Biology Now, 2e

Answers ■ A9

A2: Only photosynthetic organisms can create organic molecules from

inorganic molecules, and animals cannot carry out photosynthesis.

(There are a very few exceptions to that generalization.)

Q3: Explain how photosynthesis and cellular respiration are

“complementary” processes.

A3: They use each other’s products and reactants.

Figure 5.3

Q1: What source of energy would plants use for anabolic

reactions? Would an animal use the same kind of energy?

A1: Plants would use light energy from the sun for anabolism.

Animals, in contrast, would use energy from food or glucose.

Q2: What source of energy would plants release in catabolic

reactions? Would an animal release the same kind of energy?

A2: All living things release energy carriers, usually ATP, during

catabolic reactions.

Q3: Create a mnemonic or jingle that helps you remember the

difference between anabolism and catabolism.

A3: This question is just for fun and to aid in learning. Here’s one

possible answer: “Anabolism synthesizes; catabolism cannibalizes”

(breaks down molecules).

Figure 5.4

Q1: Define ATP in your own words.

A1: Something like this: “ATP is a molecule that cells use to store

and deliver energy.”

Q2: How is ATP involved in anabolism and catabolism? (Hint:

Review Figure 5.3.)

A2: Anabolism requires energy, which is provided most often

by ATP. Catabolism releases energy, and would be involved in

creating ATP from ADP.

Q3: Arsenic disrupts ATP production. Why would this

characteristic cause it to be a potent poison?

A3: If ATP stopped being produced, our cells could no longer

function and we would quickly die.

Figure 5.6

Q1: Is chlorophyll found only within chloroplasts?

A1: No. In bacteria it is embedded in membranes within the cell.

Q2: What could be an advantage of concentrating chlorophyll

molecules in the membranes of chloroplasts?

A2: The location of the chlorophyll molecules maximizes the

efficiency of the metabolic pathway of photosynthesis.

Q3: What is the advantage of having multiple chloroplasts per cell?

A3: Each chloroplast provides membranes needed for more and

more embedded chlorophyll molecules.

Figure 5.7

Q1: What is the source of the carbon dioxide used for

photosynthesis?

A1: Atmospheric CO 2.

Q2: Which products of the light reactions of photosynthesis does

the Calvin cycle use?

7. (See figure below)

ATP

NADPH

NADP+

ADP

Oxygen

H 2 O Sugar

Calvin

cycle

Light

reactions

CO 2

Sunlight

8. (a) 3, (b) 2, (c) 1, (d) 4


9. The Calvin cycle cannot be maintained indefinitely, because

it requires a source of energy to produce ATP. This energy

source (glucose) is created from sunlight energy during the

light reactions.

10. e


11. (a) The reaction without an enzyme requires more energy

to proceed, because its line on the graph shows a higher

peak on the y-axis representing how much energy is

needed.

(b) This reaction is catabolic because there is less energy in the

products than in the reactants, as shown by the line’s lower

position on the y-axis at the end of the reaction. Catabolic

reactions release energy; therefore, their products have less

energy than their reactants.

12. c


13. If metabolic processes occur at a higher rate than can be

sustained by cellular respiration, then it is possible to die from

lack of usable energy.

14. a

ANSWERS TO FIGURE QUESTIONS

Figure 5.2

Q1: Why is photosynthesis called “primary production”?

A1: Because photosynthesis converts two inorganic molecules

(carbon dioxide and water) into an organic molecule (glucose).

Q2: How does animal life depend on photosynthesis?