Photosynthesis Flashcards
What is the definition of photosynthesis?
Conversion of CO2 and water into sugars using light energy and releasing O2 as a byproduct.
Where does photosynthesis primarily take place?
In the chloroplasts of mesophyll cells.
What structures in the chloroplasts are utilized during photosynthesis?
Thylakoid membranes and stroma.
What are the two key stages of photosynthesis?
- Light-Dependent Reactions
- Calvin Cycle (Light-Independent Reactions)
Where do light-dependent reactions occur?
In the thylakoid membranes.
What is produced during light-dependent reactions?
- ATP
- NADPH
- O2 (from water oxidation)
What process generates ATP in light-dependent reactions?
Chemiosmosis (photophosphorylation).
Where does the Calvin Cycle occur?
In the stroma.
What is the main function of the Calvin Cycle?
Fixes CO2 into sugars using ATP and NADPH from the light reactions.
What is the first step of the Calvin Cycle?
Fixation: CO2 is attached to a 5-carbon molecule (RuBP) by Rubisco.
What are the two 3-carbon molecules produced during the fixation step?
G3P.
What is the role of ATP and NADPH in the Calvin Cycle?
Convert 3-carbon molecules into G3P.
What happens during the regeneration step of the Calvin Cycle?
Some G3P molecules regenerate RuBP for the cycle to continue.
What is chlorophyll?
A pigment that absorbs light in the blue and red wavelengths, reflecting green.
Chlorophyll’s appearance is due to the transmission and reflection of green wavelengths.
What happens to green wavelengths in chlorophyll?
They pass through or are reflected.
This characteristic is why chlorophyll appears green.
What is the role of accessory pigments in photosynthesis?
They combine with chlorophyll to broaden light absorption.
What is Photosystem II (PSII) responsible for?
Oxidizing water to supply electrons and generating O2.
What occurs in Photosystem I (PSI)?
Receives electrons from the electron transport chain and boosts them to high energy with light to reduce NADP+ to NADPH.
What is the function of antenna complexes in photosynthesis?
Funnel light energy toward reaction centers.
What does the electron transport chain establish?
A proton gradient (proton motive force/electrochemical gradient) across the thylakoid membrane.
How is ATP created during photosynthesis?
Protons flow through ATP synthase, creating ATP through chemiosmosis.
What is the outcome of cyclic electron transport?
Generates ATP but not NADPH.
In cyclic electron transport, where do electrons end up?
They are recycled to earlier in the electron transport chain.
What does cyclic electron transport help balance?
The energy requirements of the Calvin Cycle.
What are the inputs of photosynthesis?
Light, H2O, CO2
These inputs are essential for the process of photosynthesis to occur.
What are the outputs of photosynthesis?
O2, ATP, NADPH, sugars (e.g., glucose)
These outputs are the products generated from the photosynthesis process.
What is photorespiration?
Occurs when Rubisco fixes O2 instead of CO2, leading to energy loss
Photorespiration can be a significant challenge for plants during photosynthesis.
How do plants in dry climates combat photorespiration?
By concentrating CO2 around RUBISCO
This allows CO2 to outcompete O2, reducing the occurrence of photorespiration.
What is spatial concentration in the context of photosynthesis?
Concentrate CO2 in specialized cells in the leaf
This strategy helps to increase the availability of CO2 for photosynthesis.
What is temporal concentration in the context of photosynthesis?
Concentrate CO2 at night and fix during day
This method allows plants to optimize CO2 usage while minimizing water loss.
