BSC 114- Chapter 5 Practice Test

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

DNA (The backbone of a nucleic acid consists of alternating sugar and phosphate groups.)

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

dehydration reaction (When monomers are linked together to form a more complex polymer, a water molecule is removed by dehydration reactions.)

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 molecule by an ester linkage type of covalent bond.)

The a helix and B pleated sheet represent which level of protein structure?

secondary structure (Both the a helix and B pleated sheet are localized regions of polypeptides held in a given structure by hydrogen bonds.)

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

starch (Starch is a glucose storage polymer in plants.)

Carbohydrates can function in which of the following ways?

structural support and energy storage (Carbohydrates function as both storage molecules (starch, glycogen) and structural support molecules (cellulose).)

The overall three-dimensional shape of a single polypeptide is called its ____.

tertiary structure (The tertiary structure is determined by hydrogen bonds, hydrophobic R groups, ionic bonds between R groups, van der Waals interactions, and disulfide bridges.)

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

the sequence of amino acids along a polypeptide chain

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

they are all disaccharides (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

Which of the following lists rank these molecules in the correct order by size from smallest to largest?

water,glucose, sucrose, protein

What describes the difference between DNA and RNA?

-RNA molecules generally consist of a singly polynucleotide chain, whereas DNA molecules generally consist of two polynucleotide chains organized into a double helix. -Both molecules contain adenine, guanine and cytosine, but DNA also contains thymine and RNA also contains uracil. -They contain different sugars.

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

-a change in salt concentrations or pH -denaturing the protein -treating the protein with a chemical that breaks hydrogen bonds -heating the protein

Which of the following molecules is a monosaccharide?

C6H12O6 (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 precursor for many important molecules such as sex hormones.

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

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

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 (Monomers are joined together by a dehydration reaction in which two molecules are covalently bonded to each other through the loss of a water molecule.)

Carbohydrates are used in our bodies mainly for ____.

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

The sex hormones estradiol and testosterone belong to which class of molecules?

lipids (Steroids, such as estradiol 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.)

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

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

Which of the following represents a specific description of a polypeptide?

A polypeptide is a chain of amino acids that have been linked together by dehydration reactions.

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

All are associated with 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. (Complementary base pairing provides an accurate way to synthesize a new DNA molecule from an existing one, and gives RNA molecule partifulcar three-dimensional shapes necessary for their function.)

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

Denaturation breaks the intramolecular 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. (Denaturation disrupts secondary, tertiary, and quaternary protein structure, causing the protein to lose its form, and thus its function.)

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

For carbon skeletons of equal length, saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols do.

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. (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.)

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

Phospholipid molecule have a distinctly polar "head" and a distinctly nonpolar "tail", whereas triacylglycerols are predominantly nonpolar. (Triacyglycerols 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.)

Amylase is an enzyme that breaks down starch. Why cannot the same enzyme break down cellulose?

The monosaccharide monomers in cellulose are bonded together differently than those in starch. (The glucose monomers in cellulose are bonded in a B glycosidic linkage, whereas those in starch have an a glycosidic linkage. This enzyme amylase is specific for the a 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 or polar end or nonpolar end (The nonpolar hydrocarbon tails of phospholipids are hydrophobic-that is, they 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

Which of the following lists represents the chemical components of a nucleotide?

a nitrogenous base, a phosphate group, and a pentose sugar (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.)

A glucose molecule is to starch as ____.

a nucleotide is to a nucleic acid (Nucleotides are the monomers that make nucleic acid polymers, just as glucose is the monosaccharide (monomer) from which starch (polymer) is constructed.)

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

a polymer is broken up into its constituent monomers...consumed (The meaning of hydrolysis is "to break with water".)

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

adding hydrogen atoms to the fatty acid hydrocarbon chains, thereby converting carbon-carbon double bonds to single bonds (The phrase "hydrogenated vegetable oils" found on food labels means that unsaturated fats have been synthetically converted to saturated fats by the addition of hydrogen.)

Based on 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 (Polymers of amino acids are called polypeptides. A protein consists of one or more polypeptides folded into specific conformations.)

Lipids differ from the large biological molecules in that they____.

are not truly polymers (Lipids are not all made of the same type of monomer. Their association as a group (fats, phospholipids, and steroids) is related to their solubility behavior.)

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) (Cellulose contains glycosidic linkages that cannot be broken by human digestive enzymes.)

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

chitin (Chitin is the structural polysaccharide found in arthropod exoskeletons.)

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

glycogen (Humans and other vertebrates store glucose as a polysaccharide called glycogen in their liver and muscles.)

The subunits (monomers) in cellulose are linked together by____.

glycosidic linkages (The glucose monomers of cellulose are linked together by a specific type of covalent bond known as the glycosidic linkage.)

Which of the following terms can be correctly used to describe 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 lipids that form the main structural component of cell membranes are ____.

phospholipids (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.)