ATP Makers: The Power of Chemiosmosis

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• Biology
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ATP Makers: The Power of Chemiosmosis

What do you already know about how plants make ATP during photosynthesis?

Learning Objective

At the end of the lesson, you will be able to explain the process of chemiosmosis during the light reactions of photosynthesis and describe how ATP is produced in chloroplasts.

What Is Chemiosmosis?

Chemiosmosis is the process where ATP is produced as protons move down their concentration gradient across the thylakoid membrane in chloroplasts.

Role of Light Reactions

Light reactions use sunlight to break apart water molecules, release oxygen, and produce high-energy electrons needed for ATP production.

The Splitting of Water

Light energy splits water into oxygen (O2), electrons, and hydrogen ions (protons). This process provides the electrons and protons necessary for chemiosmosis.

How Protons Build Up

Creating a Gradient

This high concentration of protons sets up a concentration gradient compared to the stroma.

Protons accumulate inside the thylakoid as water splits and electrons move along the transport chain.

Inside the Thylakoid

Write down any 1 point you understood from the video.

ATP Synthase: Cellular Powerhouse

Protons diffuse from the thylakoid into the stroma through ATP synthase channels. ATP synthase converts this energy into ATP.

Electron Transport Chain

Excited electrons pass from photosystem II to an electron-acceptor, then travel down a chain of carriers to photosystem I, helping pump protons into the thylakoid.

The Role of NADPH

Electrons end up with ferredoxin and are transferred to NADP+, forming NADPH. This molecule stores energy for the next phase of photosynthesis.

Why Chemiosmosis Matters

Chemiosmosis makes ATP and NADPH, which are both essential to power the next stage of photosynthesis—where sugars are built!

Review: Key Steps in Chemiosmosis

ATP & NADPH Formation

Split Water and Build Gradient

Protons flow through ATP synthase to make ATP. Electrons make NADPH.

Light splits H2O, O2 is released, protons build up, electrons travel ETC.

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