Energy and Photosynthesis

What do all living things need?

Energy to carry out life processes.

Where do organisms get energy from?

Food molecules, especially carbohydrates.

How do plants make carbohydrates?

They use light energy to make carbohydrates from carbon dioxide and water.

What is ATP?

Adenosine triphosphate, a molecule that stores and transfers energy in cells.

What are the three parts of ATP?

Adenine, ribose sugar, and three phosphate groups.

What does ATP stand for?

Adenosine triphosphate.

What does ADP stand for?

Adenosine diphosphate.

What are the parts of ADP?

Adenine, ribose sugar, and two phosphate groups.

How does ATP release energy?

The bond between the second and third phosphate groups breaks, forming ADP and a phosphate group while releasing energy.

What is an exergonic reaction?

A reaction that releases energy.

What is an endergonic reaction?

A reaction that requires energy.

What happens when ATP loses its third phosphate group?

ATP becomes ADP and releases energy.

How is ATP made from ADP?

Energy is used to attach a third phosphate group to ADP.

What is the ATP-ADP cycle?

ATP releases energy and becomes ADP. Energy is then used to turn ADP back into ATP.

What is the first and most common molecule broken down for energy?

Carbohydrates.

How many calories per milligram and ATP are there for carbohydrates?

4 calories/mg and 36 ATP.

What are lipids?

Fats that store energy, insulate the body, and cushion organs.

How many calories per milligram and ATP are there for lipids?

9 calories/mg and 146 ATP.

What is the second molecule broken down for energy in your notes?

Lipids.

How many calories per milligram and ATP does your notes list for proteins?

4 calories/mg and 36 ATP.

Why are proteins usually the last molecules broken down for energy?

They have many other essential functions.

What is the order in which carbohydrates, lipids, and proteins are broken down for energy in your notes?

1. Carbohydrates, 2. lipids, 3. proteins.

What is photosynthesis?

The process plants use to convert light energy into chemical energy stored in sugar.

What is the overall photosynthesis equation?

6H₂O + 6CO₂ + light energy → 6O₂ + C₆H₁₂O₆

What are the reactants of photosynthesis?

Water, carbon dioxide, and light energy.

What are the products of photosynthesis?

Oxygen and glucose.

What is a chloroplast?

An organelle that carries out photosynthesis.

What is a thylakoid?

A membrane structure inside a chloroplast where the light-dependent reactions occur.

Where do the light-dependent reactions take place?

In the thylakoid membranes.

What is chlorophyll?

A green pigment that absorbs light energy.

What is the stroma?

The fluid-filled space inside a chloroplast where the Calvin cycle occurs.

Where does the Calvin cycle take place?

In the stroma.

What does ETC stand for?

Electron Transport Chain.

What are the two main stages of photosynthesis?

Light-dependent reactions and light-independent reactions (Calvin cycle).

What happens in Photosystem II?

Light excites electrons in chlorophyll, and the electrons enter the electron transport chain.

How are electrons lost by chlorophyll in Photosystem II replaced?

Water is split to provide replacement electrons.

What happens when water is split during the light-dependent reactions?

Oxygen is released, electrons replace those lost by chlorophyll, and H⁺ ions remain in the thylakoid.

Where does the oxygen released during photosynthesis come from?

From the splitting of water.

What happens to electrons as they move through the electron transport chain?

Their energy helps move H⁺ ions across the thylakoid membrane, building a gradient used to make ATP.

What is ATP synthase?

A protein that uses the movement of H⁺ ions across a membrane to make ATP.

What happens in Photosystem I?

Light excites electrons in chlorophyll, and the electrons help form NADPH.

How are electrons lost by chlorophyll in Photosystem I replaced?

By electrons arriving from the electron transport chain after Photosystem II.

What is NADP⁺?

A molecule that accepts high-energy electrons and H⁺ to form NADPH.

What is NADPH?

An electron carrier that carries high-energy electrons used in the Calvin cycle.

What two products of the light-dependent reactions are needed for the Calvin cycle?

ATP and NADPH.

What are the light-independent reactions?

The reactions of the Calvin cycle that use ATP and NADPH to help build sugar molecules.

Why is it called the Calvin cycle?

Because RuBP is regenerated, allowing the cycle to repeat.

What enters the Calvin cycle?

Carbon dioxide, ATP, and NADPH.

What enzyme helps carbon dioxide bond to RuBP?

Rubisco.

What is RuBP?

A five-carbon molecule that accepts carbon dioxide at the beginning of the Calvin cycle.

What is the role of Rubisco?

It catalyzes the attachment of carbon dioxide to RuBP.

What do ATP and NADPH provide for the Calvin cycle?

ATP provides energy, and NADPH provides high-energy electrons.

What happens to ADP and NADP⁺ after the Calvin cycle uses ATP and NADPH?

They return to the light-dependent reactions to be reused.

Why must RuBP be remade?

So it can accept more carbon dioxide and allow the Calvin cycle to continue.

How are the light-dependent reactions and Calvin cycle connected?

The light-dependent reactions produce ATP and NADPH for the Calvin cycle. The Calvin cycle returns ADP and NADP⁺ to be reused.

Which stage directly requires light?

The light-dependent reactions.

Does the Calvin cycle directly require sunlight?

No. It uses ATP and NADPH produced by the light-dependent reactions, so it depends indirectly on light.