Cell respiration

**Adenosine triphosphate** — a molecule with **three** phosphate groups.

It is the **universal, spendable** form of energy — every energy-requiring process in the cell is paid for in ATP.

In the **bond to the third phosphate group**.

**ADP + Pi** (adenosine diphosphate + an inorganic phosphate).

**ATP → ADP + Pi** releases energy; **ADP + Pi → ATP** stores it.

**Cell respiration** — it releases energy from glucose to rebuild ATP.

The continuous interconversion: ATP is broken to **ADP + Pi** (releasing energy) and rebuilt from **ADP + Pi** by respiration (storing energy).

Any two of: **active transport, muscle contraction, synthesis of macromolecules, nerve-impulse transmission**.

It releases a **small, usable** amount of energy in a **single step** (also: soluble; quickly recharged).

**ATP has three**; **ADP has two** (one phosphate is removed to release energy).

**Reused** — each molecule is recharged by respiration and recycled thousands of times a day.

Being soluble lets ATP **move freely through the cytoplasm** to wherever in the cell energy is needed.

For **active transport, building macromolecules, movement and staying organised** — all powered by ATP.

Glucose's energy must first be **released by respiration**; cells then store a usable share of it in **ATP**.

The **controlled breakdown of glucose** (and other carbon compounds) inside a cell to release energy and regenerate ATP.

The cell's **immediate, usable energy supply** — its 'energy currency'.

ATP has three phosphates; removing one gives **ADP**. Adding a phosphate back to ADP (using energy from respiration) **regenerates ATP**.

Energy released by **respiring glucose** is used to **add a phosphate to ADP**, remaking ATP.

ATP loses its third phosphate, becoming **ADP**, and **energy is released** to do work.

Releasing all the energy at once would be **wasteful and could damage the cell**; controlled steps let the cell capture energy in ATP.

The **fuel molecule that is respired** to release energy — most often **glucose**.

Respiration **releases energy from glucose**; that energy **adds a phosphate to ADP**, **regenerating ATP**.

It is the **respiratory substrate** — the fuel the yeast **respires to release energy**.

**Active transport**, **synthesis of macromolecules** (e.g. proteins) and **movement** (e.g. muscle contraction).

Aerobic respiration **uses oxygen**; anaerobic respiration takes place **without oxygen**.

Respiration that **uses oxygen** to break glucose down **fully** into carbon dioxide and water, releasing **a lot** of ATP.

Respiration that happens **without oxygen**; glucose is broken down only **partly**, releasing only **a little** ATP.

In the **mitochondria**.

In the **cytoplasm**.

**Carbon dioxide + water** (in all organisms).

**Lactate**.

**Ethanol + carbon dioxide** — the basis of bioethanol, brewing and bread.

**Aerobic** — because oxygen lets glucose be **fully** broken down, releasing most of its energy.

They switch to **anaerobic respiration**, producing **lactate** in the cytoplasm.

By **yeast** respiring **anaerobically**: glucose → **ethanol + carbon dioxide**.

'**Without**' — anaerobic respiration happens **without oxygen** (air).

Glucose is only **partly** broken down, so **most of its energy stays locked** inside the product (lactate or ethanol).

How **fast** an organism respires — usually the **oxygen used** (or **CO₂ produced**) **per unit time**.

Apparatus that measures respiration rate by detecting the **change in gas volume** (usually the **oxygen used up**) as organisms respire.

The seeds **use up oxygen**, lowering the gas volume, so the liquid is **drawn in**.

To **absorb the carbon dioxide** released, so the **only** gas change measured is the **oxygen used up**.

As a **control** — dead seeds don't respire, so the liquid shouldn't move; this proves any movement is caused by **respiration**, not temperature or pressure.

**Oxygen used**, **carbon dioxide produced**, **temperature rise**, and **mass lost**.

It **uses up oxygen** and **releases carbon dioxide**.

Respiration **releases some energy as heat**, so in an insulated flask the temperature climbs — faster respiration gives a faster rise.

Carbon leaves the organism as **carbon dioxide gas**, so its **dry mass falls**.

It **slows or stops** respiration, so **less oxygen is used** and the coloured liquid moves **less** (or not at all).

You can't watch a cell respire, but you **can** measure the gases, heat or mass it changes — so measuring one of these gives the rate.

So any change in the liquid is caused by **respiration alone** — the dead-seed control rules out temperature and pressure effects.