7.2 - Aerobic Respiration

Concept of Aerobic Respiration

• Aerobic respiration is the breakdown of glucose in the presence of oxygen to produce chemical energy.
• Oxygen oxidises glucose to produce carbon dioxide, water and energy.

Glycolysis and Oxidation of Pyruvate

Glycolysis (in the Cytoplasm)

• Aerobic respiration begins with glycolysis, the breakdown of glucose by enzymes.
• One glucose molecule is broken down into two pyruvate molecules.

Oxidation of Pyruvate (in the Mitochondrion)

• Pyruvate is oxidised through a series of reactions in the mitochondrion.
• Carbon dioxide, water and energy are produced.
• Most of the energy is used to produce adenosine triphosphate (ATP) molecules.

Word Equation for Aerobic Respiration

$\text{Glucose}+\text{Oxygen}\to \text{Carbon dioxide}+\text{Water}+\text{Energy (2898 kJ)}$

ATP Production and the ATP-ADP Cycle

• ATP is produced when an inorganic phosphate group is added to adenosine diphosphate (ADP).

$\text{ADP}+\text{Phosphate}+\text{Energy}\to \text{ATP}$

• ATP molecules have weak phosphate bonds.
• When a phosphate bond in ATP is broken, the released energy is supplied to the cell.

$\text{ATP}\to \text{ADP}+\text{Phosphate}+\text{Energy}$

Experiment: Studying Aerobic Respiration

• Problem statement: Do living organisms carry out aerobic respiration?
• Hypothesis: Living organisms use oxygen and release carbon dioxide during aerobic respiration.
• Manipulated variable: Presence of a living organism.
• Responding variable: Increase in the level of coloured liquid.
• Constant variable: Initial level of coloured liquid.
• Set up two airtight boiling tubes containing soda lime in a water bath. Place a cockroach above wire gauze in tube A; leave tube B without an organism.
• Connect each tube to a capillary tube containing coloured liquid. Mark the initial level, leave for one hour, then measure the final level.
• A respirometer estimates an organism’s respiration rate from its oxygen-consumption rate.