ATP: "The body's natural energy source."

Please allow us at least once, to talk to you in a seemingly biochemical language as we discuss the source of our body’s energy, Adenosine Triphospate (ATP), A nucleoside composed of adenosine (an adenine ring and a ribose sugar) and three phosphate groups with empirical formula: C10H16N5O13P3.

To those of us who are not biochemistry inclined, that would mean a chemical structure comprised of 10 carbons, 16 hydrogens, 5 nitrogens, thirteen oxygen’s and three phosphate groups.

The structure of ATP has an ordered carbon compound as a backbone, but the part that is really critical is the phosphorous part - the triphosphate. Three phosphorous groups are connected by oxygens to each other, and there are also side oxygens connected to the phosphorous atoms.

Under the normal conditions in the body, each of these oxygens has a negative charge, and as you know, electrons want to be with protons - the negative charges repel each other. These bunched up negative charges want to escape - to get away from each other, so there is a lot of potential energy here.

If you remove just one of these phosphate groups from the end, so that there are just two phosphate groups, the molecule is much happier. This conversion from ATP to ADP is an extremely crucial reaction for the supplying of energy for life processes. Just the cutting of one bond with the accompanying rearrangement is sufficient to liberate about 7,3 kilocalories per mole = 30,6 kJ/mol. This is about the same as the energy one gets from consumption of a single peanut.


IS THIS WHY WE CALL ATP THE BODY’S SOURCE OF ENERGY?

Yes, each of the high-energy phosphate bonds contains about 8 000 calories of energy per molecule of ATP in normal body conditions. Remember, these bonds are very labile and can be split instantly whenever energy is required to promote other cellular requirements or metabolic processes.

BUT WHAT IS THE SOURCE OF ATP?

The different foods we ingest are first digested in the digestive tract to form glucose, fatty acids and amino acids. These chemical components are then delivered to the body cells. In the cells they are eventually converted into the compound acetyl co-A, which is split in the mitochondrion (central power house) of each cell into hydrogen and carbon dioxide. The carbon dioxide (Co2) diffuses out of the mitochondrion and eventually out of the cell. The hydrogen atoms combine with carrier substances and are carried to the surface of the shelves protruding through the mitochondrion. Attached to these shelves are the so called oxidative enzymes which through a series of sequential reactions cause hydrogen atoms to combine with oxygen. During these reactions the energy released from the combination of the hydrogen with oxygen is used to activate the ATPase, which is the enzyme that drives the reaction to manufacture tremendous quantities of ATP. The ATP is then transported out of the mitochondrion into all parts of the cytoplasm and nucleoplasm (see the structure of a cell) where its energy is used to energise functions of the cell.

SO WHAT IS THE BIG DEAL ABOUT THIS ATP?

ATP is an essential energy source for cellular function. It promotes three categories of cellular functions i.e. transport across the cell membrane e.g. transport of sodium through the cell membrane during urine formation etc, synthesis of chemical compounds throughout the cell e.g. synthesis of proteins that are essential for forming different enzymes and cellular mechanical work e.g. to supply the energy needed for muscle movement. When looking at this we thus can say that ATP is the source of energy for all cellular function. ATP therefore sustains life. In summary, living organisms can use ATP like a battery. The ATP can provide power for needed reactions by losing one of its phosphorous groups to form ADP. Food energy can then be used to convert the ADP back to ATP in the mitochondria so that the energy is again available to do the required work.

WHAT ELSE DO OUR BODY’S NEED?

The normal energy requirements of an average person for quiet daily living are about 1 800 calories, whereas a person performing very heavy work may require as many as 6 000 to 8 000 calories per day. Some of the special nutrients required by the body include Vitamin A, (which is especially important to maintain the health of the different epithelial structures of the body), Thiamine, (which is necessary to form the enzyme decarboxylase, which removes carbon dioxide from various food stuffs during cellular metabolic processes, lack of which can cause the disease Beriberi. The body also needs Niacin and Riboflavin, which help to promote the oxidative metabolisms processes required for formation of ATP, the absence of which may cause the disease Pellagra. The body requires Vitamin B12 and Folic acid, needed by the bone marrow for formation of red blood cells, lack of which may cause Pernicious Anaemia. Vitamin D is vital for absorption of calcium from the intestinal tract and lack of this may cause Rickets. Vitamin K is essential for the formation of the many blood clotting factors and lack of such may cause Bleeding tendencies.

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