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Are biological catalysts because they speed up metabolic reactions. They can affect both structure and function.


Enzymes that work within cells. E.G.....                                                                                    Catalase- breaks down hydrogen peroxide into oxygen and water. It consists of 4 polypeptide chains and contains a haem group. Optimum PH is 7 for humans and 45 degrees in humans for temperature.


Enzymes that work outside cells. E.G.....                                                                                 Amylase- produced in salivary glands, breaks down starch into maltose. Also made in pancreas to catalyse reaction in lumen of small intestine                                                                             Trypsin- made in pancreas, acts in lumen of small intestine to digest proteins into peptides. Optimum PH is 7.5-8.5

  Active site 

Consists of 6-10 amino acids. The tertiary structure is crucial, as its shape is completmentary to the hape of the substrate. Its shape can be altered by PH and temperature changes, as they affect the bonds in the tertiary sturcture and thus change the shape.

Lock and Key 

The lock is the ative site and the key is the substrate as the shape of the active site is complementary to the substrate. Temporary hydrogen bonds hold the substrate in and form enzyme-substrate complex, whilst the substrate is still in the active site and have been broken down or bulit up the form enzyme-product complex. 

Induced fit

lock and key doesnt explain…


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