Chapter 3 practice test
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 3.4) a charged end and a noncharged end three fatty acid molecules, all pointing in different directions two fatty acid molecules pointing in different directions both a saturated fatty acid and an unsaturated fatty acid two charged ends
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 _____. (eText Concept 3.5) 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 amino acids together to form a polypeptide a hydrogen bond joining nucleotides together to form a nucleic acid a covalent bond joining nucleotides together to form a nucleic acid
a covalent bond joining amino acids together to form a polypeptide Correct. The specific type of covalent bond joining two amino acids is a peptide bond.
The alpha helix and beta pleated sheet represent which level of protein structure? (eText Concept 3.5) primary structure secondary structure tertiary structure quaternary structure pentiary structure
secondary structure Correct. Both the alpha helix and the beta pleated sheet are localized regions of polypeptides held in a given structure by hydrogen bonds.
A straight-chain carbon compound constructed from _____ must contain at least one carbon-carbon double bond. (eText Concept 3.1) six hydrogen, two carbon six hydrogen, three carbon six hydrogen, two carbon, one oxygen eight hydrogen, three carbon, three oxygen 14 hydrogen, 6 carbon
six hydrogen, three carbon Correct. There must be a carbon-carbon double bond for this molecule to exist.
In what polysaccharide form do plants store glucose to be available later as an energy source? (eText Concept 3.3) glycogen cellulose starch protein fatty acids
starch Correct. Starch is a glucose storage polymer in plants.
The polysaccharide that you are most likely to have eaten recently is _____. (eText Concept 3.3) chitin starch glucose lactose ribose
starch Correct. Starch is a storage polysaccharide found especially in certain plant tissues.
The lipids that form the main structural component of cell membranes are _____. (eText Concept 3.4) triacylglycerols proteins cholesterol carbohydrates 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.
Cellulose is a _____ made of many _____. (eText Concept 3.3) polypeptide ... monomers carbohydrate ... fatty acids polymer ... glucose molecules protein ... amino acids lipid ... triacylglycerols
polymer ... glucose molecules Correct. Cellulose is a polysaccharide and therefore a polymer, constructed from many monosaccharide glucose monomers.
What is ATP's importance in the cell? (eText Concept 3.1) ATP contains a long hydrocarbon tail and is important in storing energy. ATP can add phosphate groups, thereby releasing energy that can be used in cellular processes. ATP stores the potential to react with water, thereby removing a phosphate group and releasing energy for cellular processes. ATP stores energy in carbonyl groups. When a carbonyl group is removed, energy is released to be used in cellular processes. ATP is an important component of cell membranes because it is nonpolar and hydrophobic.
ATP stores the potential to react with water, thereby removing a phosphate group and releasing energy for cellular processes. Correct. ATP releases energy during a hydrolysis reaction that removes a phosphate group.
What do Alzheimer's, Parkinson's, and mad cow disease have in common?(eText Concept 3.5) They all cause the misfolding of nucleic acids. They all associated with plaque buildup in arteries (atherosclerosis). All are caused by the buildup of misfolded proteins in cells. 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.
All have been associated with the buildup of misfolded proteins in cells. Correct. These diseases and others have been associated with a buildup of misfolded versions of various proteins within cells.
Which of the following functional groups increases the solubility of organic compounds in water? (eText Concept 3.1) -SH -COOH -COH -NH2 All of the listed responses are correct.
All of the listed responses are correct. Correct. All of the functional groups are hydrophilic and thus increase the solubility of organic molecules in water.
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 3.5) denaturing the protein a change in salt concentrations or pH heating the protein mixing in a chemical that removes hydrogen bonds 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.
Which of the following molecules is a monosaccharide? (eText Concept 3.3) C51H98O6 C45H84O8PN C6H12O6 C25H43O8 C22H49O10N5
C6H12O6 Correct. Monosaccharides have molecular formulas that are multiples of CH2O.
Which is an organic molecule? (eText Concept 3.1) Ne O2 CH4 NaCl H2O
CH4
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____. (eText Concept 3.6) DNA proteins cellulose fatty acids sucrose
DNA Correct. The backbone of a nucleic acid consists of alternating sugar and phosphate groups.
Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them? (eText Concept 3.4) Saturated triacylglycerols are fats; unsaturated triacylglycerols are carbohydrates. Saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols. Saturated triacylglycerols have more double bonds than unsaturated triacylglycerols. 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.
Amylase is an enzyme that breaks down starch. Why can't the same enzyme break down cellulose? (eText Concept 3.3) The enzyme cannot attack cellulose because of its helical shape. Cellulose molecules are much too large. Starch is made of glucose; cellulose is made of fructose. The bonds between the monosaccharide monomers in cellulose are much stronger. The monosaccharide monomers in cellulose are bonded together differently than in starch.
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 overall three-dimensional shape of a single polypeptide is called the _____. (eText Concept 3.5) double helix primary structure secondary structure tertiary structure quaternary structure
tertiary structure Correct. The tertiary structure is determined by hydrogen bonds, hydrophobic R groups, ionic bonds between R groups, van der Waals interactions, and disulfide bridges.
In a 1-4 glycosidic linkage, _____. (eText Concept 3.3) the number 1 carbon in one monosaccharide is bound to the number 4 carbon in another monosaccharide the number 1 carbon in one nucleotide is bound to the number 4 carbon in another nucleotide one monosaccharide is bound to four others there are four possible isomers of the structure 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 Correct. Glycosidic linkages, the covalent bonds that link simple sugars, are named according to the carbon atoms they join.
The "primary structure" of a protein refers to _____. (eText Concept 3.5) the α helix or β pleated sheets interactions among the side chains or R groups of the 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
the sequence of amino acids Correct. The primary structure of a protein is its unique sequence of amino acids held together by the peptide type of covalent bond.
One characteristic shared by sucrose, lactose, and maltose is that _____. (eText Concept 3.3) they are all polysaccharides they are all monosaccharides they are all disaccharides they all contain fructose they are all indigestible by humans
they are all disaccharides Correct. A disaccharide consists of two monosaccharides joined together by a glycosidic linkage.
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 3.4) Cholesterol is not important for humans any more. It is a holdover from hunter-gatherer days when food was scarce. Cholesterol is an important energy storage molecule. Cholesterol is an important constituent of nucleotides. Cholesterol is the basis for many important molecules such as sex hormones. Cholesterol aids in the formation of amino acids that are used to build proteins.
Cholesterol is the basis for many important molecules such as sex hormones. Correct. Cholesterol is the basis for many steroid molecules, including sex hormones.
When a protein is denatured, why does it lose its functionality? (eText Concept 3.5) 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. 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. 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. Correct. Denaturation disrupts secondary, tertiary, and quaternary protein structure, causing the protein to lose its form, and thus its 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? (eText Concept 3.3) They have to eat a lot of it. Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units. Cows and other herbivores are exceptions and make some cellulose-digesting enzymes. 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.
Which of the following functional groups is present in all amino acids? (eText Concept 3.1) -SH -COH -OH -NH2 -OPO3-2
NH2 Correct. This is the amino group. This group is present in all amino acids.
To what does the term "polypeptide" refer? (eText Concept 3.5) organic molecules linked by dehydration reactions organic monomers covalently bonded amino acids linked by hydrolysis carbohydrates with a hydrogen bond holding them together None of the listed responses is correct.
None of the listed responses is correct. Correct. A polypeptide is a chain of amino acids that have been linked together by dehydration reactions.
Which of these is a thiol? (eText Concept 3.1) -SH -COH -OH -NH2 None of the listed responses is correct.
None of the listed responses is correct. Correct. A thiol is a molecule containing a sulfhydryl functional group.
Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)? (eText Concept 3.4) Both molecules contain a phosphate group. Triacylglycerols may be saturated or unsaturated, but all phospholipids are saturated. Phospholipids are the primary storage form for fats in our bodies. 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.
A nucleotide is made of which of the following chemical components? (eText Concept 3.6) a nitrogenous base, an amino acid, and a pentose sugar a nitrogenous base, an amino acid, and a phosphate group a nitrogenous base, a phosphate group, and a pentose sugar a nitrogenous base, a fatty acid, and an amino acid a series of nitrogenous bases, a nucleic acid backbone, and a hexose sugar
a 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.
