cellular processes

Question 1

3 types of membrane lipids

Answer 1

cholesterol, phospholipids (75%), glycolipids

Question 2

how to increase membrane fluidity

Answer 2

decrease tail length
increase double bonds
decrease cholesterol

Question 3

hydrophobic core structure

Answer 3

about 20 hydrophobic amino acids
coiled into alpha helices

Question 4

6 functions of membrane proteins

Answer 4

receptors
cell identity markers
linkers (cell - cell connections, tight junct)
enzymes/enzymatic activity
transporter proteins
ion channels

Question 5

why are unsaturated fats better than saturated fats?

Answer 5

unsaturated fat has more double bonds so arteries and plasma membranes are more fluid

Question 6

physical consequences of diffusion

Answer 6

cell size limited to 20um, membrane 8nm(10^-9m) thin

Question 7

relative concentrations of Na, K, Cl outside cell and electrochemical gradient due to electric and concentration gradient

Answer 7

Na, Cl high
K low

Na moves into cell because of both negative environment in cell and conc grad

K moves out of cell down conc grad until electric gradient prevents net movement as membrane potential at -80 mV (K conc grad larger than Cl grad?)

Cl wants to move into cell down conc grad but negative inside cell prevents net movement. Only moves into cell if membrane depolarised

Question 8

how much of resting energy does cell use to maintain electrochemical gradients

Answer 8

30%

Question 9

membrane permeability to water

Answer 9

increased with aquaporin water channels (9 isoforms)

Question 10

Pf vs Pd

Answer 10

Pd:
temperature dependent
mercury insensitive
small size

Pf:
temperature independent
mercury sensitive
large size

Question 11

channel vs carrier protein

Answer 11

channel:
only passive transport
hydrophilic water-filled pore
specificity determined by ion selectivity filter

carrier:
passive or active (primary or secondary) transport
specificity determined by shape of binding pocket
can be saturated as no pore

Question 12

primary vs secondary transport

Answer 12

both use energy to move substances AGAINST electrochemical gradient but secondary uses energy from another electrochemical gradient while primary uses energy from atp hydrolysis

Question 13

paracellular transport governed by…

Answer 13

electrochemical gradients set up by transcellular pathway and tightness of tight junctions

Question 14

which membrane is sodium potassium ATPase located?

Answer 14

basal-lateral membrane between cell and blood

Question 15

secretory diarrhoea vs pronounced diarrhoea

Answer 15

Secretory diarrhoea - caused by excessive stimulation by temporary secretagogues or enterotoxins produced by vibrio cholerae bacteria (most common) permanently binding = oversecretion of Cl-

Pronounced diarrhoea = mutation of SGLT means glucose can’t be absorbed in gut lumen so osmolarity increases and water stays in lumen

Question 16

secretagogues

Answer 16

-oversecretion caused by tumours or inflammation
-neurotransmitter or hormone stimulating opening of CFTR

Question 17

glucose movement after eating

Answer 17

secondary active transport facilitates entry of glucose from gut lumen into cell induces isotonic fluid secretion (transepithelial both transcellular -sodium glucose- and paracellular - water chloride)

exit of glucose into blood by facilitated diffusion

Question 18

glucose movement after fasting

Answer 18

glucose diffuses from blood into cell, no isotonic fluid absorption because no transepithelial transport