Chapter 10: Photosynthesis

Question 1

What is photosynthesis?

Answer 1

The process by which green plants and some other organisms use sunlight to synthesize foods with carbon dioxide and water

Question 2

What is the chemical formula for photosynthesis?

Answer 2

6CO2 + 6H2O + (light) —} C6H12O6 + 6O2

Question 3

What is the chemical formula for glucose, specifically?

Answer 3

C6H12O6

Again, specifically for glucose

Question 4

What are the stages of photosynthesis?

Answer 4

Stage One: Light-dependent reactions

Stage Two: Calvin Cycle/dark reactions/light-independent reactions

Question 5

What is the byproduct of photosynthesis?

Answer 5

Oxygen

Question 6

What is the byproduct/s of cellular respiration?

Answer 6

Carbon dioxide (and water)

Question 7

How are photosynthesis and cellular respiration the opposite of one another?

Answer 7

Photosynthesis and cellular respiration use the opposite reactants and yield opposite products

Question 8

Describe the structure of the chloroplast.

Answer 8

Refer to worksheet.

Question 9

What are the light-dependent reactions?

Answer 9

Uses light energy to make two molecules needed for the next stage of photosynthesis: ATP and NADPH; in plants, the light reactions take place in the chloroplasts, specifically in the thylakoid membranes

Question 10

What are photosystems?

Answer 10

Light-absorbing molecules that are optimized to harvest light; there are two types of photosystems: photosystem 1 (PSI) and photosystem 2 (PSII)

Question 11

Summarize what occurs in the light-dependent reactions.

Answer 11

Electrons are removed from water (H2O) and passed through PSII and PSI respectively before ending up in NADPH; this process requires light to be absorbed twice, once in each photosystem, and it makes ATP

Question 12

What happens in the light-absorption in PSII?

Answer 12

When light is absorbed in photosystem 2, energy is passed inward until it reaches the reaction center; there, energy is transferred to an electron; the high-energy electron is passed to an acceptor molecule and replaced with an electron from water; the splitting of water two times releases the O2 we breathe

Question 13

Can oxygen stand on its own?

Answer 13

No.

Question 14

What happens in ATP synthesis in the light-dependent reactions?

Answer 14

The high-energy electron travels down an electron transport chain; some of the released energy drives the pumping of H+ ions from the stroma into the thylakoid interior (lumen; active transport), thereby building a higher concentration of ions inside the thylakoid; as H+ ions flow down their gradient and into the stroma, they pass through ATP synthase, driving ATP production in a process known as chemiosmosis

Question 15

Where do the light-dependent reactions occur?

Answer 15

In the thylakoid

Question 16

Where do the light-independent reactions occur?

Answer 16

In the stroma

Question 17

What are the products of the light-dependent reactions?

Answer 17

ATP
NADPH
O2 (oxygen gas)

Question 18

What are the products of the Calvin cycle?

Answer 18

Sugar (glucose)
ADP + P
NADP+

Question 19

How many protons are pumped from an electron going from PSII to PSI?

Answer 19

Three protons

Question 20

What happens in light absorption in PSI in the light-dependent reactions?

Answer 20

The electron arrives at photosystem 1; when light energy is absorbed and passed inward to the reaction center, the electron is boosted to a very high energy level and transferred to an acceptor molecule; the special pair’s missing electron is replaced by a new elevtron from PSII (arriving via the electron try chain)

Question 21

What happens in NADPH formation in the light-dependent reactions?

Answer 21

The high-energy electron travels down the electron transport chain; at the end of the chain, the electron is passed to NADP+ to make NADPH

Question 22

Is it important to remember that an electron resides in each photosystems at one time?

Answer 22

More or less, yes.

But, do note that the splitting of water seems to only fuel the process and does not occur with PSI.

Question 23

What is the net effect of the light-dependent reactions?

Answer 23

To convert light energy into chemical energy in the form of ATP and NADPH

Question 24

What happens in the Calvin cycle/light-independent reactions?

Answer 24

In plants, CO2 enters the interior of a leaf via pores called stomata and diffuses into the stroma of the chloroplast. In the Calvin cycle, sugars are synthesized. Carbon atoms from CO2 are incorporated into larger molecules and used to build three-carbon sugars

Question 25

Why is it called the light-independent reactions?

Answer 25

These reactions are not directly driven by light

Question 26

Is the Calvin cycle fueled by and dependent on ATP and NADPH from the light-dependent reactions?

Answer 26

Yes.

Question 27

Describe the behavior of leaf stomata.

Answer 27

In leaves, stomata typically open during the day to favor CO2 diffusion when light is available (for photosynthesis) and close at night to limit transpiration and save water

Question 28

What is released from a plant in photosynthesis?

Answer 28

O2 (oxygen gas)

Sugar/glucose