Chapter 3: macromolecules

Carbon's valence of four most directly results from

• its tetrahedral shape

• its very slight electronegativity

• its four electrons in the valence shell that can form four covalent bonds

• its ability to form single, double, and triple bonds

• its ability to form chains and rings of carbon atoms

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Hydrocarbons are not soluble in water because

• they are hydrophilic

• their C-H bonds are nonpolar

• they do not ionize

• they store energy in the many C-H bonds along the carbon backbone

• they are lighter than water

The chemical group that can cause an organic molecule to act as a base is

• -COOH

• -OH

• -SH

•  $NH_2$  

•  $-CH_3$  

The chemical group that confers acidic properties to organic molecules is

• COOH

• OH

• SH

• $NH_2$

• $CH_3$

Polymerization (the formation of polymers) is a process that

• creates bonds between glucose monomers in the formation of a polypeptide

• involves the addition of a water molcule

• links the nitrogenous base of one nucleotide with the phosphate of the next

• involves a dehydration reaction

• may involve all of the above

Which of the following statements is not true of a hexose?

• it may be found in nucleic acids

• it can occur in a ring structure

• it has the formula C6 H12 O6

• it has one carbonyl and five hydroxyl groups

• it may be an aldehyde or a ketone sugar

Which of the following statements is not true of cellulose?

• it is the most abundant organic compound on Earth

• it differs from starch because of the configuration of glucose and the geometry of the glycosidic linkage

• it may be hydrogen-bonded to neighboring cellulose molecules to form microfibrils

• few organism have enzymes that hydrolyze its glycosidic linkages

• its monomers are glucose with nitrogen-containing appendages

Plants store most of their energy for later use as

• unsaturated fats

• glycogen

• starch

• sucrose

• cellulose

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Maltose is made from joining two glucose molecules in a dehydration reaction. What is the molecular formula for this disaccharide

• C6 H12 O6

• C10 H20 O10

• C12 H22 O11

• C12 H24 O13

• C12 H24 O13

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A cow can derive nutrients from cellulose because

• it can produce the enzymes that break the beta linkages between molecules

• it chews and rechews it cud so that cellulose fibers are finally broken down

• its rumen contained prokaryotes and protists that can hydrolyze the bonds of cellulose

• its intestinal tract contains termites, which harbor microbes that hydrolyze cellulose

• it has enzymes that convert cellulose to starch and then hydrolyze starch to glucose

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