(DSA3) Fundamentals of Biochemical Reactions

Question 1

What does a positive, negative, and 0 value of ΔG indicate?

DSA3 S3 LO1.a.i

Answer 1

Positive ΔG:
-nonspontaneous, requires energy

ΔG=0:
-reaction is at equilibrium

Negative ΔG:
-spontaneous, produces energy

Question 2

What are the main driving factors of reactions?

DSA3 S5 LO1.a.ii

Answer 2

Mass action (Le Catelier’s principle):

• increasing concentrations of reactants will drive reaction to products (opposite applies as well)
• increasing concentrations of products will drive reaction to reactants (opposite applies as well)

Energy coupling:
-exergonic reactions that have a common intermediate with an endergonic reaction can be used to drive the endergonic reaction if they have a sufficient ΔG

Question 3

How do the kidneys regulate acid-base balance?

DSA3 LO1.a.iv

Answer 3

The kidneys can remove H+ from the blood as NH4+ and can reabsorb HCO3-

Low Blood pH increases removal H+ and reabsorbtion of bicarb

High pH results in fewer H+ removal and less bicarb reabsorbtion

Question 4

Describe metabolic acidosis and the compensatory response.

DSA3 S8

Answer 4

Decreased pH/increased [H+] caused by the addition of an acid or loss of HCO3- buffer.

Hyperventilation compensates by reducing [H+] by conversion to H2O and CO2 (which is exhaled)

Question 5

Describe respiratory acidosis and the compensatory response.

DSA3 S8

Answer 5

Decreased pH/increased [H+] caused by increased CO2 due to hypoventilation.

Renal response will increase HCO3- reabsorption and remove H+ from the blood.

Question 6

Describe metabolic alkalosis and the compensatory response.

DSA3 S8

Answer 6

Increased pH/decreased [H+] caused by the addition of strong base or loss of strong acid.

Hypoventilation increased CO2 which is converted to H+.

Question 7

Describe respiratory alkalosis and the compensatory response.

DSA3 S8

Answer 7

Increased pH/decreased [H+] caused by by decreased CO2 due to hyperventilation.

Renal response will decrease HCO3- reabsorption

Question 8

Differentiate between apoenzymes and holoenzymes.

DSA2 S16

Answer 8

Apoenzymes:
-inactive due to absence of coenzyme

Holoenzymes:
-activated due to bound coenzyme

Question 9

What is PLP and where does it come from?

DSA3 S17 LO1.b.ii

Answer 9

Pyridoxal phosphate

Coenzyme derived from vitamin B6

Question 10

What is a catalytic triad and what amino acids are present?

DSA2 S19

Answer 10

Acid: aspartic acid

Base: Histidine

Nucleophile: Serine

Question 11

What is Km?

DSA2 S30 LO1.c.i

Answer 11

Concentration of substrate at which rate of reaction is 1/2 Vmax.

Inversely related to affinity

Question 12

Differentiate between competitive, noncompetitive, and uncompetitive inhibition. (Relate change of Km and Vmax)

DSA2 S31-35 LO1.c.ii

Answer 12

Competitive:

• binds at active site
• Km increase (more S outcompetes I)
• Vmax unchanged

Noncompetitive:

• binds at site other than active site
• decreases Vmax (inactivates E so there are less reactions)
• unchanged Km

Uncompetitive:

• binds enzyme-substrate complex
• decrease in Km and Vmax

Question 13

What medical diagnosis is elevated alkaline phosphatase indicative of?

DSA2 S45 LO1.d.ii

Answer 13

Bone disease

Question 14

What medical diagnosis is elevated sorbitol or lactate dehydrogenase indicative of?

DSA2 S45 LO1.d.ii

Answer 14

Obstructive liver disease

Question 15

What medical diagnosis is elevated acid phosphatase indicative of?

DSA2 S45 LO1.d.ii

Answer 15

Prostatic cancer

Question 16

What medical diagnosis is elevated amylase indicative of?

DSA2 S45 LO1.d.ii

Answer 16

Acute pancreatitis

Question 17

What medical diagnosis is elevated aldolase or ASH indicative of?

DSA2 S45 LO1.d.ii

Answer 17

Muscular dystrophy

Question 18

What medical diagnosis is elevated CK- MM indicative of?

DSA2 S45 LO1.d.ii

Answer 18

Liver disorder

Question 19

oxioreductase

Answer 19

tranasfers eletron from a donor to acceptor

Question 20

trasnsferases

Answer 20

trasnfer a fuctional group between molecules

Question 21

isomerases

Answer 21

rearrange/ isomreize molecules

Question 22

lyases

Answer 22

add or remove atoms to form a double bond

Question 23

ligasers

Answer 23

form bonds with hydrolysis of atp

Question 24

hydroases

Answer 24

cleave with water

Question 25

Cofactor

Answer 25

Small organic molecules, derived from vitamins

-Cosubstrate: temporary association; bind and then detach in altered state•NAD+: loosely associated, leaves in a changed form (reduced)
–Prosthetic: permanent association•FAD: tightly bound, remains in original form ie •Heme

Question 26

Chromium and iodine are ______-

Answer 26

essential ions, not “cofactors”

Question 27

Each enzyme has its own optimal ____ and ____.

Answer 27

-temp (ie denatruation) and pH (pepsin)

Question 28

Gastric proton pump inhibitors

Answer 28

also known as H+/K+ATPase.
•Found in the parietal cells that line the gastric lumen.
•Pump H+ into the lumen where it combines with Cl- to form HCl.
•Conditions like ulcers, indigestion, heartburn require decrease in gastric acid thus proton pump inhibitors are prescribed (Omeprazole, lansoprazole, esomeprazole).

Question 29

Omeprazole, lansoprazole, esomeprazole

Answer 29

gastric proton pump inhibitors

Question 30

hypochlorhydria

Answer 30

Reduced HCl production causes hypochlorhydria which can reduce absorption of nutrients, increase in sensitivity to food poisoning, reduction in gastric enzyme efficiency, particularly pepsin, gastric amylase, gastric lipase.

Question 31

Inhibiton of Metalloenzymes

Answer 31

an enzyme that requires a metallic cofactor: is inhibtied by chealting factors that bind metal ions. EDTA is an example (MN, CU, FE, PB, CO)

Question 32

Cheating agents for Pb poisioning

Answer 32

Pb inhibits ALA dehydratase and ferrochelatease

-ferrochelatase: is invovled in heme synthesis (coenzyme) of hemogolobin) this will cause lead poisioning

Question 33

Lead posioning cure

Answer 33

admister Ca EDTA: Pb has a higher affinity for EDTA than CA

Question 34

Allosteric effector

Answer 34

binds to a site, non covalently, other than the catalytic site
-effetctors can be: positive (activators) or negative (inhibitors)

Question 35

Isozyme

Answer 35

same catalytic function, different primary sequence. They hav different binding sites
-examples: markers of MI

Question 36

Troponin in MI

Answer 36

trop has a trimeric strucrure: TN-C, TN-T, and TN-I

• Tn-I has 3 subunits: cTN-I, sTN-I (cardiac and skeletal)
• trops have overtaken tradtional cardiac enzymes for dectection of MI
• max sentivity is 10-24 hours following onset of MI