Unit 4: Photosynthesis Flashcards
In what organisms does photosynthesis take place?
Plants, algae, some protists, some bacteria
Where does photosynthesis occur?
Chloroplasts
What two types of reactions occur in photosynthesis?
- Light-dependant reactions
2. Carbon reactions
What is the sight of ETS?
Thylakoids
True or false: The chloroplast stroma is the equivalent of the mitochondrial matrix
True
What is chlorophyll?
- a pigment
- in thylakoid membranes
- absorbs light energy
What does chlorophyll absorb?
Blue and red
What does chlorophyll reflect?
Green
What is another type of pigment?
Carotenoids
What do accessory pigments do?
- Absorb visible light at wavelengths Chl cannot
- Transfer light energy to Chl
What are the functions of Chl in its excited state?
- Transfer energy to another pigment
- Fluorescence
- Heat
- Used in chemical reactions
What are the products of liner photophosphorylation?
Oxygen, NADPH, proton gradient
What are the characteristics of photosystem II?
- Light is absorbed by antenna pigments
- Energy transferred to reaction center P680
- Excited electron transferred to electron acceptor
- oxygen evolving complex pulls electrons out of H2O and gives them to P680
What is the role of plastoquinone?
PQ picks up protons from stroma to form PQH2
What doe PQH2 do?
Move through the membrane; transfers electrons from PSII to cytochrome b6-f complex?
What are the characteristics of cytochrome b6-f?
- Removes protons from PQH2 and transfers them to lumen
- Transfers electrons from PQH2 to plastocyanin
What are the characteristics of plastocyanin?
- It moves across the membrane
- Transfers electrons from cyt. b6-f to photosystem I.
What are the characteristics of photosystem I?
- antenna pigments absorb light energy
- energy transferred to reaction center P700
- P700 transfers energy to electrons
- electron transfer continues to ferredoxin
What is the role of ferredoxin?
Transfer electrons to ferredoxin NADP+ reductase (FNR)
What is the role of ferredoxin NADP+ reductase?
- Transfer electrons from Fd to NADP+
- Adds H+ from stroma to NADP+
- Forms NADPH
True or false: There is a high proton concentration in the stroma.
False. It is low. The high concentration of protons is in the lumen.
What is produced with chemiosmosis?
ATP using ADP+Pi
In what direction do protons move during chemiosmosis?
From the lumen to the stroma.
What is the purpose of cyclic photophosphorylation?
- Used to produce extra ATP
- Increase H+ gradient
What are not products of cyclic photophosphorylation?
- No NADPH is produced
- No oxygen is produced
True or false: Photosystem II is not used in cyclic photophosphorylation.
True.
What are the basic steps of cyclic photophosphorylation?
- Electron transfer near the end of PSI
- Back to PQ which reacts with b6-f complex
PQH–>b6f–>PC–>PSI - energy from electron transfer used to power proton pump
What are other names (though some are inaccurate) form the Cavin Cycle?
- light-independent reactions
- dark reactions (inaccurate)
Where does the Calvin Cycle occur?
In the stroma of chloroplast
What does the Calvin do?
- Fixes CO2 (converts it to organic form)
- Uses ATP and NADPH made by light reactions
What are the 3 stages of the Calvin Cycle?
- Carboxylation (CO2 added to 5-carbon RuBP)
- Reduction (forms glyceraldehyde-3-phosphate (G3P))
- Regeneration of RuBP
What enzyme is used in carboxylation?
Rubisco
What is produced during carboxylation?
2 molecules of 3-phsophoglycerate (3PG)
What is produced during reduction?
1 molecule of 3PG produces 1 molecule of 1,3-biphosphoglycerate
Then 1 molecule of 1,3-biphosphoglycerate produces of glyceraldehyde-3-phosphate (G3P)
NOTE: a total of 6 G3P are produced since stage 1 is repeated 3 times
What happens in regeneration?
- 5 of the 6 G3P produced are used to regenerate RuBP
2. 1 of the 6 G3P produced is used to make carbohydrates
True or false: If the G3P is exported to the cytosol then sucrose is made.
True.
True or false: If the G3P remains in the chloroplast, then its converted to glucose and stored as starch.
True.
