FOOD 🍔🍕🍎

 It's vital to all organisms, providing all the materials needed to be broken down for energy, to regulate cellular activities and to build and repair tissues. Of the various food substances, carbohydrates, proteins and fats are called nutrients, and minerals, vitamins (not needed by plants) and water are accessory foods. Plants build their own nutrients (by photosynthesis), and take in minerals and water; animals take in all the substances they need and break them down by digestion. Carbohydrates A group of substances made up of carbon, hydrogen and oxygen, which exist in varying degrees of complexity. In animals, complex carbohydrates are taken in and broken down by digestion into the simple carbohydrate glucose. The breakdown of glucose (internal respiration) provides almost all the energy for life's activities. Plants build up glucose from other substances by photosynthesis. Proteins A group of substances made up of simpler units called amino acids. These contain carbon, hydrogen, oxygen, nitrogen and, in some cases, sulfur (S). Most protein molecules consist of hundreds, maybe thousands, of amino acids, joined together by links called peptide links into one or more chains called polypeptides. The many different types of protein each have a different arrangement of amino acids. They include the structural proteins (the basic components.of new cells) and catalytic proteins (enzymes), which play a vital role in controlling cell processes. Plants build up amino acids from the substances they take in by photosynthesis, and then build proteins from them. Animals take in proteins and break them down into single amino acid molecules by digestion. These are then transported in the blood to all the body cells and reassembled into the different proteins needed. Fats A group of substances made up of carbon, hydrogen and a small amount of oxygen. Plants build fats from the substances they take in, and their seeds hold most as a store of food. This can be converted to extra glucose (see carbohydrates) to provide energy for the growing plant. Digestion of fats in animals produces fatty acids and glycerol. If these need to be broken down for energy (as well as glucose), this occurs in the liver. This results in some products which the liver can convert to glucose, but others it cannot. These are instead converted elsewhere to a substance which forms a later stage of glucose breakdown. Fatty acids and glycerol not needed for energy are immediately recombined to form fat particles and stored in various body areas, e.g. under the skin. cellular = relating to or consisting of living cells tissue = any of the distinct types of material of which animals or plants are made, consisting of specialized cells and their products carbohydrate [kɑːbə(ʊ)ˈhʌɪdreɪt] digestion = the process of treating a substance with heat, enzymes, or a solvent to promote decomposition or extract essential components which happens in the alimentary canal to break down food into substances that can be absorbed and used by the body internal respiration = the exchange of gases (as oxygen and carbon dioxide) between the cells of the body and the blood by way of the fluid bathing the cells peptide [pɛptʌɪd] link = the primary linkage of all protein structures; the chemical bond between the carboxyl groups and amino groups that unites a peptide polypeptide [pɒlɪˈpɛptʌɪd] = a linear organic polymer consisting of a large number of amino-acid bonded together in a chain, forming part of (or the whole of) a protein molecule reassembled = rejoined, rebuild