94 ■ CHAPTER 05 How Cells Work
(^7) In the diagram of photosynthesis shown here, fill in each
blank with the appropriate term: (a) Sunlight; (b) CO 2 ; (c) Oxygen;
(d) H 2 O; (e) ATP and NADPH; (f) ADP and NADP+; (g) Sugar; (h) Light
reactions; (i) Calvin cycle.
(^8) Place the following steps of cellular respiration in the correct
order by numbering them from 1 to 4.
a. The Krebs cycle produces the energy carriers NADH,
FADH 2 , and ATP.
b. If oxygen levels are adequate, pyruvate is transported into
the mitochondrion. If oxygen levels are very low, fermenta-
tion proceeds.
c. Glucose is broken down to produce ATP and NADH.
d. An electron transport chain produces ATP from ADP.
Challenge Yourself
(^9) The Calvin cycle reactions are sometimes called the “light-
independent reactions” or “dark reactions” to contrast them with
the light (or light-dependent) reactions. Can the Calvin cycle be
sustained in algae that are kept in total darkness for several days?
Why or why not?
(^10) After strenuous exercise, you may notice that your muscles
burn and feel sore the next day. Which statement best explains
this phenomenon?
(a) Proteins in muscle cells are being digested to provide energy.
(b) Carbon dioxide is building up in muscle cells and changing
their pH.
(c) Spontaneous combustion occurs during strenuous exercise, so
avoid it at all costs!
THE QUESTIONS
The Basics
1
Metabolic pathways(a) always break down large molecules into smaller units.
(b) only link smaller molecules together to create polymers.
(c) are often organized as a multistep sequence of reactions.
(d) occur only in mitochondria.
(^2) Enzymes
(a) speed up reactions that would otherwise occur much more
slowly.
(b) spur reactions that would otherwise never occur.
(c) provide energy for anabolic but not catabolic pathways.
(d) are consumed during the reactions they catalyze.
(^3) The most common energy-carrying molecule in all
organisms is
(a) carbon dioxide.
(b) water.
(c) ATP.
(d) rubisco.
(^4) The major product of photosynthesis is
(a) lipids.
(b) sugar.
(c) amino acids.
(d) nucleotides.
(^5) Which of the following statements is not true?
(a) Glycolysis is the first stage of cellular respiration.
(b) Glycolysis can proceed under low oxygen levels with the
assistance of fermentation.
(c) Glycolysis produces less ATP than does either the Krebs cycle
or oxidative phosphorylation.
(d) Glycolysis produces most of the ATP required by aerobic
organisms like us.
(^6) Select the correct terms:
Photosynthesis and cellular respiration are chemically
(identical / opposite) processes. Cellular respiration is an
example of (anabolism / catabolism), which (produces /
expends) energy.