Biological Molecules

Carbon, hydrogen, oxygen

Carbon, hydrogen, oxygen

Carbon, oxygen, hydrogen, nitrogen

Large molecules made up of smaller basic units

A polymer of glucose

Composed of glucose and fructose subunits (but it is not a polymer).

Made up of a molecule of glycerol joined to three fatty acids. It is not a polymer

A polymer of amino acids, of which there are 20 types. The amino acids are linked together in long chains, which are usually twisted into spirals.

Introduce three drops of starch solution to a dimple on the spotting tile. Add several drops of iodine. The iodine solution turns blue black in the presence of starch

Introduce 2cm3 glucose solution to a test tube. Add 2cm3 Benedict’s solution. Place the test tube in a beaker of boiling water from the kettle and leave for 5 minutes. The blue solution turns orange or red if glucose is present.

Introduce 2cm3 protein solution into a test tube. Add 2cm3 sodium hydroxide solution. Add two drops of copper sulphate solution, shake and observe. The pale blue colour turns to violet.

Introduce 2cm3 oil into a test tube. Add 2cm3 ethanol and shake well. The solution becomes cloudy as an emulsion is formed.

Enzymes are biological catalysts meaning that they alter the rate of metabolic reactions without being altered or used up themselves.

• temperature • pH • enzyme concentration • substrate concentration

• Initially increases steadily with temperature • After the rate peaks, it decreases rapidly

Enzymes work best at an optimum temperature. Below this, an increase in temperature provides more kinetic energy to the molecules involved. The numbers of successful collisions between enzyme and substrate will increase so the rate will increase too. Above the optimum temperature, the enzyme begins to denature. Bonds holding the structure together will be broken down and the active site loses its shape so that it is no longer complimentary to the substrate and they will no longer be able to bind to form enzyme-substrate complexes.

As the pH changes from the enzyme’s optimum, the rate of reaction of the enzyme decreases.

Enzymes have an optimum pH, one at which they work best. If the pH changes much from the optimum, the chemical nature of the amino acids changes. This results in a change in the bonds and so the tertiary structure will be broken down. This causes the active site to change shape, meaning it is no longer complimentary to the substrate and can no longer bind with it to form enzyme-substrate

Initially, increasing the concentration of enzymes will cause a greater rate of reaction, however, after some time, it will simply plateau and increasing enzyme concentration will have no effect on the rate of reaction

At low enzyme concentration, there is great competition for the active sites and the rate of reaction is low. As the enzyme concentration increases, there are more active sites and the reaction can proceed at a faster rate. Eventually, increasing the enzyme concentration beyond a certain point has no effect because the substrate concentration becomes the limiting factor

Initially, increasing the concentration of substrates will causes a greater rate of reaction, however, after some time, it will simply plateau and increasing substrate concentration will have no effect on the rate of reaction.

At low enzyme concentration, there are many active sites that are not occupied. This means that the rate of reaction is low. When more substrate molecules are added, more enzyme-substrate complexes can be formed. So, the rate of reaction increases. Eventually, increasing the substrate concentration yet further has no effect. The active sites will be saturated so no more enzyme-substrate complexes can be formed.

An enzyme is made up of protein, and is known as biological catalyst as it speeds up metabolic reactions without being altered or used up itself

Each enzyme has a specifically shaped are called the active site. The shape of this area is complimentary to the substrate molecules with which they form an enzyme-substrate complex. Once the product has been formed the molecules leave the active sites which can then be reused. This is known as the lock-and-key theory as the substrate fits into the active site the way a key fits into a lock.