Photosynthesis Flashcards
When an atom or molecule is _________ it loses an electron
OXIDIZED
When an atom or molecule is _________ it gains an electron
REDUCED
Define:
The process in which plants and other photosynthetic organisms capture and convert light energy from the sun into chemical energy
Photosynthesis
What is the formula for photosynthesis?
6 H2O + 6 CO2 + light —–> C6H12O6 + 6 O2
Where does the light-dependant reaction occur?
The thylakoid membrane
What is a photosystem?
Clusters of chlorophyll and other pigments embedded in the thylakoid membrane
What are the two photosystems in chloroplasts
Photosystem I (PSI) & Photosystem II (PSII)
What are the steps of Photosystem II
- Light enters
- Photons excite chlorophyll molecules
- Light energy transferred to reaction center
- Photolysis occurs (splitting of water - H4 & O2)
- Oxygen released
- Hydrogen accumulates inside thylakoid lumen/space
- Hydrogen electrons are transferred to Photosystem I via electron transport chain
Define:
Chemiosmosis
Hydrogen electrons are pulled into the ATP synthesis enzyme due to concentration gradient and the the energy stored in the gradient is used to make ATP
What are the steps of Photosystem I
- Electrons move through the transport chain to PSI
- More light enters
- Chemiosmosis occurs - Hydrogen electrons are pulled into the ATP synthesis enzyme due to concentration gradient
- NADP+ combines with H+ to make NADPH
What are the products of the light-dependant reaction?
- NADPH
- Separate Oxygen and hydrogen ions
- ATP
What is ATP
- ATP is a byproduct of photosynthesis
- ATP supplies the energy for cellular function (transport, cell division, cell movement, muscle contraction, etc.)
ATP releases energy when the bond of the 3rd phosphate groups breaks, creating ADP
How is ADP formed?
ATP releases energy when the bond of the 3rd phosphate groups breaks, creating ADP
Where does the light-independent reaction (Calvin Cycle) occur?
Takes place in stroma
What is required for the Calvin Cycle to take place? (reactants)
Reactants required:
- ATP
- NADPH
- CO2
What are the three main steps in the Calvin Cycle?
- Carboxylation
- Reduction
- Regeneration
What are the steps of carboxylation (Calvin Cycle)
- Carbon dioxide diffuses through the leaf into the stroma
- Carbon dioxide is chemically combined to a 5-carbon molecule called RuBP (ribulose biphosphate) which is catalyzed by the RuBisCo enzyme
- The new 6-carbon compound very unstable and immediately breaks down to two stable 3-carbon molecules called 3-phosphoglycerate (P3G or PGAL)
What is the difference between P3G and PGAL
Nothing; they are different abbreviations for the same compound (PhosphoGlycerALdehyde)
What are the steps of reduction (Calvin Cycle)
- 3-carbon compounds are in a low energy state so they are activated by ATP which converts to ADP
- The compound is then reduced by NADPH, creating G3P
- Some G3P exit cycle to form glucose
What are the steps of regeneration (Calvin Cycle)
- ATP breaks and reforms the bonds of G3P molecules to make more RuBP
How many times must the Calvin Cycle be completed in order to produce 1 glucose molecule?
6 times
What does the light-independent cycle produce?
High Energy Compounds
(carbohydrates, fats, starch)
What is the glucose produced by the calvin cycle used for?
- Used immediately to make ATP for cellular respiration
- Transported to other cells
- Stored for a medium-term (glycogen or starch)
- Used to synthesize molecules that can store energy for long term
How is excess glucose stored in plants?
Oils (canola oil, olive oil, etc.)
