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Biological Molecules

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Biological Molecules Biological molecules serve as the building blocks of living organisms. The human body is made up of biological molecules. There are three different types of biological molecules - Proteins, Carbohydrates and Lipids. Each of these molecules has different functions in living organisms which are essential to their survival. The structure of proteins, carbohydrates and lipids can vary, and this affects their properties and functions within living organisms. A protein molecule is made up of monomers called amino acids. All amino acids contain the elements Carbon, Hydrogen, Oxygen and Nitrogen, and have the same fundamental structure. The R group stands for the variable group of amino acids, which can cause the amino acid to have a different structure and therefore a completely different function in the human body. Two or more amino acids joined together forms a peptide bond. A peptide bond is formed when two amino acids are bonded together in a condensation reaction (loss of water). Polypeptide bonds are made by repeated condensation reactions. Proteins can have a primary, secondary, tertiary or quaternary structure, depending on how their bonds form and join with one another. ...read more.


enzymes, haemoglobin, insulin. Carbohydrates can be divided into three main structures; monosaccharides, disaccharides and polysaccharides. All monosaccharides are sweet, soluble and crystallite. Different monosaccharides have different numbers of carbon atoms in their structure, therefore giving them different properties and functions within living organisms. Hexoses have six carbon atoms. There are many different isomers of hexose, which have the same number of carbon atoms but are structured in different ways, which gives them different properties and functions within the human body. For example glucose is an isomer of fructose. Although they have the same number of hydrogen, oxygen and carbon atoms, they are structured differently within the sugar. This gives glucose and fructose completely different properties. Glucose is a means of transferring energy around the body as blood sugar (amongst other things) whereas fructose is found in many sweet tasting fruits. Stereoisomers can also have completely different properties and functions even though their structures are slightly different, e.g. ? glucose and � glucose. Disaccharides consist of two monosaccharides bonded together by glycosidic bonds in a condensation reaction. A variety of different disaccharides can be formed (each with different properties and functions) ...read more.


The structure of a saturated fatty acid is relatively straight, so they pack together easily and become solid more readily therefore forming fats, e.g. animal fats. Unsaturated or polyunsaturated fatty acids (unsaturated fat with more than 1 double bond between the carbons) have bends in the hydrocarbon chain where there is a double bonded carbon, which increases the distance between the molecules, increasing fluidity. They have a low melting point and are usually liquid at room temperature, e.g. plant oils. So an addition of a double bond between the carbons in fatty acids causes them to have different structures and properties, giving them different functions in living organisms. Some lipids are a combination of glycerol 2 fatty acids and a hydrophilic phosphate group. This is known as a phospholipid. The head (polar head) of the phospholipid contains a negatively charged phosphate group which is hydrophilic (water liking). The non-polar tail of the phospholipid is hydrophobic (water hating). For this reason phospholipids are important in cell membranes as they separate water from outside the cell from the water inside the cell. Therefore water cannot enter the cell. The replacement of one fatty acid by phosphate in a lipid changes its properties and functions completely. Adeel Ahmed ...read more.

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