Module 5

A nucleotide is made of which of the following chemical components?

A nitrogenous base, a phosphate group, and a pentose sugar.

Which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form?

Chaperonins: shield proteins from "bad influences" while they are folding into their functional forms.

High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place?

Cholesterol is the basis for many important molecules such as sex hormones.

Which of the following describes a difference between DNA and RNA?

RNA molecules consist of a single polynucleotide chain, whereas DNA molecules consist of two polynucleotide chains organized into a double helix; one of their nitrogenous bases is different; and they contain different sugars

The alpha helix and beta pleated sheet represent which level of protein structure?

Secondary structure

glucose molecule is to starch as __________.

a nucleotide is to a nucleic acid

The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules?

lipids

The overall three-dimensional shape of a single polypeptide is called the __________.

tertiary structure

The "primary structure" of a protein refers to __________.

the sequence of amino acids

What do Alzheimer's, Parkinson's, and mad cow disease have in common?

All are caused by the buildup of misfolded proteins in cells.

Which of the following is true regarding complementary base pairing in DNA and RNA molecules?

Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________.

DNA

When a protein is denatured, why does it lose its functionality?

Denaturation breaks the weak bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.

Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)?

Phospholipid molecules have a distinctly polar "head" and a distinctly nonpolar "tail," whereas triacylglycerols are predominantly nonpolar.

Which of the following are pyrimidines found in the nucleic acid DNA?

Thymine and cytosine

Phospholipids are forced into this orientation because phospholipids have __________.

a charged end and a noncharged end

The peptide bond is __________.

a covalent bond joining amino acids together to form a polypeptide

Manufacturers make vegetable oils solid or semisolid at room temperature by __________.

adding hydrogen atoms to the double bonds in the fatty acid hydrocarbon chains

On the basis of the principle of complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________.

adenine; thymine

Enzyme molecules require a specific shape to perform their catalytic function. Which of the following might alter the shape of an enzymatic protein?

all the listed responses are correct: change in salt concentration or pH; mixing in a chemical that removes hydrogen bonds; heating the protein; denaturing the protein

Protein molecules are polymers (chains) of __________.

amino acid molecules

Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by __________.

ester linkages In making a fat, each of the three fatty acid molecules is bonded to a glycerol by an ester linkage type of covalent bond.

The fatty acid tails of a phospholipid are __________ because they __________.

hydrophobic; have no charges to which water molecules can adhere

To what does the term "polypeptide" refer?

none

Which of the following is the major energy storage compound of plant seeds?

oils