Biology coursework on enzymes.

The Effect of Substrate Concentration:

At low substrate concentrations the rate of reaction is directly proportional to the substrate concentration due to the fact that when the substrate concentration is increased the rate of enzyme-substrate collisions (reaction) is equally increased.

However, as the substrate concentration rises the rate of reaction will finally reach a maximum level. This is because all the active sites are saturated with substrate.

The Effect of Temperature:

At the lower temperatures, the rate of reaction rises with a very steep gradient as the temperature increases. This is because the molecules of the enzyme move faster and faster thus causing the rate of enzyme-substrate collisions to increase. The temperature rises to such a degree that the enzyme becomes denatured. This is because the molecules of the enzyme vibrate so violently that they break their weak bonds holding the structure of the enzyme together.

The perfect temperature for the majority of enzymes is 37ºC. For this reason, our body temperature is 37°C

The Effect of pH:

With a change of pH the weak bonds holding the enzyme together will break. This will denature the enzyme, thus deactivating the active site. As enzymes normally exist within cells where the pH is 7, the most favourable pH is obviously 7. A pH significantly higher or lower than 7 will kill the cells.

Salt concentration:

Each enzyme has an optimal salt concentration. Changes in the salt concentration may also denature enzymes.

Lock - Key Mechanism:

The active site on the enzyme attaches to a substrate molecule (such as a disaccharide) forming an enzyme-substrate complex. While attached to the substrate, the enzyme causes a weakening of certain chemical bonds in the substrate molecule, resulting in a breakdown (hydrolysis) of the substrate into two smaller product molecules (such as two monosaccharides). The enzyme is unaltered during the reaction and is free to catalyze the breakdown of another substrate molecule. If the active site on the enzyme is blocked by a poison molecule, this vital hydrolysis reaction cannot occur.

Lock - Key diagram

Enzymes are substances present in the cell in small amounts that function to speed up or catalyze chemical reactions. On the surface of the enzyme is usually a small crevice that functions as an active site or catalytic site to which one or two specific substrates are able to bind. (Anything that an enzyme normally combines with is called a substrate). The binding of the substrate to the enzyme causes the flexible enzyme to change its shape slightly through a process called induced fit to form a tempory intermediate called an enzyme-substrate complex

Enzymes speed up the rate of chemical reactions because they lower the energy of activation, the energy that must be supplied in order for molecules to react with one another. Enzymes lower the energy of activation by forming an enzyme-substrate complex allowing products of the enzyme reaction to be formed and released

Enzyme-Substrate Reaction

Other uses of Enzymes:

Enzymes are also used as catalysts to speed chemical reactions and in body enzymes such as amylase, lipase, protease and carbohydrase are released to digest the food we eat so the body can absorb all the nutrients and vitamins properly and quickly into it and then they are spread around by the blood stream. There are many more enzymes in humans and animals but those are the main ones that we use. Amylase is produced in our mouths its in out saliva; this helps us digest food when we start chewing. Lipase is used to digest fats, protease is used to digest proteins and carbohydrase is used to digest carbohydrates. But enzymes are also important for Circulation - Enzymes are vitally important in preventing excessive blood clotting and reducing the "stickiness" of the platelets and red blood cells. Trypsin and chymotrypsin are used in fibinolysis, a process that dissolves blood clots. Enzymes help remove metabolic waste and generally improve circulation. Inflammation - Regardless of the reason for inflammation, enzymes are essential for tissue repair. They reduce swelling and pain, decrease the duration or inflammatory process and help speed up the recovery rate. These effects are also important in the treatment of injuries. Other benefits - There are many other uses for enzymes, including autoimmune conditions, arthritis, chronic diseases, pre and post-surgery and multiple sclerosis.

Gurdeep Singh Malhi

1GK