Chemicals & Life | Biology for GCSE/IGCSE - Class 10 PDF Download

Chemical Elements

• The majority of molecules found in living organisms can be classified into three main categories: carbohydrates, proteins, and lipids.
• All of these molecular groups contain carbon and are therefore categorized as organic molecules.

Large Molecules are Made from Smaller Molecules

Carbohydrates

• Carbohydrates are composed of long chains of simple sugars.
• Glucose, a monosaccharide, is an example of a simple sugar.
• The combination of two glucose molecules forms maltose, a disaccharide.
• When numerous glucose molecules link together, they can form complex carbohydrates such as starch, glycogen, or cellulose, which are polysaccharides.

Fats

• Most fats (lipids) in the body are made up of triglycerides
• Their basic unit is 1 glycerol molecule chemically bonded to 3 fatty acid chains
• The fatty acids vary in size and structure
• Lipids are divided into fats (solids at room temperature) and oils (liquids at room temperature)

Proteins

• Triglycerides consist of long chains of amino acids.
• There are approximately 20 different types of amino acids.
• All amino acids share a common basic structure, but each has a unique 'R' group.
• Formation of proteins occurs when amino acids bond together.
• Amino acids can be sequenced in various orders, resulting in diverse proteins.
• Even a slight variance in amino acid sequence leads to the creation of a distinct protein.