Ch 3: Nonenzymatic Protein Function and Protein Analysis

Question 1

Cell Adhesion Molecules (CAMs)

Answer 1

allow cells to bind to other cells or surfaces

cadherins, integrins, selectins

Question 2

compose the cytoskeleton, anchoring proteins, and much of the extracellular matrix

Answer 2

structural proteins

Question 3

most common structural proteins are

Answer 3

collagen, elastin, keratin, actin, and tubulin

Question 4

motor proteins

Answer 4

have one or more heads capable of force generation through a conformational change

have catalytic activity, acting as ATPases to power movement

muscle contraction, vesicle movement within cells, and cell motility are the most common applications of motor proteins

Question 5

myosin, kinesin, and dynein are all examples of

Answer 5

motor proteins

Question 6

binding proteins

Answer 6

bind a specific substrate, either to sequester it in the body or hold its concentration at steady state

Question 7

cadherins

Answer 7

CAM that are calcium-dependent glycoproteins that hold similar cells together

Question 8

integrins

Answer 8

CAM that have two membrane-spanning chains and permit cells to adhere to proteins in the extracellular matrix. some also have signaling capabilities

Question 9

selectins

Answer 9

allow cells to adhere to carbohydrates on the surfaces of other cells and are most commonly used in the immune system

Question 10

Antibodies (of immunoglobins, Ig)

Answer 10

are used by the immune system to target a specific antigen, which may be a protein on the surface of a pathogen (invading organism) or a toxin

Question 11

Immunglobins contain

Answer 11

a constant region and a variable region; the variable region is responsible for antigen binding

Question 12

2 identical heavy chains and 2 identical light chains form an ____ and are held together by

Answer 12

antibody

disulfide bonds and noncovalent interactions

Question 13

Ion channels

3 main types are

Answer 13

cen be used for regulating ion flow into or out of a cell

ungated channels, voltage-gated channels, ligand-gated channels

Question 14

ungated channels

Answer 14

are always open

Question 15

voltage-gated channels

Answer 15

open within a range of membrane potentials

Question 16

ligand-gated channels

Answer 16

open in the presence of a specific binding substance, usually a hormone or neurotransmitter

Question 17

Enzyme-linked receptors

Answer 17

participate in cell signaling through extracellular ligand binding and initiation of second messenger cascades

Question 18

G protein-coupled receptors

Answer 18

membrane-bound protein associated with trimetric G protein;

Question 19

G protein-coupled receptors also initiate second messenger systems

Answer 19

ligand binding engages the G protein,

GDP is replaced with GTP; the alpha subunit dissociates from the beta and gamma subunits,

the activated alpha subunit alters the activity of adenylate cyclase or phospholipase C

GTP is dephosphorylated to GDP; then alpha subunit rebinds to the beta and gamma subunits

Question 20

Electrophoresis

Answer 20

uses a gel matrix to observe the migration of proteins in response to an electric field

Question 21

Native PAGE (electrophoresis)

Answer 21

maintains the protein’s shape, but results are difficult to compare because the mass-to-charge ration differs for each protein

Question 22

SDS-PAGE (electrophoresis)

Answer 22

denatures the proteins and masks the native charge so that the comparison of size is more accurate, but the functional protein can not be recaptured from the gel

Question 23

Isoelectric focusing (electrophoresis)

Answer 23

seperates proteins by their isoelectric point (pI); the protein migrates toward an electrode until it reaches a region of the gel where pH=pI of the protein

Question 24

Chromatography

Answer 24

seperates protein mixtures on the basis of their affinity for a stationary phase or a mobile phase

Question 25

Column Chromatography

Answer 25

uses beads of a polar compound, like silica or alumina (stationary phase) with a nonpolar solvent (mobile phase)

Question 26

Ion-Exchange Chromatography

Answer 26

uses a charged column and a variably saline eluent

Question 27

Size-exclusion Chromatography

Answer 27

relies on porous beads; larger molecules elute first because they are not trapped in the small pores

Question 28

Affinity Chromatography

Answer 28

uses a bound receptor or ligand and an eluent with free ligand or a receptor for the protein of interest

Question 29

protein structure is primarily determined through _____ after the protein is isolated, though ___ can also be used

Answer 29

xray crystallography

NMR

Question 30

amino acid composition can be determined by ____ but amino acid sequencing required sequential degradation, such as ___

Answer 30

simple hydrolysis

Edman degradation

Question 31

activity levels for enzymatic samples are determined by following the process of a known reaction, often accompanied by a ___

Answer 31

color change

Question 32

protein concentration is also determined by ____ , either by ____ or through a color change reaction

Answer 32

colorimetrically

UV spectroscopy

Question 33

BCA assay, Lowry reagent assay, and Bradford protein assay each test for

Answer 33

protein, and have different advantages and disadvantages

Question 34

Bradford Protein assay is the most common and

Answer 34

uses a color change from brown-green to blue