Lecture 10

Question 1

Cells contain numerous ______-____ compartments

Answer 1

membrane-bound

Question 2

Three classes of membrane proteins

Answer 2

integral, lipid-anchored, peripheral

Question 3

Transport across membranes is regulated by what 3 protein classes?

Answer 3

channels, pumps, transporters

Question 4

Eight roles of biological membranes

Answer 4

Allow compartmentalization
Act as barriers to diffusion
Define organelles and the cell boundary
Scaffolds for certain proteins
Transport molecules
Transmit information
Give shape
Assemble polysaccharides

Question 5

Capacitance

Answer 5

A general property of membranes, as a barrier to rapid transport of ions, electrical resistance, and charge difference. Membrane can maintain voltage of 20-80 mV

Question 6

Typical location of negative charge around plasma membrane (outside or inside cell?)

Answer 6

Inside cell

Question 7

Three classes of molecules in a plasma membrane

Answer 7

lipids, proteins, polysaccharides

Question 8

Stain used in electron microscopy to examine lipid bilayers

Answer 8

osmium tetroxide

Question 9

4 components of a phosphoglyceride

Answer 9

Glycerol, 2 fatty acids (one saturated, one unsaturated), phosphate group, polar molecule (choline, ethanolamine, or serine)

Question 10

3 components of a galactosylglyceride

Answer 10

Glycerol, 2 fatty acids (both unsaturated), galactose

Question 11

3 components of a sphingolipid

Answer 11

Sphingosine, 1 fatty acid, polar head group (sugar, choline, ethanolamine, or serine)

Question 12

Most abundant phosphoglyceride

Answer 12

phosphatidylcholine

Question 13

Phosphoglyceride that is useful in cell signaling

Answer 13

phosphatidylinositol

Question 14

Amino alcohol with long hydrocarbon tail used in certain membrane lipids

Answer 14

sphingosine

Question 15

3 components of sphingomyelin

Answer 15

Sphingosine, 1 fatty acid, choline

Question 16

3 components of glucosylcerebroside, a lipid found in neurons

Answer 16

Sphingosine, 1 fatty acid, glucose

Question 17

3 sterols used, respectively, in animals, fungi, and plants

Answer 17

cholesterol, ergosterol, stigmasterol

Question 18

Location of cholesterol synthesis

Answer 18

ER (mainly in liver); HMG-CoA reductase found on smooth ER

Question 19

6 potential products of farnesyl pyrophosphate (a cholesterol intermediate)

Answer 19

Dolichol
Heme
Ubiquinone (CoQ)
Vitamins (A, E, K)
Chlorophyll
Lipid-anchored proteins (Ras)

Question 20

5 potential products of cholesterol

Answer 20

Vitamin D
Bile acids
Steroid hormones
Cholesterol esters
Modified proteins (Hedgehog)

Question 21

Protein that moves lipid from one face of membrane to the other

Answer 21

Flippase

Question 22

To decrease freezing point of membrane (3 ways):

Answer 22

Shorter FA chain length
More double bonds
Decreased amount of sterol (concentration-dependent, so this may work the other way)

Question 23

Lipids found mainly on cytosolic face of membrane (3)

Answer 23

PS (phosphatidylserine)
PE (phosphatidylethanolamine)
PI (phosphatidylinositol)

Question 24

Lipids found mainly on exoplasmic face (2)

Answer 24

PC (phosphatidylcholine)

SM (sphingomyelin)

Question 25

Major membrane protein of erythrocytes

Answer 25

Glycophorin

Question 26

Negatively-charged sugar attached to glycophorin to repel other RBCs

Answer 26

Sialic acid (negatively charged)

Question 27

Photoreceptor in certain bacteria with 7 transmembrane helices

Answer 27

Bacteriorhodopsin

Question 28

Class of proteins related to bacteriorhodopsin

Answer 28

GPCRs (G-protein coupled receptors; 1/2 of all drugs target this class of proteins)

Question 29

Lipid component that is found equally on exoplasmic and cytosolic faces

Answer 29

Cholesterol

Question 30

Proposed functions for lipid rafts (6)

Answer 30

``` Signaling platforms Exocytosis Endocytosis Pathogen entry Apoptosis Cytoskeletal organization ```

Question 31

Microdomain in plasma membrane containing glycosphingolipids and cholesterol

Answer 31

Lipid raft

Question 32

2 groups used in lipid-anchored proteins

Answer 32

Acyl groups, prenyl groups

Question 33

Substance used to selectively solubilize and purify transmembrane lipids

Answer 33

Nonionic detergent

Question 34

Technique used to demonstrate fluidity of lipids and proteins in a membrane

Answer 34

FRAP (fluorescence recovery after photobleaching)

Question 35

Do all proteins and lipids diffuse?

Answer 35

No.

Question 36

Filaments that attach laterally to components in membrane

Answer 36

Actin

Question 37

Cytoskeleton component closely attached to plasma membrane in erythrocytes

Answer 37

Spectrin tetramers

Question 38

Band _ is the major integral membrane protein in erythrocytes. It is a bicarbonate/____ ___(symporter/antiporter) that can be cross-linked to _____.

Answer 38

3, chloride antiporter, ankyrin

Question 39

Band __ is an anchor for spectrin

Answer 39

4.1

Question 40

Band proteins that are peripheral cytosolic proteins (5 of 'em)

Answer 40

``` 1 2 4 5 6 ```

Question 41

_______ and spectrin interact with Band 4.1

Answer 41

Glycophorin

Question 42

Components of junctional complex (5)

Answer 42

Actin, adducin, spectrin dimer, band 4.1, tropomyosin

Question 43

Most common defective protein in hereditary spherocytosis

Answer 43

Ankyrin (50-60% of cases)

Question 44

Characteristics of RBCs in hereditary spherocytosis

Answer 44

Small, spherical, fragile, very susceptible to temperature changes

Question 45

2 classes of molecules that can diffuse directly through plasma membrane

Answer 45

Gases | Small uncharged polar molecules (membrane is permeable to ethanol, slightly permeable to urea and water)

Question 46

3 classes of molecules that cannot diffuse directly through plasma membrane

Answer 46

Large uncharged polar molecules (e.g. sugars) Ions Charged polar molecules (e.g. ATP, amino acids, proteins, nucleic acids, glucose-6-phosphate)

Question 47

ATP-powered pump that uses 25-50% of total cellular ATP

Answer 47

Na+/K+ ATPase

Question 48

How is the sodium-potassium pump electrogenic?

Answer 48

3 Na+ are pumped out, 2 K+ are pumped in Net increase of + charge outside cell

Question 49

Active transport with ATP-powered pumps moves substrates _______ (with/against) their concentration gradients.

Answer 49

against

Question 50

Two drugs that target Na+/K+ ATPases

Answer 50

Ouabain, digoxin

Question 51

Two examples of ion channels

Answer 51

Aquaporins, stretch-activated ion channels

Question 52

Facilitated diffusion with ion channels assists in the movement of a substrate _____ (with/against) its concentration gradient.

Answer 52

with

Question 53

Three types of transporters

Answer 53

Uniporter Symporter Antiporter

Question 54

In secondary active transport, or co-transport, a transporter couples movement of a substrate _____ (with/against) its concentration gradient to the movement of a second substrate ______ (with/against) its concentration gradient.

Answer 54

against, with