Physiology 1 (Functions of Transporters)

Question 1

Examples of membrane transport mechanisms

Answer 1

Pores
Ion Channels
Solute carries
Pumps (ATP - Dependent transporters)
Vesicular transport

Question 2

Aquaporin structure and function

Answer 2

Four subunits - each subunit has 6 alpha helical transmembrane regions
Generally open (pores)
Some only permeable to water

Question 3

Ion channel structure and function

Answer 3

Allow ions to cross membrane
Can be highly selective e.g Na+ channels
or general (non-selective cation channels)
Direction of transport determined by electrochemical gradient
Gated (open and closed states) enabling control of ion movements - gated by voltage, extra/intracellular messengers etc

Question 4

Solute carrier mechanism and example of one

Answer 4

• Solute binds to protein one side of the membrane
• Protein undergoes conformational change
• Releases solute on other side of membrane
  E.g GLUT1-4 transporting glucose

Question 5

Primary active transport - categories and mechanisms

Answer 5

ATP-binding cassettes (ABCs) and ATPase ion transporters -> require hydrolysis of ATP

Question 6

Co transporters - mechanism and example

Answer 6

2 or more solutes are carried in one cycle e.g Sodium/Potassium pumps

Question 7

2 examples of symporters and antiporters

Answer 7

Symporter -> NCC (1Na+ 1CL-) cotransporter,
-> SGLT1 (2Na+ 1Glucose) cotransporter
Antiporter ->

Question 8

Fastest to slowest forms of membrane transport

Answer 8

Water Channels - Pores (Gated)
Ion Channels - Gated
Solute carriers - Cycle
ATP Dependent - Cycle