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9.7 The Biochemistry of Movement: 1. ATP and energy
Extract from Chemistry Stage 6 Syllabus (Amended
October 2002) © Board of Studies, NSW.
[Edit: 7 Jul 09]
Prior Learning: Preliminary Modules 8.5.1 and 8.5.5.
Background: All cells require a constant supply of energy to maintain life. Energy is used to synthesise body materials, to transport substances, in animals to contract muscles and send electrical impulses and, in the case of some animals including humans, to maintain a constant body temperature.
The chemical processes of cells are collectively called cellular metabolism. The energy required to run cellular metabolism comes from our food. Cells first need to convert the chemical energy in food to chemical energy in a form that can be used in cellular metabolism. ATP is the chemical energy carrier in all living cells.
This module concentrates on how the human body used energy to move muscles of the skeleton.
solve problems and process information from a diagram or model of the structure of the adenosine triphosphate molecule to discuss the nature and organisation of the phosphate groups
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To solve the problem of the structure of
adenosine triphosphate (ATP), construct a simplified
model of its structure using a supplied diagram.
Structure of ATP
HyperPhysics, Department of Physics
and Astronomy, Georgia State University, Atlanta, USA. - Process the information obtained from the diagram and use it to make your model.
- Molecular model kits may be used or, to simplify, the adenosine ring shapes can be cut out from cardboard. The 3 phosphate groups joined together can then be the focus of the model.
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Identify the base adenine, the 5-carbon sugar ribose and
the three linearly joined phosphate groups. The ribose
and adenine are together called adenosine. The precise
structural details of the adenosine part of the molecule
are not necessary, but you should be able to reproduce
the triphosphate section of the molecule.
- Discuss the nature of the bonds between the phosphate groups and identify the joining atoms as oxygen atoms. Note the similarity to ester bonds in carbon compounds. The bonds between the phosphates release energy when they react with water, that is, they are hydrolysed.
- Use the model to demonstrate hydrolysis by removing the
terminal phosphate group using a water molecule. Two
H+ ions are released from the water and a
phosphate ion from the ATP. This reaction is called
hydrolysis. ADP is adenosine diphosphate, the adenosine
part joined to the two remaining phosphate groups.
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This equation is simplified to:
- Pi is used as a shorthand for the phosphate ion. It is not to be confused with the symbol for phosphorus.
identify that adenosine triphosphate is used as an energy source for nearly all cellular metabolic processes
explain that the biologically important part of the molecule contains three phosphate groups
- Adenosine triphosphate (ATP) is used as an energy source for nearly all cellular metabolic processes.
- The three linear phosphate groups on the ATP molecule is an arrangement that allows for the terminal phosphate to be removed easily by hydrolysis, releasing a lot of chemical energy. A free phosphate ion and ADP are formed.
- There are a number of negatively charged oxygen atoms in close proximity on the triphosphate part of the molecule. Negative charges repel each other, contributing to the high energy nature of the group.
- The energy released when ATP is hydrolysed to ADP, is used for any energy requiring reaction in the cell ie. for cellular metabolic purposes.
Interconversion of ATP and ADP , Access Excellence @ the
national health museum, USA.
process information from secondary sources to locate the site of each step of respiration in the cell
- Use the Biochemical Pathways Chart to locate the site of each step of respiration in the cell.
identify the role of enzymes as catalysts in the conversion of ATP to ADP with energy made available for metabolism, given a flow chart of the biochemical pathways
- Enzymes are protein molecules that control cellular metabolic processes. They are catalysts.
- Enzymes are responsible for the reactions that form ATP and also for the many reactions that use the chemical energy in ATP.
- All the steps shown in the Biochemical Pathways Chart are catalysed by enzymes.
explain that biochemical fuels are broken down to release energy for making ATP
- Biochemical fuels are carbohydrates and fats. Carbohydrates are the main energy source in most diets and fats are a long term storage form of energy.
- Carbohydrates such as starch are digested to the simple, soluble sugar, glucose. Glucose is absorbed into the body and supplied to cells for energy production.
- Energy in the glucose molecule is released by the process of respiration and trapped as smaller parcels in ATP. Many ATP molecules (usually 38) are formed from the breakdown of just one molecule of glucose. ATP is a suitable form and quantity of energy that can be readily used by enzymes and that can be easily transported around the cell.
- The formation of ATP from ADP and Pi is an endothermic reaction. The energy stored in ATP can be used to run endothermic processes such as movement of muscle proteins and synthesis of large molecules from small molecules.
identify mitochondria as the cell organelles involved in aerobic respiration and the site of most ATP synthesis
- During exercise most of the energy released in cells that is used to synthesise ATP comes from aerobic respiration of glucose.
- Mitochondria are the cell organelles carrying out ATP production. Over 90% of ATP production is in mitochondria, but there is some produced in the cytoplasm, from the first stage of respiration called glycolysis.
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