Chapter 5 Bio 1107

What is the process by which monomers are linked together to form polymers? (eText Concept 5.1)

* coiling
* protein formation
* hydrolysis
* monomerization
* dehydration or condensation reactions

dehydration or condensation reactions

in a hydrolysis reaction, _____, and in this process water is _____. (eText Concept 5.1)

* a monomer is broken up into its constituent polymers … produced
* monomers are assembled to produce a polymer … produced
* monomers are assembled to produce a polymer … consumed
* a polymer is broken up into its constituent monomers … produced
* a polymer is broken up into its constituent monomers … consumed

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.

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. (eText Concept 5.1)

* hydrogen
* ionic
* van der Waals
* peptide
* covalent

covalent

Which of the following is a polymer? (eText Concept 5.2)

cellulose, a plant cell wall component
fructose, a component of sucrose
glucose, an energy-rich molecule
triacylglycerol, or fat
testosterone, a steroid hormone

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.

Cellulose is a _____ made of many _____. (eText Concept 5.2)

*polymer … glucose molecules
* carbohydrate … fatty acids
* lipid … triacylglycerols
* protein … amino acids
* polypeptide … monomers

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

Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass? (eText Concept 5.2)

* Cows and other herbivores are exceptions and make some cellulose-digesting enzymes.
* They have to eat a lot of it.
* Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units.
* The flat teeth and strong stomach of herbivores break the cellulose fibers so that the cows get enough nutrition from the cell contents.
* All of the listed responses are correct.

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.

In what polysaccharide form do plants store glucose to be available later as an energy source? (eText Concept 5.2)

* protein
* starch
* glycogen
* cellulose
* fatty acids

starch

Which of the following carbohydrate molecules has the lowest molecular weight? (eText Concept 5.2)

* glucose
* cellulose
* sucrose
* chitin
* lactose

glucose

Which of the following molecules is a monosaccharide? (eText Concept 5.2)

* C25H43O8
* C22H49O10N5
* C51H98O6
* C45H84O8PN
* C6H12O6

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

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 _____. (eText Concept 5.2)

* chitin
* glycogen
* cellulose
* collagen
* linoleic acid

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

Carbohydrates are used in our bodies mainly for _____. (eText Concept 5.2)

* building genetic material
* lipid storage
* structural molecules, such as hair and fingernails
* energy storage and release
* membrane construction

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

The polysaccharide that you are most likely to have eaten recently is _____. (eText Concept 5.2)

* glucose
* starch
* ribose
* chitin
* lactose

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

One characteristic shared by sucrose, lactose, and maltose is that _____. (eText Concept 5.2)

* they are all disaccharides
* they are all indigestible by humans
* they are all polysaccharides
* they all contain fructose

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

A polysaccharide that is used for storing energy in human muscle and liver cells is _____. (eText Concept 5.2)

* chitin
* glucose
* starch
* glycogen
* cellulose

glycogen

Carbohydrates can function in which of the following ways? (eText Concept 5.2)

* structural support
* energy storage
* information storage
* enzymatic catalysis
* structural support and energy storage

structural support and energy storage

In a 1-4 glycosidic linkage, _____. (eText Concept 5.2)

* one monosaccharide is bound to four others
* the number 1 carbon in one monosaccharide is bound to the number 4 carbon in another monosaccharide
* there are four possible isomers of the structure
* the number 1 carbon in one nucleotide is bound to the number 4 carbon in another nucleotide
* one glycerol molecule is bound to four fatty acids

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

Amylase is an enzyme that breaks down starch. Why can’t the same enzyme break down cellulose? (eText Concept 5.2)

* The enzyme cannot attack cellulose because of its helical shape.
* The monosaccharide monomers in cellulose are bonded together differently than in starch.
* Cellulose molecules are much too large.
* The bonds between the monosaccharide monomers in cellulose are much stronger.
* Starch is made of glucose; cellulose is made of fructose.

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.

the subunits (monomers) in cellulose are linked together by _____. (eText Concept 5.2)

* glycosidic linkages
* peptide bonds
* ionic bonds
* phosphodiester linkages
* ester linkages

glycosidic linkages

Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least? (eText Concept 5.2)

* cellulose (in the lettuce)
* starch (in the croutons)
* protein (in the bacon bits)
* sugar (in the dressing)
* oil (in the dressing)

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

What is a distinguishing feature of most naturally occurring fats? (eText Concept 5.3)

* Nearly all naturally occurring unsaturated fats have cis double bonds.
* Most unsaturated fats have trans double bonds, causing a kink in the hydrocarbon chain wherever they occur.
* All organisms share an equal ratio of saturated and unsaturated fatty acids.
* They all share four fused rings as a carbon skeleton.
* They are distinguished from other lipid forms by their chief role as components of cell membranes.

