Chapter 8: Photosynthesis

Question 1

What is photosynthesis?

Answer 1

Fixation of CO₂ and reduction to carbohydrates using light energy.

Question 2

Where does photosynthesis occur?

Answer 2

In chloroplasts.

Question 3

What are the two main stages of photosynthesis?

Answer 3

Light-dependent reactions and light-independent reactions.

Question 4

What is the role of chlorophyll in photosynthesis?

Answer 4

It absorbs light and acts as the primary pigment in reaction centers.

Question 5

What is the difference between primary and accessory pigments?

Answer 5

Primary pigments directly participate in light reactions; accessory pigments transfer light energy to them.

Question 6

What is the primary pigment of photosystem I?

Answer 6

Chlorophyll a.

Question 7

What are photosystems

Answer 7

and how many types are there?

Question 8

What process splits water during photosynthesis?

Answer 8

Photolysis.

Question 9

What is the main purpose of light-dependent reactions?

Answer 9

To produce ATP and NADPH.

Question 10

What is the role of NADP in photosynthesis?

Answer 10

Final electron acceptor in light-dependent reactions.

Question 11

What occurs during non-cyclic photophosphorylation?

Answer 11

Electrons flow through both photosystems in the ‘Z scheme.’

Question 12

What happens to excited electrons in photosystem II?

Answer 12

They are transferred to electron carriers after photoactivation.

Question 13

How is ATP generated in photosynthesis?

Answer 13

Through chemiosmosis.

Question 14

What is cyclic photophosphorylation?

Answer 14

ATP synthesis using only photosystem I.

Question 15

When does cyclic photophosphorylation occur?

Answer 15

When NADPH accumulates or light is not limiting.

Question 16

What is the Calvin cycle?

Answer 16

Light-independent reactions for carbon fixation.

Question 17

Where does the Calvin cycle take place?

Answer 17

In the stroma of chloroplasts.

Question 18

What is the first step of the Calvin cycle?

Answer 18

CO₂ fixation with RuBP.

Question 19

What enzyme catalyzes the first step of the Calvin cycle?

Answer 19

Rubisco.

Question 20

What happens to triose phosphates in the Calvin cycle?

Answer 20

Most regenerate RuBP; some form starch

Question 21

What structures in the chloroplast are key for light-dependent reactions?

Answer 21

Thylakoid membranes.

Question 22

What are grana?

Answer 22

Stacks of thylakoids in chloroplasts.

Question 23

How do chloroplasts store energy products?

Answer 23

As starch grains and lipid droplets.

Question 24

What factors affect the rate of photosynthesis?

Answer 24

Light intensity

Question 25

What happens at the light compensation point?

Answer 25

Photosynthesis equals respiration.

Question 26

What is photophosphorylation?

Answer 26

ATP synthesis using light energy.

Question 27

What connects grana in chloroplasts?

Answer 27

Intergranal membranes.

Question 28

Why do plants store glucose as starch?

Answer 28

Starch is insoluble and suitable for storage.

Question 29

How is oxygen produced in photosynthesis?

Answer 29

From the splitting of water during photolysis.

Question 30

What is the role of the stroma?

Answer 30

Site for the Calvin cycle and storage of materials like DNA and ribosomes.

Question 31

What is chemiosmosis?

Answer 31

The process of generating ATP using a proton gradient.

Question 32

Why is rubisco considered inefficient?

Answer 32

It can bind to O₂ instead of CO₂

Question 33

What are the by-products of photosynthesis?

Answer 33

Oxygen and glucose.

Question 34

What are chemoautotrophs?

Answer 34

Organisms using chemical energy instead of light.

Question 35

Give an example of a chemoautotroph.

Answer 35

Nitrifying bacteria.

Question 36

What role do nitrifying bacteria play in the nitrogen cycle?

Answer 36

They oxidize ammonia to nitrites or nitrates.

Question 37

Why is photosynthesis crucial for life on Earth?

Answer 37

It provides energy and oxygen for living organisms.

Question 38

What is the primary role of light in the light-dependent reactions?

Answer 38

To excite electrons in chlorophyll.

Question 39

What molecule donates replacement electrons to photosystem II during photolysis?

Answer 39

Water (H₂O).

Question 40

What is the main product of photolysis?

Answer 40

Oxygen (O₂).

Question 41

What is the 'Z scheme' in photosynthesis?

Answer 41

The pathway of electron flow involving both photosystems.

Question 42

What happens to electrons in photosystem I during cyclic photophosphorylation?

Answer 42

They return to photosystem I via electron carriers.

Question 43

What are the two energy molecules produced during the light-dependent reactions?

Answer 43

ATP and NADPH.

Question 44

Where in the chloroplast do light-dependent reactions take place?

Answer 44

In the thylakoid membranes.

Question 45

What is the role of ATP synthase in light-dependent reactions?

Answer 45

To produce ATP from ADP and inorganic phosphate.

Question 46

What creates the proton gradient in the thylakoids?

Answer 46

The splitting of water and the activity of electron carriers.

Question 47

What is the final electron acceptor in the light-dependent reactions?

Answer 47

NADP⁺.

Question 48

What energy source drives the Calvin cycle?

Answer 48

ATP and NADPH from light-dependent reactions.

Question 49

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

Answer 49

Six turns.

Question 50

What happens if rubisco fixes oxygen instead of carbon dioxide?

Answer 50

Photorespiration occurs

Question 51

Why is NADPH always shown leaving the thylakoid membrane in diagrams?

Answer 51

It is used in the Calvin cycle in the stroma.