BIOLOGY-Y10

Biology Revision Notes

Living Things

  • Living organisms are composed of four classes of biomolecules:

    • Lipids

    • Proteins

    • Carbohydrates

    • Nucleic Acids

Carbohydrates

  • Composition: Composed of Carbon (C), Hydrogen (H), and Oxygen (O).

  • Types of Carbohydrates:

    • Monosaccharides: Simplest form of carbohydrates. These are single sugars.

    • Example: Glucose - chemical formula: C6H12O6C_6H_{12}O_6

    • Disaccharides: Formed by chemically bonding two monosaccharides.

    • Examples:

      • Maltose: Composed of two glucose molecules.

      • Sucrose: Composed of glucose + fructose.

    • Polysaccharides: Composed of many monosaccharides chemically bonded together.

    • Examples:

      • Starch: Stores polysaccharides in plants, utilized and broken down in humans, stored as glycogen.

      • Cellulose: Another polysaccharide found only in plants, primarily composed of glucose, and is present in cell walls.

Reducing Sugars

  • Definition: A type of sugar that can be oxidized, thereby reducing other compounds.

    • Example: Glucose.

Benedict's Test for Reducing Sugars

  • Results:

    • Blue: No reducing sugars present.

    • Yellow: Trace amounts of reducing sugars.

    • Orange: Moderate amounts of reducing sugars.

    • Red: Large amounts of reducing sugars.

Proteins

  • Composition: Composed of Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

  • Structure: Made up of units called amino acids. There are about 20 different amino acids.

    • Examples: Glycine, Alanine, Valine, Cysteine, etc.

  • Protein Formation: Example of a small protein formation: Gly-Val-Val-Cys-Ala-Gly-Ala-Val.

  • Functions:

    • Proteins are crucial for the structure of cells: cytoplasm, nucleus, and cell membranes.

    • Enzymes: A category of proteins that act as biological catalysts, facilitating chemical reactions.

Protein Denaturation

  • Definition: The process where proteins lose their shape.

  • Causes: Can be caused by high temperatures or certain chemicals.

Biuret Test for Proteins

  • Results:

    • Positive Result: Color changes from blue to purple/violet.

    • Negative Result: Solution remains blue.

Tests for Other Biomolecules

  • Ethanol Emulsion Test for Fats:

    • Positive Result: Solution becomes cloudy.

    • Negative Result: Solution remains transparent.

  • Iodine Test for Starch:

    • Positive Result: Changes to dark blue.

    • Negative Result: Remains brown.

Fats (Lipids)

  • Composition: Composed of Carbon (C), Hydrogen (H), and Oxygen (O). Built from fatty acids and glycerol.

Enzymes

  • Definition: Biological catalysts that control all chemical reactions in organisms.

  • Factors Affecting Enzyme Activity:

    • Environmental conditions such as pH and temperature.

    • Enzymes have an optimum temperature and/or pH for maximum activity.

    • As temperature increases, the rate of enzyme activity increases until a certain point; beyond that, it decreases significantly due to denaturation.

    • Enzyme activity also increases with rising pH until reaching its optimal level, after which very high or low pH can stop enzyme activity.

Enzyme-Substrate Interaction

  • Enzymes have a complementary shape to substrates, which allows them to attach at the active site.

  • This mechanism is similar to a lock-and-key fit, resulting in the formation of enzyme-substrate complexes.

  • Ideal pH is typically around 7 for most human enzymes.

  • Changes in pH can affect the bonds holding the enzyme’s shape, altering the active site and potentially inhibiting function.