Lecture 6

Question 1

What is photosynthesis?

Answer 1

It is the process by which green plants and certain organisms convert light energy into chemical energy, producing oxygen and energy-rich organic compounds.

Question 2

Why is photosynthesis important?

Answer 2

Photosynthesis is essential for life on Earth as it produces food, organic matter, and atmospheric oxygen.

Question 3

What is the chemical equation for photosynthesis?

Answer 3

6CO2 + 6H2O → C6H12O6 + 6O2.

Question 4

What are the two main stages of photosynthesis?

Answer 4

Light-dependent reactions and light-independent reactions (Calvin cycle).

Question 5

What happens during light-dependent reactions?

Answer 5

Solar energy is converted into chemical energy in the form of ATP and NADPH, which are used in the Calvin cycle.

Question 6

What is the Calvin cycle?

Answer 6

It is the light-independent stage of photosynthesis where ATP and NADPH are used to convert carbon dioxide into glucose.

Question 7

What are the main organic products of photosynthesis?

Answer 7

Carbohydrates, such as starch and sucrose.

Question 8

What are oxidation and reduction in photosynthesis?

Answer 8

Oxidation is the removal of electrons, and reduction is the gain of electrons; both occur during the conversion of light energy to chemical energy.

Question 9

What is respiration in plants?

Answer 9

It is the process where plants convert stored energy in carbohydrates into usable energy (ATP) for life processes.

Question 10

What is the chemical equation for respiration?

Answer 10

C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP.

Question 11

How is respiration related to photosynthesis?

Answer 11

Respiration is the reverse of photosynthesis in terms of inputs and outputs.

Question 12

What are the three main steps of respiration?

Answer 12

Glycolysis, Krebs cycle, and electron transport chain.

Question 13

What is glycolysis?

Answer 13

It is the first step of respiration, occurring in the cytoplasm, where glucose is broken into pyruvic acid, producing a small amount of ATP.

Question 14

What is the Krebs cycle?

Answer 14

Also known as the citric acid cycle, it is a series of chemical reactions in the mitochondria that release electrons and carbon dioxide.

Question 15

What is the electron transport chain?

Answer 15

It is the final stage of respiration, where electrons release energy to create ATP through oxidative phosphorylation.

Question 16

How do temperature changes affect photosynthesis and respiration?

Answer 16

Both processes increase with temperature, but photosynthesis levels off at high temperatures, while respiration continues to escalate.

Question 17

What is net primary productivity?

Answer 17

The amount of biomass available for the food chain, calculated by subtracting energy lost to respiration from total photosynthetic energy.

Question 18

What are plant growth regulators?

Answer 18

Organic compounds that influence plant structure or physiological processes in low concentrations.

Question 19

Name five major classes of plant hormones.

Answer 19

Auxins, gibberellins, cytokinins, ethylene, and abscisic acid.

Question 20

What is the role of auxins?

Answer 20

Promote cell elongation, internode growth, leaf growth, and apical dominance.

Question 21

How do cytokinins benefit plants?

Answer 21

Promote cell division, delay leaf aging, and are used in tissue culture techniques.

Question 22

What is the role of abscisic acid?

Answer 22

Acts as a growth inhibitor, involved in stress responses like drought tolerance.

Question 23

What are natural and synthetic auxins?

Answer 23

Natural: Indole acetic acid (IAA); Synthetic: Indole butyric acid (IBA) and α-naphthyl acetic acid (NAA).

Question 24

What are gibberellins used for in plants?

Answer 24

They promote stem growth, vegetative growth, flower initiation, and fruit development, including parthenocarpy.

Question 25

How do cytokinins delay senescence (aging)?

Answer 25

By preventing the breakdown of chlorophyll in leaves.

Question 26

What is ethylene’s role in plants?

Answer 26

It is a gaseous hormone involved in fruit ripening, flower wilting, and leaf abscission.

Question 27

Where is abscisic acid (ABA) found, and what does it do?

Answer 27

Found in leaves, stems, flowers, and fruits; it inhibits growth and helps plants respond to stress.