Unit 3 Homework (Extra credit)

Some proteins serve as _______, which increase the rate of chemical reactions.

enzymes

Which type of enzyme is released outside of a cell?

extracellular enzyme

Denatured proteins are usually biologically active.

false

During a process called dissociation, the polypeptides of a protein with quaternary structure separate and unfold, losing their individual tertiary structure.

false

The final 3-D shape of a protein is determined entirely by its primary structure.

false

quaternary structure

only found in proteins composed of more than one polypeptide chain Refers to the way several different polypeptide chains fit together to form the final protein

The special type of covalent bond found in a protein linking amino acids together is a(n)

peptide bond

What type of bonds link individual amino acids together?

peptide bonds

The _____ level of protein structure is the linear sequence of amino acids.

primary

Enzymes are

proteins

In feedback inhibition, the inhibitor of the biochemical pathway is often

the final product of the biochemical pathway.

When normal environmental conditions are reestablished after protein denaturation, almost all proteins can spontaneously refold back into their natural shape.

false

What changes are associated with a spontaneous reaction?

A negative delta G, which indicates the energy of the reactants is more than the energy of the products.

In the example shown, which best describes the role of thiamine pyrophosphate in the reaction to cleave pyruvate?

It behaves like a catalyst and is not consumed during the reaction.

If a chemical that inhibits Enzyme #3 was added to the system containing the biochemical pathway illustrated in the animation, which of the following would result?

Product #2 would accumulate in the system. Substrate #3 would accumulate in the system. Substrate #4 would be depleted in the system. The final product would be depleted in the system.

a. B is influenced by temperature b. A is lowered by an enzyme c. B is lowered by an enzyme

a. True b. True c. False

When proteins are denatured, which type of bond is NOT disturbed?

covalent

Which part of an enzyme interacts with a substrate?

active site

Enzymes catalyze reactions by

lowering the activation energy

What happens to sucrase when it binds to sucrose?

Sucrase goes through a conformational change.

In the example above, how does the final product of the pathway inhibit the pathway?

By binding to an allosteric site of the first enzyme in the pathway.

Chronic Myelogenous Leukemia (CML) is a type of cancer that is caused by a specific chromosomal alteration that leads to the inappropriate expression of a kinase called Abl. Kinases are enzymes that put phosphate groups onto macromolecules such as proteins. A drug used to treat CML, imatinib, binds to the active site of Abl kinase. Why does this drug work to treat this type of cancer?

By binding to the active site, the drug prevents the ability of Abl kinase to bind to its substrate.

Consider the biochemical pathways illustrated below. Product D will act as an allosteric inhibitor of what enzyme to regulate its own production?

E2

A protein that has many hydrophobic R-groups pointing to the outside of the protein would be found where?

Embedded within a membrane

Your friend is studying a specific exergonic reaction. Your friend hypothesizes that the addition of enzyme X will reduce the delta-G of this reaction, thus allowing it to proceed spontaneously. What do you think of your friend's hypothesis?

Enzymes do not change delta-G, so this hypothesis does not fit with what is known about this reaction.

If a protein's environment is altered, the protein may change its shape or even unfold completely, a process called dissociation.

False

Proteins have a narrow range of conditions in which they fold properly; outside that range, proteins tend to renature.

False

True or False: An enzyme binds the product more tightly than the substrate.

False

Consider the biochemical pathways illustrated below. If product D is abundant, why is it preferable to inhibit E2 rather than E1?

Inhibition of E2 will prevent the production of D, but still allow synthesis of E

FAD is a coenzyme associated with the succinate dehydrogenase enzyme complex in the respiratory citric acid cycle and electron transport chain. Succinate dehydrogenase becomes reduced due to the oxidation of succinate. Which of the following would occur if the FAD coenzyme were not associated with succinate dehydrogenase?

Succinate dehydrogenase would not oxidize succinate

A mutation occurred in the gene that encodes the enzyme sucrase, resulting in a single amino acid substitution in the active site of the enzyme; a polar amino acid changed to a nonpolar amino acid. What is probably the result of this mutation?

Sucrase will not be able to bind sucrose in the active site.

If thiamine pyrophosphate was not available to the enzyme in the animation which of the following would occur?

The enzyme would not be able to cleave pyruvate

primary structure

The first level of protein structure; the specific sequence of amino acids making up a polypeptide chain.

tertiary structure

The overall 3-D shape of a polypeptide or protein Results from the bending and folding of a polypeptide chain that occurs due to a variety if interaction between the amino acid side chains

An enzyme may catalyze a reaction by stressing or destabilizing the bonds of the substrates. The most critical stage in the enzymatic reaction is the

Transition state

Consider the biochemical pathway used to synthesize the amino acid proline. A large increase in the level of proline will most likely lead to

a decrease in proline production.

Secondary structure

alpha helix or beta pleated sheet results from hydrogen bonds between polar group in the polypeptide backbone repeated pattern of coiling or folding within a polypeptide chain

The subunits of proteins are

amino acids

The enzyme in the animation is most likely catalyzing what

an anabolic reaction.

In the stable form of protein, what is generally oriented to the interior of the protein molecule?

hydrophobic portions

Consuming B vitamins in excess of need will

increase B vitamins in urine.

Protein function is determined by protein

shape

Which of the following binds most tightly to the active site of an enzyme?

substrate

What function do many B vitamins serve in the production of energy?

they function as co-enzymes

Cells use chaperones both to accomplish the original folding of some proteins and to restore the structure of incorrectly folded ones.

true

If the 3-D structure of a protein depends only on its primary structure and the surrounding environmental conditions, then when the protein is denatured and subsequently returned to its native conditions it will spontaneously refold back into its native structure.

true

Proteins can denature when the pH, temperature, or ionic concentration of the surrounding solution changes.

true

Some diseases may occur because a protein with the correct amino acid sequence fails to correctly fold into its final functional form.

true

Some proteins require other proteins called chaperones in order to correctly fold into their normal 3-D shape.

true

Sucrase uses ____ to cleave sucrose into two monosaccharides.

water

When forming a semi-solid gel such as gelatin, which molecules does the process of protein coagulation entrap?

water molecules