End of Question 20

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? (eText Concept 5.3)

* It is one of the only unsaturated fatty acids that is produced by humans.
* Omega-3 fatty acids are distinguished by the presence of three trans double bonds in their hydrocarbon chain.
* Omega-3 fatty acids are typically lacking in a vegetarian diet and must be provided by taking animal-derived supplements.
* Like other saturated fatty acids, a diet rich in omega-3 fatty acids can promote plaque formation in the blood vessels.
* None of the listed responses correctly describes a distinguishing key feature of omega-3 fatty acids

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

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

* do not contain nitrogen and phosphorus atoms
* do not have specific shapes
* are much larger
* are not truly polymers
* do not contain carbo

are not truly polymers

Which is the term for compounds that do not mix with water? (eText Concept 5.3)

* proteins
* hydrophilic
* hydrogen-bonded
* phospholipids
* hydrophobic

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

Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them? (eText Concept 5.3)

* Saturated triacylglycerols have more double bonds than unsaturated triacylglycerols.
* Saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols.
* Saturated triacylglycerols are fats; unsaturated triacylglycerols are carbohydrates.
* Saturated triacylglycerols are liquid at room temperature.
* All of the listed responses are correct.

Saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols. Correct. Saturated triacylglycerols are saturated with hydrogen atoms

The lipids that form the main structural component of cell membranes are _____. (eText Concept 5.3)

* carbohydrates
* triacylglycerols
* cholesterol
* proteins
* phospholipids

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.

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 _____. (eText Concept 5.3)

* two charged ends
* three fatty acid molecules, all pointing in different directions
* a charged end and a noncharged end
* both a saturated fatty acid and an unsaturated fatty acid
* two fatty acid molecules pointing in different directions

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.

Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)? (eText Concept 5.3)

* Both molecules contain a phosphate group.
* Phospholipids are the primary storage form for fats in our bodies.
* Triacylglycerols may be saturated or unsaturated, but all phospholipids are saturated.
* Phospholipid molecules have a distinctly polar "head" and a distinctly nonpolar "tail," whereas triacylglycerols are predominantly nonpolar.
* In nature, phospholipids occur in fused rings (sterol form), whereas triacylglycerols maintain a straight-chain form.

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.

The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules? (eText Concept 5.3)

* proteins
* lipids
* amino acids
* nucleic acids
* carbohydrates

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.

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? (eText Concept 5.3)

* Cholesterol aids in the formation of amino acids that are used to build proteins.
* Cholesterol is an important energy storage molecule.
* Cholesterol is an important constituent of nucleotides.
* Cholesterol is not important for humans any more. It is a holdover from hunter-gatherer days when food was scarce.
* Cholesterol is the basis for many important molecules such as sex hormones.

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

Manufacturers make vegetable oils solid or semisolid at room temperature by _____. (eText Concept 5.3)

* adding hydrogen atoms to the single bonds of the fatty acid hydrocarbon chains
* adding hydrogen atoms to the double bonds in the fatty acid hydrocarbon chains
* removing hydrogen atoms and forming additional double bonds in the fatty acid hydrocarbon chains
* removing hydrogen atoms and forming additional single bonds in the fatty acid hydrocarbon chains
* None of the listed responses is correct.

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.

Which of the following is the major energy storage compound of plant seeds? (eText Concept 5.3)

* cellulose
* glycogen
* lipids
* amylose
* oils

oils

Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by _____. (eText Concept 5.3)

* ester linkages
* glycosidic linkages
* peptide bonds
* ionic bonds
* phosphodiester linkages

ester linkages

The fatty acid tails of a phospholipid are _____ because they _____. (eText Concept 5.3)

* hydrophobic … have no charges to which water molecules can adhere
* hydrophobic … dissolve easily in water
* hydrophobic … consist of units assembled by dehydration reactions
* hydrophilic … consist of units assembled by dehydration reactions
* hydrophilic … are easily hydrolyzed into their monomers

hydrophobic … have no charges to which water molecules can adhere

The overall three-dimensional shape of a single polypeptide is called the _____. (eText Concept 5.4)

* secondary structure
* primary structure
* tertiary structure
* double helix
* quaternary structure

tertiary structure

When a protein is denatured, why does it lose its functionality? (eText Concept 5.4)

* Denaturation destroys the primary structure of the protein, and the protein breaks down to monomers.
* Different amino acids are substituted into the sequence, so the protein’s properties change.
* 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.
* Denaturation breaks the covalent bonds that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.
* The protein’s pH changes, causing it to 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 lists ranks these molecules in the correct order by size? (eText Concept 5.4)

* water, sucrose, glucose, protein
* protein, sucrose, glucose, water
* protein, water, glucose, sucrose
* water, protein, sucrose, glucose
* glucose, water, sucrose, protei

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

To what does the term "polypeptide" refer? (eText Concept 5.4)

* organic molecules linked by dehydration reactions
* carbohydrates with a hydrogen bond holding them together
* amino acids linked by hydrolysis
* organic monomers covalently bonded
* None of the listed responses is correct.

