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Lesson · Grade 11 · Life Sciences

Aerobic and anaerobic organisms

  • Grade 11
  • Life Sciences
  • 1 min 39 s
  • British Columbia
  • BC11-SC-171

One diagram builds up step by step: glucose splits into aerobic respiration with oxygen, making carbon dioxide and water and about 30 to 32 ATP per glucose, and fermentation without oxygen, where yeast makes ethanol and carbon dioxide and sprinting muscles make lactic acid, for only 2 ATP. Underneath it lists aerobic organisms, shows that yeast can use both pathways, and introduces obligate anaerobes, bacteria killed by oxygen that live in deep mud and the gut, before ending on the recap that not all life needs oxygen but oxygen gives far more ATP.

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In one sentence

The question this lesson answers

Do all living things need oxygen to get energy from their food?

Cells break down glucose, a sugar, to make ATP, the molecule that carries energy inside cells.

Transcript

What the lesson says

Do all living things need oxygen to get energy from their food?

Cells break down glucose, a sugar, to make ATP, the molecule that carries energy inside cells.

How a cell does this depends on oxygen. Aerobic means with oxygen; anaerobic means without it.

With oxygen, cells carry out aerobic respiration, breaking glucose down completely into carbon dioxide and water.

This releases about 30 to 32 ATP from each glucose.

Aerobic organisms include humans, plants, most animals and many bacteria.

Without oxygen, many cells use fermentation instead, which breaks glucose down only partly.

Yeast ferments sugar into ethanol and carbon dioxide, and the gas makes bread rise.

In a hard sprint, your muscles run short of oxygen and make lactic acid for a while.

Fermentation releases only 2 ATP per glucose, far less than with oxygen.

Yeast, a single-celled fungus, can use both pathways, so it can live with or without oxygen.

Some bacteria are obligate anaerobes: oxygen kills them, so they must live without it.

They live where there is little or no oxygen, such as deep mud or the gut.

So not all life needs oxygen, but using oxygen gets far more ATP from each glucose.

Curriculum

Where this fits

British Columbia, Grade 11

Life Sciences 11, Diversity of life: single-celled and multi-celled organismsBC11-SC-171

Next: Body Symmetry and Cephalization in Animals

The outcomes and strands follow the British Columbia curriculum.

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