photosynthesis (4.1, 4.2, 5.1, 5.2, 5.4, 5.6) (in depth) Flashcards
What are the two stages of photosynthesis?
Light-dependent reactions and light-independent reactions (Calvin cycle)
The light-dependent reactions capture light energy, while the Calvin cycle uses that energy to fix CO2 into sugar.
What occurs during the light-dependent reactions?
Direct absorption of photons, synthesis of NADPH and ATP, splitting of water
Water molecules are split to provide electrons, establishing a proton gradient.
What is the primary function of ATP in the Calvin cycle?
To provide energy for converting CO2 into sugar
ATP is generated during light-dependent reactions and used in the Calvin cycle.
What is produced from CO2 during the Calvin cycle?
3-carbon carbohydrate called G3P
G3P can be used to form larger molecules such as glucose.
Where do the light-dependent and independent reactions take place?
In the chloroplasts
Chloroplasts are organelles with three membranes: outer membrane, inner membrane, and thylakoid membrane.
What is the role of pigment molecules in photosynthesis?
To absorb light energy and transfer it to chlorophyll
Pigment molecules include chlorophylls and carotenoids.
What are the three outcomes for an excited-state electron in a pigment molecule?
- Returns to ground state and releases energy as thermal energy or fluorescence
- Transfers energy to a different electron
- Accepted by a primary acceptor and becomes reduced
Fluorescence emits lower energy light than absorbed.
What are the primary photosynthetic pigments?
Chlorophyll a and chlorophyll b
Carotenoids are accessory pigments that help transfer energy to chlorophyll a.
What is the absorption spectrum of chlorophyll a?
Strongly absorbs blue and red light but does not absorb green and yellow light
This characteristic affects the efficiency of photosynthesis.
What happens in photosystem II?
Splitting of water into electrons, protons, and oxygen gas
Energy absorbed from light excites electrons in P680 chlorophyll.
What is the function of the primary electron acceptor?
Accepts electrons from excited chlorophyll and becomes reduced
This initiates the electron transport chain.
What is linear electron transport?
Transfer of high energy electrons through a series of proteins, generating ATP and NADPH
Involves photosystems I and II.
What is chemiosmotic synthesis of ATP?
Creation of ATP using a proton gradient across the thylakoid membrane
High concentration of protons in lumen drives ATP synthase.
What is carbon fixation?
Conversion of inorganic CO2 into organic sugar
This process is facilitated by the enzyme rubisco.
What are the three phases of the Calvin cycle?
- Fixation
- Reduction
- Regeneration
Each phase plays a role in synthesizing glucose.
What is produced during the reduction phase of the Calvin cycle?
Glyceraldehyde-3-phosphate (G3P)
This occurs after 3-phosphoglycerate receives a phosphate and is reduced by NADPH.
What is the role of light energy in photosynthesis?
Excites electrons, allowing them to move from low energy (water) to high energy (NADPH)
This process is crucial for the conversion of light energy into chemical energy.
What is cyclic electron transport?
Electrons are donated back to plastoquinone, producing more ATP
This process does not produce NADPH and contributes to the proton gradient.
what is aerobic cellular respiration? and how does it work?
a cellular respiration process using oxygen to harvest energy from organic compounds. it breaks down glucose with oxygen and water and CO2
what are obligate aerobes?
organisms that can’t live without O2 so they use cellular respiration
what is substrate level phosphorylation?
formation of ATP by a direct transfer of Pi from a substrate
what is oxidative phosphorylation?
it forms ATP by indirect energy transfers from redox reactions
what are the four steps of cellular respiration?
glycolysis
pyruvate oxidation
citric acid cycle
electron transport chain
what is glycolysis in cellular respiration
happens in the cytosol and breaks down two carbon molecules of pyruvate (ATP and NADH byproduct)
