MCB 450 UIUC EXAM 3 UPDATED ACTUAL QUESTIONS AND CORRECT ANSWERS

MCB 450 UIUC EXAM 3 UPDATED ACTUAL QUESTIONS
AND CORRECT ANSWERS

Question:
1. Which of the following properties of a chemical reaction are altered when the reaction is catalyzed by an
enzyme?
-The energy level of the initial state (reactants) is lowered
-The energy level of the final state (products) is lowered
-The energy level of the transition state is lowered
-The reaction equilibrium is altered to favor the products
Answer:
The energy level of the transition state is lowered

Question:
2. Which of these statements about Km is correct?
-Km is the substrate concentration that will give maximal reaction velocity
-Km is the substrate concentration that will give half-maximal reaction velocity
-Km is the same as Vmax divided by the total enzyme concentration
-Km is the same as the 'turnover number' enzyme
Answer:
Km is the substrate concentration that will give half-maximal reaction velocity

Question:
3. How does a ligand-gated channel work?
Answer:
When a ligand binds to an ion channel, the channel changes conformation and the ion channel opens,
allowing ions to cross the membrane

Question:
4. Hormonal activation of a signaling pathway that includes heterotrimeric GTP-binding proteins would
most likely involve the activation of which of the following protein kinases?
-Tyrosine kinases
-Ca2+ -calmodulin dependent kinase and protein kinase C
-AMP dependent protein kinase and protein kinase B (Akt)
-cAMP dependent protein kinase A
Answer:
cAMP dependent protein kinase A

Question:
5. In cells, NADH serves as a carrier of which of the following?
-electrons
-acetyl groups
-methyl groups
-phosphoryl groups
-hydroxyl groups

, Answer:
electrons

Question:
6. In cells, biotin serves as a carrier of which of the following?
-carboxyl groups
-phosphoryl groups
-electrons
-methyl groups
-acetyl groups
Answer:
carboxyl groups

Question:
7. Which of the following are reasons that glucose is a common metabolic fuel used in living organisms?
-only sugar used by the brain
-has a stable ring structure and unlikely to glycosylate proteins
-unlikely to glycosylate proteins
-has a stable ring structure
-has a stable ring structure, it is unlikely to glycosylate proteins, and it is the only sugar used by the brain
Answer:
It has a stable ring structure and unlikely to glycosylate proteins

Question:
8. Which of the following glycolytic reactions constitutes a major thermodynamic driving force for
glycolysis in vivo?
-2-phosphoglycerate -> phosphoenolpyruvate + H2O
-glyceraldehyde 3-PO4 + Pi + NAD+ -> 1,3-biphosphoglycerate + NADH + H+
-dihydroxyaceton-PO4 -> glyceraldehyde-PO4
-glucose 6-PO4 -> fructose 6-PO4
-phosphoenolpyruvate + ADP -> pyruvate + ATP
Answer:
phosphoenolpyruvate + ADP -> pyruvate + ATP

Question:
9. Glycogen phosphorylase releases glucose units from glycogen in what state?
Answer:
glucose 1-phosphate

Question:
10. A hereditary deficiency in aldolase B leads to which of these conditions?
-hypoglycemia, hyperuricemia, liver failure
-nerve damage, liver damage, cataracts
-benign accumulation of fructose in the urine
-hemolytic anemia
-recurrent diarrhea