Biology B9

During aerobic respiration, glucose reacts with oxygen. This reaction transfers energy that your cells can use. This energy is vital for everything that goes on in your body. The waste products of this reaction are carbon dioxide plus water.

Aerobic respiration is an exothermic reaction, this means that this reaction transfers energy to the environment.

Some of the energy transferred in respiration is used for all the reactions that take place in a cell.

The reaction for aerobic respiration is as follows:

Glucose + oxygen ------------> carbon dioxide + water (energy transferred to the environment)

C6H12O6 + 6O2 ----------------> 6CO2 + 6H2O

Aerobic respiration takes place in the mitochondria of your cells.

Mitochondria are the organelles found in almost all plant and animal cells. They have a folded inner membrane which provides a large surface area for the enzymes involved in aerobic respiration.

The need for respiration

• Living cells need energy to carry out the basic functions of life
• In animals, energy from respiration helps muscles contract
• Mammals and birds keep a constant body temperature, meaning that the energy from respiration keeps them warm
• In plants, energy is used to transfer mineral ions from the soil to the root hair cells

Muscle tissue is made up of protein fibres which contract when energy is transferred from respiration.

Muscles also store glucose as glycogen. 

When muscular activity changes, a lot of other changes happen inside your body;

• Heart rate increases - arteries supplying blood to muscles get wider which means that the oxygen being produced increases.
• Breathing rate increases
• Glycogen turns back to glucose to supply the cells with the fuel they need.

Equation for anaerobic respiration is;

                    Glucose --------> lactic acid (energy transferred to the environment)

The build up of lactic acid in the muscles due to muscle fatigue creates an oxygen debt.

Oxygen debt repayement;

Lactic acid + oxygen ------> carbon dioxide plus water 

When plants respite anaerobically, they do not produce lactic acid, they produce ethanol and carbon dioxide.

Anaerobic respiration in yeast cells is known as fermentation.

Glucose -------> ethanol + carbon dioxide (energy transferred to the environment)

The metabolism of an organism is the sum of all the reactions that take place in a cell or body. Some of the most common metabolic reactions include;

• The conversion of glucose to starch, glycogen and cellulose
• Formation of lipid molecules from a molecule of glycerol and three fatty acids
• Use of glucose and nitrate ions to form amino acids which are used to make proteins
• Respiration
• Photosynthesis 
• Breakdown of excess proteins in the liver to form urea for excretion in the urine by kidneys.

The liver has many roles, some include

• Detoxifying poisonous substances such as ethanol from alcoholic drinks
• Passing the breakdown products into the blood so they can be secreted in the urine via the kidneys
• Breaking down old, worn out blood cells and storing the iron until it is needed to synthesize more cells.