Photosynthesis

Question 1

Describe the structures of a leaf

Answer 1

Upper and Lower epidermis.
Stomata and Guard Cells. CO2 goes in, O2 goes out.
Mesophyll cells inside that contain chloroplasts

Question 2

Describe the structures of chloroplasts

Answer 2

Double membrane.
Thylakoid disks that contain pigments that absorb specific wavelengths of energy (ie chlorophyll).
Disks stacked up to form Granum.
Stroma is the fluid inside a chloroplast.
Lumen is inside the thylakoid disks.

Question 3

Identify the starting materials and final products of photosynthesis

Answer 3

Light E + H20 + CO2 –> C6H12O6 + O2

Question 4

Acknowledge that there are two steps to Photosynthesis and in general what each step does

Answer 4

Light Rxn & Calvin Cycle.
Light Rxn:
Takes in photons. Takes in H2O. O2 is a biproduct. ATP and NADPH are products that are sent to the Calvin Cycle.
Calvin Cycle:
Takes in ATP and NADPH. Takes in CO2. Produces sugar/Glucose/carbohydrate

Question 5

Describe the role of NADPH in the plant cell

Answer 5

Serves as a taxi for electrons

Question 6

Describe the structures of thylakoids

Answer 6

Phospholipid membrane, Photosystem 2, Photosystem 1, lumen

Question 7

Describe the structures of PSII

Answer 7

Light harvesting complex with pigments, reaction center with special pigments (P680) and primary acceptor,

Question 8

Describe the structures of PSI

Answer 8

Light harvesting complex full of pigments. Reaction center containing 2 special pigments (P700) and a primary acceptor.

Question 9

Explain what is happening in a light reaction including the role of photons, H2O, electrons, electron transport chain, ATP synthase, and NADP+, nadp+ Reductase, PS1, and PSII.
“Tell the story of photosynthesis’s Light Reaction.”

Answer 9

1. A photon strikes a pigment in PSII which excites its electron and causes it to jump to the next energy level.
2. This causes a chain of events of which the other pigment’s electron get excited.
3. The special pigments’s P680’s electrons, found in the reaction center of PSII, get so excited that they jump right out of the atom to the primary acceptor.
4. H2O is oxidized (donates electrons) in order to replenish PSII, leaving 1/2 O2 + 2H+.
5. The electrons from PSII are transferred to Pq –> Cytochrome complex –> Pc –> PSI. In doing so, ATP is produced.
6. A photon strikes a pigment found within the light harvesting complex of PSI which excites the electrons causing them to jump to the next energy level.
7. P700’s electrons (in reaction center) get so excited that they jump right out of the atom, to the primary acceptor (reducing P700 to P700+).
8. These electrons are transferred to Fd –> NAD+ + H+ –NAP+ Reductase–> NADPH .
9. H+’s from this linear electron flow go down their gradient (from inside the thylakoid) through a protein called ATP Synthase (out into the stroma)…this provides energy required to synthesize ATP from ADP + P.

Question 10

Explain the importance of maintaining an electrochemical gradient between the thylakoid lumen and stroma

Answer 10

Without this gradient, there would be no energy to power ATP Synthase protein, so ATP couldn’t be made!

Question 11

Describe the three phases of the Calvin Cycle including the importance of RuBP, Rubisco, CO2, and G3P

Answer 11

1. Carbon Fixation:
   RuBP + CO2 –Rubisco enzyme–> 3PG
2. Reduction & Carbohydrate Production:
   6x 3PG + NADPH + ATP –> 6x G3P. 1 out of 6 G3P’s are a sugar output
3. Regeneration:
   5x G3P + ATP –> RuBP
   5 out of 6 G3P’s are used to regenerate RuBP, which is the CO2 acceptor

Question 12

Identify the final products of photosynthesis

Answer 12

O2 + C6H12O6

Question 13

What are the Trophic Levels? (Autotrophs/Heterotrophs)

Answer 13

Autotrophs convert inorganic substances into organic substances. They capture all the energy for our biosphere!

