Photosynthesis

Question 1

6CO2 + 6 H20 + light —–>

Answer 1

C6H12O6 + 6O2

Question 2

“excited” electrons

Answer 2

These energized electrons are unstable and almost immediately re-emit the absorbed energy.

Question 3

Two main processes of photosynthesis: Light-dependent and light-independent reactions

Define them

Answer 3

1. Light-dependent- The light reactions use light energy directly to produce ATP that powers the light-independent reactions.
2. Light-independent reactions - This reaction consists of the Calvin cycle, which produces sugar. To power the production of sugar, the Calvin cycle uses ATP formed during the light reactions.

Both reactions occur when light is present.

Question 4

Photosynthetic pigments

Answer 4

absorbs light energy and use it to provide energy to carry out photosynthesis.

Question 5

Non-cyclic Photophosphorylation-
Light dependent reaction:

1.Photosystem II

Answer 5

Electrons trapped by P680 in photosystem II are energized by light.

Question 6

Non-cyclic Photophosphorylation-
Light dependent reaction:

2. Primary electron acceptor

Answer 6

Two excited e- passed to a primary electron acceptor; called primary because it is the first in chain of acceptor.

Question 7

Non-cyclic Photophosphorylation-
Light dependent reaction:

3.Electron transport chain

Answer 7

Consists of a plastoquinone complex (PSII) which contains proteins like CYTOCHROME and cofactor Fe+; analogous(comparable) to oxidative phosphorylation.

Question 8

Non-cyclic Photophosphorylation-
Light dependent reaction:

4.Phosphorylation

Answer 8

2e- (electrons) move “down” the chain—> they lose energy.(energy used to phosphorylate about 1.5 ATP.)

Question 9

Non-cyclic Photophosphorylation-
Light dependent reaction:

5.Photosystem I

Answer 9

e- transport chain terminates with PS I(with P700).

They are again energized by sunlight and passed on to another primary e- acceptor. From this point forward, it can go to cyclic or noncyclic. If noncyclic then….

Question 10

Non-cyclic Photophosphorylation-
Light dependent reaction:

6. NADPH

Answer 10

2e- then pass down a short electron transport chain( with proteins like FERRODOXIN) to combine NADP+ plus H+ 2e- ——–> NADPH(coenzyme)
Like NADH in respiration, NADPH is an energy-rich molecule.

Question 11

Non-cyclic Photophosphorylation-
Light dependent reaction:

7. Splitting of Water

Answer 11

The loss of 2e- from PSII(initially) is replaced when H20 splits into 2e-, 2H+, and 1/2 O2 (H+ goes for NADPH formation and 1/2 O2 that contributes to release as oxygen gas. This occurs at PSII.

{H20 + ADP + Pi + NADP+ plus light —> ATP + NADPH + O2 + H+}

Question 12

Light-dependent reactions or simply light reactions.

H20 + ADP + P + NADP+ + light —->

Answer 12

In summary, photophosphorylation takes the energy in light and the electrons in H20 to make the energy-rich molecules ATP and NADPH. Because the reactions require light, the are called LIGHT-DEPENDENT reactions.

ATP + NADPH + O2 + H+.

Question 13

Cyclic Photophosphorylation

Answer 13

This replenishes ATP when Calvin cycle consumes it.

-When excited 2e- from PSI join with protein carriers in the first electron transport chain and generate 1 ATP as they pass through; these 2e- are recycled into PSI and can take either cyclic or noncyclic path.

Question 14

Calvin Cycle:

Step 1. Carboxylation

Answer 14

Step 1. fixes CO2, repeat 6 times, uses 6CO2 to produce C6H12O6(glucose)

Question 15

Calvin Cycle:

Step 2. Reduction

Answer 15

Step 2.) 12 ATP and 12 NADPH—–> 12G3P or 12PGAL; energy is incorporated; by-products(NADP+ and ADP) go into non-cyclic phosphorylation.

Question 16

Clavin Cycle:

Step 3. Regeneration

Answer 16

3.) 6 ATP convert 10 G3P—-> 6RuBP. (allows cycle to repeat)

Question 17

Calvin Cycle:

Step 4: Carbohydrate Synthesis

State what is does and it’s formula.

Answer 17

The remaining 2 G3P are used to build glucose and other monosaccharides like fructose and maltose.

6O2 + 18ATP + 12NADPH + H+ ——> 18ADP + 18Pi + 12NADP+ plus 1 glucose(2G3P)

Question 18

Light-independent reactions/dark reactions

Answer 18

No light directly used in the Calvin cycle.

Question 19

Chloroplasts:

1. Outer membrane

Answer 19

This membrane, like plasma membrane, consists of a double layer of phospholipids.

Question 20

Chloroplasts:

2. Intermembrane space

Answer 20

Area in between inner and outer membranes,

Question 21

Chloroplasts:

3. Inner membrane

Answer 21

This is the second membrane. This is also a double phospholipid bilayer.

Question 22

Chloroplasts:

4. Stroma

Answer 22

Where the light-independent reactions occur.

Fluid material that fills inside the inner membrane.mThe Calvin Cycle occurs here, fixing carbon from CO2 to generate carbohydrate precursors(G3P).

Question 23

Chloroplasts:

5. Thylakoids

Answer 23

Within the stroma are stacks of pancake-like membranes.

Individual membrane layers are THYLAKOIDS.

An entire stack of thylakoids is a granum.

Question 24

Chloroplasts:

6. Thylakoid lumen

Answer 24

This is the inside(lumen) of the thylakoid. H+ ions(protons) accumulate here.

Question 25

Chemiosmosis

Answer 25

the mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane.

Th

Question 26

Chemiosmosis in Chloroplasts:

Step 1:

Answer 26

1. H+ ions(protons) accumulate inside thylakoids.

Question 27

Chemiosmosis in Chloroplasts:

Step 2:

Answer 27

A pH and electrical gradient across the thylakoid membrane is created.

Question 28

Chemiosmosis in Chloroplasts:

Step 3. ATP synthases generate ATP

Answer 28

Channel proteins called ATP synthases, allow the H+ to flow through the thylakoid membrane and out to the stroma.

The energy generated by the passage of the H+ provides the energy for the ATP synthases to phosphorylate ADP to ATP.

Question 29

Chemiosmosis in Chloroplasts:

Step 4

Answer 29

The Calvin cycle produces 2G3P using NADPH and CO2 and ATP at then end of the e- transport chain following PSI, 2e- produces NADPH.

Question 30

Photorespiration:

Answer 30

Fixation of oxygen by rubisco—> produces no ATP or sugar. Not ‘efficient’ because rubisco will fix both CO2 and oxygen at the same time if both are present.

Peroxisomes breakdown the products of this process.

Question 31

Peroxisomes:

Answer 31

They are found near chloroplasts, where they function to break down photorespiration products.

Question 32

Caretenoids

Answer 32

red,orange, yellow.

Question 33

Antenna pigments

Answer 33

Chlorophyll b, carotenoids, phycobilins(red algae pigment) capture wavelengths that chlorophyll a does not.

Question 34

C4 Photosynthesis

Answer 34

Evolved from C3, when CO2 enters leaf; absorbed by mesophyll cells; instead of being fixed by rubisco into PGA, CO2 combines with PEP to form OAA by