exam 2 chapter 9 pt 2

Question 1

How do lipids influence curvature?

Answer 1

Cone-shaped lipids induce bends

Question 2

Proteins in curvature?

Answer 2

Integral or scaffolding proteins stabilize curved membranes.

Question 3

Function of membrane remodeling?

Answer 3

Essential for cell movement, division, organelle shaping.

Question 4

Passive diffusion?

Answer 4

Solutes move down their concentration gradient without proteins.

Question 5

Facilitated diffusion?

Answer 5

Transport proteins accelerate solute movement down gradient.

Question 6

Difference between passive and facilitated diffusion?

Answer 6

Facilitated shows saturation kinetics; passive is linear.

Question 7

Ion movement depends on?

Answer 7

Both concentration gradient and membrane potential.

Question 8

Active transport?

Answer 8

Moves solutes against gradient, requiring energy.

Question 9

Primary active transport?

Answer 9

Uses ATP directly

Question 10

Secondary active transport?

Answer 10

Uses pre-existing ion gradients to drive solute movement.

Question 11

Symport vs antiport?

Answer 11

Symport: same direction; antiport: opposite directions

Question 12

Na⁺,K⁺-ATPase role?

Answer 12

Maintains intracellular Na⁺ low, K⁺ high; crucial for neurons.

Question 13

How many ions per cycle?

Answer 13

3 Na⁺ out, 2 K⁺ in.

Question 14

Ca²⁺-ATPase in muscle?

Answer 14

Pumps Ca²⁺ into sarcoplasmic reticulum; regulates contraction.

Question 15

H⁺,K⁺-ATPase in stomach?

Answer 15

Acidifies stomach lumen; creates extreme pH gradient.

Question 16

Osteoclast proton pumps?

Answer 16

V-type ATPases acidify bone surface for resorption.

Question 17

Function?

Answer 17

ATP-driven transport of molecules in or out of cells.

Question 18

Domain structure?

Answer 18

2 transmembrane domains + 2 nucleotide-binding domains.

Question 19

Role in drug resistance?

Answer 19

Pump out toxic compounds or drugs.

Question 20

Retinal chromophore role?

Answer 20

Absorbs light; covalently linked to Lys216 via Schiff base.

Question 20

Bacteriorhodopsin function?

Answer 20

Light-driven H⁺ pump in Halobacterium membranes.

Question 21

Proton transfer pathway?

Answer 21

Asp96 → Lys Schiff base → Asp85 → extracellular release.

Question 22

Retinal isomerization?

Answer 22

All-trans → 13-cis triggers conformational changes.

Question 22

Lipid motion near surface vs bilayer center?

Answer 22

More ordered near surface; more flexible toward center.

Question 23

Lateral diffusion of lipids?

Answer 23

Supports membrane fluidity and signaling.

Question 24

Lateral protein movement?

Answer 24

Proteins diffuse slower than lipids; influenced by cytoskeleton.

Question 25

Rotational motion of lipids?

Answer 25

Lipids can rotate about their long axis within the bilayer.

Question 26

Flippases?

Answer 26

Move lipids from outer → inner leaflet (ATP-dependent).

Question 27

Floppases?

Answer 27

Move lipids from inner → outer leaflet (ATP-dependent).

Question 28

Scramblases?

Answer 28

Bidirectional, ATP-independent; randomize lipid distribution.

Question 29

Microdomains (rafts)?

Answer 29

Lipid-protein clusters for specialized functions.

Question 30

Dynamic exchange?

Answer 30

Lipids and proteins continuously move in/out of domains.

Question 31

Nanoscale clusters?

Answer 31

5–100 nm; dozens to hundreds of lipids, few proteins.

Question 32

Microscale structures?

Answer 32

Several micrometers; coordinate protein function.

Question 33

KcsA channel structure?

Answer 33

Tetramer of four subunits forming central K⁺ pore.

Question 34

Selectivity filter?

Answer 34

Loops from each subunit create K⁺ binding sites.

Question 35

Voltage-dependent gating?

Answer 35

Conformational change opens/closes pore in response to membrane potential.

Question 36

tetrameric assembly advantage?

Answer 36

Ensures rapid, selective ion conduction.

Question 37

Function in E. coli?

Answer 37

Multidrug resistance; pumps toxins out using ion gradients.

Question 38

tripartite complex?

Answer 38

AcrB (inner membrane) + AcrA + TolC (periplasm/outer).

Question 39

Mechanism?

Answer 39

H⁺-drug antiporter; proton flow drives drug export

Question 40

transport cycle?

Answer 40

Loose → Tight → Open conformations move drugs across membrane.

Question 41

How do membranes enable signaling?

Answer 41

Proteins and lipids relay information within and between cells.

Question 41

Why are membranes selective barriers?

Answer 41

Hydrophobic core prevents free passage of polar molecules.

Question 42

Membrane fluidity depends on?

Answer 42

pid composition, temperature, cholesterol content.

Question 43

hy do cells maintain asymmetry?

Answer 43

for signaling, recognition, and membrane function.

Question 44

hy are membranes dynamic?

Answer 44

ateral/rotational movement allows adaptation to environmental changes.

Question 45

how does curvature affect function?

Answer 45

nables vesicle formation, endocytosis, and organelle shaping.

Question 46

Why are protein-lipid interactions important?

Answer 46

stabilize structure, mediate transport, and coordinate signaling.

Question 47

General role of active transport?

Answer 47

Moves molecules against gradients to maintain homeostasis and energy balance.