Question

What is released when sugar is broken down

Answer 1

Mainly there's 3 types of respiration (the breakdown of sugar to release energy). Aerobic respiration, anaerobic respiration in muscles and anaerobic respiration in organisms such as yeast.

Aerobic respiration is to use oxygen and glucose to release water and carbon dioxide. Most of our cells undergo aerobic respiration to generate energy.

Anaerobic respiration in muscles is to only use glucose to generate lactic acid and energy (not carbon dioxide). Anaerobic respiration only happens when we have lack of oxygen, such as during vigorous exercises. Note that this kind of respiration creates a oxygen debt.

Anaerobic respiration in yeasts is to use glucose and release ethanol and carbon dioxide. Since they release ethanol, this respiration is commonly used in wine brewing. And due to that they also release carbon dioxide, they're used in baking bread (alcohol evaporates by the time the bread bakes).