B9: Respiration

Aerobic respiration

An exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells.

Equations for aerobic respiration

Glucose + oxygen → carbon dioxide + water (+energy) / C6H12O6 + 6O2 → 6CO2 + 6H2O (+energy)

Location of aerobic respiration

In the mitochondria

Purpose of energy from respiration

Synthesis of larger molecules, muscle contraction, maintenance of body temperature, active transport

Anaerobic respiration

An exothermic reaction in which glucose is broken down to release energy in the absence of oxygen.

Equation for anaerobic respiration

Glucose → lactic acid (+energy)

Inefficiency of anaerobic respiration

Glucose is not completely broken down, so less energy is transferred.

Cause of muscle fatigue in anaerobic respiration

Lactic acid (product of anaerobic respiration) builds up in muscles, preventing efficient contraction.

Oxygen debt

The amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration.

Fermentation

A type of anaerobic respiration that occurs in yeast cells.

Equation for fermentation

Glucose → ethanol + carbon dioxide (+energy)

Importance of fermentation reaction

Used in the production of bread and alcoholic drinks.

Differences between aerobic and anaerobic respiration

Aerobic requires oxygen; anaerobic does not. Aerobic produces CO2 and water; anaerobic produces lactic acid or ethanol + CO2. Aerobic transfers a greater amount of energy.

Muscle glucose storage

As glycogen

Changes with increased muscular activity

Heart rate and breathing rate increase, arteries dilate, stored glycogen is converted back into glucose.

Transport of lactic acid from muscles

Blood flow through the muscles transports lactic acid to the liver, where it is oxidized back to glucose.

Metabolism

The sum of all the reactions that take place in a cell or an organism.

Cell use of energy from respiration

To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules.

Examples of metabolic reactions

Glucose into starch/glycogen/cellulose, glycerol and fatty acids into lipids, glucose and nitrate ions into amino acids, photosynthesis, respiration, breakdown of excess proteins into urea