RESPIRATION
It is the process by which energy is generated from the breaking down of carbohydrates in living cells.
Types of respiration
 Aerobic
 Anaerobic
Aerobic respiration
The release of relatively large amounts of energy from the breaking down of carbohydrates in the presence of oxygen
Word & symbol equation of anaerobic respiration
Glucose + oxygen ENZYMES
carbon dioxide + water + energy
C6 H12 O6 (aq) + 6O2 (g)
ENZYMES
6CO2 (g) + 6H2O (l) + 2830KJ/mol
Uses of energy released from respiration
1. It is used to maintain a constant body temperature
2. It is used during active transport, in the selective reabsorption of vital minerals
3. It is used in the synthesis of macromolecules from micromolecules e.g. synthesis of proteins from amino
acids
4. It is used during mitotic cell division which results in the growth of an organism
5. It is used during transmission of nerve impulses
Anaerobic respiration
It is the release of fairly small amounts of energy from the breaking down of carbohydrates in the absence of oxygen.
Word & symbol equations of anaerobic respiration
(In plants)
Glucose
carbon dioxide + ethanol + energy
ENZYMES
C6 H12 O6 (aq) +
CO2 (g) + C2 H5 OH (l) + 118KJ/mol
ENZYMES
(In animals)
Glucose
lactic acid + energy
ENZYMES
C6 H12 O6 (aq) +
ENZYMES
2C3H6O3 (g) + --------------+ 118KJ/mol
Difference between Aerobic & Anaerobic respiration
Aerobic Respiration
Occurs in the presence of oxygen
Occurs in the mitochondrion
Releases fairly large amounts of energy
Releases CO2 and H2O as by-products
Anaerobic Respiration
Occurs in the absence of oxygen
Occurs in the cytoplasm matrix
Releases fairly small amounts energy
Releases ethanol & lactic acid as a by product
Fermentation
It is the release of fairly small amounts of energy from breaking down of glucose by extra -cellular enzymes of
microorganisms in the absence of oxygen
Both the word & symbol equation of fermentation are similar to that of anaerobic respiration in plants.
Glucose
carbon dioxide + ethanol + energy
ENZYMES
C6 H12 O6 (aq) +
ENZYMES
CO2 (g) + C2 H5 OH (l) + 118KJ/mol
ACTIVITY; Experiment to show fermentation of flour by yeast
Oil
Glucose +
Yeast
suspension
Lime water
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
How Lactic Acid is produce in muscles during exercise
During exercise, the O2 supply may be insufficient to meet the energy demand. When this happens the cells produce
energy by anaerobic respiration, lactic acid is produced as a by product. The accumulation of lactic acid causes
muscles fatigue but is eventually reduced as oxygen intake returns to normal after the period of exercise. This shortfall
of oxygen is called “Oxygen debt” and can be repaid by increased O2 intake. i.e. the person will continue to breathe
fast & deep in order to draw more O2 into the lungs. This O2 will be used to oxidize lactic acid to carbon dioxide & water
The Graph Showing Effect of Exercise on the Lactic Acid Concentration of Blood.
Normal
period of
O2 debt
normal
Courtesy of Lebsy mb 71726846
activity
repaid