Unit 4.5 Photosynthesis

Question 1

What are the light dependant reactions? (3)

Answer 1

light energy used to split H2O :
oxygen –> waste
protons –> protons grandient used by ATP synthase to make ATP
electrons –> electron transport chain energy used to make H+ gradient added to NADP+ –> NADPH

Question 2

What are the carbon reactions?

Answer 2

ATP and NADPH used to fixt CO2 into glucose (CO2 inorganic –> carbohydrate organic)

Question 3

In what does photosynthesis occur?

Answer 3

plants, algae, some protists, some bacteria

Question 4

In the site of photosynthesis, describe the thylakoid space?

Answer 4

Site where H+ accumulate

Question 5

In the site of photosynthesis, describe the thylakoids?

Answer 5

Membrane site of ETS

Question 6

What is chlorophyll (Chl)

Answer 6

a pigment in thylakoid membranes absorbs light energt

Question 7

Describe the process of this light absorbing pigments?

Answer 7

Chlorophyll (ground state) absorbs light it becomes excited Chl*. It is very unstable and transfers its energy to 1. another pigment 2. release as heat 3. fluorescence 4. use for chemical reactions transfer e-

Question 8

What are accessory pigments?

Answer 8

• Expand wavelengths that can be absorbed (ex.: cartenoids red, orange, yellow)
• provide photo-protection when light absorbed is excessive (absorb light energy and release as heat)
• antioxidants

Question 9

Resume light-dependant reactions?

Answer 9

electron transfer from H2O to NADP+ –> NADPH

Question 10

Linear photophosphorylation: what is produced using which complex?

Answer 10

Produces oxygen + NADPH + proton gradient

PSII –> PQ –> cyt B6f –> pC –> PSI –> Fd –> FNR –> NAD+

Question 11

What is the role of photosystem II ?

Answer 11

w/Chl -absorbs light energy w/P680 -pair of Chl -transfer to e- excits e-. OEC -oxygen evolving O2 complex pulls electrons out of H20 and gives them to P680

Question 12

What is the role of PQ?

Answer 12

Plastoquinone transfers e- from PSII to cytodrome b6f. Also picks up H+ from stroma

Question 13

Role of cytochrome b6f

Answer 13

removes protons from PQ transfers proton (H+ pump) to lumen. transfer electrons from PQ to pC

Question 14

Role of pC

Answer 14

Plastocyanin tranfer e- from cyt b6f to PSI

Question 15

Role of PSI

Answer 15

absorbs light energy, energy transfer to reaction center p700, use energy to re-energize e-. transfers continues to Fd

Question 16

Role Fd

Answer 16

transfers electrons to ferredozin NADP+ reductase

Question 17

Role of NADP+ reductase (FNR)

Answer 17

transfers electrons from Fd to NADP+ adds H+ from stroma to NADP+ forms NADPH

Question 18

Explain what is chemiosmosis

Answer 18

using proton gradient and ATP synthase to make ATP from ADP+ Pi

Question 19

Describe cyclic photophosphorylation.

Answer 19

electron tranfer from (near the end of PSI: almost FNR) back to PQ.
PQ–>PQH2 –> b6f –> PC –> PSI –> Fd back to PQ

Question 20

What is the purpose of cyclic photophosphorylation

Answer 20

increase proton gradtient –> (increase ATP)

no NADPH, no oxygen consumed b/c water not split

Question 21

Describe carbon reactions (Calvin cycle/ light-independant reactions)

Answer 21

Occur in stoma of chloroplast, converts CO2 to organic form (fixes CO2), uses ATP and NADPH made by light reactions.

Question 22

What are the three stages of the calvin cycle

Answer 22

1. Carboxylation - CO2 added to 5-carbon RuBP to get 2 molecules of 3PGA (enzyme rubisco)
2. Reduction - each 3PGA use ATP to make 1,3-bisphosphoglycerate and then NADPH to form glyceraldehyde-3-phosphate (G3P)
3. Regeneration of RuBP. 5 of 6 G3P (3-carbons) produced used to regenerate 3 RuBP (5-carbons)

Question 23

Facts about enzyme rubisco

Answer 23

most abyndant enzyme of Earth, very slow: fixes 3CO2 per second

Question 24

What is done with 1 of the G3P produced (not used to regenerate RuBP)

Answer 24

use to make carbohydrates:

• if exported to cytosol –> sucrose (12-carbon)
• if stays in cp –. converted to glucose, stored as starch

Question 25

What are the raw materials of photosynthesis (other than electron transfer compounds and ATP and enzymes)

Answer 25

H20, CO2, light

Question 26

What are the end product of photosynthesis (other than electron transfer compounds and ATP)

Answer 26

glucose, O2

Question 27

Where within the cell does the process of photosynthesis take place

Answer 27

chloroplast

Question 28

Principal electron transfer molecule

Answer 28

NADPH

Question 29

Specific location of electron transport system

Answer 29

Thylokoid membrane

Question 30

Source of electrons for electron transport system

Answer 30

water

Question 31

Terminal electron acceptor for electron transport system

Answer 31

NADP+