Photosynthesis Flashcards
Photosynthesis definiton and function
“Stynthesis using light”
- is responsible for almost all the planters energy resources
Photosynthesis equation
6CO2 + 6H20 ——(plant,light)—-> C6H12O6 + 6O2
Chloroplasts are..
The site of photosynthesis
Two parts of photosynthesis
- Light reactions
- Calvin cycle
STURCTURE (parts) of the chloroplast - label and locate
Three membranes:
Outer membrane
Inner membrane
Thylakoid (3rd membrane complex folded up - where light reactions occur)
Three compartments:
Stroma (where carbon fixation occurs)
Thylakoid space (protein gradient inside)
Inter membrane space
DNA
Ribosomes
What do the light reactions do
- capture light energy and convert it to chemical energy using pigment and protien complexes embedded in the thylakoid membrane
The light reactions- photosystems function
Photo systems capture light energy
- Photo systems are protein complexes that contain chlorophyll
- Chlorophyll absorbs light energy
- Light energy absorbed by chlorophyll produces high energy electrons
- High energy electrons travel though the photosynthetic electron transport chain
Photosynthetic electron transport chain
Light comes into photosystem 2 and chlorophyll capture the light energy, producing high energy electrons
- high E electrons leave the photosystem and travel to cytochrome complex - they go into the complex with a lot of energy and leave with less energy, the energy had been used to pump protons across membrane
- lower energy electrons then go to photosystem 2, which is also absorbing light energy thus giving the protons a boost, making them high energy electrons again
- high E electrons then leave and go to energy carrier NADPH (first output, light energy to high E electrons that are now stored in NADPH)
- the two electrons in this process come from water - photosystem pulls electrons from water, splits water and releases oxygen as a by product as well as protons
- the protons built up on the inner of the membrane then moves through ATP synthase making ATP from ADP+Pi
Pigment protein complexes
What are the products of the light reactions and what are the used for?
- ATP and NADPH
- used to fix CO2 and produce carbohydrate in the Calvin cycle
Where does the Calvin cycle take place?
In the chloroplast stroma
Bottom line of the Calvin cycle:
- 3 CO2 molecules are fixed, and that produces 3 carbon sugars (which then can be made into a 6 carbon glucose)
- takes 3 low carbon molecules and uses chemical energy from the light reactions to make high energy sugar molecules
3 steps of Calvin cycle:
- FIXATION
- REDUCTION
- REGENERATION
CALVIN CYLE 1: FIXATION
- React CO2 with a 5 carbon molecule which splits and creates 2 X 3 (low energy) carbon molecules (doesn’t require energy)
CALVIN CYCLE 2: REDUCTION
- 3 Carbon molecules converted into a different (higher energy) 3 carbon molecule
- using ATP and NADPH from light reactions and putting into the 3 carbon molecule - (produces 6 ADP and 6 NADP+)
CALVIN CYCLE 3: REGENERATION
One of the 3 carbon molecules goes back into the Calvin cycle
- converting the 3 carbon molecule back into the 5 carbon molecule - this requires energy (3ATP)
- 3 ADP is produced as a by product
