Forces Across Membranes 1

Question 1

In simple terms, what does the cell membrane do?

Answer 1

Seperates the ECF and the ICF, is responsible for the composition difference between the two

Question 2

Give an example of some concentration differences between the ECF and the ICF?

Answer 2

Na⁺ > in ECF

K⁺ > in ICF

Cl^- > in ECF

HCO₃^- > in ECF

Phosphate/Sulphate > in ICF

Protein > in ICF

Question 3

How do cell membranes acts as a selective barrier?

Answer 3

Permeable and impermeable to different substances

Question 4

What substances can freely cross the cell membrane?

Answer 4

O₂

Nutrients

CO₂

Waste

H₂O

Question 5

What substances cannot cross the cell membrane and the capillary wall?

Answer 5

Ions cannot cross the cell membrane

Plasma proteins cannot cross the capillary wall

Question 6

Does permeability of the cell membrane change at different times?

Answer 6

Yes

Question 7

How are membranes dynamic?

Answer 7

They are constantly being formed, changed or dismantled

Question 8

What forms most of the cell membrane?

Answer 8

Thin layer of phopholipids as a bilayer

Question 9

Why are membranes flexible?

Answer 9

Fatty acids behave like oil

Question 10

What could happen to membranes if they are overstretched?

Answer 10

They could rupture

Question 11

Why are membranes a good insulator against electrical charge?

Answer 11

They prevent the passage of electrons

Question 12

How to proteins and carbohydrates relate to membranes?

Answer 12

Membranes are embedded with proteins and associated with carbohydrates

Question 13

Are membrane carbohydrates intra or extra cellular

Answer 13

Extracellular, they are linked to proteins and lipid

Question 14

What are the carbohydrates of the cell membrane linked to?

Answer 14

Proteins and lipids

Question 15

What are the carbohydrates of the membrane important for?

Answer 15

Cell-cell communication

Question 16

What are glycoproteins?

Answer 16

Proteins with carbohydrate groups attatched to the polypeptide chain

Question 17

What are glycolipids?

Answer 17

Lipids with a carbohydrate group attatched

Question 18

What are the four classes of membrane proteins?

Answer 18

Receptor

Transporters (carrier and channel proteins)

Enzymes

Peripheral proteins

Question 19

What are integral membrane proteins?

Answer 19

Proteins which are integrated into the structure of the membranes, such as receptors, transporters and enzymes

Question 20

Are peripherial proteins embedded into the membrane?

Answer 20

No, they are associated with the membrane byt not embedded in it

Question 21

What are receptors?

Answer 21

Allows communication of an extracellular signal to an intraceullular space to create an intracellular response

Question 22

Why is the cellular response of a receptor specific?

Answer 22

Not all receptors are present on all cells, with receptors being unique to different substances

Question 23

What are transporters?

Answer 23

Proteins which allow movement of ions or molecules across the membrane

Question 24

What are the two types of transporters?

Answer 24

Channel proteins

Carrier proteins

Question 25

How do channel proteins operate?

Answer 25

They create a pore through the membrane which molecules (usually water and ions) can flow through

Question 26

What are the two types of channel proteins?

Answer 26

Open (water) or gated (ions) which open in response to signals

Question 27

How do carrier proteins work?

Answer 27

They do not create a continuous pore, they are only open at one side at any time

Question 28

What is an enzyme?

Answer 28

Catalyses reactions on the cell membrane

Question 29

What are enzymes often associated to?

Answer 29

Receptors

Question 30

What are some roles of peropheral proteins?

Answer 30

Maintain structure of cells by anchoring the membrane to intracellular cytoskeleton Attatches cells to the extracellular matrix Perform signilling functions within cells

Question 31

Give some examples of how membranes differ in their protein content to suit their function?

Answer 31

Myelin 18% protein as lipids are better for insulation Most cells are 50% proteins Membranes involved in energy transduction such as mitochondria inner membrane are 75% proteins