B3 - Functions of Proteins

Proteins have many different functions There are hundreds of different proteins and the each have a different function, you only need to know 4 of them Carrier molecules - used to transport smaller molecules e.g. haemoglobin binds to oxygen molecules and transports them all around the body Hormones - used to carry messages all around the body e.g. insulin is a hormone released by the pancreas into the blood to regulate blood sugar levels Structural proteins - are physically strong e.g. collagen is a structural that strengthens connective tissues like cartilage and ligaments

Enzymes control cell reactions Cells have lots of chemical reactions going on inside them all the time such as respiration, photosynthesis and protein synthesis Reactions like these need to be carefully controlled - making sure that they have the right amount of substances in them and keep the organism working properly The reaction can be made quicker by raising the temperature, this also speeds up the unwanted reactions, there is also a limit of how high you can raise the temperature of a living thing without the cell getting damaged  So living things produce enzymes which act as a biological catalyst Enzymes reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body Every different biological reaction has its own enzyme which is designed especially for it Each enzyme is coded for by a different gene, and has an unique shape which it needs to do its job

Enzymes are very specific Chemical reactions usually involve things either being split or joined together The substrate is the molecule changed in the reaction Every enzyme has an active site - the part where it joins on to its substrate to catalyse the reaction Enzymes are picky, they usually only work with one substrate (enzymes have a high specificity for their substrate This is because, for the enzyme to work, the substrate has to fit into the active site. If the substrate's shape doesn't match the active sites's shape, then the reaction won't be catalysed. This is called the lock and key mechanism

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