4 Biological molecules
Organic molecules
- Provide energy for life processes
- Provide raw materials for growth and repair
- Known as biological molecules
Chemical element
Carbohydrate
- Carbon, Hydrogen, Oxygen
- Made up of many sugar molecules
- Stored in cells and used in respiration to provide energy for the organism
- Glucose - simple sugar / monosaccharide
- 2 glucose molecules join together - disaccharide
- Polysaccharide - glycogen, starch
- Use iodine to test for for starch
- Use benedict's solution to test for glycogen
Protein
- Carbon, Hydrogen, Oxygen, Nitrogen
- Long chain of amino acids joining together
- Basic structure of DNA
- About 20 different types of amino acids
- Contain the same structure but the ‘R’ group is different for each one
- Radiation affects double helix structure of DNA and causes cancer
- Use biuret solution to test for presence
Lipids
- Carbon, Hydrogen, Oxygen
- Most are made up of triglycerides
- Basic unit is 1 glycerol molecule bonded to 3 fatty acid chains
- Fats - solid at room temperature
- Oils - liquid at room temperature
- Fatty acids vary in size and structure
- Use the ethanol test to check for presence of lipids
Test for vitamins
- DCPIP test - vitamin C
Structure of DNA molecule
- Deoxyribonucleic acid
- Contains the instructions for the growth and development of an organism
- Consists of 2 strand of DNA wound around each other in double helix
structure
- Found in nucleus and mitochondria
- Individual units of DNA - nucleotides
- Adenine (A)
- Cytosine(C)
- Thymine(T)
- Guanime(G)
Nucleotides
- A pairs with T, C pairs with G
- All nucleotides contain the same phosphate and deoxyribose sugar (backbone)
- Differ from each other in the base attached (ATCG)
- Bases on each strand pair up, holding two strands together
- Each strand is used separately
- A gene is a strand of bases, not a strand of base pairs
Testing for Biochemicals
Glucose
Positive test will show colour change from blue to green to orange to brick red
- Use tongs to handle test tubes
- Wear safety goggles and heat proof gloves
1. Pour Benedict’s solution into test tube
a. Benedict’s solution is tested on simple carbohydrates
2. Add liquid sample into test tube
3. Boil mixture for 5 minutes
4. Observe
5. Colour change in mixture if a reducing sugar is present
Starch
A positive test will show a colour change from orange-brown to blue-black
1. Peel sample, e.g potato
2. 5 drops of iodine solution directly onto potato skin
a. Iodine solution is tested on more complex carbohydrates
3. Observe for colour change
Protein
A positive test will show a colour change from blue to violet/purple
1. Add food sample into test tube
2. Add drops of biuret solution
3. Observe for colour changes
Lipids
Positive test will show cloudy emulsion forming
1. Add sample into test tube
2. Add in drops of ethanol and shake
3. Pour ethanol into test tube of distilled water
4. If solution turns cloudy, food contains lipids
Vitamin C
A positive test will show the blue colour of the dye disappearing
1. Add DCPIP solution into test tube
2. Add drops of food sample into same test tube
3. Positive DCPIP test result would show colourless solution
