3.5: Photosynthesis

Question 1

Where does the energy that fuels photosynthesis come from?

Answer 1

Light energy from the sun.

Question 2

What organism first evolved photosynthesis?

Answer 2

Prokaryotes such as cyanobacteria were the first.

Question 3

Identify one piece of evidence that supports oxygenation to atmosphere from cyanobacteria.

Answer 3

They were able to perform photosynthesis, so they released oxygen as a by product.

Question 4

What are light dependent reactions?

Answer 4

The fist part of photosynthesis where the chlorophyll pigments in the thylakoid absorb light from the sun. It then transforms this energy into usable chemical energy stored in ATP and NADPH (synthesized from NADP+ in calvin cycle and H20).

Question 5

Where do light dependent reactions take place?

Answer 5

In the chlorophyll in the thylakoid.

Question 6

How is ATP synthesized in light dependent reactions?

Answer 6

The hydrogen gradient in the thylakoid pushes ADP through ATPase, creating ATP, which stores chemical energy in its additional phosphate bond.

Question 7

How is NADPH synthesized in the light dependent reactions?

Answer 7

NADP+ from the calvin cycle combines with H20, which creates NADPH that stores chemical energy in its bonds.

Question 8

What is chlorophyll?

Answer 8

A pigment that is able to absorbs energy from light.

Question 9

How does chlorophyll aid in energy capture?

Answer 9

They convert sunlight to high energy electrons .

Question 10

Where is chlorophyll located?

Answer 10

Thylakoid

Question 11

What happens to electrons after absorbing energy from light?

Answer 11

They are used to create a proton gradient that reduces NADP+ to NADPH (reduction is when you add H protons)

Question 12

How is the photosystem organized to aid in energy capture?

Answer 12

They capture light is the chloroplasts thylakoid membrane.
Photosystem II- Uses light energy to hydrolyze water to produce the beginnings of a H proton gradient inside the thylakoid.
Photosystem I- uses photons and converts them t chemical energy that is stored in NADPH.

Question 13

How is the thylakoid membrane organized to aid in energy capture?

Answer 13

Photosystems are embedded in the membrane. Between them there is an electron transport chain that increases the H proton gradient.

Question 14

What is the relationship between the photosystem and the electron transport chain?

Answer 14

PS II and PS I pass high energy electrons to the ETC.

Question 15

What is the direction that the protons are pumped during the light dependent reactions to generate a proton gradient?

Answer 15

Protons are pumped into the thylakoid to create a concentration gradient.

Question 16

How does the proton gradient result in ATP synthesis?

Answer 16

It uses passive transport to generate ATP from ADP. The H protons push ADP through ATPase to create ATP. Now the ATP is outside the thylakoid and in the stroma.

Question 17

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

Answer 17

The light reactions produce NADPH and ATP, which is used to help stimulate the calvin cycle (along with CO2). The NADP+ and ADP from the Calvin cycle is then given back to the light dependent reactions to continue the cycle.

Question 18

What are the stages of the calvin cycle?

Answer 18

1. Carbon fixation-3CO2 molecules are added
2. Reduction- NADPH and ATP converted to ADP and NADP+ and outputs sugar
3. Regeneration of RuBP and converts some ATP to ADP in the process