Biological Molecules And Carbohydrates

Biological Molecules And Carbohydrates Quite simply, molecules are many atoms chemically bonded together. They are the most basic structural formation of an element and make up everything, from the air we breathe to ground we walk on. Some important molecules make up cells which are the most basic forms of life; every living thing is made up of cells. Cells mainly consist of water molecules but there are a number of other important biological molecules vital to allow life to exist. Macromolecules are among the most important as they can offer structural support to the cell, hold energy like a battery, act as a catalyst for biochemical reactions and store genetic information as well as having many other important functions. Macromolecules are formed of monomers – simple molecules that can bond together with others to form larger more complicated molecules. When two monomers react, they create a separate water molecule as monomers always have hydrogen and oxygen atoms in their molecular structure. A covalent bond is formed in the absence of the hydrogen and oxygen atoms, connecting the two monomers together. This is called a condensation reaction and it can continue happening until a large chain of molecules forms, eventually making a macromolecule. The reverse effect, called a hydrolysis reaction, can also occur where water will displace a covalent bond in a macromolecule reverting it back to a monomer though a catalyst is usually needed for this reaction to take place. The following image displays these reactions very well. These larger molecules are called polymers and macromolecules are biopolymers (naturally produced polymers). These consist of four types; the carbohydrates, proteins, lipids and nucleic acids with each type being made up of its own specific monomers. Carbohydrates Carbohydrates are molecules made from the elements carbon, hydrogen and oxygen. They are often called sugars and they supply a large percentage of energy to animal and human cells. The monomers of carbohydrate m acromolecules are called monosaccharides (simple sugars) with only one unit of sugar. All monosaccharides have the chemical structure (CH2O)n with n equalling 3, 4, 5, 6 or 7 depending on the number of carbon atoms the monosaccharide has – for example as glyceraldehyde has three carbon atoms the formula will be C3H6O3 and as fructose has six carbon atoms the formula will be C6H12O6. Most monosaccharides form ring shaped molecular structures when dissolved in water (see below image, depicting glucoses three forms). One of the most common monosaccharides is glucose – a vital ingredient for almost all life on earth. Plants make this monomer by using photosynthesis in the following way (CH2O represents glucose). H2O + CO2 + Sunlight and Chlorophyll = (CH2O) + O2 When these simple monosaccharide monomers such as glucose join together to form carbohydrate polymers they become disaccharides (with two sugar units), oligosaccharides (between 3 and 10 units) and polysaccharides (10 or more units also known as complex carbohydrates). The term for this joining together is called glycosidic linkages where the molecules will covalently bond by a condensation reaction (mentioned in the introductions) with each other. The disaccharide sucrose is a polymer of glucose combined with fructose, and lactose is a polymer of glucose bonded with galactose – both of these are also known as table sugar and the sweetness in milk. Cellulose, a polysaccharide, is made from many thousand conjoined glucose molecules and is the main part of plant cell walls. Another polysaccharide, starch, is again made from a large amount of glucose molecules but it is found in many food stuffs such as many vegetables, seeds, grains and fruits. Starch is very useful in that it can be stored in reserves and broken down quickly to release the energy when it’s most needed – for example a deciduous tree will need starch in the winter when it can’t carry out photosynthesi s.