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Characteristics of Life

  • Metabolism: Refers to all chemical reactions occurring within organisms, encompassing energy production and utilization.

  • Growth and Development: Involves an increase in size and complexity over time.

  • Reproduction: The process of producing new individuals, ensuring species continuity.

  • Homeostasis: The ability of an organism to maintain a stable internal environment despite external changes.

  • Response to Stimuli: Describes how organisms react to changes in their surroundings.

  • Adaptation: Evolutionary changes that enhance an organism's survival across generations.

  • Organization: Refers to the structured arrangement of cells and systems within an organism.

Organisation of Life

  • Chemical Level: Fundamental components such as atoms and molecules (e.g., water, proteins).

  • Cellular Level: The basic unit of life, exemplified by cells (e.g., muscle cells).

  • Tissue Level: Groups of similar cells working together (e.g., muscle tissue).

  • Organ Level: Tissues that perform specific functions collectively (e.g., heart).

  • Organ System Level: Multiple organs functioning together (e.g., circulatory system).

  • Organism Level: A complete living being comprising various systems (e.g., humans).

Inorganic and Organic Differences

  • Inorganic Compounds: Compounds that lack carbon-hydrogen bonds (e.g., water, minerals).

  • Organic Compounds: Compounds that contain carbon-hydrogen bonds (such as carbohydrates, lipids, proteins, and nucleic acids).

Water

  • Properties:

    • Polar Molecule: Exhibits uneven charge distribution, leading to polarity.

    • Universal Solvent: Capable of dissolving a variety of substances.

    • High Heat Capacity: Helps regulate temperature in organisms.

    • Cohesion and Adhesion: Contributes to surface tension and capillary action.

  • Functions in Living Organisms:

    • Acts as a transport medium (e.g., blood plasma).

    • Serves as a medium for chemical reactions.

    • Assists in temperature regulation (e.g., through sweating).

    • Provides lubrication (e.g., in joints and eyes).

Minerals

  • Essential for various biological functions:

    • Calcium (Ca): Vital for bone and teeth strength, as well as muscle function.

    • Iron (Fe): Key component of hemoglobin, facilitating oxygen transport.

    • Phosphorus (P): Critical for DNA, RNA, and energy molecules (ATP).

    • Magnesium (Mg): Acts as an enzyme activator and is a component of chlorophyll.

    • Potassium (K) and Sodium (Na): Involved in nerve impulses and muscle contraction.

pH Scale

  • Definition: Measures the acidity or alkalinity of a substance.

  • Scale Range: 0-14

    • 0-6: Acidic (high H⁺ concentration).

    • 7: Neutral (pure water).

    • 8-14: Alkaline/Basic (low H⁺ concentration).

  • Biological Importance:

    • Enzyme activity is dependent on pH levels.

    • Blood pH (7.35-7.45) is crucial for maintaining bodily functions.

Carbohydrates

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

  • Types:

    • Monosaccharides: Single sugar molecules (e.g., glucose, fructose).

    • Disaccharides: Two monosaccharides linked together (e.g., sucrose, lactose).

    • Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).

  • Functions:

    • Serve as a primary energy source.

    • Provide structural support (e.g., cellulose in plant cell walls).

Lipids

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

  • Types:

    • Fats and Oils: Function as energy storage.

    • Phospholipids: Essential for cell membrane structure.

    • Steroids: Includes hormones (e.g., cholesterol).

  • Functions:

    • Long-term energy storage.

    • Provide insulation and protection.

    • Are integral components of cell membranes.

Proteins

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

  • Building Blocks: Made up of amino acids.

  • Types and Functions:

    • Structural Proteins: Provide support (e.g., collagen).

    • Enzymes: Catalyze and speed up chemical reactions.

    • Transport Proteins: Carry substances throughout the body (e.g., hemoglobin).

    • Hormones: Regulate various physiological processes (e.g., insulin).

    • Antibodies: Play a crucial role in the immune response.

Food Tests

  • Test for Starch:

    • Reagent: Iodine solution.

    • Positive Result: Blue-black color.

  • Test for Glucose:

    • Reagent: Benedict’s solution.

    • Positive Result: Brick-red precipitate (after heating).

  • Test for Proteins:

    • Reagent: Biuret solution.

    • Positive Result: Purple color.

  • Test for Lipids:

    • Reagent: Ethanol and water.

    • Positive Result: Milky-white emulsion.

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