Photosynthesis

Question 1

What is the first step of photosynthesis?

Answer 1

The first step is the absorption of light by chlorophyll in the photosystem II complex, located in the thylakoid membrane. This light energy excites electrons in the chlorophyll, boosting them to a higher energy state.

Question 2

What happens after light absorption in photosynthesis?

Answer 2

The energized electrons are passed from photosystem II to the electron transport chain (ETC). Meanwhile, water molecules are split in a process called photolysis, releasing oxygen (O₂), protons (H⁺), and electrons that replace the ones lost from chlorophyll.

Question 3

What is the function of the electron transport chain (ETC) in photosynthesis?

Answer 3

As electrons pass through the ETC, their energy is used to pump protons into the thylakoid lumen, creating a proton gradient. This movement of electrons is essential for generating the energy required to make ATP.

Question 4

How is ATP produced in photosynthesis?

Answer 4

ATP synthase, an enzyme embedded in the thylakoid membrane, uses the proton gradient generated by the ETC to power the synthesis of ATP from ADP and inorganic phosphate (Pi). This process is called chemiosmosis.

Question 5

What is the final electron acceptor in the light-dependent reactions?

Answer 5

The final electron acceptor is NADP+. Electrons reach photosystem I, where they are re-energized by light and used to reduce NADP+ to NADPH, which carries electrons to the Calvin cycle for carbon fixation.

Question 6

What is the first step of the Calvin cycle?

Answer 6

The first step is carbon fixation, where the enzyme RuBisCO attaches a carbon dioxide molecule (CO₂) to a 5-carbon molecule called ribulose bisphosphate (RuBP), producing a 6-carbon compound that immediately splits into two molecules of 3-phosphoglycerate (3-PGA).

Question 7

What happens after carbon fixation in the Calvin cycle?

Answer 7

Each 3-PGA molecule is phosphorylated by ATP and reduced by NADPH, transforming it into glyceraldehyde-3-phosphate (G3P), a 3-carbon sugar.

Question 8

What is the role of ATP and NADPH in the Calvin cycle?

Answer 8

ATP provides the energy, and NADPH donates high-energy electrons needed to reduce 3-PGA into G3P during the second stage of the Calvin cycle, known as reduction.

Question 9

What happens to G3P in the Calvin cycle?

Answer 9

Some G3P is used to synthesize glucose and other carbohydrates, while the rest is used in the regeneration phase to regenerate RuBP, allowing the Calvin cycle to continue.

Question 10

What are the two main stages of photosynthesis?

Answer 10

The light-dependent reactions and the Calvin cycle (light-independent reactions).

Question 11

Where do light-dependent reactions occur?

Answer 11

In the thylakoid membrane of the chloroplast.

Question 12

What are the main products of the light-dependent reactions?

Answer 12

ATP, NADPH, and oxygen (O₂).

Question 13

Where does the Calvin cycle take place?

Answer 13

In the stroma of the chloroplast.

Question 14

What molecule is fixed in the Calvin cycle to produce glucose?

Answer 14

Carbon dioxide (CO₂).

Question 15

What is photosynthesis?

Answer 15

Photosynthesis is a series of metabolic reactions occurring inside of plant cells

Question 16

Where does photosynthesis happen in plant cells?

Answer 16

Chloroplasts

Question 17

After the electron travel down the electron transport chain, losing energy along the way, what happens after the pumping of H+ ions into the thylakoid space?

Answer 17

It creates a proton gradient across the thylakoid membrane.

Question 18

After the hydrogen ion pass through the ATP synthase, creating energy, what is the energy used for?

Answer 18

It’s is used to add a phosphate to ADP and generate the high energy molecule ATP.

Question 19

What happens after the electrons as they reach photosystem 1?

Answer 19

They are once again at a low energy state, they are then excited again by the sun light. They then jump to another electron transport chain.

Question 20

What happens after the electrons in photo system 1 jump onto the next electron transport chain?

Answer 20

They then are passed to the electron acceptor NADP+ to then generate NADPH.

Question 21

What are the key products of the light reactions in photosynthesis?

Answer 21

ATP, NADPH, and O2

Question 22

Plants “breath in” CO2 and “breath out” oxygen. The oxygen produced during photosynthesis comes from what?

Answer 22

H2O

Question 23

What is the final electron acceptor in the light reaction?

Answer 23

NADP+

Question 24

If we poked holes in the thylakoid membrane that allowed H+ to leak across the membrane, how would this affect the production of ——

Answer 24

ATP

Question 25

At the end of the light reactions, you have made “blank”?

Answer 25

O2 which diffuses away. A proton gradient, making the thylakoid space acidic. The high energy molecules ATP and NADPH.

Question 26

Where does the Calvin Cycle ( or “Dark reactions) take place?

Answer 26

The reaction takes place in the stroma.

Question 27

What are the 3 main steps of the Calvin cycle?

Answer 27

1. Carbon fixation
2. Reduction
3. Regeneration

Question 28

What is the first step of the Calvin cycle?

Answer 28

A 5-carbon molecule called RuBP binds to Rubisco. CO2 also binds to Rubisco.

Question 29

What is the second part of step 1.

Answer 29

Rubisco catalyzes the splitting of CO2 and adds the carbon from CO2 into RuBP to form a new 6-carbon molecule.

Question 30

What is the 3rd part of step 1.

Answer 30

The 6-carbon molecule rearranges itself to form two 3-carbon molecules called PGA.

Question 31

What is step 2 of the Calvin cycle?

Answer 31

The high energy products of the light reaction last are used to further modify PGA.

Question 32

What happens to each PGA molecule in step 2 of the Calvin cycle.

Answer 32

Each PGA molecule, one ATP and one NADPH are used to generate a molecule called G3P.

Question 33

What is step 3 of the Calvin cycle?

Answer 33

After 3CO2 molecules have enters the cycle, we have 6 G3P molecules, this is the threshold amount for stage 3 to occur.

Question 34

What happens after part 1 of stage 3 in the Calvin cycle?

Answer 34

One G3P will leave the cycle and be used as a building block for glucose. The remaining 5 will be used to regenerate RuBP. This regeneration process requires ATP.

Question 35

How many G3P molecules are needed to make glucose?

Answer 35

It takes 2 G3P molecules to make one molecule of glucose.

Question 36

How many molecules of CO2, ATP and NADPH does it take to make one glucose?

Answer 36

It’s take 6CO2 molecules, 18 ATP molecules and 12 NADPH molecules to make one molecule of glucose.

Question 37

In the Calvin Cycle, what does ATP and NADPH provide?

Answer 37

ATP provide the energy and NADPH provide the electrons and hydrogens needed to build sugar.

Question 38

What is the key product of the Calvin Cycle?

Answer 38

G3P or the technical term Glyceraldhyde 3-phosphate

Question 39

In step 3 of the Calvin cycle: Regeneration, what happens to the 5 out of 6 G3P molecules?

Answer 39

They are converted back to the starting compound, RuBP.

Question 40

What is needed to make the 3 RuBP molecules in step 3 of the Calvin cycle: Regeneration?

Answer 40

ATP is needed again to be used as the energy source.

Question 41

What is the overall Photosynthesis Equation?

Answer 41

6CO2+6H2O = C6H12O6+6O2

Question 42

How many G3P molecules are needed to make glucose and explain in how many carbons are being used and needed.

Answer 42

There are 3 carbon atoms in a single G3P molecule, and there are 6 carbon atoms needed for 1 glucose molecule. So over all there needs to be 2 G3P molecules to make 1 glucose molecule.