Journal of Clinical Nutrition & Dietetics

Description

Organism metabolism is the set of chemical reactions that sustain life. Metabolism performs three primary functions: The process by which food's energy is converted into energy that can be used by cellular processes; the transformation of food into the components that go on to make proteins, lipids, nucleic acids and some carbs; as well as the removal of metabolic wastes. Organisms are able to grow, reproduce, maintain their structures and respond to their surroundings thanks to these enzymecatalyzed reactions. The term metabolism can also refer to the total number of chemical reactions that take place in living things, like digestion and the movement of substances into and out of cells. In this case, the set of reactions in the cells that were just mentioned is called intermediate metabolism. There are two types of metabolic reactions: Catabolic, which involve the breakdown of compounds (such as the conversion of glucose to pyruvate through cellular respiration); or anabolic, the process of building up compounds (synthesis) like proteins, carbohydrates, lipids and nucleic acids. Most of the time, anabolism uses up energy while catabolism makes energy.

Group of Carboxylic Acids

The metabolic chemical reactions are organized into metabolic pathways, each of which involves the conversion of one chemical into another through a series of steps facilitated by a specific enzyme. By coupling them to spontaneous reactions that release energy, enzymes enable organisms to drive desirable reactions that require energy but will not occur on their own. As catalysts, enzymes enable a reaction to progress at a faster rate and also permit the rate of a metabolic reaction to be controlled, for example in response to changes in the cell's environment or signals from other cells. An organism's metabolic system decides which substances are beneficial to it and which are harmful. For instance, although hydrogen sulfide is toxic to animals, some prokaryotes use it as a nutrient. An organism's basal metabolic rate is a measure of how much energy is used by all of these chemical reactions. The resemblance of the fundamental metabolic pathways between vastly different species is a striking feature of metabolism. For instance, all known organisms contain the group of carboxylic acids that serve as intermediates in the citric acid cycle. These acids can be found in species as diverse as the single-celled bacterium Escherichia Coli and massive multicellular organisms like elephants. The early appearance of these metabolic pathway similarities in evolutionary history and their persistence are probably to do with their effectiveness. Normal metabolism is disrupted in a number of diseases, including cancer, type II diabetes and metabolic syndrome. Additionally, the metabolism of cancer cells differs from that of normal cells. These differences can be used to identify therapeutic targets for cancer. The four primary classes of molecules that make up the majority of the structures that make up animals, plants and microbes are: Carbohydrates, nucleic acids, lipids (also known as fats) and amino acids due to the fact that these molecules are essential to life, metabolic reactions either focus on making them during the formation of cells and tissues or on breaking them down and utilizing them for energy through digestion. Together, these biochemicals can form polymers like DNA and proteins, which are vital macromolecules for life. Amino acids are arranged in a linear chain that are joined by peptide bonds to form proteins. The enzymes that catalyze the chemical reactions in metabolism are found in a lot of proteins. The proteins that make up the cytoskeleton, a system of scaffolding that keeps the shape of the cell, are one example of a structural or mechanical function. Cell signalling, immune responses, cell adhesion, active transport across membranes and the cell cycle all depend on proteins. By providing a carbon source for entry into the citric acid cycle (tricarboxylic acid cycle), amino acids also contribute to cellular energy metabolism, particularly in situations in which cells are under metabolic stress or when a primary source of energy.

Polymers of Fatty Acids

The most diverse class of biochemicals are lipids their primary structural applications are as components of internal and external biological membranes, such as the cell membrane. They can also be used for their chemical energy. The polymers of fatty acids called lipids have a long, non-polar hydrocarbon chain and a small, polar region where oxygen is present. Lipids, which dissolve in organic solvents like ethanol, benzene and chloroform, are typically described as biological molecules that are either hydrophobic or amphipathic. A large group of compounds called fats contain glycerol and fatty acids; A triacylglyceride is a molecule of glycerol that is linked to three fatty acids by ester linkages. Backbones like sphingosine in sphingomyelin and hydrophilic groups like phosphate in phospholipids are two variations on this basic structure. Another important class of lipids are steroid compounds like sterol. Aldehydes or ketones with a lot of hydroxyl groups attached are carbohydrates, which can be straight chains or rings. The most prevalent biological molecule, carbohydrates serve a variety of functions, including the storage and transportation of energy (through starch and glycogen) and structural components (cellulose in plants, chitin in animals). Galactose, fructose and, most importantly, glucose are the fundamental monosaccharide units of carbohydrates. There are nearly infinite ways that monosaccharides can be linked together to form polysaccharides. DNA and RNA are both nucleic acids that are polymers of nucleotides. A phosphate is attached to a ribose or deoxyribose sugar group that is attached to a nitrogenous base on each nucleotide. The interpretation of genetic information through transcription and protein biosynthesis is made possible by using and storing nucleic acids. Mechanisms for DNA repair keep this information safe and spread through DNA replication. Reverse transcription is used to generate a DNA template from the viral RNA genome of many viruses, including HIV. In that it is capable of catalyzing chemical reactions, RNA in ribozymes like spliceosomes and ribosomes is comparable to enzymes. Attaching a nucleobase to a ribose sugar is how individual nucleosides are made. These bases, also known as purines or pyrimidines, are heterocyclic rings that contain nitrogen. In metabolic-group-transfer reactions, nucleotides also serve as coenzymes.