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1. Biomolecules and Cell Biology

Biology - Class 11

MCQ questions

1. Biomolecules and Cell Biology (15 Hours)

1.1 Biomolecules:

  • Introduction: Biomolecules are the building blocks of life, essential for various biological processes.
  • Functions of Biomolecules:
    • Carbohydrates: Serve as a primary energy source, structural components (e.g., cellulose in plants), and storage forms (e.g., glycogen in animals).
    • Proteins: Function as enzymes, hormones, structural components (e.g., muscle proteins), transporters (e.g., hemoglobin), and antibodies in the immune system.
    • Lipids: Act as energy reserves, provide insulation and protection, form cellular membranes, and play a role in signaling molecules (e.g., steroids).
    • Nucleic Acids: DNA and RNA are involved in the storage and transmission of genetic information and protein synthesis.
    • Minerals: Essential for various biological functions (e.g., calcium for bones, iron in hemoglobin, magnesium for enzyme activity).
    • Enzymes: Biological catalysts that speed up chemical reactions in the body without being consumed in the process.
    • Water: A universal solvent, water facilitates biochemical reactions, maintains temperature, and transports nutrients and waste in cells.

1.2 Cell Biology:

  • Introduction of Cells:
    • Prokaryotic Cells: Simpler cells lacking a membrane-bound nucleus and organelles (e.g., bacteria).
    • Eukaryotic Cells: Complex cells with a true nucleus and membrane-bound organelles (e.g., plant and animal cells).
  • Structure and Functions of Eukaryotic Cell Organelles:
    • Cell Wall: Provides structural support and protection (found in plant cells, fungi, and some prokaryotes).
    • Cell Membrane: Regulates the entry and exit of substances, maintaining homeostasis (found in all cells).
    • Mitochondria: The powerhouse of the cell, responsible for producing energy (ATP) through cellular respiration.
    • Plastids: Found in plant cells; includes chloroplasts for photosynthesis.
    • Endoplasmic Reticulum (ER):
      • Rough ER: Involved in protein synthesis and modification (with ribosomes attached).
      • Smooth ER: Involved in lipid synthesis and detoxification.
    • Golgi Bodies: Modify, package, and transport proteins and lipids.
    • Lysosomes: Contain enzymes for digestion and breaking down waste materials and cellular debris.
    • Ribosomes: Synthesize proteins by translating mRNA.
    • Nucleus: Contains the genetic material (DNA) and controls cellular activities.
    • Chromosomes: Structures composed of DNA that carry genetic information.
    • Cilia and Flagella: Hair-like structures that aid in cell movement and locomotion.
    • Cell Inclusions: Non-living components within the cytoplasm, such as pigments, stored nutrients, and crystals.

1.3 Cell Division:

  • Cell Cycle: The life cycle of a cell, consisting of growth (interphase) and division (mitotic phase).
  • Types of Cell Division:
    • Amitosis: A simple form of cell division without the typical mitotic process, often observed in unicellular organisms.
    • Mitosis: The process of cell division that results in two genetically identical daughter cells, crucial for growth, repair, and asexual reproduction.
    • Meiosis: A type of cell division that reduces the chromosome number by half, producing four genetically unique gametes, essential for sexual reproduction.
  • Significance:
    • Amitosis: Maintains unicellular organisms and tissue maintenance in some cases.
    • Mitosis: Ensures genetic continuity and tissue repair.
    • Meiosis: Promotes genetic diversity and is key to sexual reproduction.