Chapter 8

Question 1

What is the overall equation for photosynthesis?

Answer 1

6CO2 + 12H2O → C6H12O6 + 6H2O + 6O2

Question 2

Which organisms carry out oxygenic photosynthesis?

Answer 2

Cyanobacteria, 7 groups of algae, and all land plants.

Question 3

What are the two main stages of photosynthesis?

Answer 3

Light-dependent reactions and carbon fixation reactions (light-independent reactions).

Question 4

What occurs during light-dependent reactions?

Answer 4

They require light to capture energy from sunlight, make ATP, and reduce NADP+ to NADPH.

Question 5

What occurs during carbon fixation reactions?

Answer 5

They do not require light and use ATP and NADPH to synthesize organic molecules from CO2.

Question 6

What is the thylakoid membrane?

Answer 6

The internal membrane of chloroplasts that contains chlorophyll and other photosynthetic pigments.

Question 7

What are grana?

Answer 7

Stacks of flattened sacs of thylakoid membrane.

Question 8

Who demonstrated that plant substance is not solely derived from soil?

Answer 8

Jan Baptista van Helmont.

Question 9

What did Joseph Priestly discover about vegetation?

Answer 9

Living vegetation adds something to the air.

Question 10

What did Jan Ingenhousz propose about plants?

Answer 10

Plants carry out a process that uses sunlight to split carbon dioxide into carbon and oxygen (O2 gas).

Question 11

What was F.F. Blackman’s conclusion about photosynthesis?

Answer 11

Photosynthesis is a multistage process, only one portion of which uses light directly.

Question 12

What did C. B. van Niel find about purple sulfur bacteria?

Answer 12

They do not release O2 but accumulate sulfur.

Question 13

What is the absorption spectrum?

Answer 13

The range and efficiency of photons a molecule is capable of absorbing.

Question 14

What are pigments?

Answer 14

Molecules that absorb light energy in the visible range.

Question 15

What is the role of chlorophyll a?

Answer 15

It is the main pigment in plants and cyanobacteria that can convert light energy to chemical energy.

Question 16

What is the structure of chlorophyll?

Answer 16

It contains a porphyrin ring with a magnesium ion at the center.

Question 17

What is the action spectrum?

Answer 17

The relative effectiveness of different wavelengths of light in promoting photosynthesis.

Question 18

What are carotenoids?

Answer 18

Accessory pigments that can absorb photons with a wide range of energies and scavenge free radicals.

Question 19

What is the function of the antenna complex in photosystems?

Answer 19

It captures photons and feeds the captured light energy to the reaction center.

Question 20

What happens when a chlorophyll in the reaction center absorbs a photon?

Answer 20

An electron is excited to a higher energy level and can be transferred to the primary electron acceptor.

Question 21

What is cyclic photophosphorylation?

Answer 21

A process in sulfur bacteria that generates ATP via electron transport using only one photosystem.

Question 22

What is the role of photosystem II?

Answer 22

It can generate an oxidation potential high enough to oxidize water.

Question 23

What is the Calvin cycle?

Answer 23

A process that uses ATP and NADPH to build carbohydrates from CO2.

Question 24

What is the key step in the Calvin cycle?

Answer 24

The attachment of CO2 to RuBP to form PGA.

Question 25

What are the three phases of the Calvin cycle?

Answer 25

Carbon fixation, reduction, and regeneration of RuBP.

Question 26

What are the three phases of the Calvin cycle?

Answer 26

1. Carbon fixation: RuBP + CO2 → PGA 2. Reduction: PGA is reduced to G3P 3. Regeneration of RuBP: PGA is used to regenerate RuBP

Question 27

How many turns of the Calvin cycle are needed to produce G3P and glucose?

Answer 27

3 turns incorporate enough carbon to produce a new G3P. 6 turns incorporate enough carbon for 1 glucose.

Question 28

What is the direct product of the Calvin cycle?

Answer 28

Glucose is not a direct product of the Calvin cycle. ## Footnote G3P is a 3 carbon sugar used to form sucrose.

Question 29

What is G3P used for in plants?

Answer 29

G3P is used to form sucrose, the major transport sugar in plants, and to make starch, an insoluble glucose polymer stored for later use.

Question 30

How do photosynthesis and respiration interact?

Answer 30

Photosynthesis uses the products of respiration as starting substrates, while respiration uses the products of photosynthesis as starting substrates.

Question 31

What are the two enzymatic activities of Rubisco?

Answer 31

1. Carboxylation: Addition of CO2 to RuBP, favored under normal conditions. 2. Photorespiration: Oxidation of RuBP by the addition of O2, favored when stomata are closed in hot conditions.

Question 32

What are the types of photosynthesis?

Answer 32

1. C3: Plants that fix carbon using only C3 photosynthesis (the Calvin cycle). 2. C4 and CAM: Add CO2 to PEP to form a 4 carbon molecule using PEP carboxylase.

Question 33

What is the process of carbon fixation in C4 plants?

Answer 33

C4 plants initially fix carbon using PEP carboxylase in mesophyll cells, producing oxaloacetate, which is converted to malate and transported to bundle-sheath cells.

Question 34

What is a disadvantage of the C4 pathway?

Answer 34

To produce a single glucose requires 12 additional ATP compared with the Calvin cycle alone.

Question 35

What is unique about CAM plants?

Answer 35

CAM plants, such as cacti and pineapples, open their stomata at night and close them during the day, fixing CO2 using PEP carboxylase during the night.

Question 36

How do CAM plants minimize photorespiration?

Answer 36

When stomata are closed during the day, organic acids are decarboxylated to yield high levels of CO2, driving the Calvin cycle.

Question 37

How do C4 and CAM pathways differ?

Answer 37

C4: Two pathways occur in different cells. CAM: C4 pathway at night and the C3 pathway during the day.