Unit 4.5 Photosynthesis Flashcards
(31 cards)
What are the light dependant reactions? (3)
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
What are the carbon reactions?
ATP and NADPH used to fixt CO2 into glucose (CO2 inorganic –> carbohydrate organic)
In what does photosynthesis occur?
plants, algae, some protists, some bacteria
In the site of photosynthesis, describe the thylakoid space?
Site where H+ accumulate
In the site of photosynthesis, describe the thylakoids?
Membrane site of ETS
What is chlorophyll (Chl)
a pigment in thylakoid membranes absorbs light energt
Describe the process of this light absorbing pigments?
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-
What are accessory pigments?
- 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
Resume light-dependant reactions?
electron transfer from H2O to NADP+ –> NADPH
Linear photophosphorylation: what is produced using which complex?
Produces oxygen + NADPH + proton gradient
PSII –> PQ –> cyt B6f –> pC –> PSI –> Fd –> FNR –> NAD+
What is the role of photosystem II ?
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
What is the role of PQ?
Plastoquinone transfers e- from PSII to cytodrome b6f. Also picks up H+ from stroma
Role of cytochrome b6f
removes protons from PQ transfers proton (H+ pump) to lumen. transfer electrons from PQ to pC
Role of pC
Plastocyanin tranfer e- from cyt b6f to PSI
Role of PSI
absorbs light energy, energy transfer to reaction center p700, use energy to re-energize e-. transfers continues to Fd
Role Fd
transfers electrons to ferredozin NADP+ reductase
Role of NADP+ reductase (FNR)
transfers electrons from Fd to NADP+ adds H+ from stroma to NADP+ forms NADPH
Explain what is chemiosmosis
using proton gradient and ATP synthase to make ATP from ADP+ Pi
Describe cyclic photophosphorylation.
electron tranfer from (near the end of PSI: almost FNR) back to PQ.
PQ–>PQH2 –> b6f –> PC –> PSI –> Fd back to PQ
What is the purpose of cyclic photophosphorylation
increase proton gradtient –> (increase ATP)
no NADPH, no oxygen consumed b/c water not split
Describe carbon reactions (Calvin cycle/ light-independant reactions)
Occur in stoma of chloroplast, converts CO2 to organic form (fixes CO2), uses ATP and NADPH made by light reactions.
What are the three stages of the calvin cycle
- Carboxylation - CO2 added to 5-carbon RuBP to get 2 molecules of 3PGA (enzyme rubisco)
- Reduction - each 3PGA use ATP to make 1,3-bisphosphoglycerate and then NADPH to form glyceraldehyde-3-phosphate (G3P)
- Regeneration of RuBP. 5 of 6 G3P (3-carbons) produced used to regenerate 3 RuBP (5-carbons)
Facts about enzyme rubisco
most abyndant enzyme of Earth, very slow: fixes 3CO2 per second
What is done with 1 of the G3P produced (not used to regenerate RuBP)
use to make carbohydrates:
- if exported to cytosol –> sucrose (12-carbon)
- if stays in cp –. converted to glucose, stored as starch
