Chapter 8: Cell Biology and Biotechnology

Class 10 – Science Part 2 | Exploring the microscopic world of cells and harnessing biological processes for human welfare.

Cell Structure
Organelles
Cell Division
Biotechnology
Genetic Engineering
DNA Technology
Subject: Science Part 2
Grade Level: Class 10
Chapter: 8
Topic: Biology & Biotechnology

1. Introduction

Cell biology deals with the structure and functions of cells, which are the basic units of life. Biotechnology uses living cells and biological processes to develop useful products for human welfare. Both subjects play an important role in medicine, agriculture, and industry.

Basic Cell Structure

[Diagram showing typical animal and plant cell structures]

Key components: Cell membrane, nucleus, cytoplasm, organelles

2. Discovery of Cell

Historical Milestones in Cell Biology:

  • 1665 - Robert Hooke discovered cells while observing cork under a microscope (coined the term "cell")
  • 1674 - Anton van Leeuwenhoek observed living cells (bacteria, protozoa) using improved microscopes
  • 1838 - Matthias Schleiden proposed that all plants are made of cells
  • 1839 - Theodor Schwann proposed that all animals are made of cells
  • 1855 - Rudolf Virchow stated "Omnis cellula e cellula" (All cells come from pre-existing cells)
  • Cell Theory - All living organisms are composed of cells; cells are the basic unit of life; all cells arise from pre-existing cells

3. Cell Structure

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Prokaryotic Cells

Simple cells without true nucleus

  • No membrane-bound nucleus
  • No membrane-bound organelles
  • Genetic material in nucleoid region
  • Smaller in size (1-10 μm)
  • Examples: Bacteria, Archaea
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Eukaryotic Cells

Complex cells with true nucleus

  • Membrane-bound nucleus
  • Membrane-bound organelles
  • Genetic material in chromosomes
  • Larger in size (10-100 μm)
  • Examples: Plants, Animals, Fungi, Protists
Feature Prokaryotic Cells Eukaryotic Cells
Nucleus Absent (nucleoid region) Present (membrane-bound)
Organelles No membrane-bound organelles Membrane-bound organelles present
Size Small (1-10 μm) Large (10-100 μm)
DNA Circular, naked Linear, associated with proteins
Cell Division Binary fission Mitosis/Meiosis
Examples Bacteria, Cyanobacteria Plants, Animals, Fungi

4. Cell Organelles and Their Functions

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4.1 Cell Wall

Structure and Function:

  • Present in: Plant cells, fungi, bacteria (not in animal cells)
  • Composition: Cellulose in plants, chitin in fungi, peptidoglycan in bacteria
  • Functions:
    • Provides shape, rigidity, and structural support
    • Protects against mechanical stress and pathogens
    • Prevents over-expansion from water uptake
    • Allows passage of water and dissolved substances
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4.2 Cell Membrane (Plasma Membrane)

Structure and Function:

  • Present in: All living cells
  • Structure: Phospholipid bilayer with embedded proteins (fluid mosaic model)
  • Functions:
    • Controls movement of substances in and out of the cell (selectively permeable)
    • Maintains internal balance (homeostasis)
    • Provides structural support and shape
    • Site for cell recognition and communication
    • Protects cell from external environment
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4.3 Nucleus

Structure and Function:

  • Present in: All eukaryotic cells
  • Structure: Double membrane (nuclear envelope), nucleolus, chromatin
  • Functions:
    • Controls all cell activities (control center of the cell)
    • Contains genetic material (DNA)
    • Site of DNA replication and transcription
    • Produces ribosomes in nucleolus
    • Regulates gene expression
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4.4 Mitochondria

Structure and Function:

  • Present in: All eukaryotic cells
  • Structure: Double membrane, inner membrane folded into cristae, matrix
  • Functions:
    • Known as the "powerhouse of the cell"
    • Produces energy (ATP) through cellular respiration
    • Site of Krebs cycle and electron transport chain
    • Contains its own DNA (endosymbiotic theory)
    • Regulates cellular metabolism
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4.5 Ribosomes

Structure and Function:

  • Present in: All living cells (prokaryotic and eukaryotic)
  • Structure: Composed of rRNA and proteins, no membrane
  • Functions:
    • Help in protein synthesis (translation)
    • Site where amino acids are assembled into proteins
    • Can be free in cytoplasm or attached to rough ER
    • Read mRNA and translate genetic code into proteins
Organelle Structure Main Function Found in
Endoplasmic Reticulum (ER) Network of membranous tubes Transport of materials, protein synthesis (Rough ER), lipid synthesis (Smooth ER) Eukaryotic cells
Golgi Apparatus Stack of flattened sacs (cisternae) Modifies, packages, and transports proteins; forms lysosomes Eukaryotic cells
Lysosomes Membrane-bound vesicles containing digestive enzymes Digest waste materials, old organelles; known as "suicide bags" Animal cells (rare in plant cells)
Vacuole Membrane-bound sac Stores food, water, waste; large central vacuole in plant cells provides turgor pressure All eukaryotic cells (larger in plants)
Chloroplast Double membrane with thylakoids Site of photosynthesis; contains chlorophyll Plant cells, some algae
Cytoplasm Jelly-like substance (cytosol + organelles) Site of many metabolic activities; supports organelles All cells

5. Cell Division

5.1 Mitosis

Characteristics and Importance:

