BIOCHEMISTRY

Question 1

Amphoteric

Answer 1

Amino acids that can donate and accept protons.

Question 2

pKa

Answer 2

pH at which half of the species are depronated ; [HA]= [A-]

Question 3

Amino acids exist in different forms at different pH values

Answer 3

1. At low pH, AA is fully pronated
2. At pH near the pI the AA, the AA is neutral zwitterion
3. At high pH, AA is depronated

Question 4

Isoelectric point (PI)

Answer 4

Averaging 2 pka points.

1. AA without charge side chains have PI of around 6
2. acidic AA have PI well below 6
3. Basic AA have PI well above 6

Question 5

Dipeptide

Answer 5

2 AA resuides

Question 6

Tripeptide

Answer 6

2 AA residues

Question 7

Oligopeptide

Answer 7

have few AA residues

Question 8

Polypetide

Answer 8

have many (> 20) AA residues

Question 9

Peptide bond formation

Answer 9

Formed by condensation or dehydration reaction (Loss of H2O). Breaking a peptide bond is a hydrolysis reaction.

Question 10

Primary Structure

Answer 10

Linear sequence of AA in a peptide and is stabilized by peptides bond

Question 11

Secondary Structure

Answer 11

Local structure of neighboring AA and stabilized by hydrogen bonds. Alpha helices and Beta pleated sheets. Proline can cause kinks in this structure.

Question 12

Tertiary Structure

Answer 12

3D shape of polypeptide chain, stabilized by hydrophobic interactions, acid-base interactions, hydrogen bonds and disulfide bonds

Question 13

Quaternary Structure

Answer 13

Interaction between peptides in proteins that contain multiple subunits

Question 14

Denaturation

Answer 14

The process through which a protein is unfolded or loses its proper 3D structure. Often losing function.

Question 15

Enzymes

Answer 15

Biological catalysts. Lower activation energy, increase rate of reaction, do not alter equilibrium constant, are not consumed by reactions, are pH and temperature sensitive, don’t affect overall ∆ G, Very specific

Question 16

Oxidoreductase

Answer 16

Enzyme that catalyzes oxidation-reduction reactions that involves the transfer of electrons. Ex: Dehydrogenase.

Question 17

Transferases

Answer 17

Enzymes that move function groups from one molecule to the other
Ex: Kinase

Question 18

Hydrolases

Answer 18

Enzyme that break bonds with the addition of water.

Ex: Protease

Question 19

Isomerases

Answer 19

Enzyme that rearrange bonds within a molecule.

Ex: Mutase

Question 20

Ligases

Answer 20

Enzymes responsible for joining 2 large biomolecules

Question 21

Exergonic reactions

Answer 21

reactions that release Energy, ∆ is negative

Question 22

Endergonic reactions

Answer 22

reactions require energy input, ∆ G is positive

Question 23

Lock and Key theory

Answer 23

hypothesizes that enzymes and substrate are exactly complementary

Question 24

induced fit model

Answer 24

Hypothesizes that the enzymes and substrate undergo conformational changes to interact fully.

Question 25

Cofactors or coenzymes

Answer 25

nonprotein molecules that help enzymes, are recruited when needed.

Question 26

Saturation kinetics

Answer 26

As substrate concentration increases, the reaction rate does well until the maximum values is reached

Question 27

Cooperative enzymes

Answer 27

Display sigmoidal curve because of change in activity with substrate binding

Question 28

Feedback inhibition

Answer 28

catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway

Question 29

Reversible inhibition

Answer 29

Ability to replace the inhibitor with a compound of greater affinity or remove it using mild lab treatment

Question 30

Competitive inhibition

Answer 30

Inhibitor binds to active site, Km increases, Vmax unchanged. We will see change on X axis of line weaver- burk plot

Question 31

Noncompetitive inhibition

Answer 31

Inhibitor binds at allosteric site, Km unchanged, Vmax decreases. We will see change on Y axis of line weaver- burk plot

Question 32

Uncompetitive inhibition

Answer 32

Inhibitor binds allosteric site. Km decreases and max decreases. We will see change on X and Y axis of line weaver- burk plot

Question 33

Irreversible Inhibition

Answer 33

Alters enzymes in that active site is unavailable for prolonged period or permanently changed

Question 34

Regulatory enzymes

Answer 34

1. Allosteric enzymes - can be occupied by activators, increase either affinity of enzymatic turnover
2. Phosphorylation or glycosylation can alter activity or selectivity of enzymes
3. Zymogens- secreted as inactive form and activated by cleavage