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The role of proteins

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Introduction

Debbie Spicer The role of proteins Proteins are made up of amino acids which are joined together to form one or more polypeptide chains these chains are folded into a three-dimensional shape which is different from protein to protein. The shape is determined by the order that the amino acids are arranged in this is the primary structure of the protein. The secondary structure of the protein is held together by hydrogen bonds. The polypeptide chains may coil to form a ? helix or they may lie in a ?-plated sheet. The chain may be folded again to give its tertiary structure. Some proteins are made up of more than one polypeptide chain and the way in which these chains are held together determines its quaternary structure. Haemoglobin is made out of four polypeptide chains so it has a quaternary structure. Each of the polypeptide chains in haemoglobin is attached to a haem group, which is important in the transport of oxygen around the body. ...read more.

Middle

Antibodies are types of proteins called immunoglobulins they have a unique antigen-biding site, so it can detect self from non-self cells. The antibody attaches to particular molecules on the microorganisms surface. This triggers off mechanisms that lead to their destruction and the infection is controlled. Antibodies have a specific shape that only allows them to be effective against one type of virus. Proteins play and important part in cell processes as they are found in the membranes of cells. They act as carriers for water-soluble molecules such as glucose. The molecules bind to these molecules then change their shape, releasing the molecule to the other side of the membrane. Proteins also form ion channels so that charged particles such as sodium and chloride ions can diffuse across the membrane. Active transport uses Carrier proteins and ATP to move substances against a concentration gradient. Proteins in a cell membrane form receptor sites that enable hormones and nerve transmitters to bind with specific cells. Synapses are the junctions between two neurones. ...read more.

Conclusion

The numbers of cells that collagen and elastin produce decreases as you get older. This means that there are fewer fibres, so they undergo structural changes and become larger and less resilient. Collagen molecules are made up of three molecules of collagen and glucose molecules become attached to amino acids in the collagen molecules. This eventually forms cross linkages between the fibres as aging occurs. The collagen fibres reduce the space for other molecules, as they get larger. This causes the skin to dry out, as there is no space for lipids and water, and it sags and forms wrinkles. Proteins are made up of essential and non-essential amino acids. Essential acids are amino acids that we have to have in our diet because we cannot synthesise them from other substances. Non-essential amino acids can be synthesised from essential amino acids. Non-essential amino acids are produced from essential amino acids in the liver by a chemical reaction called transamination. Trasamination involves the transfer of an amino (NH2) group from an essential amino acid to a molecule of another substance called a keto acid. This produces a non-essential amino acid and a molecule of a different sort of keto acid. ...read more.

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