A glucose molecule is to starch as _____. (eText Concept 3.6) a steroid is to a lipid a protein is to an amino acid a nucleic acid is to a polypeptide a nucleotide is to a nucleic acid an amino acid is to a nucleic acid
a nucleotide is to a nucleic acid Correct. Nucleotides are the monomers that make nucleic acid polymers, just as glucose is the monosaccharide (monomer) from which starch (polymer) is constructed.
In a hydrolysis reaction, _____, and in this process water is _____. (eText Concept 3.2) a polymer is broken up into its constituent monomers ... consumed a monomer is broken up into its constituent polymers ... produced monomers are assembled to produce a polymer ... consumed monomers are assembled to produce a polymer ... produced a polymer is broken up into its constituent monomers ... produced
a 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.
What is the three-dimensional shape created by hybrid orbitals that are formed when a carbon atom is covalently bonded with four other atoms? (eText Concept 3.1) a flat sheet with carbon in the center a triangle with carbon in the center a cube with carbon in the center a tetrahedron with carbon in the center All of the listed responses are possible.
a tetrahedron with carbon in the center Correct. The pairs of bonding electrons are oriented as distantly as possible from one another in a tetrahedron with the carbon atom at the center and the other four atoms at the vertices of the tetrahedron.
Manufacturers make vegetable oils solid or semisolid at room temperature by _____. (eText Concept 3.4) 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 adding hydrogen atoms to the single bonds of 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 Correct. 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.
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 3.6) adenine ... thymine adenine ... guanine thymine ... guanine adenine ... cytosine thymine ... cytosine
adenine ... thymine Correct. Adenine and thymine form a complementary base pair.
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 3.3) collagen cellulose linoleic acid chitin glycogen
chitin Correct. Chitin is the structural polysaccharide found in arthropod exoskeletons.
Although the structures of the functional groups that are most important to life vary, they share one thing in common: They _____. (eText Concept 3.1) all contain oxygen all have at least one double bond always cause the carbon to which they are attached to become an asymmetric carbon, thus converting the molecule into an enantiomer all are hydrophilic and increase the organic compound's water solubility force straight chains of carbons into closed rings of carbon End of Question 10
all are hydrophilic and increase the organic compound's water solubility Correct. Functional groups are all hydrophilic
Ethanol, propanol, and methanol are three simple alcohols. They can be grouped together because they _____. (eText Concept 3.1) all share the same functional group: a hydroxyl are soluble in water are hydrophobic all contain a carbonyl group increase the acidity of solutions
all share the same functional group: a hydroxyl Correct. Alcohols are distinguished by the presence of the hydroxyl (-OH) functional group.
Protein molecules are polymers (chains) of _____. (eText Concept 3.5) DNA molecules fatty acid molecules sucrose molecules amino acid molecules purines and pyrimidines
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 3.4) are much larger are not truly polymers do not have specific shapes do not contain carbon do not contain nitrogen and phosphorus atoms
are not truly polymers Correct. 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 these is found in all amino acids? (eText Concept 3.1) -COOH -COH -OH -NH2 both -COOH and -NH2
both -COOH and -NH2 Correct. For a compound to be an amino acid, it must contain at least one carboxyl functional group and one amino functional group. In addition, it may contain one or more of the other functional groups.
Which element is always associated with organic chemistry? (eText Concept 3.1) carbon sulfur nitrogen hydrogen oxygen
carbon
Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least? (eText Concept 3.3) sugar (in the dressing) oil (in the dressing) starch (in the croutons) cellulose (in the lettuce) protein (in the bacon bits)
cellulose (in the lettuce) Correct. Cellulose contains glycosidic linkages that cannot be broken by human digestive enzymes.
Which of the following is a polymer? (eText Concept 3.2) testosterone, a steroid hormone cellulose, a plant cell wall component glucose, an energy-rich molecule triacylglycerol, or fat fructose, a component of sucrose
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.
The subunits (monomers) in cellulose are linked together by _____. (eText Concept 3.3) ionic bonds glycosidic linkages peptide bonds phosphodiester linkages ester linkages
glycosidic linkages Correct. The glucose monomers of cellulose are linked together by a specific type of covalent bond known as a glycosidic linkage.
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 3.2) hydrogen covalent ionic peptide van der Waals
covalent Correct. 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.
