My aim in this investigation is to investigate how the concentration of amylase affects its rate of reaction with starch.

Biology Investigation (Coursework)- GCSE

Aim-

Introduction-

My investigations main topic is enzymes and how they break up foods, I will be mainly concentrating on how concentration affects the reaction of amylase on starch and how fast this reaction occurs.

Enzymes are biological catalysts. They speed up the chemical reactions, which go on inside living things.

What Are Enzymes-

Enzymes are protein molecules, made by living cells, which act as catalysts and speed up the rate of metabolic reactions, by lowering the activation energy required. In the absence of enzymes, the anabolic and catabolic reactions that make up metabolism would be far too slow to maintain life. The reactions occurring inside our living cells are called metabolism. Some of the reactions build things up (anabolism), for example- glucose is built up into glycogen for storage, and amino acids are linked together to form protein for bodybuilding. Other reactions break things down (catabolism), for example- glucose is broken down into carbon dioxide and water with the transfer of energy. Enzymes enable all these reactions to occur.

Types Of Enzymes-

Enzymes come in two main parts, breaker enzymes and builder enzymes.

- Breaker enzyme, these break down large insoluble molecules into smaller soluble materials.

- Builder enzyme, these are small molecules joined together to form large molecules. These speed up reactions.

Enzymes work on substances called substrates; this takes place on part of a surface called the active site.

Breaker enzyme-

Builder enzyme-

Enzymes are produced inside our living cells. After they are formed, the enzyme may leave the cell and do its job on the outside. Theses enzymes are called extracellular enzymes. These include the digestive enzymes, which break down food substances in our gut. Other enzymes do their job inside the cell it was formed in. This is called intracellular enzymes. Their job is to speed up the reactions. This type of enzyme also controls the reaction.

Properties Of Enzymes-

Enzymes have five important properties-

They are always proteins,

This is one reason why we need proteins in our food.

They are specific in their action,

This means that each enzyme controls one particular reaction, or type of reaction. Example- maltase will only act on maltose, sucrase on sucrose.

They can be used over and over again,

This is because they are not altered by the reaction in which they take part.

They are destroyed by heating,

This is because heating destroys enzymes, in common with all proteins. This is called denaturation. Most enzymes stop working if the temperature rises above 45°C.

They are sensitive to pH,

The term pH refers to the degree of acidity or alkalinity of a solution. Most intracellular enzymes work best in neutral conditions, example- conditions that are neither acidic nor alkaline.

How Do Enzymes Work-

An enzyme binds the substrate, the molecule or molecules, which take part in the reaction. The substrate binds to one part of the enzyme, the active site that is usually a groove or cleft in the globular protein molecule, this is shown in the lock and key theory.

Enzymes are highly selective about what they will bind. Carbohydrase can only break down carbohydrates, proteases can only break down proteins and lipases can only break down fats. This is because the shape of the active site will only allow one shape of the molecule to fit.

Once a substrate has bound, the enzyme allows a particular reaction to occur much more quickly. Reactions are not magical jumps from a substrate to a product. Electrons move, bonds are broken and formed. There are all sorts short-lived intermediates before the final product is formed. Some are unstable; others need a lot of energy to set them up, even if it is released again afterwards. Enzymes hold the substrates in ideal positions for the reaction, stabilize intermediates and provide a environment where less energy is needed for reactions to take place. As a result, individual molecules are more likely to react. Overall, the rate of reaction increases. Enzymes are not fairy godmothers of the cell, making the impossible to happen. Rather, they are like slick men, making the right contacts and providing congenial places for deals to be struck.

Enzymes work in certain environments just like they work for specific substrates as well. Most enzymes prefer neutral conditions, some prefer acidic or alkaline conditions. Most enzymes work at a certain optimum temperature of 37°C-40°C, this is because that is the body’s optimum temperature. Enzymes are denatured when they reach over 40°C because the enzyme gets more energy and starts to vibrate faster and faster, which causes the bonds to break. As the bond breaks the enzymes shape changes and the substrate no longer fits into the active site. This also may happen when enzymes are at the wrong ...