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Summary Topic 12: Respiration
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Topic 7: Human nutrition: IGCSE Biology course notes which will help you study for your papers. By studying these notes I achieved a 9 - A* on my Igcse
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IGCSE Biology Topic 1 (Characteristics & Classification of Living Organisms)
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Class notes biology: Characteristics of living organisms
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Class and mark scheme notes Biology Cambridge IGCSE with Biology Coursebook with CD-ROM
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TOPIC 12: RESPIRATION12.1 RESPIRATION
→Respiration: a chemical process that involves the breakdown of nutrient molecules (specifically glucose) in order to release the
energy stored within the bonds of these molecules.
-Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically). Much less energy is released for each
glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically
-Respiration occurs in all living cells. Most of the chemical reactions in aerobic respiration take place in the mitochondria.
Uses of energy in the human body:
-Humans need this energy to do the following things:
→Contract muscle (so we can move parts of our body).
→Synthesise proteins (making protein molecules by linking
together amino acids into long chains).
→Cell division (to make new cells / repair damaged tissues)
→Grow (cells)
→Enable active transport to take place (so that substances
can move across cell membranes up a concentration
gradient)
→Allow nerve impulses to be generated (to transfer
information quickly from one part of the body to another).
→Maintain a constant internal body temperature
RESPIRATION IS A SERIES OF REACTIONS THAT ARE
CONTROLLED BY ENZYMES.
-This energy comes from the food we eat which is digested, broken down into smaller molecules, which are absorbed in the
small intestine into the blood.
-The blood transports the nutrients absorbed to all the cells in the body.
-The main nutrient provided to cells for respiration is called glucose (contains chemical energy)
-To make use of this energy, cells break down the glucose molecules and release energy from them.
-They do this in a series of metabolic reactions called respiration (involves enzymes).
12.2 AEROBIC RESPIRATION
→Anaerobic respiration: the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.
-Aerobic respiration requires oxygen
-It is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes
-It produces carbon dioxide and water as well as releasing useful cellular energy
-Aerobic respiration occurs in the mitochondria
Investigating Uptake of Oxygen by Respiring Organism
-We can investigate aerobic respiration in living organisms by measuring the amount of oxygen that they take from the air
-This is done by measuring the change in volume in an enclosed tube containing the organisms
-However, as they respire the organisms release carbon dioxide, which increases the gas volume
-The carbon dioxide must therefore be removed from the tube using a chemical like soda lime or sodium hydroxide, otherwise it
will make the experiment results inaccurate
-Any small organisms can be used in the apparatus, including seeds or arthropods.
-The apparatus (shown below) is known as a respirometer
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