Biological Molecules

• Biological molecules are molecules found in living organisms, and are produced by cells.
• Nutrients are substances that are needed for growth, repair, and metabolism.
• Carbohydrates are molecules made from atoms of carbon, hydrogen, and oxygen.
• In a complex carbohydrate, there are chemical bonds between the monomers. If these chemical bonds are broken, the complex carbohydrates can be broken down into simple carbohydrates (e.g. starch can be broken down into glucose molecules).

  
• This break down of complex carbohydrates into simple carbohydrates (simple sugars) is carried out by enzymes in the mouth and small intestine.

  
• Proteins are made up of long chains of amino acids bonded together. A protein is a polymer, whilst the amino acids it is made from are the monomers.

  
• Amino acids are mainly made from carbon, hydrogen, oxygen, and nitrogen atoms.

  
• Enzymes in the stomach and small intestine break proteins down into amino acids.

  
• The term 'lipids' refers to both fats and oils. A fat is a lipid that's solid at room temperature, whilst an oil is a lipid that's liquid at room temperature. Lipids contain a single glycerol molecule attached to three fatty acid molecules.

  
• These fatty acid molecules are often different lengths, and it's the length and structure of the fatty acid molecules that determines whether a lipid is a fat or an oil.

  
• Lipids are made of carbon, hydrogen, and oxygen atoms.
• Remember that lipids are not polymers, because they aren't formed from long chains of monomers. This is a key difference between lipids (not polymers), and carbohydrates and proteins (are polymers).
• Enzymes in the small intestine are responsible for breaking lipids down inside the body.