Chapter 5 Bio

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

All have been associated with the buildup of misfolded proteins in cells.

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

All of the listed responses are correct. Correct. All of the listed responses would affect the shape and therefore the catalytic activity of the enzymatic protein.

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.

Which of the following molecules is a monosaccharide?

C6H12O6 Correct. Monosaccharides have molecular formulas that are multiples of CH2O.

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. Correct. Cholesterol is the basis for many steroid molecules, including sex hormones.

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.

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. Correct. Cows have digestive chambers populated by microorganisms that can produce certain hydrolytic enzymes that cows cannot. The enzymes hydrolyze (digest) the cellulose polymer into glucose monomers.

What is a distinguishing feature of most naturally occurring fats?

Nearly all naturally occurring unsaturated fats have cis double bonds. No. Unsaturated fats with trans double bonds are formed in the industrial process of hydrogenating unsaturated plant oils.

What is a key feature of omega-3 fatty acids that distinguishes them from other types of fatty acids?

None of the listed responses correctly describes a distinguishing key feature of omega-3 fatty acids.

To what does the term "polypeptide" refer?

None of the listed responses is correct

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. Correct. Triacylglycerols consist of three (nonpolar) fatty acid tails attached to a glycerol molecule. Phospholipids have two fatty acid tails and a hydrophilic head containing a negatively charged phosphate group.

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. Correct. Saturated triacylglycerols are saturated with hydrogen atoms

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

The first three listed responses all describe differences.

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. Correct. The glucose monomers in cellulose are bonded in a beta glycosidic linkage, whereas those in starch have an alpha glycosidic linkage. The enzyme amylase is specific for the alpha glycosidic linkage.

If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules form 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 noncharged end Correct. The hydrocarbon tails of phospholipids are hydrophobic and are excluded from water. The negatively charged phosphate group and its attachments form a hydrophilic head that is attracted to water.

The peptide bond is _____.

a covalent bond joining amino acids together to form a polypeptide

A glucose molecule is to starch as _____.

a nucleotide is to a nucleic acid

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

adding hydrogen atoms to the double bonds in the fatty acid hydrocarbon chains No. If hydrogen atoms were removed, additional double bonds would be formed.

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 Correct. Polymers of amino acids are called polypeptides. A protein consists of one or more polypeptides folded into specific conformations.

Lipids differ from other large biological molecules in that they _____. (eText Concept 5.3)

are not truly polymers

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

cellulose (in the lettuce) Correct. Cellulose contains glycosidic linkages that cannot be broken by human digestive enzymes.

Which of the following is a polymer?

cellulose, a plant cell wall component Correct. The polysaccharide cellulose is a major component of plant cell walls. It is a polymer composed of many glucose monomers joined together by glycosidic linkages.

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

chaperonins Correct. Chaperonins shield proteins from "bad influences" (interactions with other molecules in the cytoplasm) while they are folding into their functional forms.

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

chitin Correct. Chitin is the structural polysaccharide found in arthropod exoskeletons.

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

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

dehydration or condensation reactions

Carbohydrates are used in our bodies mainly for _____.

energy storage and release Correct. Simple sugar molecules, stored in polysaccharides such as glycogen in animals and starch in plants, are a major energy source for cellular work

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

ester linkages

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

glucose

A polysaccharide that is used for storing energy in human muscle and liver cells is _____.

glycogen

the subunits (monomers) in cellulose are linked together by _____.

glycosidic linkages

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

hydrophobic Correct. Hydrophobic compounds are those that are insoluble in water.

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 Correct. Steroids, such as estrogen, progesterone, and testosterone, are lipids based on their insolubility in water. The molecules are characterized by a carbon skeleton consisting of four fused rings of carbon atoms.

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

nitrogenous base, a phosphate group, and a pentose sugar Correct. Each nucleotide consists of three parts: an organic molecule, called a nitrogenous base; a 5-carbon sugar, called a pentose; and a phosphate group that serves in the phosphodiester covalent bond that forms a bridge between adjacent nucleotides.

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

oils

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

phospholipids Correct. Phospholipids have a hydrophilic head and two hydrophobic tails. This permits the phospholipids to be arranged in a bilayer, or double layer, which forms a boundary between the cell and its external environment.

Cellulose is a _____ made of many _____.

polymer ... glucose molecules Correct. Cellulose is a polysaccharide and therefore a polymer, constructed from many monosaccharide glucose monomers.

in a hydrolysis reaction, _____, and in this process water is _____.

polymer is broken up into its constituent monomers ... consumed In hydrolysis water is utilized as a reactant; water is not a product of a hydrolysis reaction.

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

protein, sucrose, glucose, water Correct. In this case, the ranking is from largest to smallest.

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

secondary structure

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

starch

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

starch Correct. Starch is a storage polysaccharide found especially in certain plant tissues.

Carbohydrates can function in which of the following ways?

structural support and energy storage

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

tertiary structure

In a 1-4 glycosidic linkage, _____.

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

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 disaccharides Correct. A disaccharide consists of two monosaccharides joined together by a glycosidic linkage.

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

thymine and cytosine