Heterotrophs eat the autotrophs. Heterotrophs convert an organic substance into chemical energy known as ATP.

A plant gets 10% of the energy from light energy. When we eat a plant, we get 10% of that 10%.

Question 14

In general, what 3 things are required for Photosynthesis?

Answer 14

Sunlight, H2O, and CO2

Question 15

What do pigment molecules do?

Answer 15

They capture light energy

Question 16

Where does the Light RXNs take place? Calvin Cycle?

Answer 16

Thylakoid membrane.

Stroma.

Question 17

The electrons of PSII are excited and transferred to electron carriers. From which molecule or structure do the PSII replacement electrons come?

Answer 17

H2O

Question 18

What is the chemical reaction for producing NADPH? include the enzyme req’d!

Answer 18

NADP+ + 2electrons + H+ –NADP+ reductase–> NADPH

Question 19

Describe the level of excitement of an electron as it travels through these reaction steps

Answer 19

At the beginning the electron has low energy. Then, a photon strikes the pigment molecule which excites the electron. The energy level of the electron slowly goes back down while going through the ETC. Then, at the PSI, another photon strikes a pigment molecule, exciting the electrons high again. This energy and electrons are used to make NADPH

Question 20

As electrons are passed through the system of electron carriers associated with PSII, they lose energy. What happens to this energy?

Answer 20

It is used to establish and maintain a proton gradient

Question 21

What is Cyclic Electron Flow?

Answer 21

Used by some photoautotrophs to make extra ATP

Question 22

What are the products of linear electron flow?

Answer 22

ATP and NADPH

Question 23

What can the G3P products be used for? (2)

Answer 23

Building up larger carbohydrates. Glucose –> cellulose/starch; Sucrose –> cell respiration in other plants

Cellular Respiration.

Question 24

Does the Light Reaction produce or use chemical energy? Calvin Cycle?

Answer 24

Produce.

Use.

Question 25

What is the primary function of the Calvin Cycle?

Answer 25

Synthesize simple sugars from CO2

Question 26

What do mesophylls contain?

Answer 26

Chloroplasts

Question 27

There are ~_____ chlorophyll’s in a cell.

Answer 27

20-50

Question 28

Chlorophyll _______ green light.

Answer 28

Reflects

Question 29

Why is it advantageous to have many different pigment molecules?

Answer 29

Because then you can capture more energy.

Question 30

______ is the 1st pigment to decay when fall/winter hits.

Answer 30

Chlorophyll

Question 31

Overall, in the Light RXNs, we are just ______________.

Answer 31

Transferring electrons

Question 32

The energy source of the proton gradient found in the Light RXNs is _____________

Answer 32

The electrons

Question 33

The O2 biproduct comes from ______ and leaves the chloroplast out of the __________.

Answer 33

H2O, stomata

Question 34

Carbon Fixation is catalyzed by _______________

Answer 34

Rubisco enzyme

Question 35

What 3 things can influence both the efficiency and the way the Calvin Cycle works?

Answer 35

1. Light intensity
2. Temperature
3. H2O availability

Question 36

Rubisco mainly uses CO2, but it can also use _________.

Answer 36

O2

Question 37

RuBP + O2 –Rubisco–> ???….these are then released as _______

Answer 37

A different set of molecules.

CO2

Question 38

Why would there be a lot of O2 in the plant cell?

Answer 38

On really hot days, H2O comes out…we don’t want to dehydrate our plant, so we close the stomata. O2 will build up! (And Rubisco may start using O2, which WE DONT WANT!

Question 39

Talk about C4 plants. What is unique about their light reaction and Calvin cycle processes? What is their structure? Tell the story of its pathways.

Answer 39

[see diagram]

Question 40

Talk about CAM plants. What is unique about their light reaction and Calvin cycle processes? What happens at night vs. in the day? Tell the story of its pathway.

Answer 40

[see diagram]

Question 41

Why does Photorespiration happen?

Answer 41

Because there is a build up of O2 in the cell

Question 42

Why is Photorespiration a bad thing?

Answer 42

Because we are CREATING CO2 instead of USING IT to make sugar!