  • Occurs in: Body cells (somatic cells)
  • Purpose: Growth, repair, asexual reproduction
  • Chromosome number: Remains same (diploid → diploid)
  • Stages: Prophase, Metaphase, Anaphase, Telophase (PMAT)
  • Result: Two identical daughter cells
  • Duration: Relatively short
  • Examples: Skin cell division, plant root growth

5.2 Meiosis

Characteristics and Importance:

  • Occurs in: Reproductive cells (germ cells)
  • Purpose: Formation of gametes, sexual reproduction
  • Chromosome number: Reduced by half (diploid → haploid)
  • Stages: Two divisions: Meiosis I and Meiosis II
  • Result: Four genetically different daughter cells
  • Duration: Longer than mitosis
  • Importance: Genetic variation, evolution
Aspect Mitosis Meiosis
Type of cells Somatic/body cells Germ/reproductive cells
Purpose Growth, repair, asexual reproduction Gamete formation, sexual reproduction
Number of divisions One Two (Meiosis I & II)
Daughter cells Two identical diploid cells Four genetically different haploid cells
Chromosome number Same as parent cell (2n→2n) Half of parent cell (2n→n)
Genetic variation No (clones) Yes (crossing over, independent assortment)
Examples Skin cell renewal, plant growth Sperm/egg production, spore formation

6. Introduction to Biotechnology

Biotechnology is the use of living organisms or their parts to produce useful products for human welfare. It combines biology with technology to solve problems and create new products.

Historical Development:

  • Ancient biotechnology: Fermentation for bread, wine, cheese (6000 BC)
  • 19th century: Pasteur's work on fermentation, Koch's germ theory
  • 20th century: Discovery of DNA structure (Watson & Crick, 1953)
  • 1973: First recombinant DNA technology (Cohen & Boyer)
  • 1980s: Development of PCR technique, genetic engineering
  • 1990s: Human Genome Project, cloning (Dolly the sheep, 1996)
  • 21st century: CRISPR gene editing, synthetic biology

7. Applications of Biotechnology

7.1 Medical Field

  • Production of vaccines - Hepatitis B, HPV vaccines using recombinant DNA technology
  • Insulin production - Human insulin produced by genetically modified bacteria
  • Gene therapy - Treating genetic disorders by correcting defective genes
  • Monoclonal antibodies - For cancer treatment, diagnostic tests
  • Stem cell therapy - Tissue regeneration, treating degenerative diseases
  • Diagnostic kits - Pregnancy tests, HIV tests, COVID-19 RT-PCR tests
  • Artificial organs - Tissue engineering for organ replacement

7.2 Agriculture

  • Development of high-yield crops - Through selective breeding and genetic modification
  • Disease-resistant plants - Bt cotton, virus-resistant papaya
  • Biofertilizers - Nitrogen-fixing bacteria (Rhizobium), mycorrhizal fungi
  • Biopesticides - Bacillus thuringiensis (Bt) toxin against pests
  • Tissue culture - Micropropagation of disease-free plants
  • Golden Rice - Vitamin A enriched rice to combat deficiency
  • Drought-resistant crops - For water-scarce regions

7.3 Industrial Uses

  • Production of enzymes - Amylase, protease, lipase for detergents, food processing
  • Fermentation processes - Alcohol, organic acids, antibiotics production
  • Biofuels - Ethanol from sugarcane/corn, biodiesel from plant oils
  • Bioremediation - Using microorganisms to clean oil spills, toxic waste
  • Textile industry - Enzymatic treatment of fabrics (biostoning of denim)
  • Food industry - Cheese making, yogurt production, brewing
  • Paper industry - Enzymatic pulping to reduce chemical use

8. Genetic Engineering

Genetic engineering involves modification of genetic material to obtain desired traits. It allows scientists to transfer genes between unrelated species, creating genetically modified organisms (GMOs).

Steps in Genetic Engineering:

  • 1. Identification and isolation of gene - Locating and extracting the desired gene from donor organism
  • 2. Insertion into vector - Placing the gene into a carrier (plasmid, virus)
  • 3. Transfer to host organism - Introducing the vector into the host cell
  • 4. Selection and multiplication - Identifying transformed cells and allowing them to multiply
  • 5. Expression of desired trait - Host organism produces the desired protein/trait

Tools of Genetic Engineering:

  • Restriction enzymes - Molecular scissors that cut DNA at specific sequences
  • DNA ligase - Molecular glue that joins DNA fragments
  • Vectors - Carriers that transfer DNA into host cells (plasmids, viruses)
  • Host organisms - Bacteria, yeast, plants, animals that receive foreign DNA
  • PCR (Polymerase Chain Reaction) - Technique to amplify specific DNA sequences

9. Importance of Cell Biology and Biotechnology

Significance and Impact:

  • Helps understand fundamental life processes at cellular and molecular level
  • Improves medical treatment through new drugs, vaccines, and therapies
  • Increases agricultural productivity with high-yield, resistant crops
  • Supports industrial development with eco-friendly bioprocesses
  • Enhances environmental protection through bioremediation
  • Advances forensic science with DNA fingerprinting
  • Promotes sustainable development with renewable resources
  • Creates new career opportunities in biotech industries
  • Addresses global challenges like food security, disease control
  • Expands scientific knowledge and technological innovation

10. Key Exam Points

Cell Biology
Biotechnology
Cell Structure
Organelles
Prokaryotic
Eukaryotic
Mitosis
Meiosis
Genetic Engineering
DNA Technology
Recombinant DNA
GMOs
Cell Division
Molecular Biology
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