Metabolism is defined the sum of all chemical reactions which occur and are involved in sustaining life of a cell, and thus an organism. Metabolism is of two types: Catabolism: in this process molecules break down producing energy
Anabolism: in this process synthesis of essential compounds needed by the cells are produced (such as DNA, RNA, and protein synthesis).
Bioenergetics describes the metabolic pathways by which a cell obtains energy. Nutrition science studies the relation between the food substance and living things. The study deals with:
1) Body requirements of various substances.
2) The function of various substances in the body.
3) The amount of the substances needed.
4) The lower levels below which health gets affected.
The food which we eat supplies energy (calories) and supplies essential chemicals which the body cannot synthesize by itself. Food provides substances that are essential for building and repair of body tissues. Food provides substances for efficient functioning of the body.
Energy is trapped in complex chemical compounds and nutrients. These compounds are broken down to obtain energy. Humans acquire energy from carbohydrates, lipids and proteins. The chemical energy in these molecules is altered into thermal, kinetic, and other chemical forms.
Lipids, Carbohydrates, and proteins serve as a fuel for the human body. The nutrients are broken down into smaller units in the alimentary tract and are absorbed into the blood. The chemical energy of digestive end products is transformed into useful work by the tissues and the cells. The majority of the absorbed products contain monosaccharides, glucose, and monoacylglycerol, long chain of fatty acids, peptides and amino acids. Once these products are into the bloodstream, the different cells metabolize them.
MECHANISM OF ATP SYNTHESIS
The living cells obtain energy and use them to live, grow and reproduce. The process involved is called as energy metabolism. Energy is released when the chemical bonds of the nutrient molecules break and form high-energy compounds such as ATP. The main chemical energy carrier in all the cells is the ATP. ATP synthesis can occur by two mechanisms:
1) Synthesis from ADP and inorganic phosphate that takes place in the mitochondrion.
2) Synthesis by transfer of high-energy phosphoryl groups to ADP. Both mitochondria and the cytoplasm can carry out the synthesis process.
OXIDATIVE PHOSPHORYLATION: THE MAIN MECHANISM OF ATP SYNTHESIS IN MOST HUMAN CELLS
In ATP synthesis, oxidation-reduction reactions are very essential. The electrons are transferred to two major electron carrier enzymes. The protein complexes transport the electrons. The protein complexes are present in the inner mitochondrial membrane. The complexes contain attached chemical groups that are capable of accepting or donating one or more electrons. The protein complexes are known as the electron transfer system (ETS). The ETS allow distribution of the free...