RESPIRATION
OBJECTIVES
Describe respiration as the release of energy from food substances in all living cells
describe aerobic respiration as the release of a relatively large amount of energy by the
breakdown of food substances in the presence of oxygen
state the equation for aerobic respiration using words and symbols
Describe the uses of energy in the body of humans e.g. muscle contraction, cell division,
growth, growth, protein synthesis, active transport, transmission of nerve impulses and
maintenance of constant temperature
Describe anaerobic respiration as the release of a relatively small amounts of energy by
the breakdown of food substances in the absence of oxygen
state the equation for anaerobic respiration in plants and animals using words and
symbols
DESCRIBE THE PRODUCTION OF LACTIC ACID IN MUSCLES DURING EXERCISE
Describe fermentation process as a form of anaerobic respiration
Demonstrate the release of energy through anaerobic respiration using yeast
Respiration is the process by which energy is released from the breaking down of food substances in all living cells.
Types of respiration.
Aerobic
Anaerobic
Aerobic respiration
The release of a relatively large amount of energy from the breakdown of food substances in the presence of oxygen.
Word equation of aerobic respiration
ENZYMES
Glucose + oxygen carbon dioxide + water + energy
Symbol equation of aerobic respiration
ENZYMES
C6 H12 O6 (a q) + 6O2 (g) 6CO2 (g) + 6H2O (l) + 2830kJ
Uses of energy in the body
1. Maintenance of a constant body temperature
2. active transport
3. synthesis of proteins
4. cell division
5. transmission of nerve impulses
6. Muscle contraction
7. growth
ANAEROBIC RESPIRATION/ FERMENTATION
It is the release of a relatively small amount of energy from the breakdown of food substances in the absence of
oxygen. Anaerobic respiration differs in plants and animals i. e. the intermediate products produced
There are two forms of anaerobic respiration:
1. Lactic acid fermentation- in animals and bacteria
2. Alcoholic fermentation- in plants and fungi
Word equation of anaerobic respiration
In plants- alcoholic fermentation
ENZYMES
Glucose carbon dioxide + ethanol + energy
ENZYMES
C6 H12 O6 (aq) + CO2 (g) + C2 H5 OH (l) + 118kJ
In animals- lactic acid fermentation
ENZYMES
Glucose lactic acid + energy
ENZYMES
C6 H12 O6 (aq) 2 C3H6O3 (g) +118 kJ
Difference between Aerobic & Anaerobic respiration
Aerobic Respiration Anaerobic Respiration
Occurs in the presence of oxygen Occurs in the absence of oxygen
Occurs in the mitochondrion Occurs in the cytoplasm
Releases relatively large amounts of energy Releases relatively small amounts energy
Releases Carbon dioxide and water as by-products/ no Releases ethanol or lactic acid as by products/
intermediate products/ complete breakdown of food intermediate products/ incomplete breakdown of food
substance substances
How Lactic Acid is produced in muscles during exercise
During exercise, the O2 supply may be insufficient to meet the energy demand. When this happens the cells release
energy by anaerobic respiration, lactic acid is produced as a by- product. The accumulation of lactic acid causes
muscle fatigue and pains but is eventually reduced as oxygen intake returns to normal after the period of exercise. This
shortage of oxygen causes an “Oxygen debt” and can be paid by increased oxygen intake. i.e. the person will continue
to breathe faster & deeper in order to draw more Oxygen into the lungs. This Oxygen will be used to break down lactic
acid to carbon dioxide & water.
The Graph Showing Effect of Exercise on the Lactic Acid Concentration of Blood.
Lactic
Acid
concn
Normal period of O2 debt normal
Demonstration of Fermentation
ACTIVITY; Experiment to show fermentation of flour by yeast
Oil
Glucose +
Yeast Lime water
suspension
Procedure
1. Boil the water to expel the entire O2 and allow it cool
2. Use boiled water make a solution of 5% glucose & 10% suspension of yeast
3. Place 5cm of glucose solution in a test tube
4. Add 1cm of yeast suspension to the glucose in the test tube
5. Add a layer of paraffin / oil to exclude atmospheric O2
6. Connect the apparatus as shown above
7. Follow the same instructions to prepare a control experiment. This time use yeast suspension that has been
boiled to kill yeast cells & denature enzymes
8. Wait for 15minutes before taking observations. The start of the experiment may be shown by bubbles escaping
into lime water
- In the case the experiment takes long to commence, warm the mixture in a warm water bath for 5minutes at 30 0C
Results:
The bubbles of the gas from the living yeast will turn lime water milky showing that CO2 is released.
In the control set the lime water will not turn milky because the enzymes in the yeast cells were denatured
by boiling therefore no fermentation took place
