3. Active Transport. Transport Across Epithelial Layer

Question 1

What is active transport and give example

Answer 1

Requires energy in form ATP
Against concentration gradient

Na+/k+ pump

Question 2

What is primary active transport

Answer 2

When ATP energy source is directly coupled to the transport process, it is called primary active transport.

Na+/k+
Ca2+ in SR and ER
H+/k+ in gastric parietal cells and renal cells

Question 3

What is secondary active transport

Answer 3

Energy from ATP used indirectly, energy is used in primary

Primary creates gradient for secondary mechanism

One of the solutes, usually Na+, moves down its electro- chemical gradient (downhill), and the other solute moves against its electrochemical gradient (uphill).

Question 4

What are the 2 types of secondary active transport

Answer 4

Cotransport/symport: If the uphill solute moves in the same direction as Na+

Countertransport/antiport: If the uphill solute moves in the opposite direction of Na+

Question 5

What mechanisms do you need for larger molecules

Answer 5

Cytosis

Phagocytosis, pinocytosis, receptor mediated cytosis ( enough clatherin has to bind to receptor then invagination then endosome)

Exocytosis- vesicle fuses w membrane and releases contents into extra cellular space

Question 6

What is transcellular

Answer 6

Substances move THROUGH cells

Included active and passive transport

Question 7

What is paracellular

Answer 7

Substances can move AROUND cells

These just follow a gradient like a electrochemical gradient

Paracellins are proteins that control this