Bio Chem: concept checks exam #4

Which type of reaction is typically highly favorable and spontaneous?

hydrolysis

Which factor does NOT influence the actual free energy change in a cell?

enzyme catalysis

what role does NAD+ play in cellular redox reactions?

electron acceptor

Which statement is true about NAD and NADP?

dissociate from enzymes after reaction

Flavin cofactors differ from NAD cofactors because they:

can transfer one or two electrons

Which of the follow statements best describes a molecule with a high (positive) standard reduction potential (E^o)?

it has a strong tendency to accept electrons and be reduced

For a reaction to be negative ΔG^o and proceed spontaneously, what must be true of ΔE^o?

it must be positive

Which product of glucose metabolism is important for DNA and RNA synthesis

pentose phosphates

Why is glycolysis considered to be one of the earliest metabolic pathways?

it can function without oxygen

which of the following best describes the preparatory phase of glycolysis?

glucose activation via phosphorylation

What is the main purpose of the payoff phase of glycolysis?

production of pyruvate and ATP

What is the “Cori Cycle” primarily responsible for?

recycling lactate to glucose in the liver

Which of the following best describes lactic acid fermentation?

converts pyruvate to lactate to regenerate NAD+

What prevents futile cycling between glycolysis and gluconeogenesis?

use of different enzymes and regulation

Which statement about gluconeogenesis is true?

it bypasses irreversible glycolytic steps with distinct enzymes

Which of the following molecules can’t serve as a precursor for gluconeogenesis in animals?

Acetyl-CoA

Which of the following enzymes is used in gluconeogenesis but not in glycolysis, to bypass an irreversible step?

Fructose-1,6-bisphosphatase

What is the main function of fructose 2,6-bisphosphate?

regulation of glycolysis and gluconeogenesis

What is the primary purpose of metabolic regulation?

To maintain homeostasis and respond to changes in demand

What is the effect of phosphorylation on enzyme activity?

can either activate or deactivate depending on the enzyme

reactions that are far from equilibrium are typically:

good targets for regulation

What does a high AMP/ATP ration typically indicate?

low energy state

Why is glucose stored as glycogen in cells instead of being kept as free glucose molecules?

glycogen reduces osmotic pressure that would result from free glucose accumulation

Which enzyme removes glucose residues from glycogen?

glycogen phosphorylase

Which of the following best describes the effect of glucagon or epinephrine signaling on glycogen metabolism?

it initiates a phosphorylation cascade that activates glycogen phosphorylase

How does glycogen metabolism differ between liver and muscle?

muscle uses glycogen for ATP, liver for blood glucose