None of the listed responses is correct

Enzyme molecules require a specific shape to perform their catalytic function. Which of the following might alter the shape of an enzymatic protein? (eText Concept 5.4)

* mixing in a chemical that removes hydrogen bonds
* a change in salt concentrations or pH
* heating the protein
* denaturing the protein
* All of the listed responses are correct.

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.

the alpha helix and beta pleated sheet represent which level of protein structure? (eText Concept 5.4)

* secondary structure
* pentiary structure
* tertiary structure
* primary structure
* quaternary structure

secondary structure

The peptide bond is _____. (eText Concept 5.4)

* a covalent bond joining amino acids together to form a polypeptide
* a hydrogen bond joining amino acids together to form a polypeptide
* a covalent bond joining simple sugars together to form a polypeptide
* a covalent bond joining nucleotides together to form a nucleic acid
* a hydrogen bond joining nucleotides together to form a nucleic acid

a covalent bond joining amino acids together to form a polypeptide

Protein molecules are polymers (chains) of _____. (eText Concept 5.4)

* sucrose molecules
* DNA molecules
* amino acid molecules
* purines and pyrimidines
* fatty acid molecules

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

the "primary structure" of a protein refers to _____. (eText Concept 5.4)

* interactions among the side chains or R groups of the amino acids
* the α helix or β pleated sheets
* the sequence of amino acids
* coiling due to hydrogen bonding between amino acids
* the weak aggregation of two or more polypeptide chains into one functional macromolecule

the sequence of amino acids

Which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form? (eText Concept 5.4)

* fibrous proteins
* enzymes
* receptor proteins
* antibodies
* chaperonins

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

What do Alzheimer’s, Parkinson’s, and mad cow disease have in common?(eText Concept 5.4)

* They all cause the misfolding of nucleic acids.
* All are associated with the buildup of lipids in brain cells due to faulty lysosome activity.
* All have been associated with the buildup of misfolded proteins in cells.
* They all associated with plaque buildup in arteries (atherosclerosis).
* All are caused by the buildup of misfolded proteins in cells.

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

A glucose molecule is to starch as _____. (eText Concept 5.5)

* a nucleic acid is to a polypeptide
* a protein is to an amino acid
* a nucleotide is to a nucleic acid
* a steroid is to a lipid
* an amino acid is to a nucleic acid

a nucleotide is to a nucleic acid

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____. (eText Concept 5.5)

* proteins
* DNA
* sucrose
* cellulose
* fatty acids

DNA

On the basis of the principle of complementary base pairing, you would expect the percentage of _____ to be equal to the percentage of _____. (eText Concept 5.5)

* adenine … thymine
* thymine … guanine
* thymine … cytosine
* adenine … guanine

adenine … thymine

Which of the following are pyrimidines found in the nucleic acid DNA? (eText Concept 5.5)

* thymine and cytosine
* guanine and cytosine
* thymine and adenine
* uracil and guanine
* adenine and guanine

thymine and cytosine

Which of the following describes a difference between DNA and RNA? (eText Concept 5.5)

* 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.
* They contain different sugars.
* The first and second listed responses are correct differences.
* The first three listed responses all describe differences.

The first three listed responses all describe differences.

A nucleotide is made of which of the following chemical components? (eText Concept 5.5)

* a series of nitrogenous bases, a nucleic acid backbone, and a hexose sugar
* a nitrogenous base, an amino acid, and a pentose sugar
* a nitrogenous base, an amino acid, and a phosphate group
* a nitrogenous base, a fatty acid, and an amino acid
* a nitrogenous base, a phosphate group, and a pentose sugar

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 true regarding complementary base pairing in DNA and RNA molecules? (eText Concept 5.5)

* Complementary base pairing within single strands of DNA and RNA gives them particular three-dimensional structures that are necessary for their function.
* Complementary base pairing promotes an antiparallel orientation in the structure of 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.
* Although a DNA molecule demonstrates complementary base pairing between two DNA polynucleotides to form a double helix, an RNA molecule can only base pair along stretches of nucleotides in the same RNA molecule, such as in transfer RNA molecules.
* None of the listed responses is correct

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.