Light Reactions and Electron Transport

The video explains the light reactions in photosynthesis, focusing on the thylakoid membranes where photosystems I and II absorb light to excite electrons. These electrons move through an electron transport chain, resulting in the formation of NADPH and ATP. The process involves water splitting, oxygen release, and the establishment of a proton gradient used by ATP synthase to produce ATP. The energy stored in ATP and NADPH is then used in the Calvin cycle. The light reactions are continuous in the presence of sunlight, involving a series of chemical reactions on the thylakoid membranes.

What are the specialized molecules in the thylakoid membranes that perform the light reactions called?

• Chloroplasts

• Photosystems

• Mitochondria

• Ribosomes

Which photosystem is the first to absorb light in the light reactions?

• Photosystem IV

• Photosystem I

• Photosystem II

• Photosystem III

What is the byproduct of water splitting in Photosystem II?

• NADPH

• Glucose

• Oxygen

• Carbon dioxide

Where do the excited electrons move after leaving Photosystem II?

• To the cytochrome complex

• To Photosystem I

• To the Calvin cycle

• To the stroma

What happens to the electrons when they reach Photosystem I?

• They are released into the air

• They are stored as ATP

• They are used to form glucose

• They are excited again by photons of light

What is the final electron acceptor in the light reactions?

• ADP

• NADP+

• Water

• Oxygen

What molecule is formed when NADP+ accepts electrons?

• Glucose

• ADP

• ATP

• NADPH

What enzyme uses the proton gradient to form ATP?

• NADP+ reductase

• ATP synthase

• Cytochrome complex

• ATPase

What is the energy stored in ATP and NADPH used for?

• Fermentation

• Krebs cycle

• Glycolysis

• The Calvin cycle

What drives the continuous nature of the light-driven electron transport chain?

• Presence of water

• Presence of glucose

• Presence of sunlight

• Presence of oxygen