Biology Aqa Notes

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Module 2.1: Biological Molecules
* State the functions of biological molecules in organisms Carbohydrates – energy storage and supply, structure (in some organisms) Proteins – Structure, transport, enzymes, antibodies, most hormones Lipids – Membranes, energy supply, thermal insulation, protective layers/padding, electrical insulation in neurones, some hormones Vitamins and minerals – From parts of some larger molecules and take part in some metabolic reactions, some act as coenzymes or active enzyme activators Nucleic acids – information molecules, carry instructions for life Water – Takes part in many reactions, support in plants, solvent/medium for most metabolic reactions, transport

* Define metabolism
Metabolism is the sum total of all the biochemical reactions taking place in the cells of an organism.

* Name the monomers and polymers of carbohydrates, proteins and nucleic acids. | Monomer | Polymer |
Carbohydrates| Monosaccharides (simple sugars) | Polysaccharides | Proteins| Amino acids| Polypeptides and proteins|
Nucleic Acids| Nucleotides| DNA and RNA|

* Describe the general features of condensation and hydrolysis reactions. Condensation reactions link monomers together. The same reaction is repeated many times to make a polymer and is used to link subunits in lipid molecules.

In condensation reactions a water molecule is released, a covalent bond is formed and a larger molecule is formed by the bonding together of smaller molecules.

When a larger molecule splits this is called a hydrolysis reaction. In hydrolysis reactions a water molecule is used, a covalent bond is broken, smaller molecules are formed from splitting larger ones.

* State the structural difference between α and β glucose. The two ring structures are virtually identical but the OH and H groups are either above or below the plane of carbon 1. In glucose the OH at carbon 1 is below the plane of the ring. In β glucose he OH at carbon 1 is above the plane of the ring.

* Describe the formation and breakage of glycosidic bonds in the synthesis and hydrolysis of a disaccharide. A condensation reaction joins to monosaccharides together to form a disaccharide molecule. A covalent bonds called a glycosidic bond is formed. Water breaks the glycosidic bond in a hydrolysis reaction. A H and OH from each molecule is used to form water. When you break down large molecules in digestion which breaks the glycosidic bonds.

* Describe the molecular structure of alph-glucose as an example of a monosaccharide carbohydrate. 3- carbon monosaccharides are called triose sugars.
5-carbon monosaccharides are called pentose sugars
6-carbon monosaccharides are called hexose sugars. (Fructose and glucose).

* Explain how the structure of glucose relates to its functions in living organisms. As the glycosidic bonds between glucose is covalently bonded which is a strong bond, a lot of energy is released when these bonds are broken so this is a good energy store. This energy can be used to make ATP which holds small packets of energy for use in cell processes. Animals and plants can only break down glucose but cannot break down β glucose.

* Compare and contrast the structure and functions of amylose and cellulose. Amylose (in Starch) | Cellulose|
Long, straight chained amylose molecules. Stored in chloroplasts and elsewhere in plant cell in membrane-bound starch grains. Starch can be broken down to glucose molecules which can be respired to release energy. Made of α glucose monomers. | Made of β glucose monomers which form a long, straight polymer called a cellulose chain found only in plants. These form fibres because they contain OH groups which H bond which also form bundles called microfibrils and then macrofibrils. This has great mechanical strength and when embedded in a polysaccharide glue of substance called pectins they form cell walls. |

* Describe the structure of...
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