Biology Exam 2

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In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by

polar covalent bonds.

The partial negative charge in a molecule of water occurs because

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S

will not form hydrogen bonds with each other

Which of the following effects is produced by the high surface tension of water?

A water strider can walk across the surface of a small pond.

Liquid water's high specific heat is mainly a consequence of the

absorption and release of heat when hydrogen bonds break and form

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

the release of heat by the formation of hydrogen bonds

Why does ice float in liquid water?

Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

Hydrophobic substances such as vegetable oil are

nonpolar substances that repel water molecules.

One mole (mol) of glucose (molecular mass = 180 daltons) is

both 180 grams of glucose and 6.02 × 10^23 molecules of glucose

How many molecules of glycerol (; molecular mass = 92) would be present in 1 L of a 1 M glycerol solution?

6.02 × 10^23

The element present in all organic molecules is

Carbon

The complexity and variety of organic molecules is due to

the chemical versatility of carbon atoms.

How many electron pairs does carbon share in order to complete its valence shell?

4

A carbon atom is most likely to form what kind of bond(s) with other atoms?

Covalent

Which of the following statements best describes the carbon atoms present in a seed-eating bird?

They were incorporated into organic molecules by plants, they were processed into sugars through photosynthesis, and they are ultimately derived from carbon dioxide

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

Which of the following statements correctly describes cis-trans isomers?

They have variations in arrangement around a double bond.

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that

are mirror images of one another.

What determines whether a carbon atom's covalent bonds to other atoms are in a tetrahedral configuration or a planar configuration?

the presence or absence of double bonds between the carbon atom and other atoms

Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will

be more constrained in structure.

A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?

It should dissolve in water.

Which of the following is a false statement concerning amino groups?

They are nonpolar.

Which two functional groups are always found in amino acids?

carboxyl and amino

Amino acids are acids because they always possess which functional group?

carboxyl

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other?

Testosterone and estradiol have different functional groups attached to the same carbon skeleton.

Which polymers are composed of amino acids?

Protiens

Which of the following is not attached to the central carbon atom in an amino acid?

an oxygen

Which part of an amino acid is always acidic?

Carboxyl functional group

Which monomers make up RNA?

Nucleotides

Which of the following statements about the formation of polypeptides from amino acids is true?

A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.

True

In animal metabolism, most of the monomers released by digestion of food macromolecules are metabolized to provide energy. Only a small portion of these monomers are used for synthesis of new macromolecules. The net result is that

water is consumed by animal metabolism.

What is the chemical reaction mechanism by which cells make polymers from monomers?

dehydration reactions

How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?

10

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down?

glycogen

On food packages, to what does the term insoluble fiber refer?

cellulose

Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?

as a disaccharide

Which of the following is true of both starch and cellulose?

They are both polymers of glucose.

Which of the following is true of cellulose?

It is a major structural component of plant cell walls.

Humans can digest starch but not cellulose because

humans have enzymes that can hydrolyze the α glycosidic linkages of starch but not the β glycosidic linkages of cellulose.

Which molecule is not a carbohydrate?

Lipid

Which of the following statements about monosaccharide structure is true?

Monosaccharides can be classified according to the spatial arrangement of their atoms.

True or false? Peptidoglycan is a polysaccharide found only in bacteria.

True.

Which complex carbohydrate contains only a-1,4-glycosidic linkages?

Amylose

Which of the following complex carbohydrates is listed with its correct function?

Cellulose: structural component of plant cell walls

Which polysaccharide contains a modified monosaccharide?

Peptidoglycan

Glycogen is _____.

a polysaccharide found in animals

glucose + glucose —> _____ by _____.

maltose + water ... dehydration synthesis

Which of these is a source of lactose?

milk

Which of these is a polysaccharide?

cellulose

_____ is the most abundant organic compound on Earth.

Cellulose

Which of the following statements is true for the class of biological molecules known as lipids?

They are insoluble in water.

The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. What is the result of adding hydrogens to vegetable oil?

The hydrogenated vegetable oil stays solid at room temperature

Which of the following is true regarding saturated fatty acids?

They are the principal molecules in lard and butter.

Which of these is rich in unsaturated fats?

Olive oil

Why are human sex hormones considered to be lipids?

They are not soluble in water

The bonding of two amino acid molecules to form a larger molecule requires

the release of a water molecule.

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes

Defensive proteins are manufactured by the _____ system.

immune

Proteins are polymers of _____.

amino acids

What type of bond joins the monomers in a protein's primary structure?

peptide

The secondary structure of a protein results from _____.

hydrogen bonds

Tertiary structure is NOT directly dependent on _____.

peptide bonds

There are 20 different amino acids. What makes one amino acid different from another?

different side chains (R groups) attached to an α carbon

What aspects of protein structure are stabilized or assisted by hydrogen bonds?

secondary, tertiary, and quaternary structures, but not primary structure

Which type of interaction stabilizes the α helix and the β pleated sheet structures of proteins?

hydrogen bonds

Which level of protein structure do the α helix and the β pleated sheet represent?

secondary

The amino acids of the protein keratin are arranged predominantly in an α helix. This secondary structure is stabilized by

hydrogen bonds

Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded polypeptides?

Alzheimer's and Parkinson's only

Changing a single amino acid in a protein consisting of 325 amino acids would

always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and affect its biological activity.

Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits

altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered.

One of the primary functions of RNA molecules is to

function in the synthesis of proteins.

What is the structural feature that allows DNA to replicate?

complementary pairing of the nitrogenous bases

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