Enzymes

Enzymes

Describe and give the role of enzymes.

Enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms. The role of enzymes is to catalyse reactions that affect metabolism at a cellular and whole organism level. They reactions can be anabolic, two substrate products are condensed into one, or catabolic, one substrate molecules hydrolysed into two. Together anabolism and catabolism make metabolism; the sum of all reactions.

Describe the mechanism of action of enzyme molecules.

In the lock and key hypothesis the enzyme has an active site complementary to its substrate. The substrate bonds to the enzyme’s active site to form an E-S complex. The substrates then react and the products are formed in an enzyme-product complex. The products are then released leaving the enzyme unchanged.

The induced-fit hypothesis suggests the enzyme’s active site is flexible and changes shape slightly as the substrate binds, to form a closer fit between active site and substrate.

Both models substrate interacts with R groups in the active site leading to bond strain in the molecule, weakening the bonds therefore lowering the activation energy for the reaction.

Describe catalyse, amylase and trypsin as examples of intracellular and extracellular enzymes.

The intracellular enzyme catalase ensures hydrogen peroxide is broken down to oxygen, preventing it’s accumulation as this is dangerous to plant and animal cells.

Amylase is produced by the salivary glands and pancreas to break starch molecules down into maltose. Maltase in the small intestine then breaks this substrate down into glucose which is small enough to travel in the bloodstream.

Trypsin catalyses the digestion of proteins into smaller peptides, which are then catalysed further by other proteases into amino acids. Trypsin is produced in the pancreas and released into the small intestine. The amino acids are absorbed by the cells lining the digestive system and then absorbed into the bloodstream.

Describe and explain the effects of temperature on enzyme activity.

An increase in temperature increase the kinetic energy of the particles so the particles move faster and collide more frequently, leading to more E-S compleses and a higher rate of reaction.

The temperature coefficient Q₁₀ of a reaction is ameasure of how much the rate of reaction increases with a 10 degree increase in temperature. This no longer applies when the enzymes have denatured.

However, if the temperature becomes too high the bonds will start to vibrate more until finally the bonds break, causing a change in the precise tertiary structure of the protein, resulting in being denatures…