HESI - Chapter 5 Questions/Answers

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

1. RNA molecules consist of a single polynucleotide chain, whereas DNA molecules consist of two polynucleotide chains organized into a double helix. 2. One of their nitrogenous bases is different. 3. They contain different sugars. (the first three choices all describe differences)

Which one of the following molecules is in a monosaccharide?

C6H1206

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

What is the process by which monomers are linked together to form polymers?

Coiling

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

DNA

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

Denaturation breaks the weak bonds, such as hydrogen bonds and van der Walls interactions, that hold the protein in its 3-dimensional shape. Without the proper shape, the protein cannot function.

Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?

Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units.

To what does the term "polypeptide" refer?

No answer listed (none of the above)

Amylase is an enzyme that breaks down starch. Why can't the same enzyme break down cellulose?

The monosaccharide monomers in cellulose are bonded together differently than in starch.

In a 1-4 glycosidic linkage

The number 1 carbon in one monsaccharide is bound to the number 4 carbon in another monosaccharide.

If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules from a 'ball of spaghetti" with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have ____.

a charged end and a non-charged end

The peptide bond is ____.

a covalent bond joining amino acids together to from a polypeptide

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

a nitrogenouse base, a phosphate group, and a pentose sugar

A glucose molecule is to starch as _____.

a nucleotide is to a nucleic acid

In a hydrolysis reaction ____ and in this process water is ____.

a polymer is broken up into its constituent monomers; consumed

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

adding hydrogen atoms to the double bonds in the fatty and 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

Protein molecules are polymers (chains) of ____.

amino acid molecules

Lipids differ from other large biological molecules in that they ____.

are not truly polymers

Which one of the following components of a tossed salad will pass through the human digestive tract and be digested the lease?

cellulose (in the lettuce)

Which of the following is a polymer?

cellulose, a plant cell wall component

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

chaperonins

At a conference, the speaker's grand finale was sauteing meal worms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide ____.

chitin

The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) ____ bond.

covalent

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

denaturing the protein, a change in salt concentrations or pH, heating the protein, mixing in a chemical that removes hydrogen bonds (all of the above)

Carbohydrates are used in our bodies mainly for ____.

energy storage and relase

Which one of the following carbohydrate molecules has the lowest molecular weight?

glucose

A polsaccharide that is used for storing energy in human muscle and liver cells is ____.

glycogen

The subnits (monomers) in cellulose are linked together by ____.

glycosidnic linkages

Which is the term for compounds that do not mix with water?

hydrophobic

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

hydrophobic; have no charges to which water molecules can adhere

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

lipids

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

oils

Which of the following lists ranks these molecules in the correct order by size?

protein, sucrose, glucose, water

Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them?

saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols.

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

secondary structure

In what polysaccharide from do plants store glucose to be available later as an energy source?

starch

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

One characteristic shared by sucrose, lactose, and maltose is that ____,

they are all disaccarides

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

thymine and cytosine

The lipids that form the main structural component of cell membranes are ____.

phospholipids

Carbohydrates can function in which of the following ways?

structural support AND energy storage

Which one 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.

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

ester linkages

Cellulose is a ____ made of many ____.

polymer; glucose molecules

The polysaccharide that you most likely to have eaten recently is ____.

starch