membranes and membrane proteins

Question 1

what is amphipathic?

Answer 1

‘comprising hydrophobic and hydrophilic regions’

Question 2

what are the three major membrane lipid?

Answer 2

glycerophospholipid
sphingolipids
sterols

Question 3

structure of glycerophospholipid?

Question 4

structure of sphingolipids?

Question 5

structure of sterols?

Question 6

what are the composition and properties of membranes?

Answer 6

outer and inner layers have different composition
different cells and organelles have different membrane compositions
self-sealing so cell remains intact and undamaged
selectively permeable separating inside and outside of the cell

Question 7

what does composition effect?

Answer 7

thickness, curvature and fluidity of membrane

Question 8

what are the functions of membrane proteins?

Answer 8

channels pores transporters
receptors and adhesion molecules
enzymes
immune recognition and activity

Question 9

how do molecules move down channel proteins?

Answer 9

either passive or active
require several polypeptide subunits

Question 10

what can the difference on either side of the membranes be?

Answer 10

chemical
electrical

Question 11

what is diffusion process influenced by?

Answer 11

steepness of concentration gradient
temperature
surface area
diffusion distance
size of substance
number of channels

Question 12

what is exocytosis?

Answer 12

‘secretion of proteins out across the cytoplasmic membrane’

Question 13

what is endocytosis?

Answer 13

uptake of macromolecules across cytoplasmic membrane

Question 14

what pinocytosis?

Answer 14

constitutive and continuous process involves uptake of fluid via small membrane vesicle

Question 15

what is phagocytosis?

Answer 15

specialised endocytosis that digest bacteria

Question 16

what is receptor-mediated endocytosis?

Answer 16

‘clathrin-coated pits formed and vesicles formed
triskelion forms basket like structure to stabilize endocytic vesicle’

Question 17

what are cellular membranes formed from?

Answer 17

lipid bilayer

Question 18

what are membranes?

Answer 18

dynamic structures that include different molecules that control cell signalling and communication actions

Question 19

what do adhesion molecules and receptors do?

Answer 19

bind extracellular molecules allowing cells to sense their enviornment

Question 20

what can pass through membranes and what can’t?

Answer 20

water, gases and urea pass through without aid
water still requires facilitated porins
ions, sugars, amino acids require aid

Question 21

how does diffusion occur?

Answer 21

differences on either side of the membrane

Question 22

what do transporters allow?

Answer 22

movement of substances against concentration gradient
requires energy from ATP

Question 23

examples of transporters?

Answer 23

uniporters, symporters, antiporters
ATP-binding cassette system
all require ATP hydrolysis

Question 24

what allows the movement of compounds along their concertation gradient?

Answer 24

channels, carriers, gated ion channels, gap junction channels

Question 25

how do gated ion channels open?

Answer 25

in response to specific signals

Question 26

types of gated ion channels

Answer 26

ligand-gated
voltage-gated

Question 27

what are gap junctions?

Answer 27

connect with neighbouring cells

Question 28

what does secondary active transport do?

Answer 28

transports molecule down its concentration gradient using energy from ATP hydrolysis indirectly to establish a proton gradient

Question 29

what are proton gradients for?

Answer 29

‘drive activity of mitochondrial ATP synthase and generation of ATP’

Question 30

what are symporters?

Answer 30

co-transporters that transporter two molecules at the same time in the same direction

Question 31

what are antitransporters?

Answer 31

co-transporter that transports molecules opposite directions

Question 32

what is the ATP-Binding Cassette (ABC) transporters?

Answer 32

in humans they’re cl- transporter that mutates in cystic fibrosis conditions
also involved in multi-drug resistance- pumping drugs out of cell usually cancer cells
requires energy from ATP hydrolysis

Question 33

what are the functions of receptors?

Answer 33

bind extracellular molecules and allow them to sense their environment
detect ligands and growth factors
‘receptor ligands change the cytoplasmic domain of receptor protein through clustering receptors or inducing a
conformational change of the receptor protein’
initiate a cascade of signalling molecules

Question 34

what is the process of exocytosis?

Answer 34

packaged into vesicles
vesicles fuse with cytoplasmic membrane and release contents
active process and constitutive

Question 35

what are translocases?

Answer 35

transporters for bacteria

Question 36

examples of receptor biding molecules?

Answer 36

antagonist- block activation of target by ligand
agonist- activate target as a ligand

Question 37

examples of signal transduction blockers?

Answer 37

kinase inhibitors is being developed for cancer treatment