Forces Acting Across Membranes

Question 1

What are aquaporin channels

Answer 1

Channels that are permanently open to water

Question 2

What are the Na, K+, protein levels of the 3 body compartments

Answer 2

Question 3

What are key characteristics of membranes

Answer 3

Flexible
Phospholipid bilayer
Insulators against electrical charge
Embedded with proteins
Selective barrier

F*PIES

Question 4

What are the protein contents in Myelin, Plasma, inner membranes of mitochondria

Answer 4

Myelin - 18%
Plasma - 50%
Inner membranes - 75%

Question 5

What are the functions of membrane proteins

Answer 5

1. Maintenance of cell structure
2. Enzymes
3. Transport
4. Receptors
5. Communication

Question 6

What are functions of receptors

Answer 6

• Penetrate ECF to ICF
• Allow comms of extra cellular signal ->intracellular response

Question 7

What are the functions of Transporters

Answer 7

Allow movement of molecules across membrane
Two types:
1. Channel proteins - creates pore through the membrane, gated/water types
2. Transporters - Open to one side of ECF or ICF at a time

Question 8

What are the functions of Enzymes

Answer 8

Catalyse chemical reactions on membrane
Used to convert signals from receptors -> intracellular response

Question 9

What are the functions of structural proteins

Answer 9

Hold cell membrane to intracellular skeleton to the extracellular matrix

Question 10

What is the function of Communication in membranes

Answer 10

Glycoproteins alert cell of own body/foreign cells

Question 11

What is an electrochemical gradient

Answer 11

Combination of chemical gradient and electrical potential difference

Question 12

What is endocytosis

Answer 12

Invagination of cell membrane to form vesicle
Disintegrates on cytoplasmic surface
Release contents into cell

Question 13

What is exocytosis

Answer 13

Reverse process of endocytosis

Question 14

What is diffusion

Answer 14

Movement of molecules from an area of high->low concentration

Question 15

What is the difference between facilitated diffusion and passive diffusion

Answer 15

Passive diffusion - substance moves directly through bilayer
Facilitated diffusion - Substance needs assistance from membrane protein

Question 16

What molecules pass through via passive diffusion

Answer 16

**Small
Uncharged **
Lipophilic

Question 17

What are the different membrane proteins in facilitated diffusion

Answer 17

1. Channels
   Can be ligand gated or voltage gated
2. Carrier-mediated transport
   For larger molecules
   Opens to one side of ECF and ICF at a time

Question 18

What is active transport

Answer 18

Molecules transported against c.g
Uses ATP to transport substances

Question 19

What is the function of Na+/K+ pump

Answer 19

Pumps 3 Na+ ions out of cells
Pumps 2 K+ ions into the cell
40% of resting energy used by this pump

Question 20

What is osmosis

Answer 20

Net movement of H20 from high -> low regions

Question 21

What is the osmolarity of human plasma

Answer 21

285mOsmol/l
(300)

Question 22

what is the difference between osmolarity and tonicity

Answer 22

Question 23

What happens to cells in hypotonic solutions

Answer 23

Swell

Question 24

Difference between a cell with non penetrating and penetrating particles

Answer 24

Question 25

What happens to cells in hypertonic solutions

Answer 25

Shrink

Question 26

Practice question

Answer 26

Very little
Living people are different
Putting cells in pure water is different to humans

Question 27

How many molecules in 1 mol

Answer 27

6.02x10^23