membrane transport

Question 1

explain passive diffusion

Answer 1

movement of molecules down their concentration gradient directly through the membrane

Question 2

explain aqueous diffusion

Answer 2

via a channel down a concentration gradient

Question 3

what are aquaporins

Answer 3

aqueous pores in membrane

Question 4

explain facilitated diffusion

Answer 4

via specialised carrier proteins

Question 5

explain active transport

Answer 5

via specialised carrier proteins requires energy and can move against concentration gradient

Question 6

explain endocytosis

Answer 6

molecule is in vesicle the released into cell

Question 7

how does active transport use energy

Answer 7

ATP hydrolysis

Question 8

name non-coupled transport

Answer 8

passive and aqueous diffusion

Question 9

what does the Nernst equation represent

Answer 9

difference in electrical potential

Question 10

log P= 2 means?

Answer 10

lipophilic

Question 11

fricks law

Answer 11

diffusion of non-charged molecules across membranes

Question 12

what form of drug can permeate the membrane

Answer 12

non-ionised

Question 13

what type of molecules enter the cell through specialised carrier proteins

Answer 13

hydrophilic polar

Question 14

what is responsible for insulin secretion by pancreatic beta cells

Answer 14

facilitated diffusion of glucose by GLUT1

Question 15

glucose transporters (GLUT) are members of

Answer 15

SLC super family

Question 16

what GLUT is responsible for facilitated diffusion of fructose and glucose in gut

Answer 16

GLUT2 GLUT5

Question 17

give an example of primary active transport

Answer 17

Na K ATPase

Question 18

energy in the Na gradient is used to drive

Answer 18

secondary active transport systems

Question 19

explain SGLT1

Answer 19

In the intestines, sodium (Na⁺) moves down its gradient, which allows glucose to be transported into the cell against its concentration gradient

Question 20

what does digoxin inhibit

Answer 20

Na K ATPase pump

Question 21

what subunit does digoxin bind to and what effect does it have

Answer 21

alpha
increase in intracellular Na reduces action of Na/Ca exchanger increasing intracellular Ca increasing contraction

Question 22

P-glycoprotein

Answer 22

primary active transport

Question 23

symport

Answer 23

same direction

Question 24

antiport

Answer 24

different directions

Question 25

give an example of a symporter

Answer 25

SGLT3

Question 26

give an example of an anti porter

Answer 26

Na Ca exchanger

Question 30

Where does Na⁺/H⁺ exchange occur in the jejunum, and what are its functions?

Answer 30

Na⁺/H⁺ exchange occurs at both the apical (NHE2, NHE3) and basolateral (NHE1) membranes. NHE2 and NHE3 contribute to Na⁺ absorption and intracellular pH regulation, while NHE1 acts as a cellular pH housekeeper. Apical exchange is stimulated by the alkaline lumen (high pH) due to pancreatic bicarbonate.

Question 30

What is the primary mechanism of Na⁺ absorption in the interdigestive period of the ileum and proximal colon?

Answer 30

Na⁺/H⁺ and Cl⁻/HCO₃⁻ exchange occurs in the ileum and proximal colon during the interdigestive period. This electroneutral process is regulated by cAMP, cGMP, and Ca²⁺, which reduce NaCl absorption. Decreased NaCl absorption can lead to diarrhea, such as in E. coli infections that increase intracellular cAMP.

Question 30

What are the major mechanisms of postprandial Na⁺ absorption in the jejunum?

Answer 30

Na⁺/glucose and Na⁺/amino acid cotransport are the primary mechanisms of postprandial Na⁺ absorption in the jejunum. Both are examples of secondary active transport and are electrogenic, generating a transepithelial potential (VTE) that makes the lumen negative. This negativity drives parallel Cl⁻ absorption.