CHAPTER 4

Question 2

What is photosynthesis?

Answer 2

The process of converting sunlight energy into chemical energy.

Question 3

Which organisms are capable of photosynthesis?

Answer 3

Plants, algae, and cyanobacteria.

Question 4

Define autotrophs.

Answer 4

Organisms that can produce their own food.

Question 5

Define heterotrophs.

Answer 5

Organisms that cannot produce their own food.

Question 6

Where does photosynthesis primarily occur in plants?

Answer 6

In the mesophyll layer within the leaves.

Question 7

What is the specific organelle where photosynthesis takes place?

Answer 7

Chloroplast.

Question 8

True or False: Human cells can perform photosynthesis.

Answer 8

False.

Question 9

How is light energy described?

Answer 9

A type of kinetic energy that we can see.

Question 10

What is the relationship between wavelength and energy in light?

Answer 10

The longer the wavelength, the lower the energy.

Question 11

What are photons?

Answer 11

A package of light.

Question 12

What is the role of pigments in plants?

Answer 12

To absorb light energy.

Question 13

Define photosystems.

Answer 13

Protein complexes consisting of proteins and pigments that can absorb light energy and convert it into chemical energy.

Question 14

How many photosystems are there in plants?

Answer 14

2 Photosystems.

Question 15

What do light-harvesting complexes do?

Answer 15

They pass light energy to the reaction center.

Question 16

What is contained in the reaction center of a photosystem?

Answer 16

A special pair of chlorophyll a molecules that can give up electrons.

Question 17

What is the first step of light-dependent reactions?

Answer 17

Photosystem II captures sunlight and excites electrons.

Question 18

What is the equation for water splitting in photosynthesis?

Answer 18

2 H2O + light → O2 + 4e−.

Question 19

What is the key product of the light-dependent reactions?

Answer 19

ATP, NADPH, and oxygen.

Question 20

What does chemiosmosis refer to?

Answer 20

The diffusion of ions across a semipermeable membrane.

Question 21

What is the end product of the Calvin cycle?

Answer 21

Glyceraldehyde 3-phosphate (G3P).

Question 22

What is RuBisCO?

Answer 22

An enzyme involved in carbon fixation during the Calvin cycle.

Question 23

Fill in the blank: The Calvin cycle does not directly require light but relies on the products of the light-dependent reactions, _______ and NADPH.

Answer 23

ATP.

Question 24

What is the relationship between light-dependent reactions and the Calvin cycle?

Answer 24

Light-dependent reactions provide ATP and NADPH for the Calvin cycle.

Question 25

What is the major precursor for the synthesis of carbohydrates produced by photosynthesis?

Answer 25

Glucose.

Question 26

True or False: Photosynthesis and cellular respiration are interconnected processes.

Answer 26

True.

Question 27

What does G3P leave the Calvin cycle to produce?

Answer 27

Glucose.

Question 28

What is the first stage of the Calvin cycle?

Answer 28

Carbon Fixation: This stage begins with a molecule called ribulose-bisphosphate (RuBP), a five-carbon sugar. The enzyme RuBisCO catalyzes the reaction between RuBP and carbon dioxide (CO₂) from the atmosphere, forming an unstable six-carbon intermediate that splits into two molecules of 3-phosphoglycerate (3-PGA). Therefore, carbon dioxide is 'fixed' from an inorganic form into an organic molecule.

Question 29

What occurs during the Reduction/Sugar Generation stage of the Calvin cycle?

Answer 29

Each molecule of 3-phosphoglycerate (3-PGA) is phosphorylated by ATP to form 1,3-bisphosphoglycerate (1,3-BPG). Then, NADPH reduces 1,3-bisphosphoglycerate (1,3-BPG) to form glyceraldehyde 3-phosphate (G3P). For every three molecules of CO₂ that enter the cycle, six molecules of G3P are produced, with one G3P molecule leaving the cycle to be used to make glucose and other organic molecules.

Question 30

What happens in the Regeneration stage of the Calvin cycle?

Answer 30

The remaining five molecules of glyceraldehyde 3-phosphate (G3P) are used in a series of reactions that require ATP to regenerate ribulose-bisphosphate (RuBP). This regeneration of RuBP is crucial because it allows the Calvin cycle to continue fixing carbon dioxide.