NCSU BCH 451 EXAM 2 STUDY QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
2024/2025
Average Blood Glucose level in humans
60-150 mg/dL
How any cell in the body can use Glucose for energy
Cellular respiration
Glycolisis
the breakdown of glucose by enzymes, releasing energy and pyruvic acid
Overview of Glucose to ATP in cells
glycolysis > Krebs cycle > eletron transport chain (atp)
Fed State
High glucose levels after a meal; cells can use glucose in blood for glycolysis
Glycogen
An extensively branched glucose storage polysaccharide found in the liver and muscle
of animals; the animal equivalent of starch; a storage form of glucose; like a string of
glucose molecules
Which graph correctly illustrates the effect of a negative modifier (effector) on the
velocity curve of an allosteric enzyme? The solid blue curve represents the
unmodified enzyme. The dashed green curve represents the enzyme in the
presence of the effector.
,green curve same shape, more to right than blue curve
Which of the following is NOT true regarding the enzyme chymotrypsin?
Hydrolytic cleavage is achieved through a molecule of water breaking a peptide bond.
Which of the following IS true regarding the enzyme chymotrypsin?
The hydrophobic pocket is the most significant characteristic of the enzyme in
determining where the polypeptide will be cleaved and around which residues cleavage
occurs.
Preparation of nucleophiles is accomplished through the Histidine residue serving as
general base.
Aspartate's hydrogen bonding with Histidine allows for the latter to have a higher pKa,
thus becoming a stronger base.
The oxyanion hole stabilizes carbonyl oxygen through hydrogen bonding with Serine
and Glycine residues.
Chymotrypsin cleaves peptide bonds adjacent to
tyrosines, phenylalanines, and tryptophans (aromatics)
During strenuous activity, the demand for ATP in muscle tissue vastly increases.
In rabbit leg muscle or turkey flight muscle, ATP production is almost exclusively
a product of lactic acid fermentation. Phosphoglycerate kinase and pyruvate
kinase catalyze the two reactions that form ATP in the payoff phase of glycolysis.
If skeletal muscle were devoid of lactate dehydrogenase, could it still generate
, ATP at a high rate by glycolysis in order to carry out strenuous physical activity?
Why or why not?
No. Lactate dehydrogenase recycles NAD+ from the NADH formed during the oxidation
of glyceraldehyde 3-phosphate
Why does a congenital defect in the liver enzyme fructose 1,6-bisphosphatase
result in abnormally high levels of lactate in the blood plasma
Defects in this enzyme prevent the entry of lactate into gluconeogenesis, causing
lactate to accumulate in the blood
Homeostatic mechanisms maintain the concentration of glucose in human blood
plasma at about 5 mM. The concentration of free glucose inside a myocyte
(muscle cell) is much lower.
Why is the concentration so low in the cell?
Enzymes inside the cell convert glucose to other molecules
How does ATP regulate the activity of PFK-1?
1. ATP binds to the catalytic site as a substrate, increasing PFK-1 activity.
2. ATP binds to the allosteric site as an inhibitor, decreasing PFK-1 activity.
The regulated steps of glycolysis in intact cells can be identified by studying the
catabolism of glucose in whole tissues or organs. For example, the glucose
consumption by heart muscle can be measured by artificially circulating blood
through an isolated intact heart and measuring the concentration of glucose
before and after the blood passes through the heart.
If the circulating blood is deoxygenated, heart muscle consumes glucose at a
steady rate. When oxygen is added to the blood, the rate of glucose consumption
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
2024/2025
Average Blood Glucose level in humans
60-150 mg/dL
How any cell in the body can use Glucose for energy
Cellular respiration
Glycolisis
the breakdown of glucose by enzymes, releasing energy and pyruvic acid
Overview of Glucose to ATP in cells
glycolysis > Krebs cycle > eletron transport chain (atp)
Fed State
High glucose levels after a meal; cells can use glucose in blood for glycolysis
Glycogen
An extensively branched glucose storage polysaccharide found in the liver and muscle
of animals; the animal equivalent of starch; a storage form of glucose; like a string of
glucose molecules
Which graph correctly illustrates the effect of a negative modifier (effector) on the
velocity curve of an allosteric enzyme? The solid blue curve represents the
unmodified enzyme. The dashed green curve represents the enzyme in the
presence of the effector.
,green curve same shape, more to right than blue curve
Which of the following is NOT true regarding the enzyme chymotrypsin?
Hydrolytic cleavage is achieved through a molecule of water breaking a peptide bond.
Which of the following IS true regarding the enzyme chymotrypsin?
The hydrophobic pocket is the most significant characteristic of the enzyme in
determining where the polypeptide will be cleaved and around which residues cleavage
occurs.
Preparation of nucleophiles is accomplished through the Histidine residue serving as
general base.
Aspartate's hydrogen bonding with Histidine allows for the latter to have a higher pKa,
thus becoming a stronger base.
The oxyanion hole stabilizes carbonyl oxygen through hydrogen bonding with Serine
and Glycine residues.
Chymotrypsin cleaves peptide bonds adjacent to
tyrosines, phenylalanines, and tryptophans (aromatics)
During strenuous activity, the demand for ATP in muscle tissue vastly increases.
In rabbit leg muscle or turkey flight muscle, ATP production is almost exclusively
a product of lactic acid fermentation. Phosphoglycerate kinase and pyruvate
kinase catalyze the two reactions that form ATP in the payoff phase of glycolysis.
If skeletal muscle were devoid of lactate dehydrogenase, could it still generate
, ATP at a high rate by glycolysis in order to carry out strenuous physical activity?
Why or why not?
No. Lactate dehydrogenase recycles NAD+ from the NADH formed during the oxidation
of glyceraldehyde 3-phosphate
Why does a congenital defect in the liver enzyme fructose 1,6-bisphosphatase
result in abnormally high levels of lactate in the blood plasma
Defects in this enzyme prevent the entry of lactate into gluconeogenesis, causing
lactate to accumulate in the blood
Homeostatic mechanisms maintain the concentration of glucose in human blood
plasma at about 5 mM. The concentration of free glucose inside a myocyte
(muscle cell) is much lower.
Why is the concentration so low in the cell?
Enzymes inside the cell convert glucose to other molecules
How does ATP regulate the activity of PFK-1?
1. ATP binds to the catalytic site as a substrate, increasing PFK-1 activity.
2. ATP binds to the allosteric site as an inhibitor, decreasing PFK-1 activity.
The regulated steps of glycolysis in intact cells can be identified by studying the
catabolism of glucose in whole tissues or organs. For example, the glucose
consumption by heart muscle can be measured by artificially circulating blood
through an isolated intact heart and measuring the concentration of glucose
before and after the blood passes through the heart.
If the circulating blood is deoxygenated, heart muscle consumes glucose at a
steady rate. When oxygen is added to the blood, the rate of glucose consumption
