Principles of Biochemistry Test 1 Review Questions

Examples of macromolecules include ____.

proteins

When compared to fatty acids, nucleic acids, and carbohydrates, proteins are found to contain more _____.

nitrogen

The most important function of DNA in prokaryotes and eukaryotes is _____.

to serve as a repository for genetic information

The passage of information from DNA → RNA is known as _____.

transcription

During catabolism…

Large, complex molecules are converted into many smaller, simple molecules

Proteins are made up of long chains of ___.

amino acids attached by peptide (amide) bonds

Genetic information for living things is stored in ___.

DNA, also known as deoxyribonucleic acid

Messenger RNA is a specialized molecule whose most important function is to ___.

carry information form DNA to ribosomes to direct protein synthesis

Amphipathic molecules are likely to be found within cell membranes because ___.

they are soluble in both lipids and aqueous solution and can help stabilize the membrane in contact with the aqueous environment outside the cell

Without knowing the structures of the molecules, you could predict that hydrogen bonds could not form between molecules of ___.

CH4

The most important buffer present in blood plasma is ___.

HCO3- / H2CO3

Acid strength is…

directly proportional to Ka

The strength of acid is ___.

inversely proportional to pKa

In a buffer solution made up of a weak acid and its salt, if the salt concentration is 100 times the concentration of acid, the pH will be ___.

two units above the pK

The weakest acid in the following list is

carbonic acid

A solution having a pH of 5 would have ____ many times as much hydrogen ion concentration as a solution having a pH of 9.

10,000

Hydrophobic molecules are ___.

Generally nonpolar and relatively insoluble in aqueous solutions

To precipitate proteins from solution, technicians often adjust the pH to the isoelectric point of the protein. The purpose in doing this is to ___.

decrease solubility of protein molecule

The zwitterion form of valine ___.

is the form that exists in a solution near a pH of 7.0

Treatment of one mole of glutamic acid with a mole of sodium hydroxide forms monosodium glutamate, a meat tenderizer sometimes known as MSG. If you added one mole of glutamic acid to one mole of sodium hydroxide, the glutamic acid would react first ___.

At the —COOH group having the lowest pK

The pKB s of lysine are 2.18, 8.95, and 10.79. The correct isoelectric point of lysine is ___.

9.87

If a mixture of an acidic, a basic, and a neutral amino acid are placed on an electrophoresis gel or strip at a pH of 7.0, the acidic amino acid will move ___.

toward the positive electrode

If a pentapeptide made up of alanine, phenylalanine, tyrosine, lysine, and valine were added to water, the pH of the solution would probably ___.

rise

For an amino acid to be classified as basic, it must ___.

contain in its structure more basic groups than acidic groups

Hemoglobin contains two α chains of protein and two β chains. The maximum degree of protein structure shown by hemoglobin is ____.

quaternary

Suppose that you determined ΔG for a reaction at room temperature and then carried out the same reaction at a higher temperature. At higher temperatures, ΔG for the reaction will be ___.

a larger negative number than at room temperature

Enzymes have a distinct advantage over nonbiological catalysts because they ___.

are very efficient, specific, and sensitive to control

Most synthetic reactions in which carbon dioxide is used require the vitamin biotin. The biotin becomes covalently bound to a lysine molecule that is part of an enzyme, and the biotin can then attach to and carry the carbon dioxide molecule. Biotin is best referred to as an ___.

coenzyme

If you wanted to explain the concept of Km to someone who didn’t know as much about biochemistry as you, you might say that ___.

Km is the substrate concentration that allows the reaction to proceed at half the maximum velocity

Methanol is a very poisonous substance, accounting for a number of deaths and many cases of blindness yearly. While the methanol itself is sometimes not toxic, it may be metabolized by the liver to more toxic molecules such as formic acid or formaldehyde. Before more efficacious treatments were developed, a person who had ingested methanol was often given a large amount of ethanol orally. The purpose of this treatment was ___ .

To allow the ethanol to act as a competitive inhibitor of the metabolism of methanol

Most coenzymes may be included in classes of foodstuffs known as ___.

vitamins

The major effect of a catalyst on a reaction is to ___.

lower the activation energy

An enzyme in liver that removes glucose from blood has a high Km; another that does the same thing in brain tissue has a small Km. The usefulness of these two different values is that ___.

the enzyme in brain tissue can take glucose from the bloodstream even when levels are low, and the enzyme in liver will not take glucose from blood unless levels are high

A molecule of an enzyme that has a high turnover number ___.

converts substrate to product very rapidly