Anaerobic respiration

Give the function of respiration, and write the word equation for anaerobic respiration.
Explain the concept of oxygen debt.
Compare the relative amount of energy released by aerobic and anaerobic respiration.
Describe anaerobic respiration (fermentation) in microorganisms like yeast, write its word equation, and give examples of its human uses.

During short bursts of intense exercise (e.g., sprinting, lifting heavy weights). The body can't get enough oxygen to the muscles for aerobic respiration to meet the high energy demand.
So glucose is broken down without oxygen to release a small amount of energy quickly. Unfortunately, this also produces lactic acid.

glucose → lactic acid (+ energy released)

Lactic acid acid can build up in muscles, causing fatigue and painful cramps.
After intense exercise, you keep breathing heavily for a while because you need extra oxygen to break down the lactic acid that has built up. This need for extra oxygen is called the oxygen debt.
Aerobic respiration is normally used instead of anaerobic respiration because it releases much more energy from each glucose molecule and it doesn't produce painful lactic acid.

Humans aren't the only organisms that can respire without oxygen. Some microorganisms, like yeast, also use anaerobic respiration.
This process in microorganisms is often called fermentation.
Yeast breaks down sugars (like glucose) without oxygen to produce ethanol (a type of alcohol) and carbon dioxide gas.

glucose → ethanol + carbon dioxide (+ energy released)

Humans have used fermentation for thousands of years for:
- Bread Making: The carbon dioxide produced by yeast makes bread dough rise. (The ethanol evaporates during baking).
- Brewing and Winemaking: The ethanol produced by yeast fermenting sugar (from grapes or barley) is the alcohol found in beer and wine.

Anaerobic respiration: Respiration that occurs without oxygen.
Reactants: The substances that go into a chemical reaction.
Products: The substances that are produced by a chemical reaction.
Oxygen: The gas that is absent or in short supply during anaerobic respiration.
Lactic acid: The waste product produced during anaerobic respiration in humans.
Oxygen debt: The extra amount of oxygen needed after intense exercise to break down accumulated lactic acid.
Fermentation: The term often used for anaerobic respiration in microorganisms.
Yeast: A type of microorganism that performs fermentation, converting sugars into ethanol and carbon dioxide.
Ethanol: A type of alcohol produced during fermentation by yeast.
Carbon dioxide: A gas produced during fermentation by yeast (and also during aerobic respiration).
Aerobic respiration: Respiration that occurs with oxygen, releasing much more energy.

Investigate how athletes train to improve their tolerance to lactic acid buildup and reduce their oxygen debt during and after intense physical activity.
Research other types of fermentation carried out by different microorganisms (e.g., bacteria used to make yoghurt or cheese) and explore other industrial applications of fermentation.