Exam 3

Humans store glucose as:

glycogen

Digestion of starch and glycogen involves:

hydrolysis of glycosidic links between adjacent glucose monomers

Individuals that present with bloating, diarrhea, and dehydration after consumption of dairy products are most likely deficient in:

lactase

Absorption of glucose from the gut through the intestinal epithelial cells into the blood involves all of the following EXCEPT:

phosphorylation of glucose as soon as it enters the epithelial cells

Which statement is INCORRECT?

After dietary glucose enters the blood, it travels immediately to red blood cells

Enzyme A has a Km of 10 micromolar and enzyme B has a Km of 0.1 micromolar. Which of the following statements is CORRECT?

Enzyme A has a higher affinity for its substrate compared with enzyme B

Which of the following statements about protein structure is INCORRECT?

Fibrous proteins stretch easily

Which phrase about an activated intermediate in an enzyme reaction is INCORRECT?

accumulates in the reaction

Maltose

disaccharide with alpha 1-->4 glycosidic link

Which statement about phosphorylation is FALSE?

carried out by phosphatase

Which statement regarding O2 binding by myoglobin and hemoglobin is INCORRECT?

At low oxygen concentrations, hemoglobin binds oxygen more tightly (higher affinity) than does myoglobin

__________ are substrates for plants (autotrophs), __________ are substrates for animals (heterotrophs), while __________ is the source of all energy.

CO2 and water; glucose and O2; solar energy

Which of the following statements is FALSE concerning enzymes and the reactions they catalyze?

Most enzymes can work on a large number of chemically different substrates

Which of the following statements regarding enzymes is/are CORRECT?

b and c are both correct: -enzymes increase reaction rates by lowering the energy of activation for their reaction -enzymes increase reaction rates by increasing the local concentration of reactants

The item labeled Z:

b and c are correct: -is a portion of the protein backbone folded into an alpha helix -an example of the secondary structure of a protein

Lactose is a:

disaccharide of glucose and galactose, found in milk

Humans cannot obtain metabolic energy from cellulose because:

humans do not have an enzyme that can hydrolyze the beta 1-->4 glycosidic links in cellulose polymers

The formation of a disulfide bond is an example of what type of reaction?

oxidation

In living organisms, related chemical reactions are often organized into metabolic pathways. Which of these is NOT usually a feature of a metabolic pathway?

regulation of each enzyme in the pathway

Which of the following statements concerning sickle cell anemia is FALSE?

Sickle cell hemoglobin binds only half as much oxygen as normal hemoglobin

Met-enkephalin is a brain peptide involved in pain sensation. Below is its primary sequence. Which of the following is NOT a valid interpretation of Met-enkephalin's primary structure? Tyr-Gly-Gly-Phe-Met

The amino group of methionine (Met) is not joined to any other amino acid

Metal ions such as Zn++ and Mg++ are often required for enzyme activity. These ions are examples of:

cofactors

Which statement about transport across membranes is INCORRECT?

all are correct: -small hydrophobic molecules can diffuse unaided across membranes -transport against a concentration gradient requires energy -symporters move ions and solutes simultaneously in the same direction - an electrochemical gradient is an unequal distribution of charged ions between two sides of a membrane

Which of the following is NOT an example of allosteric binding or allosteric regulation?

binding of oxygen to myoglobin at low O2 concentration

Cellulose

polysaccharide with only beta 1-->4 glycosidic links

Which statements below correctly describe isozymes?

a and b are both correct: -all isozymes of an enzyme catalyze the same biochemical reaction -isozymes of an enzyme can often be separated from one another by electrophoresis at the appropriate pH

Which of the following statements concerning the interaction labeled Y is/are true?

a and b are both correct: -it is an example of an ionic interaction -this type of interaction would be disrupted at pH 1.0

Which statement about bioenergetics is INCORRECT?

a and d are incorrect: -a +delta G means that a reaction will occur spontaneously -a +delta G means that the products of a reaction have less energy than the reactants

The branched-chain structure of glycogen is a wise metabolic strategy because:

it allows for very rapid mobilization of free glucose monomers

What is the effect of an enzyme on the equilibrium constant for the reaction it catalyzes?

it has no effect on the equilibrium constant

Which statement about carbohydrate digestion is CORRECT?

it involves di-saccharidases in the small intestine

Amylopectin

polysaccharide with alpha 1-->4 and alpha 1-->6 glycosidic links