Chapter 3: Molecules of Life

Question 1

A polypeptide chain is a linear polymer of amino acids. Peptide bonds are present between which of the two following groups?

1. the carbon atom of the carboxyl group and the oxygen atom double-bonded to it
2. the carbon atom of the carboxyl group and the adjacent carbon atom of the chain’s backbone
3. the carbon atom of the carboxyl group and the nitrogen atom of the amino group
4. the carbon atom of the carboxyl group and the OH bound to it
5. All of the above are true.

Answer 1

the carbon atom of the carboxyl group and the nitrogen atom of the amino group

Question 2

Which of the following are all monosaccharides?

1. glucose, fructose, and galactose
2. starch, cellulose, and glycogen
3. fructuse and cellulose
4. glucose and maltose
5. glycogen and glucose

Answer 2

glucose, fructose, and galactose

Question 3

Phospholipids assemble spontaneously into bilayers driven by the attraction of their “tail” portions to each other and of their “head” portions to each other. The tail regions are:

1. hydrophilic.
2. cohesive.
3. hydrophobic.
4. molecularly charged.
5. adhesive.

Answer 3

hydrophobic

Question 4

On food packages, “insoluble fiber” refers to plant material that we can’t fully digest but is important for maintaining a healthy digestive tract. This substance refers to a(n):

1. amino acid.
2. carbohydrate.
3. protein.
4. lipid.
5. nucleic acid.

Answer 4

carbohydrate

Question 5

All lipids are:

1. polymers of fatty acids.
2. not soluble in water.
3. triglycerides.
4. polar.
5. hydrophilic.

Answer 5

not soluble in water

Question 6

Saturated fatty acids have _________________ than unsaturated fatty acids, which is why they exist as a ____________ at room temperature.

1. more carbon atoms; solid
2. fewer double bonds; solid
3. double bonds; liquid
4. fewer hydrogen atoms; solid
5. more glycerol molecules; liquid

Answer 6

fewer double bonds; solid

Question 7

Sucrose (table sugar) and lactose (the sugar found in milk) are examples of:

1. simple sugars.
2. polyunsaccharide sugars.
3. disaccharides.
4. monosaccharides.
5. naturally occurring enzymes.

Answer 7

disaccharides

Question 8

A complex polymer built of amino acids is called a(n):

1. polysaccharide.
2. fatty acid.
3. monosaccharide.
4. amine.
5. polypeptide.

Answer 8

polypeptide

Question 9

Which of the following statements about enzymes is NOT true?

1. Enzymes often induce shape changes in the molecules to which they bind.
2. Enzymes are permanently changed when they take place in a chemical reaction.
3. Enzymes are proteins.
4. Enzymes help initiate chemical reactions.
5. Enzymes speed up chemical reactions.

Answer 9

Enzymes are permanently changed when they take place in a chemical reaction

Question 10

An unsaturated fatty acid is one in which:

1. carbon-carbon double bonds are present in the hydrocarbon chain.
2. not all of the carbons in the hydrocarbon chain are bonded to hydrogen atoms.
3. there are an odd number of subunits in the hydrocarbon chain.
4. there are an even number of subunits in the hydrocarbon chain.
5. carbon-carbon double bonds are not present in the hydrocarbon chain.

Answer 10

carbon-carbon double bonds are present in the hydrocarbon chain

Question 11

In DNA, adenine from one strand binds to ______ in the complementary strand.

1. guanine
2. cytosine
3. thymine
4. uracil
5. adenine

Answer 11

thymine

Question 12

Glycogen belongs in the class of molecules known as:

1. amino acids.
2. monosaccharides.
3. proteins.
4. polysaccharides.
5. nucleic acids.

Answer 12

polysaccharides

Question 13

Carbohydrates:

1. act as a relatively quickly available source of fuel.
2. serve as carbon skeletons that can be rearranged to form other molecules that are essential for biological structures and functions like nucleic acids.
3. that are glucose can be used to make larger forms of carbohydrates.
4. are a good source of sustained energy when they come in the form of polysaccharides.
5. All of the above.

Answer 13

all of the above

Question 14

A complex polymer built of monosaccharides is called a(n):

1. polypeptide.
2. polysaccharide.
3. protein.
4. ketone.
5. aldehyde.

Answer 14

polysaccharide

Question 15

A partial sequence of a molecule is “AACTGCT.” The molecule is:

1. a polypeptide.
2. a protein.
3. a nucleic acid.
4. a triglyceride.
5. a polysaccharide.

Answer 15

a nucleic acid

Question 16

Phosphate groups are important components of:

1. triglycerides.
2. nucleic acids.
3. amino acids.
4. structural polysaccharides.
5. All of the above are correct.

Answer 16

nucleic acids

Question 17

Enzymes:

1. catalyze reactions that release energy, but not those that consume energy.
2. sometimes increase the amount of energy necessary to initiate a reaction.
3. reduce the energy released by a reaction by one of four different mechanisms.
4. are always consumed by catalyzing a reaction.
5. increase the rate at which a reaction occurs.

Answer 17

increase the rate at which a reaction occurs

Question 18

Which of the following statements about cellulose is FALSE?

1. The cellulose we eat passes right through our digestive system unused.
2. Cellulose has a slightly different three-dimensional structure from starch.
3. Although it is not digestible, cellulose is still important to humans’ diets.
4. Cellulose and starch are made from similar molecules.
5. All of the above statements about cellulose are TRUE.

Answer 18

All of the above statements about cellulose are true

Question 19

Which of the following is a polysaccharide?

1. glucose, the chief cellular energy source
2. cellulose, the primary component of plant cell walls
3. fructose, one of the most important blood sugars
4. insulin, the chief blood sugar regulator
5. All of the above are polysaccharides.

Answer 19

cellulose, the primary component of plant cell walls

Question 20

Figuratively, the primary structure of proteins is often described as amino acids connected like “beads on a string.” In this same vein, which of the following images BEST describes protein quaternary structure?

1. rungs on a ladder
2. needle in a haystack
3. links on a chain
4. coils in a spring
5. threads in a cloth

Answer 20

threads in a cloth