Biology (B2) - Proteins and Their Functions

This set is for B2 Biology, GCSE, AQA and specifically for Proteins and Their Function. This topic has five sub-topics which are:

Protein Structure, Shapes and Functions          Characteristics of Enzymes          Digestive Enzymes          Enzymes Used in the Industry          Home Use of Enzymes

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Protein Structure, Shape and Functions

Proteins make up your hair, nails, fat, in the form of haemoglobin they carry oxygen in your blood and help if you are injured by clotting the blood. 

All proteins contain carbon, hydrogen, oxygen and nitrogen. The are made of a long chain of smaller, soluble molecules, amino acids. These amino acids are joined together by a long chain called polypeptide.

The sequence of every amino acid in this chain is specific to every protein. On the surface of the molecules there is a deppression or a pocket called the binding site which other molecules can fit into.

Some proteins form minute fibres which give structure to tissues such as muscle tissue.

Proteins also make up hormones and antibodies.

Antibodies are produced by white blood cells to fight antigens which helps us against harmful microorganisms.

There are also protein enzymes which speed up reactions as a biological catylist. 

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Characteristics of Enzymes

For chemical reactions to speed up substances can be broken down which is done by enzymes. The starting substance is a substrate and is converted into the product.

Some enzymes will have a hole that is the exact same shape as the substrate, the substrate fits into the whole like a lock and key.

From there it is broken down into the product and come out of the whole, leaving more substance with the same shape to also be broken down.

When the temperature increases so does the rate of reaction to a certain point, beyond this point the enzymes denature and reactions can no longer work, this temperature is usually around 37 degrees celcius.

The effect of changing the pH value depends on the enyme as different enzymes have different optimum pH conditions.

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Digestive Enzymes

The food that we eat needs to be broken down into soluble substances so we can then absorb and use them. The breaking down of these substances is done by enzymes.

Different enzymes break down different substances.

Proteins --> broken down by protease --> forming amino acids

Starch --> broken down by amylase --> forming glucose.

Fats --> broken down by protease --> forming fatty acids or glycerol.

All of these enzymes are produces in the pancreas and small intestine and all need alkaline conditions and work in the small intestine.

Protease is also produced in the stomach and need acidic conditions and work in the stomach.

Amylase is also produce in the salivary glands and need slightly alkaline conditions and work in the mouth.

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Enzymes Used in Industry

Many amounts of microorganisms are grown in the industry to be used as enzymes which are passed out of the cell. They are grown relatively cheaply and quickly in vats, fermenters, and no expensive equipment is needed. The fermenters are kept at 27° C to keep cost low.

Enzymes are used as catylists in enzyme technology. They are efficient as only small amounts are required. 

They are also used in the cooking industry in baby foods, as they are pre-digested foods, making the food softer and easier for the babies to digest.

The can also be used to sweeten foods, this is done by breaking done starch to sugar syrup using carbohydrase to catalyse the reaction. 

Isomerase is an enzymme used to convert glucose syrup to fructose syrup which is sweeter than glucose so less needs to be added to foods, this is useful for slimming foods and low calorie drinks.

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Home Uses of Enzymes

Enzymes in washing powders are obtained through bacteria and they work at moderately high temperatures, this is useful as washing detergents work best at higher temperatures.

Most dirt on or clothes are proteins, fats and sugars. All biological detergents break down the dirst so they can be washed away but having protease and lipase speeds up this process.

Protease helps break down proteins which are present in blood, grass and egg.           Lipase helps break down lipids which are found in fats, oils and grease. 

These enzymes work best at 30° C however denature the the temperature is higher. Also, some people can have an allergic reaction to them.

ADVANTAGES OF ENZYMES: Bring about reactions at normal temperatures and pressure so save energy and money.          They save on expensive equipment.          More effective at lower temperatures.

DISADVANTAGES: Denature at high temperatures         Expensive to produce          Some people may have allergies

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