The Need for CO2

Concept: Photorespiration

6m

Concept: C4 Plants

10m

Concept: CAM Plants

2m

The Need for CO2 Additional Practice Problems

Describe the structure and function of stomata in the leaves. How does their function relate to movement of substances in xylem and phloem?

Watch Solution

Compare C3, C4 and CAM mechanisms of photosynthesis. 

a) What are the molecules that accept CO2 in each of the mechanisms? 

b) What are the products of CO2 fixation? 

c) What are the first enzymes in CO2 fixation, where are they located? 

Watch Solution

Which type of plant (C3, C4, or CAM) might you expect to do best if exposed to continuous daylight under hot, dry conditions? Why?

Watch Solution

 Describe the fundamental differences between C3, C4, and CAM plants in terms of how they carry out photosynthesis.

Watch Solution

For most lawn grasses to grow well in hot, dry weather, they must be watered so that their stomata will remain open for longer periods of time to let in O2

a. True

b. False

Watch Solution

The rise of photosynthetic organisms increased the concentration of CO 2 in the atmosphere, raised global temperature and raised sea level. 

a. True

b. False

Watch Solution

How do C4 plants minimize photorespiration? 

a. Stomata are only opened at night, storing oxygen in malate. During the day the oxygen is released for photosynthesis.

b. The light reactions and carbon reactions occur in different cells, so carbon dioxide does not come into contact with rubisco.

c. Stomata are only opened at night, storing carbon dioxide in malate. During the day the carbon dioxide is released for photosynthesis.

d. The light reactions and carbon reactions occur in different cells, so oxygen does not come into contact with rubisco.

Watch Solution

Why is photorespiration more of a problem for a plant when their stomata are closed? 

a. Oxygen levels increase from photosynthesis and compete with carbon dioxide for rubisco's active site.

b. Carbon dioxide levels increase from photosynthesis and compete with oxygen for rubisco's active site.

d. Oxygen cannot enter the leaf, blocking normal respiration, so the plants switch to photorespiration.

e. Glucose cannot leave through the stomata and levels increase inside of the plant cell, causing dehydration by osmosis.

Watch Solution

Which plants keep their stomata open only at night? 

a. CAM

b. C3

c. C4

Watch Solution

Which plants are best adapted to cool wet conditions? 

a. C4

b. C3

c. CAM

Watch Solution

Which of the following statements about PEP carboxylase (the enzyme responsible for “fixing” CO2 in C4 plants) is  false?

a. PEP carboxylase has a greater affinity for CO2 than rubisco does.

b. PEP carboxylase is not found in C3 plants. 

c. PEP carboxylase can function when the stomata are closed.

d. None of the above. 

Watch Solution