C1.3 Photosynthesis HL

Question 1

Photosystems

Answer 1

Complexes of pigments and proteins in photosynthetic membranes that absorb light and generate excited electrons.

Question 2

Advantage of Pigment Arrays

Answer 2

Arrays allow absorption of light across a broader range of wavelengths, enhancing the efficiency of photosynthesis.

Question 3

Reaction Centre

Answer 3

A specific chlorophyll molecule in a photosystem where a photochemical reaction occurs, emitting an excited electron

Question 4

Photolysis of Water

Answer 4

Process in photosystem II where water is split to replace lost electrons, producing oxygen as a waste product.

Question 5

Chlorophyll a and b

Answer 5

Primary pigments in photosystems; chlorophyll a is at the reaction centre, and both pigments absorb light of different wavelengths.

Question 6

Photosystem I vs. Photosystem II

Answer 6

PS I is most sensitive to 700 nm light; PS II is most sensitive to 680 nm light and is the first activated in the light-dependent reactions.

Question 7

Oxygen Generation in Photosynthesis

Answer 7

Oxygen is produced as a by-product during the photolysis of water in photosystem II, contributing to the light-dependent reactions.

Question 8

Chemiosmosis

Answer 8

Process in thylakoids producing ATP from ADP during photosynthesis, driven by a proton gradient across the thylakoid membrane

Question 9

Cyclic Photophosphorylation

Answer 9

A type of photophosphorylation where electrons from photosystem I return to it after ATP production, not producing NADPH

Question 10

Non-Cyclic Photophosphorylation

Answer 10

Photophosphorylation process involving both photosystems, producing ATP and NADPH by transferring electrons to NADP+.

Question 11

Reduction of NADP in Photosynthesis

Answer 11

Process where NADP+ accepts electrons and H+ ions to become NADPH, catalyzed by photosystem I

Question 12

Role of Thylakoid in Photolysis

Answer 12

Thylakoids provide space for water splitting, releasing oxygen and providing electrons for the light-dependent reactions

Question 13

Importance of Thylakoid Membrane

Answer 13

Houses photosystems, electron transport chain, and ATP synthase; essential for chemiosmosis and ATP production

Question 14

Photophosphorylation

Answer 14

The process of converting ADP to ATP using light energy during photosynthesis, occurring in thylakoids

Question 15

Rubisco in Carbon Fixation

Answer 15

Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes the fixation of atmospheric CO2 by adding it to RuBP, forming two molecules of glycerate 3-phosphate (GP). It’s a crucial step in the Calvin cycle.

Question 16

Glycerate 3-Phosphate to Triose Phosphate

Answer 16

Glycerate 3-phosphate (GP) is converted to triose phosphate using ATP for energy and reduced NADP for adding hydrogen. This step is critical for synthesizing glucose.

Question 17

Regeneration of RuBP

Answer 17

In the Calvin cycle, RuBP is regenerated from triose phosphate, using the energy of ATP. This step is essential for the cycle’s continuation.

Question 18

Importance of Rubisco

Answer 18

Rubisco is significant because it initiates the process of carbon fixation in the Calvin cycle, leading to the production of carbohydrates in photosynthetic organisms.

Question 19

Role of ATP in Calvin Cycle

Answer 19

ATP provides the necessary energy for synthesizing triose phosphate from GP and for regenerating RuBP from triose phosphate.

Question 20

Role of Reduced NADP

Answer 20

Reduced NADP is used in the Calvin cycle to add hydrogen to GP, converting it into triose phosphate, an important step in glucose synthesis.

Question 21

Calvin Cycle Efficiency

Answer 21

The Calvin cycle requires a high concentration of Rubisco due to its slow nature and high energy requirement, making it relatively inefficient at low CO2 concentrations.

Question 22

Triose Phosphate

Answer 22

A product of the Calvin cycle, triose phosphate is the basis for synthesizing various carbon compounds in plants, such as carbohydrates, amino acids, and fatty acids.

Question 23

Calvin Cycle Role in Carbon Compound Synthesis

Answer 23

The Calvin cycle synthesizes carbohydrates, amino acids, fatty acids, and nucleotides in plants. Each compound follows its specific metabolic pathway.

Question 24

Calvin Cycle’s Connection to Nucleotides

Answer 24

The Calvin cycle contributes to nucleotide synthesis by providing ribose sugar, derived from triose phosphate. Nucleotides are crucial for DNA and RNA formation.

Question 25

Light-Dependent Reactions’ Products

Answer 25

The light-dependent reactions of photosynthesis produce ATP and reduced NADP, which are essential for driving the light-independent reactions.

Question 26

Light-Independent Reactions’ Dependency

Answer 26

Light-independent reactions depend on the products of light-dependent reactions (ATP and reduced NADP) and cannot continue in the absence of light.

Question 27

Interdependence of Photosynthesis Reactions

Answer 27

Light-dependent reactions require NADP and ADP, while light-independent reactions need ATP and reduced NADP, illustrating their mutual dependency.

Question 28

Impact of CO2 on Light-Dependent Reactions

Answer 28

A lack of CO2, halting light-independent reactions, can severely impede the light-dependent reactions due to reduced availability of NADP and ADP.