exam 2 chapter 9

Question 1

Primary barrier function of membranes?

Answer 1

Protect cells from toxins and harmful substances.

Question 2

How do membranes regulate transport?

Answer 2

Control nutrient uptake and waste removal

Question 3

Role of membranes in energy transduction?

Answer 3

Participate in processes like ATP synthesis.

Question 4

Membrane contribution to motility and reproduction?

Answer 4

facilitate cell movement and division.

Question 5

Membrane role in signal transduction?

Answer 5

Convey signals within and between cells

Question 6

Membrane involvement in cell-cell interactions?

Answer 6

Enable communication and adhesion between cells

Question 7

What drives self-assembly of membranes?

Answer 7

Amphiphilic nature of lipids.

Question 8

How does the hydrophobic effect shape membranes?

Answer 8

Nonpolar lipid tails avoid water, driving aggregation

Question 9

Role of polar interactions?

Answer 9

Head groups interact with water and each other

Question 10

How do membranes support protein organization?

Answer 10

Lipids provide a scaffold for protein binding.

Question 11

Membrane protein content varies between membranes?

Answer 11

Ranges from 15–80% depending on function.

Question 12

High-protein membranes are specialized for?

Answer 12

Enzymatic reactions and transport.

Question 13

High-lipid membranes are specialized for?

Answer 13

Structural integrity and insulation.

Question 14

Peripheral proteins?

Answer 14

Loosely associated with membrane surfaces.

Question 14

How do cells tailor membranes?

Answer 14

Adjust lipid composition to meet functional needs.

Question 14

Key concept of the fluid mosaic model?

Answer 14

Membranes are fluid bilayers with laterally mobile lipids and proteins.

Question 14

Lipid-anchored proteins?

Answer 14

Covalently linked to lipids, can be reversible.

Question 15

What is critical micelle concentration (CMC)?

Answer 15

Minimum concentration needed for micelle formation.

Question 15

Lipid structures in water?

Answer 15

Lipids spontaneously form monolayers, micelles, or bilayers.

Question 15

Monotopic proteins?

Answer 15

Attached to only one side of the membrane.

Question 16

Peripheral proteins?

Answer 16

Loosely attached, removable by mild conditions.

Question 16

Integral proteins?

Answer 16

Embedded within the lipid bilayer

Question 16

Integral proteins?

Answer 16

Firmly embedded, often transmembrane.

Question 16

Lipid motion within membranes

Answer 16

Chains can bend, tilt, rotate, and diffuse laterally.

Question 17

Glycophorin A example?

Answer 17

Single-pass, bitopic integral protein; blood group antigen.

Question 17

Bitopic proteins?

Answer 17

Span the membrane once.

Question 18

Polytopic proteins?

Answer 18

Span the membrane multiple times.

Question 19

Why are α-helices common in transmembrane proteins?

Answer 19

Hydrogen bonds stabilize polar backbone in nonpolar membrane interior.

Question 20

Bacteriorhodopsin example?

Answer 20

7-transmembrane α-helices; light-driven proton pump.

Question 20

Hydropathy plots?

Answer 20

Predict transmembrane regions based on hydrophobicity.

Question 20

What is membrane protein topology?

Answer 20

Orientation and number of transmembrane segments.

Question 21

Positive-inside rule?

Answer 21

Positive residues usually face cytoplasmic side.

Question 21

Role of Trp, His, Tyr?

Answer 21

Amphipathic, often at membrane-water interfaces.

Question 22

Porins?

Answer 22

β-barrel proteins forming pores in bacterial outer membranes.

Question 23

Why β-sheets in membrane proteins?

Answer 23

Fewer residues needed per segment → genetic economy.

Question 24

α-helical barrels?

Answer 24

Some outer membrane proteins form α-helical pores (e.g., Wza).

Question 25

Myristoyl anchors?

Answer 25

N-terminal Glycine linked to myristic acid.

Question 26

hioester-linked (acyl) anchors?

Answer 26

Lipids attached to Cys, Ser, or Thr.

Question 26

Thioether-linked prenyl anchors?

Answer 26

Cys in CAAX motif linked to farnesyl/geranylgeranyl.

Question 27

GPI anchors?

Answer 27

Protein linked via oligosaccharide and phosphatidylinositol to outer leaflet.

Question 28

Lateral asymmetry?

Answer 28

Lipids and proteins cluster within the same leaflet.

Question 29

Transverse asymmetry?

Answer 29

Inner and outer leaflets have different compositions.

Question 30

Membrane dynamics?

Answer 30

Lipids and proteins are laterally mobile, supporting function.

Question 31

Hop diffusion?

Answer 31

Restricted lateral diffusion across membrane compartments

Question 32

Microdomains?

Answer 32

Lipid and protein clusters enabling specialized functions.

Question 33

Gel (So) phase?

Answer 33

Low temperature; tightly packed, ordered acyl chains.

Question 34

Liquid-disordered (Ld) phase?

Answer 34

High temperature; chains bent, mobile, thinner bilayer.

Question 35

Liquid-ordered (Lo) phase?

Answer 35

Sphingolipid + cholesterol; ordered but mobile.

Question 36

Membrane phase transitions?

Answer 36

Gel → liquid-crystalline at lipid-specific Tm.