Biochem Exam 1: Set 2 (Acid-Base, Enzymes and Catalysis)

Question 1

Name a prevalent amphipathic biological molecule

Answer 1

phosopholipid

Question 2

What is normal blood pH?

Answer 2

7.35-7.45

Question 3

What is the Henderson-Hasselbalch equation, and what is it used for?

Answer 3

pH= pKa + log([A-]/[HA])

Used to relate the concentration of buffer species, the pKa of the buffer, and the solution pH

Question 4

What are the three biological buffer systems?

Answer 4

Biocarbonate, phosphate, and protein systems

Question 5

How is Hb affinity for oxygen effected if pH is lowered

Answer 5

lower oxygen affinity

Question 6

The pKr of which amino acid is close to biological pH?

Answer 6

Histidine

Question 7

What are normal serum bicarbonate levels?

Answer 7

24-28 mmol/L

Question 8

What indicates metabolic acidosis, and what causes it?

Answer 8

decreased pH, low HCO3-

caused by increased acid production (which causes an increased anion gap) or loss of HCO3- (e.g. diarrhea)

Question 9

What indicates respiratory acidosis?

Answer 9

decreased pH, high pCO2

Question 10

What is Kussmaul’s respiration?

Answer 10

rapid deep breaths usually associated with diabetic ketoacidosis

Question 11

How do catalysts effect the reaction rate and equilibrium?

Answer 11

increases rate, equilibrium is constant

Question 12

How would you test for liver damage?

Answer 12

ALT assay- ALT is a liver enzyme that is released into the blood after liver damage

Question 13

What is the general function of oxidoreductase enzymes?

Answer 13

transfer of electrons

Question 14

What is the general function of hydrolase enzymes?

Answer 14

addition of water

Question 15

What is the general function of isomerase enzymes?

Answer 15

interconvert between isomers

Question 16

What is the general function of transferase enzymes?

Answer 16

transfer a functional group

Question 17

What is the general function of lyase enzymes?

Answer 17

form or remove double bonds

Question 18

What is the general function of ligase enzymes?

Answer 18

condensation of two molecules to form bond

Question 19

How to enzymes effect the change in free energy of a reaction?

Answer 19

lower the change in free energy

Question 20

Why are transition state analogs a target for drug development?

Answer 20

enzymes favor binding transition state, and transition state analogs are stable as opposed to unstable transition state of natural substrates, which makes the drugs bind more tightly than the substrate

Question 21

How do enzymes increase the effective concentration of a substrate?

Answer 21

Brings substrates closer together and undergoes a conformational change: Proximity and Orientation

Question 22

How does acid-base catalysis function?

Answer 22

residues in active site donate/accept protons

Question 23

How does covalent catalysis function?

Answer 23

covalent intermediate is formed between substrate and enzyme

Question 24

What is a zymogen?

Answer 24

an inactive form of an enzyme (typically digestive proteases)

Question 25

What is the Michaelis-Menton equation?

Answer 25

V0=Vmax[S]/(Km+[S])

Question 26

What is kcat a measure of?

Answer 26

kcat= turnover number; measures molecules catalyzed per time

Question 27

Given the in vivo [S] for an enzyme, how could you approximate the Km of the enzyme?

Answer 27

Km ~ typical in vivo [S]

Question 28

How would you obtain a Lineweaver-Burk plot

Answer 28

reciprocal of M-M equation

Question 29

In a Lineweaver-Burk plot was is the slope of the line?

Answer 29

Km/Vmax

Question 30

Where does a competitive inhibitor bind and how does it effect Km and Vmax?

Answer 30

binds active site Raises Km, Vmax is unchanged

Question 31

Statins act as what type of inhibitor of HMG-CoA reductase?

Answer 31

competitive

Question 32

Where does a noncompetitive inhibitor bind and how does it effect Km and Vmax?

Answer 32

binds to allosteric site Km is unchanged, Vmax is decreased

Question 33

How do uncompetitive inhibitors function?

Answer 33

binds the enzyme-substrate complex

Question 34

Give an example of isozymes

Answer 34

Hexokinase and Glucokinase

Question 35

Phosphorylation and dephosphorylation occur on what amino acids?

Answer 35

Ser, Thr, Tyr

Question 36

What are some characteristics of rate-limiting steps in a reaction?

Answer 36

Thermodynamically unfavorable Kinetically slow Subject to regulatory mechanisms Often inhibited by final product of reactions