Unit 3 Light-Dependent Reactions

What do light-dependent reactions absorb?

Photons of sunlight

Where do light-dependent reactions occur in?

Thylakoid membranes

What are the inputs of light-dependent reactions?

Sunlight, water, NADP+, ADP, and unhooked phosphate group

What is NADP+?

Electron-accepting molecule

What are the outputs of light-dependent reactions?

Oxygen, NADPH, and ATP

What is NADPH?

Energy-carrying molecule

What is the main function of light-dependent reactions?

Generate energy-carrying molecules in the form of ATP and NADPH for the next stage of photosynthesis 

What is the area where light hits a thylakoid called?

Photosystem

What are photosystems?

Clusters of pigments in thylakoid membranes

What pigments make up photosystems?

Chlorophyll a, chlorophyll b, and accessory pigments

What is the first photosystem that receives light called?

Photosystem II

What is photosystem II?

Reaction center that receives light from wavelengths at 680 nm

What is the second photosystem that receives light called?

Photosystem I

What is photosystem I?

Reaction center that accepts wavelengths at 700 nm

What is the first step of light-dependent reactions?

Photolysis

What is photolysis?

Splitting of water to form oxygen, hydrogen ions, and electrons 

What are electrons obtained from photolysis transferred to?

Photosystem II

What does the absorption of sunlight by chlorophyll molecules in photosystem II do?

Excite/energize the electrons in photosystem II

What does sunlight oxidize when absorbed by photosystems?

Chlorophyll

What excited electrons from photosystem II passed down after being transferred to a primary electron acceptor?

Electron transport chain (ETC)

What are electron transport chains?

Series of proteins embedded in the thylakoid membrane similar to a staircase

What does the gradual energy loss of electrons based down the electron transport train allow for?

Pumping of H+ from the stroma across the thylakoid membrane and into the interior of the thylakoid 

What does the pumping of H+ from the stroma across the thylakoid membrane create?

Electrochemical gradient of H+ inside the interior of thylakoids

What are the unexcited electrons at the bottom of the electron transport chain transferred to?

Photosystem I

What happens at photosystem I?

Sunlight strikes and excites transferred electrons

What do the excited electrons of photosystem I do?

Travel down another shorter electron transport chain 

What are electrons at the end of the shorter electron transport chain transferred to?

NADP+

What combines to form NADPH?

NADP+, electrons, and H+

What helps create NADPH?

NADP+ reductase

Where does NADPH transfer electrons/energy?

Stroma to be used in light-independent reactions 

What starts the process of the generation of NADPH again?

Photolysis 

What does the electrochemical gradient of H+ built up inside thylakoids pass through the membrane via?

ATP synthase 

How does ATP synthase make ATP?

By adding a phosphate group to ADP

What is the type of ATP production ATP synthase conducts called?

Photophosphorylation

Where is the ATP made by ATP synthase sent?

Stroma to be used in light-independent reactions 

What is the production of ATP in light-dependent reactions called?

Chemiosmosis