Photosynthesis: Understanding the Two Stages and Their Key Components, Slides of Plant physiology

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BELL RINGER^ •

Explain what happens in each of thetwo phases of photosynthesis. What isrequired and what is made?

KEY CONCEPT

Photosynthesis requires a series of chemicalreactions.

•^

Photosystem II captures and transfers energy.– chlorophyll absorbs

energy from sunlight

• energized electrons

enter electrontransport chain

• water molecules are

split

• oxygen is released as

waste

• hydrogen ions are

transported acrossthylakoid membrane

•^

Photosystem I captures energy and produces energy-carrying molecules.– chlorophyll absorbs

energy from sunlight

• energized electrons

are used to makeNADPH

• NADPH is transferred

to light-independentreactions

•^

The light-dependent reactions produce ATP.– hydrogen ions flow through a channel in the thylakoid

membrane

• ATP synthase attached to the channel makes ATP

•^

Light-independentreactions occur in thestroma and use CO

2

molecules.

The second stage of photosynthesis uses energy fromthe first stage to make sugars.

• two three-carbon molecules bond to form a sugar– remaining molecules stay in the cycle -^

A molecule of glucose is formed as it stores some of theenergy captured from sunlight.