lec 7

Question 1

how do parietal cells in the stomach epithelium maintain homeostasis in their acidic environment?

Answer 1

H+K+ ATPase

Question 2

how does NaK pump work?

Answer 2

the starting state is hella Na in cell, hella K in ECF
1. Na+ binds to pump
2. ATP comes in and binds, causing a conformation change in the pump. Na+ is sent out into ECF
3./4. ATP hops off pump but leaves behind a phosphate
3./4. K+ enters into the enzyme where Na+ exited
5. Pi hops off, resetting conformational change. pump returns to original state
6. K+ is released into the cell

ATP is needed since the ions move against their concentration gradients

rate is 3 Na+ out for 2 K+ in

Question 3

what is an example of the NaK pump in practice?

Answer 3

GETTING GLUCOSE INTO EPITHELIAL CELLS
by pumping 3 Na+ out of the cell, the basal side has less Na+ than the apical side. this means the diffusion gradient favours Na+ moving in towards the small intestine.
to get in, a cotransporter will usher Na+ as well as glucose, which is moving against its concentration gradient –> by coupling transport, glucose is brought into the cell

Question 4

how does freshwater gill ion transport work for PNA- cells?

Answer 4

at gills, CO2 is formed as a byproduct of metabolism (surprise tool we’ll use for later)

CO2 reacts w water –> HCO3- and H+

the H+ are pumped out into the environ (cell becomes [-])

because Na+ has a favourable gradient and the cell has a [-] charge, Na+ moves from pond into PNA- cell
(important note: cell keeps low Na+ conc for this to occur)

HCO3- and Na+ are then moved together into the body via cotransporter to maintain electroneutrality

Question 5

how does freshwater gill ion transport work for PNA+ cells?

Answer 5

at gills, CO2 is formed as a byproduct of metabolism (surprise tool we’ll use for later)

CO2 reacts w water –> HCO3- and H+

HCO3- is pumped out of the cell in exchange for Cl- ions pumping in the cell ([-] charge for [-] charge = electroneutrality)

H+ ions are pumped into bloodstream (basal side) (cell loses [+] –> becomes [-])

to return to electroneutrality, Cl- moves into the bloodstream as well (passive or active?)

Question 6

what is the difference between catadromous and anadromous fish?

Answer 6

catadromous: live in freshwater, go to saltwater to spawn

anadromous: live in saltwater, go to freshwater to spawn

both need adaptations to survive in either environment

Question 7

what is a big obstacle that animals in the north need to overcome? how do endotherms do it?

Answer 7

its really fuckng cold in the north

endotherms have to increase food intake to bulk up on energy + heat as a byproduct of metabolism

Question 8

what is energy partioning?

Answer 8

using energy on diff things

ex. some energy for recovery + repair, some energy is reserved for hunting, but a majority of energy goes to offspring synthesis