What is the process by which monomers are linked together to form polymers? (eText Concept 3.2) hydrolysis monomerization protein formation coiling dehydration or condensation reactions
dehydration or condensation reactions Correct. When monomers are linked together to form a more complex polymer, a water molecule is removed by dehydration (condensation) reactions.
Carbon atoms are the most versatile building blocks of the molecules used by living organisms because _____. (eText Concept 3.1) carbon is the central atom of carbon dioxide, a necessary molecule for photosynthesis carbon is the central atom in urea, a molecule used by many living organisms to transport wastes from the body each carbon atom acts as an intersection point from which a molecule can branch off in up to four directions carbon can combine with hydrogen to form hydrocarbons All of the listed responses are correct.
each carbon atom acts as an intersection point from which a molecule can branch off in up to four directions Correct. Carbon has the potential to form molecules that can be straight, branched, or ringed. Along with the ability to form double and triple bonds, this ability permits the formation of an almost infinite number of different molecules.
Carbohydrates are used in our bodies mainly for _____. (eText Concept 3.3) membrane construction structural molecules, such as hair and fingernails building genetic material energy storage and release lipid storage
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 _____. (eText Concept 3.4) glycosidic linkages ionic bonds peptide bonds phosphodiester linkages ester linkages
ester linkages Correct. In making a fat, each of the three fatty acid molecules is bonded to a glycerol by an ester linkage type of covalent bond.
Glucose and hexanoic acid each contain six carbon atoms, but they have completely different properties. Glucose is a nutrient found in food; hexanoic acid is poisonous. Their differences must be due to different _____. (eText Concept 3.1) monomers macromolecules isomers quaternary structures functional groups
functional groups Correct. Functional groups most commonly determine chemical properties such as the polarity and reactivity of molecules.
Which of the following carbohydrate molecules has the lowest molecular weight? (eText Concept 3.3) sucrose lactose glucose cellulose chitin
glucose Correct. Glucose is a monosaccharide.
A polysaccharide that is used for storing energy in human muscle and liver cells is _____. (eText Concept 3.3) glucose glycogen starch chitin cellulose
glycogen Correct. Humans and other vertebrates store glucose as a polysaccharide called glycogen in their liver and muscles.
Which is the term for compounds that do not mix with water? (eText Concept 3.4) phospholipids hydrophobic hydrophilic proteins hydrogen-bonded
hydrophobic Correct. Hydrophobic compounds are those that are insoluble in water.
The fatty acid tails of a phospholipid are _____ because they _____. (eText Concept 3.4) hydrophobic ... dissolve easily in water hydrophobic ... have no charges to which water molecules can adhere hydrophilic ... consist of units assembled by dehydration reactions hydrophilic ... are easily hydrolyzed into their monomers hydrophobic ... consist of units assembled by dehydration reactions
hydrophobic ... have no charges to which water molecules can adhere Correct. Phospholipid tails, which consist of nonpolar hydrocarbon chains, are hydrophobic.
Which of the following are properties of hydrocarbons? (eText Concept 3.1) hydrophobic, polar, charged hydrophilic, good source of stored energy, consisting primarily of carbon and hydrogen hydrophobic, nonpolar, good source of stored energy hydrophilic, containing numerous carboxyl groups, nonpolar hydrophobic, containing numerous amine groups, polar
hydrophobic, nonpolar, good source of stored energy Correct. Because they are nonpolar, hydrocarbons are hydrophobic. They also provide energy in the forms of things such as fossil fuels and fats.
The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules? (eText Concept 3.4) proteins amino acids lipids carbohydrates nucleic acids
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.
Which of the following lists ranks these molecules in the correct order by size? (eText Concept 3.5) water, sucrose, glucose, protein protein, water, glucose, sucrose water, protein, sucrose, glucose protein, sucrose, glucose, water glucose, water, sucrose, protein
protein, sucrose, glucose, water Correct. In this case, the ranking is from largest to smallest.
Carbohydrates can function in which of the following ways? (eText Concept 3.3) structural support energy storage information storage enzymatic catalysis structural support and energy storage
structural support and energy storage Correct. Carbohydrates function as both storage molecules (starch, glycogen) and as structural support molecules (cellulose).