By the end of the topic, the learner should be able to:
Meaning and significance of respiration
1. Mitochondrion - structure and function
2. Aerobic respiration (Details of kreb's cycle not required)
3. Anaerobic respiration in plants and animals, the products and byproducts
4. Application of anaerobic respiration in industry and at home
5. Compare the energy output of aerobic and anaerobic respiration78
1. Carry out experiments to investigate
2. The gas produced when food is burnt
3. The gas produced during fermentation
4. Heat production by germinating seeds
Meaning and Significance of Respiration
Respiration is the process by which energy is liberated from organic compounds such as glucose.
It is one of the most important characteristics of living organisms.
Energy is expended (used) whenever an organism exhibits characteristics of life, such as feeding, excretion and movement.
Respiration occurs all the time and if it stops, cellular activities are disrupted due to lack of energy.
This may result in death e.g., if cells in brain lack oxygen that is needed for respiration for a short time, death may occur.
This is because living cells need energy in order to perform the numerous activities necessary to maintain life.
The energy is used in the cells and much of it is also lost as heat.
In humans it is used to maintain a constant body temperature.
Mitochondrion Structure and Function
Adaptations of Mitochondrion to its Function
Anaerobic respiration involves breakdown of organic substances in the absence of oxygen.
It takes place in some bacteria and some fungi.
Organisms which obtain energy by anaerobic respiration are referred to as anaerobes.
Obligate anaerobes are those organisms which do not require oxygen at all and may even die if oxygen is present.
Facultative anaerobes are those organisms which survive either in the absence or in the presence of oxygen.
Such organisms tend to thrive better when oxygen is present e.g. yeast.
Products of Anaerobic Respiration
The products of anaerobic respiration differ according to whether the process is occurring in plants or animals.
Anaerobic Respiration in Plants
Glucose is broken down to an alcohol, (ethanol) and carbon (IV) oxide.
The breakdown is incomplete.
Ethanol is an organic compound, which can be broken down further in the presence of oxygen to provide energy, carbon (IV) oxide and water.
This is the term used to describe formation of ethanol and carbon (IV) oxide from grains
Yeast cells have enzymes that bring about anaerobic respiration.
This is the term given to anaerobic respiration in certain bacteria that results in formation of lactic acid
Anaerobic Respiration in Animals
Anaerobic respiration in animals produces lactic acid and energy.
When human muscles are involved in very vigorous activity, oxygen cannot be delivered as rapidly as it is required.
The muscle respire anaerobically and lactic acid accumulates.
A high level of lactic acid is toxic.
During the period of exercise, the body builds up an oxygen debt.
After vigorous activity, one has to breathe faster and deeper to take in more oxygen.
Rapid breathing occurs in order to break down lactic acid into carbon (IV) oxide and water and release more energy.
Oxygen debt therefore refers to the extra oxygen the body takes in after vigorous exercise.
To Show the Gas Produced When the Food is burned
Comparison between Aerobic and Anaerobic Respiration
Comparison between Energy Output in Aerobic and Anaerobic Respiration
Substrates for Respiration
Carbohydrate, mainly glucose is the main substrate inside cells.
Lipids i.e. fatty acids and glycerol are also used.
Fatty acids are used when the carbohydrates are exhausted.
A molecule of lipid yields much more energy than a molecule of glucose.
Proteins are not normally used for respiration.
However during starvation they are hydrolysed to amino acids, dearnination follows and the products enter Kreb's cycle as urea is formed.
Use of body protein in respiration result to body wasting, as observed during prolonged sickness or starvation.
The ratio of the amount of carbon (IV) oxide produced to the amount of oxygen used for each substrate is referred to as Respiratory Quotient (RQ) and is calculated as follows:
Carbohydrates have a respiratory quotient of 1.0 lipids 0.7 and proteins 0.8.
Respiratory quotient value can thus give an indication of types of substrate used.
Besides values higher than one indicate that some anaerobic respiration is taking place.
Application of Anaerobic Respiration in Industry and at Home
respiration audio visuals
AEROBIC VS ANAEROBIC RESPIRATION