Biological molecules
- Carbohydrates: made of carbon, hydrogen, oxygen
- Fats: made of carbon, hydrogen, oxygen
- Proteins: made of carbon, hydrogen, oxygen, nitrogen
Biological molecules are macromolecules. Their large molecules are made from smaller molecules.
- Starch, glycogen and cellulose are made from glucose
- Proteins from amino acids
- Fats and oils from 3x fatty acids and 1x glycerol
Food tests
To test for:
- Starch: iodine (turns from brown to blue black)
- Reducing sugars (sugars that contain bonds that allows it to act as a reducing agent): add benedict's solution and heat in water bath (turns from blue to red)
- Protein: biuret (turns from blue to purple)
- Vitamin C: DCPIP (turns from blue to colourless)
- Fats: add ethanol then water and shake (turns from colourless to cloudy white emulsion)
| Test for | Reagent / method | Colour change |
|---|---|---|
| Starch | iodine | turns from brown to blue black |
| Reducing sugars | add benedict's solution and heat in water bath | turns from blue to red |
| Protein | biuret | turns from blue to purple |
| Vitamin C | DCPIP | turns from blue to colourless |
| Fats | add ethanol then water and shake | turns from colourless to cloudy white emulsion |
Structure of a DNA molecule
- Two strands coiled together to form a double helix
- Each strand contains chemicals called bases
- Bonds between pairs of bases hold the strands together
- Bases always pair up in the same way: A with T, and C with G
Extended
Glucose is a simple sugar (monosaccharide). 2 glucose joined together is called maltose (disaccharide). When many glucose join together, starch, glycogen or cellulose forms (polysaccharide).