- Biological molecules are important in organisms to build structures and for use in metabolic reactions.
- Large molecules are made when smaller molecules bind together.
1) Describe the Biological Molecules
Carbohydrates:
- Made up of glucose (small sugar molecule), containing Carbon, Hydrogen and Oxygen.
- When many glucose molecules bind together in a chain, cellulose (make up cell wall), starch (stored on plants) and glycogen (stored in animals) can be made.
Fats:
- Fats and oils are made up of glycerol and fatty acids, containing Carbon, Hydrogen and Oxygen.
- Fats are used for insulation, energy, waterproofing, and protection around delicate organs.
Proteins:
- Made up of amino acids, containing Carbon, Hydrogen, Oxygen, Nitrogen and Sulfur.
- Many amino acids bind together to make protein.
- Different arrangement of amino acids make up different protein and form different shape.
- Enzymes are protein, and each enzyme's active site has a specific shape, allowing it to bind to a specific substrate molecule to catalyze metabolic reactions. *Another example is the binding sites of Antibodies.
2) State that large molecules are made from smaller molecules
Basic Unit (Monomer) |
Larger Molecules (Macromolecules) |
Glucose |
Cellulose, Starch and Glycogen |
Fatty Acids and Glycerol |
Fats and Oils |
Amino Acids |
Proteins |
3) Chemical Tests
Test for Starch |
Add few drops of iodine solution to sample. Color change to blue-black indicate presence of starch |
Test for Reducing Sugars eg. Glucose |
Add Benedict’s solution (blue color). Then heat mixture in water bath for 2 to 3 minutes. A brick-red precipitate indicate presence of reducing sugar. |
Test for Proteins |
Add Biuret solution (blue color). Color change to purple indicate presence of protein. |
Test for Fats and Oils |
Emulsion test. Place sample in a test tube, add ethanol and shake to dissolve. Add distilled water and shake gently. A milky-white emulsion indicate presence of fats or oils. |
Test for Vitamin C |
Place sample in a test tube, add DCPIP (blue color) and shake to dissolve. Color change to colorless indicate vitamin C is present. |
*4) Describe the structure of DNA
Source: Beverlyhigh
- Made up of long chains of nucleotides, forming into two strands.
- A Nucleotide is a 5-carbon sugar molecule joined to a phosphate group (-PO3) and an organic base.
- In DNA the sugar is deoxyribose.
- The organic base is either adenine (A), thymine (T), cytosine (C) or guanine (G).
- The nucleotides are joined by their phosphate groups to form long chain, often thousands of nucleotides long. The phosphate and sugar molecules are the same all the way down the chain but the bases may be any one of the four listed.
- The DNA in a chromosome consist of two strands (chains of nucleotides) held together by chemical bonds between the bases.
- The size of the molecules ensures that A always pairs with T, and C pairs with G.
- The double strand is twisted to form a helix.
*5) Importance of Water as Solvent
- Water is a good solvent and many substances dissolves in water to move in and out of the cells.
- Dissolved substances can be easily transported around plant via the xylem and phloem
- Digested food molecules dissolves in water so they can be moved to the blood and transported to cells all over the body that needs them.
- In excretion, toxic substances such as urea and substances in excess of requirements such as salts can dissolve in water which makes them easy to remove from the body in urine.
