$$6\ \mathrm{CO}_2 + 6\ \mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow C_6H_{12}O_6$ + 6\ \mathrm{O}_2$$

Question 1

Which of the following best describes the difference between autotrophs and heterotrophs?

Accepted Answer

Autotrophs produce organic molecules from inorganic sources, while heterotrophs must consume organic molecules produced by other organisms.

Question 2

Which structure within the chloroplast is the primary site of the light reactions of photosynthesis?

Accepted Answer

Thylakoid membrane

Question 3

The overall equation for photosynthesis can be summarized as:

Accepted Answer

$$6\ \mathrm{CO}_2 + 6\ \mathrm{H}_2\mathrm{O} + 	ext{light energy} ightarrow C_6H_{12}O_6$ + 6\ \mathrm{O}_2$$

Question 4

Which experiment demonstrated that the oxygen produced during photosynthesis comes from water and not carbon dioxide?

Accepted Answer

Van Niel's experiment using isotopically labeled $$\mathrm{H}_2$$^{18}$$\mathrm{O}$$

Question 5

What is the main function of the stomata in plant leaves?

Accepted Answer

To regulate gas exchange, allowing $$\mathrm{CO}_2 in $$and $$\mathrm{O}_2$$ out

Question 6

Which of the following best describes photophosphorylation?

Accepted Answer

The synthesis of ATP from ADP and inorganic phosphate using energy derived from light

Question 7

What is the three-carbon sugar produced directly by the Calvin cycle that is used to synthesize glucose?

Accepted Answer

Glyceraldehyde 3-phosphate (G3P)

Question 8

Which pigment is primarily responsible for absorbing light in the blue and red regions of the spectrum during photosynthesis?

Accepted Answer

Chlorophyll a

Question 9

What is the role of the enzyme RuBP carboxylase/oxygenase (rubisco) in the Calvin cycle?

Accepted Answer

It fixes carbon dioxide to ribulose bisphosphate, forming two molecules of 3-phosphoglycerate.

Question 10

Which of the following best explains why photorespiration is considered energetically wasteful for C3 plants?

Accepted Answer

It consumes ATP and NADPH without producing sugars, and releases fixed carbon as $$\mathrm{CO}_2.$$

Question 11

How do C4 plants avoid photorespiration under hot and dry conditions?

Accepted Answer

By spatially separating carbon fixation and the Calvin cycle in different cell types.

Question 12

Which of the following statements about the chemiosmotic mechanism in chloroplasts and mitochondria is correct?

Accepted Answer

Both generate a proton gradient across the inner membrane, but ATP synthesis occurs in the stroma of chloroplasts and the matrix of mitochondria.

Question 13

Which wavelength of light is photosystem II most efficient at absorbing?

Accepted Answer

$$680\ \mathrm{nm}$$

Question 14

What is the function of ferredoxin in the light reactions of photosynthesis?

Accepted Answer

It transfers electrons from photosystem I to NADP+ reductase for the reduction of NADP+ to NADPH.

Question 15

Which of the following best describes the absorption spectrum of chlorophyll a?

Accepted Answer

It absorbs light most efficiently in the blue-violet and red regions.

Question 16

How many turns of the Calvin cycle are required to produce one molecule of glucose?

Accepted Answer

Six

Question 17

Which ion is found at the center of the porphyrin ring in chlorophyll a, and what is the function of the hydrophobic tail?

Accepted Answer

Magnesium; the tail anchors chlorophyll in the thylakoid membrane

Question 18

Which device is used to measure the absorption spectrum of pigments such as chlorophyll?

Accepted Answer

Spectrophotometer

Question 19

Which of the following is a key adaptation of CAM plants that allows them to survive in arid environments?

Accepted Answer

They fix carbon dioxide at night and perform the Calvin cycle during the day.

Question 20

What is the fate of most of the sugar produced by photosynthesis in plants?

Accepted Answer

It is used immediately for cellular respiration and metabolism by the plant.

Chapter 8: Photosynthesis – Structure, Mechanisms, and Evolutionary Adaptations

Study Guide - Practice Questions