Lec 9/11

Question 1

phospholipid structure

Answer 1

• polar head on surface, hydiphilic
• Fatty acyl tails inward, hydrophobic, form weak noncovalent bonds
• amphipathic(lipophilic/hydrophobic and hydrophilic)

Question 2

unit membrane

Answer 2

• inner leaflet(inner surface Protoplasmic or P-face)
• outer leaflet(outer surface Ectoplasmic or E-face)
• 1:1 phospholipid to protein ratio

Question 3

what are proteins on inner leaflet?

Answer 3

• phosphatidylserine(PS)

- phosphatidylethanolamine(PE)

Question 4

what are proteins on outer leaflet?

Answer 4

• phosphatidylcholine(PC)

- phosphatidylglycerol(PG)

Question 5

what is apoptosis?

Answer 5

• programmed cell death
• stimulus or signal to undergo programmed cell death (DNA fragmentation~180bp, followed by morphological changes to cell/membranes)

Question 6

signs of apoptosis

Answer 6

cell shrinkage, fragmentation, engulfment/degradation, no inflammation, limited tissue damage

Question 7

signs of necrosis

Answer 7

cell swelling, organelle rupture, membrane rupture, tissue damage, inflammation

Question 8

what happen in a healthy cell

Answer 8

PS asymmetry, active “flippase” process, slight negative charge

Question 9

what happen in an apoptosis cell?

Answer 9

PS asymmetry lost, lippase activity lower, PS externalized–> “eat me” signal

Question 10

annexin assay

Answer 10

• protein binds to - charged phospholipid (PS)
• protein is couples to fluorophore (fluorescent)
• fluorescence can be visualized using microscopy
• apoptotic cells will be labled and glow or fluorescent

Question 11

EX of amphipathic molecules

Answer 11

• phospholipids(fatty acyl tails increase membrane fluidity)
• glycolipids
• cholesterol(decreases membrane fluidity)

Question 12

protein membrane components

Answer 12

• integral/transmembrane proteins (span membrane, ion channel, transport protein), multipass(signaling), more on P-face
• periferal proteins(mainly cytoplasmic face)

Question 13

fluid mosaic model

Answer 13

• come mobility of integral proteins

- limited in polarized cells(apical, basolateral)-related to cellular function

Question 14

glycocalyx-cell coat

Answer 14

• up to 50nm thick

- stains w/ lectins, Alcain blue (Ingrain blue)or ruthenium red

Question 15

glycocalyx-carbohydrate chains

Answer 15

may be linked to transmembrane proteins, phospholipids

Question 16

glycocalyxextracellular matrix(ECM)

Answer 16

may be constituent

Question 17

glycocalyx-function

Answer 17

protect cell(physical or chemical insults)

Question 18

how do nonpolar O2, uncharged polarH2O move acrsoss membrane?

Answer 18

• freely along [] gradients

- simple diffusion(passive diffusion)

Question 19

how do ions and small molecules move across membrane?

Answer 19

• facilitated diffusion(passive diffusion)

- along [] gradients

Question 20

2 types of membrane transport proteins(facilitate transfer of hydrophilic molecules)

Answer 20

• channel proteins:gated, move ions

- carrier proteins: move small proteins, molecules

Question 21

channel proteins

Answer 21

• hydrophilic pores or ion channels(>100 types, gated, few are ungated)
• ion channel(hydrophobic aa face periphery, towards fatty acyl tails) and hydrophilic aa face inwards, toward inner channel surface

Question 22

voltage-gated channels

Answer 22

• in ‘‘closed” position
• closed position is more stable(refractory period is milisec, gate cant be reopened)
• move to open position(Na+ channels, depolarization/transmission of nerve impulse)

Question 23

Ligand-gated channels

*Ion-channel linked receptors

Answer 23

• binding of ligand triggers opening of channel

- remains open until ligand dissociates

Question 24

Ligand-gated channel

*Neurotransmitter-gated channels

Answer 24

post-synaptic neuron

Question 25

Ligand-gated channel | *Nucleotide-gated channels

Answer 25

- cAMP in olfactory receptors | - cGMP in retinal receptors

Question 26

mechanically-gated channel

Answer 26

- stereocilia(projections) in tectorial membrane - sounds create movement of basilar membrane - stereoilia bend - triggers ion channel opening - depolariztion and nerve transmission - nerve impulse translates sound

Question 27

G-protein-gated ion channel | * what is G-protein complex?

Answer 27

- heterotrimeric GTP-binding protein | - 7 helix transmembrane, intra-, extracellular domains

Question 28

G-protein-gated ion channe | * how do extracellular ligand changes conformation?

Answer 28

- GTP replaces GDP activating intracellular signaling | - activated protein interacts to open ion channel

Question 29

ungated channel

Answer 29

- K+ leak channel | - creates voltage(potential) across membrane

Question 30

what is aquaporins?

Answer 30

- impermeable to protons - involved in proper kidney function, clearance - AqpZ: passage of water - GlpF: passage of glycerol

Question 31

carrier proteins

Answer 31

- bind molecules or ions on both sides - extra & intracellular face - involved reversible conformation changes

Question 32

carrier proteins-Uniport

Answer 32

- single molecule moving one way | - GLUT1 uniport carrier-faciliated transport

Question 33

carrier proteins-symport

Answer 33

- 2 molecules moving one way - SGLT(sodium-glucose linked transport) in nephron, renal glucose reabsorption, small intestine, oral rehydration therapy

Question 34

carrier proteins-antiport

Answer 34

- 2 molecules moving opposite - in oral and pharyngeal cancers - importTryptophan (biosynthesis and metabolism substrate) - export Kynurenine(down regulation of CD8 or Tcell)

Question 35

what is EX of primary active transport?

Answer 35

- Na-K pump(coupled antiport carrier protein) | - require ATP (maintain >K inside, >Na outside)

Question 36

Na-K pump

Answer 36

- 3 Na bind inside, ATP is hydrolyzed, ATPase is phosphorylated by phosphate, phosphorylation-->conformation change--> Na is transported outside - 2K bind outside-> dephosphorylationof ATPase-> protein return to old conformation->K is transported inside

Question 37

secondary active transport

Answer 37

- gradient driven - can be symport or antiport - K and glucose bind outside face of carrier protein->shape change->transfer and release into cytoplasm

Question 38

types of cell surface receptors

Answer 38

- ion-channel linked receptors - enzyme-linked receptors - G-protein-linked receptors