Why cells respire and how ATP is generated
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Flip to reveal answersWhy do cells need a constant supply of energy?
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Question
Why do cells need a constant supply of energy?
Answer
For **active transport, building macromolecules, movement and staying organised** — all powered by ATP.
Question
Why can't cells just use the energy in glucose directly?
Answer
Glucose's energy must first be **released by respiration**; cells then store a usable share of it in **ATP**.
Question
Define cell respiration.
Answer
The **controlled breakdown of glucose** (and other carbon compounds) inside a cell to release energy and regenerate ATP.
Question
What is ATP?
Answer
The cell's **immediate, usable energy supply** — its 'energy currency'.
Question
What is the relationship between ATP and ADP?
Answer
ATP has three phosphates; removing one gives **ADP**. Adding a phosphate back to ADP (using energy from respiration) **regenerates ATP**.
Question
How is ATP regenerated?
Answer
Energy released by **respiring glucose** is used to **add a phosphate to ADP**, remaking ATP.
Question
What happens when a cell USES ATP?
Answer
ATP loses its third phosphate, becoming **ADP**, and **energy is released** to do work.
Question
Why is glucose broken down in small steps, not all at once?
Answer
Releasing all the energy at once would be **wasteful and could damage the cell**; controlled steps let the cell capture energy in ATP.
Question
What is a respiratory substrate?
Answer
The **fuel molecule that is respired** to release energy — most often **glucose**.
Question
Outline how a cell generates ATP.
Answer
Respiration **releases energy from glucose**; that energy **adds a phosphate to ADP**, **regenerating ATP**.
Question
In a yeast experiment, what is the function of the sugar (sucrose) added?
Answer
It is the **respiratory substrate** — the fuel the yeast **respires to release energy**.
Question
Name three processes a cell spends ATP on.
Answer
**Active transport**, **synthesis of macromolecules** (e.g. proteins) and **movement** (e.g. muscle contraction).
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Topic 3.2 hub
Cell respiration
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