06/12 Photosynthesis and Biological Energy Capture Free Online FlashCards

What is the overall function of photosynthesis?

Photosynthesis converts light energy into chemical energy stored in organic molecules; oxygenic photosynthesis uses water and carbon dioxide to produce carbohydrate and oxygen.

Where do the light-dependent reactions occur?

The thylakoid membrane contains chlorophyll, photosystems, electron carriers, and ATP synthase, so it is the site of the light-dependent reactions.

Why do many leaves appear green?

Chlorophyll absorbs blue and red light strongly but reflects or transmits more green light, making many leaves appear green.

In what order do electrons pass through the two photosystems?

Electrons pass through Photosystem II before Photosystem I. Their numbers reflect discovery order, not the sequence of electron flow.

What is the source of oxygen released in photosynthesis?

Water is oxidized at Photosystem II, supplying replacement electrons and releasing protons and O₂. The released oxygen comes from water, not carbon dioxide.

How does electron transport create a proton gradient?

Electron transport moves protons from the stroma into the thylakoid lumen, creating a higher proton concentration in the lumen than in the stroma.

How does chemiosmosis produce ATP in chloroplasts?

ATP synthase allows protons to flow from the thylakoid lumen into the stroma; the released energy drives ADP phosphorylation to form ATP.

What is NADPH's role in photosynthesis?

At Photosystem I, energized electrons ultimately reduce NADP⁺ to NADPH. NADPH carries reducing power to the Calvin cycle.

What reaction does RuBisCO catalyze?

RuBisCO adds CO₂ to RuBP. The unstable six-carbon intermediate immediately splits into two molecules of 3-PGA.

What is required to produce one net G3P?

Producing one net G3P requires three CO₂, nine ATP, and six NADPH. Five of the six G3P molecules formed are used to regenerate RuBP.

How does C₄ photosynthesis reduce photorespiration?

C₄ plants first fix CO₂ into a four-carbon compound in mesophyll cells, then release CO₂ near RuBisCO in bundle-sheath cells, reducing photorespiration.

How does CAM photosynthesis conserve water?

CAM plants generally open stomata at night, store captured carbon dioxide in organic acids, and release it during the day while stomata are closed.