Carbohydrates, lipids, proteins and enzymes


Carbohydrates and Lipids


Carbohydrates are made up of carbon, hydrogen and oxygen. There are two differentn types of carbohydrates-

  • simple carbohydrates: They are either made up of one unit of sugar (glucose C6H12O6) or two units of sugar (sucrose- sugar) 
  • Complex carbohydrates- such as starch and cellulose. They are made up of chains of simple sugar units bonded together. A water molecule is produced when the sugar units are bonded.

Some Carb foods: Bread, pasta, rice. These are broken up into glucose in the body and used in cellular respiration.


These are fats and oils. They are the most efficient energy store in the body. They are also made up of carbon, hydrogen and oxygen. They are made up of three molecules of fatty acids joined to a molecule of glycerol. The glycerol is always the same but there are different types of fatty acids making it either a solid or liquid.

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Proteins are made up of long chains of amino acids. The long chains are folded to form a specific shape. Other molecules can fit into these specific shapes. If the protein is heated, the shape is changed and the protein is denatured. 

Functions of proteins:

  • structural components of tissues such as muscles and tendons
  • hormones such as insulin 
  • antibodies, which destroy pathogens (immune system)
  • enzymes, which act as catalysts in the cells.
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Catalysts and enzymes

Catalysts and enzymes:

  • Chemical reactions in cells are controlled by proteins called enzymes.
  • enzymes are biological catalysts- speed up reactions.
  • enzymes are large proteins and the shape of the enzyme is vital for its function. This shape has an area where other molecules can fit- the active site.
  • The substrate in a reaction can be held in the active site and be either connected to another molecules or broken down.

Enzymes can:

  • build large molecules from smaller ones (build starch from glucose molecules)
  • change one molecule into another (convert a sugar into a different sugar)
  • break down large molecules into smaller ones (digestion!)

Practical for catalysts: Breaking down Hydrogen peroxide.

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Factors affecting enzyme action


  • enzyme reactions are similar to other reactions when the temperature is increased (up to a point)
  • Reactions take place faster when it is warmer. At higher temperatures, the molecules move around more quickly and so collide with each other more often, and with more energy.
  • if the temp gets too hot, the enzymes active site changes shape making it denatured.


  • Each enzyme works best at a certain PH value. Either acidic or alkaline. 
  • If the PH is not right for them they will become denatured.

Digestive enzymes:

  • Digestive enzymes are produced by specialised cells in glands and in the lining of the gut.
  • The enzymes pass out of the cells and comes into contact with the food so it is digested
  • Digestion involves the breakdown of large insoluble molecules into smaller soluble molecules.
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Making use of enzymes

Some microorganisms produce enzymes that pass out of their cells. These enzymes have many uses in industry but can be costly to produce.

  • Biological detergents contain proteases and lipases that digest food stains. They work at lower temps than normal washing powders. This saves energy and money spent on electricity.
  • Proteases are used to pre-digest proteins in baby foods.
  • isomerase is used to convert glucose syrup into fructose syrup. this is much sweeter so less is needed, so food is not as fattening.
  • carbohydrases are used to convert starch into sugar syrup for use in foods.
  • In industry, enzymes are used to bring about reations at normal temps and pressures. Traditional chemical processes require expensive equipment and lots of energy to produce high temp and pressures.
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