Enzymes
Summary
- Enzymes are globular proteins, which act as catalysts by lowering activation energy.
- Each enzyme acts on only one specific substrate, because there has to be a perfect match between the shape of the substrate and the shape of the enzyme's active site to form an enzyme - substrate complex.
- Anything which affects the shape of the active site, such as high temperature, a change of pH, or the binding of a non-competitive inhibitor with the enzyme, will slow down the rate of reaction.
- Competitive inhibitors also slow down the rate of reaction, by competing with the substrate for the active site of the enzyme.
Terms to Know
- Enzymes are protein molecules, which can be defined as biological catalysts.
- Enzymes are globular proteins, catalysts, are coiled into a three dimensional shape with hydrophilic R-groups on the outside of the molecule ensuring they are soluble
- Active Site: special feature of enzymes, a region usually a cleft or depression, to which another molecule or molecules can bind
- Substrate: the section which completes the enzymes and attaches to the active site
- Enzymes-substrate complex: the combined structure of an enzyme and substrate (a substrate is specific to the enzyme)
- Interactions between R groups of the enzyme and the atoms of the substrate can break, or encourage the formation of, bonds in the substrate molecule, forming one, two, or more products.
- Activation energy: the extra energy to convert the substrate into a product
- The rate of an enzyme controlled reaction is always fastest at the beginning, this rate is called the initial rate of reaction, measure this by calculating the slope of a tangent to the curve as close to zero as possible.
- The enzyme molecule begins to lose it shape and activity and is said to be denatured, is often irreversible.
- The temperature at which an enzyme catalyzes a reaction at the maximum rate is called the optimum temperature.
- The active is the substrate of the enzyme. The shape of the active site allows the substrate to fit perfectly, and to be held in place by temporary bonds which form between the substrate and some of the R groups of the enzyme's amino acids. This combined structure is termed the enzyme - substrate complex.