Photosynthesis

Question 1

What is photosynthesis?

Answer 1

The process by which the energy of sunlight is converted into the energy of glucose.

Question 2

What is the word equation for photosynthesis?

Answer 2

Carbon dioxide + water → glucose + oxygen.

Question 2

Who carries out photosynthesis?

Answer 2

Plants and other autotrophs.

Question 2

What is the chemical equation for photosynthesis?

Answer 2

6CO2 + 6H2O → C6H12O6 + 6O2

Question 3

Where does photosynthesis occur in plants?

Answer 3

In the chloroplasts.

Question 4

Which cells contain most of the chloroplasts in a leaf?

Answer 4

The mesophyll cells.

Question 5

What is the structure of chloroplasts?

Answer 5

Chloroplasts are double-membraned organelles with an outer and inner membrane.

Question 5

What is the liquid filling inside the chloroplast?

Answer 5

The liquid inside is called the stroma.

Question 6

What are the stacks inside the inner membrane of chloroplasts called?

Answer 6

The stacks are called grana.

Question 6

What do the grana in the chloroplast contain?

Answer 6

Grana are filled with chlorophyll, the green, light-absorbing pigment.

Question 7

Q: What wavelengths of light are absorbed by chlorophyll?

Answer 7

Red and blue light are absorbed by chlorophyll.

Question 8

What happens to green light in plants?

Answer 8

Green light is reflected by chlorophyll.

Question 9

When does photosynthesis occur?

Answer 9

Photosynthesis only occurs during the day.

Question 10

What happens to other wavelengths of light in the leaf?

Answer 10

Other wavelengths of light are transmitted through the leaf.

Question 10

How does carbon dioxide enter the leaf?

Answer 10

Carbon dioxide enters the leaf through openings called stomata.

Question 11

How does water reach the leaves for photosynthesis?

Answer 11

Water is absorbed by the roots and transported to the leaves.

Question 12

Where are stomata located on a leaf?

Answer 12

Stomata are small openings found on the underside of a leaf.

Question 13

What is the role of stomata in plants?

Answer 13

Stomata are the sites for gaseous exchange in the plant.

Question 14

What surrounds the opening of the stoma?

Answer 14

The stoma is surrounded by two guard cells.

Question 15

What happens when stomata are open?

Answer 15

Water evaporates and is lost to the atmosphere.

Question 15

What does the plant do on hot, dry days to prevent dehydration?

Answer 15

The plant will close its stomata to avoid excessive water loss.

Question 15

What happens to the stomata during the day?

Answer 15

The stomata are open, allowing CO₂ to enter for photosynthesis and O₂ to leave the leaf.

Question 16

Where does the light-dependent reaction of photosynthesis occur?

Answer 16

In the grana (thylakoid membrane) of the chloroplasts.

Question 17

What happens to light in the light-dependent reaction?

Answer 17

Light is absorbed by the green pigment chlorophyll in the grana.

Question 18

What happens when chlorophyll absorbs light?

Answer 18

Chlorophyll becomes excited, and H₂O is split into H⁺ ions, electrons, and O₂.

Question 19

What is produced in the light-dependent reaction?

Answer 19

ATP and NADPH (electron carrier) are made from unloaded carriers ADP and NADP⁺.

Question 19

What is released during the light-dependent reaction?

Answer 19

O₂ is released.

Question 19

Where does the light-independent reaction (Calvin cycle) occur?

Answer 19

In the stroma of the chloroplast.

Question 20

What is used in the light-independent reaction to make glucose?

Answer 20

Energy is transferred from ATP and NADPH (provided from the light-dependent reaction) to carbon dioxide to make glucose.

Question 21

What are the factors affecting the rate of photosynthesis?

Answer 21

Temperature, carbon dioxide concentration, light intensity, and water availability.

Question 22

Q: How does temperature affect the rate of photosynthesis?

Answer 22

The stages of photosynthesis are catalyzed by enzymes. The temperature that is optimum for the enzymes' functioning will also be the temperature at which the maximum rate of photosynthesis occurs.

Question 22

How does CO₂ concentration affect the rate of photosynthesis?

Answer 22

CO₂ concentration is usually the main limiting factor in photosynthesis. An increase in CO₂ concentration increases the rate of photosynthesis, to a point. When the graph plateaus, the rate becomes constant, often due to all enzymes being saturated or another factor (water or light) becoming limiting.

Question 22

How does light intensity affect the rate of photosynthesis?

Answer 22

At a constant temperature and with unlimited carbon dioxide, the rate of photosynthesis increases as light intensity increases until it reaches the light saturation point. At this point, photosynthesis occurs at a maximum rate because either enzymes are operating at full capacity or another input (CO₂ or water) has become the limiting factor.

Question 23

How does water availability affect the rate of photosynthesis?

Answer 23

If water availability increases, the rate of photosynthesis would also increase. However, in hot and dry conditions, plants close their stomata to prevent water loss, which also prevents gas exchange (CO₂ in, O₂ out), leading to a decreased rate of photosynthesis.

Question 24

How is the energy stored in glucose released for use by cells?

Answer 24

The energy stored in glucose by photosynthesis is released through cellular respiration and repackaged into the energy of ATP.