Respiration Handout

Respiration
Respiration is the release of energy from food and occurs in all cells. This must be done to
provide us with energy. This energy is used for movement. ATP – Adenosine triphosphate is
called the ‘energy currency’ of the cell. It is the organic compound composed of the
phosphate groups, adenine, and the sugar ribose. These molecules provide energy for
various biochemical processes in the body. These ATP molecules are synthesized by
Mitochondria; therefore it is called powerhouse of the cell.
Energy released by ATP is used by cells:
 To manufacture complex biologically important molecules, e.g. proteins, DNA
 For cell growth and repair
 For cell division
 In active transport
 For special functions in specialised cells, e.g. contraction of muscle cells, transmission
of impulses in nerve cells
 Some of the energy is released as heat and this helps to maintain the body
temperature at 37⁰C.
How is Energy Produced by the ATP molecules?
The three phosphate groups present in this ATP molecule are called high energy bonds as
they are involved in the liberation of a huge amount of energy when they are broken. This
molecule provides energy for various life processes without which life cannot exist.
ATP + water ADP + Pi + free energy

Aerobic Respiration
The energy that is released from food in the presence of oxygen is known as aerobic
respiration. It takes place in the mitochondria of the cell. It produces Carbon Dioxide, water
and 38 ATP molecules per molecule of glucose.
Glucose + Oxygen Carbon Dioxide + Water + ATP
Anaerobic Respiration
The process by which energy is released from food without the use of oxygen. It takes place
in the cytoplasm of the cells. The products of anaerobic respiration vary, and it produces
considerably less energy per molecule of glucose than aerobic respiration. Yeast cells, certain
bacteria and muscle cells can carry out anaerobic respiration.
In Yeast cells:
Yeast cells carry out anaerobic respiration known as fermentation show below.
Glucose Ethanol + Carbon Dioxide + ATP
When making bread, yeast ferments sugars producing carbon dioxide bubbles that causes
the dough to rise. When baked, heat from the oven causes the bubbles to expand, kills the
yeast and evaporates the ethanol.
When making alcoholic beverages such as beer, wine, rum and other spirits, the yeast
ferments sugars present in grains, fruits or molasses. Fermentation stops when ethanol
concentration reaches about 14-16% because it kills yeast cells, so the ethanol content of
beer or wine is always below about 16%. Spirits are made by the distillation of the
fermentation mixture.
In Bacteria:
Certain bacteria e.g. Lactobacillus, ferment the lactose in milk forming lactic acid. The lactic
acid curdles the milk proteins forming thick yoghurt and giving it its sour taste.
Glucose Lactic Acid + ATP
Other bacteria are used to break down organic matter, e.g. manure and garden waste,
anaerobically in an anaerobic digester. This produces biogas which is a mixture of
approximately 60% methane and 40% carbon dioxide and traces of other gases like
hydrogen sulphide. Biogas can be used as a fuel for cooking, heating and to generate
electricity.
In Muscle Cells:
Muscle cells carry out anaerobic respiration during strenuous exercise. If oxygen cannot be
delivered to the muscle cells quickly enough for the demands of aerobic respiration, the cells
begin to respire anaerobically.
Glucose Lactic Acid + ATP
Lactic acid builds up in the muscle cells and begins to harm them, causing fatigue and
eventually collapse as they stop contracting. The muscle cells are said to have built up an
oxygen debt. This debt must be repaid directly after exercise by resting and breathing deeply
so that the lactic acid can be removed by respiring it aerobically.
Differences between Aerobic and Anaerobic Respiration
Aerobic Anaerobic
Location Mitochondria Cytoplasm
Oxygen Requirements Uses Oxygen Does not use Oxygen
End Products Carbon Dioxide and Water Yeast: Ethanol and Carbon
Dioxide
or
Animals: Lactic Acid
Energy Produced 36-38 ATP 2 ATP
Mouth to mouth resuscitation (rescue breathing)

Mouth-to-mouth resuscitation is a technique used to supply oxygen to a person who has
stopped breathing. The rescuer forces his or her exhaled air, which contains about 16%
oxygen, into the victim’s lungs every few seconds, allowing for passive exhalation between.
To perform mouth-to mouth resuscitation:
 Lie the victim on his or her back.
 Gently tilt the victim’s head backwards to open the airways by lifting the chin.
 Open the victim’s mouth and remove any debris.
 Pinch the victim’s nostrils to close them and breathe in.
 Seal your lips over the victim’s open mouth and breathe out into the mouth for 1
second.
 If the victim’s chest rises, breathe into the mouth a second time.
 Continue rescue breathing by giving one breath every 5 seconds until normal
breathing resumes or medical help arrives.

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Respiration

How is Energy Produced by the ATP molecules?

ATP + water ADP + Pi + free energy

Differences between Aerobic and Anaerobic Respiration

Mouth to mouth resuscitation (rescue breathing)

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