How do cholesterol restrict the movement of phospholipids?

Answer 9

They bind to the hydrophobic tails of the phospholipids to hol them close together.

Question 10

What do channel and carrier proteins do?

Answer 10

These help transport substances, such as
ions, sugars and amino acids, that cannot
diffuse across the membrane but are still
vital to a cell’s functioning.

Question 11

What is the function of peripheral proteins?

Answer 11

They act as receptors for hormones or neurotransmitters or are involved in cell recognition.

Question 12

How does a temperature below 0 degrees celsius impact the cell membrane?

Answer 12

The phospholipids don’t move much due to low energy, the carrier proteins freeze and it causes the permeability to decrease.

Question 13

How does a temperature above 45 degrees celsius impact the cell membrane?

Answer 13

The bilayer starts to melt, which makes the membrane more permeable. The water in the cell also starts to expand and puts pressure on the membrane. Also the carrier proteins denature so they can’t control what enters and leaves the cell.

Question 14

What is simple diffusion?

Answer 14

A passive process involving the net movement of particles from a high to a low concentration.

Question 15

What makes a molecule easier and quicker to diffuse?

Answer 15

Being smaller and having a lower polarity.

Question 16

What type of particles can not diffuse across a membrane?

Answer 16

Charged particles.

Question 17

What are the key factors impacting the rate of diffusion?

Answer 17

Concentration, temperature, diffusion pathway(thickness of diffusion surface) and surface area.

Question 18

What does Fick’s Law state?

Answer 18

The rate of diffusion is proportional to surface area x difference in concentration all over the length of the diffusion pathway.

Question 19

What is facilitated diffusion?

Answer 19

A passive process which includes the use of carrier or channel proteins to facilitate the movement of large or charged particles.

Question 20

What do channel proteins do?

Answer 20

Facilitate the diffusion of charged particles.

Question 21

What do carrier proteins do?

Answer 21

To faciliate the diffusion of large molecules by allowing them to attach and change shape to be released on the other side.

Question 22

What factors affect facilitated diffusion?

Answer 22

When the concentration gradient reaches equilibirum, facilitated diffusion slows down. The number of channel and carrier proteins.

Question 23

What is the definition of osmosis?

Answer 23

The net movement of water molecules across a partially permeable membrane from an area of high water potential to an aera of low water potential.

Question 24

What is water potential?

Answer 24

Water potential is the potentinal of a water molecule to diffuse in or out of a solution.

Question 25

What does pure water have a water potential of?

Answer 25

Zero.

Question 26

What happens if you add solutes to pure water?

Answer 26

It lowers the water potential.

Question 27

What is active transport?

Answer 27

An active process which involves the movement of particles from an area of low concentration to high concentration using ATP.

Question 28

What are co-transporters a type of?

Answer 28

Carrier proteins.

Question 29

What is a key example of the use of co transport?

Answer 29

The absorption of glucose involves the binding to sodium and a sodium-potassium pump.