بيولوجيا عامة - السنة الثالثة - قسم العلوم

General Biology - Year 3 - Science Section

• Subject: Biology
• Grade Level: Year 3, secondary school, science section
• Academic Year: 2022 - 2021
• Teacher: Nu'ima Kafo
• Unit 1: Microorganisms and their Applications in Biotechnology

Microorganisms and their Applications in Biotechnology

• Source of Microorganisms:

  • Two categories of scientists:
    • Organisms created spontaneously
    • Organisms originated from pre-existing living organisms.
  • Spontaneous Generation:
    • English scientist Needham (1745) supported the idea of spontaneous generation.
  • Refutation of Spontaneous Generation:
    • Louis Pasteur (1895-1822) disproved the theory. He demonstrated that microorganisms in Needham's flasks originated from contaminated air.

• Microorganism Definition: Tiny organisms invisible to the naked eye, commonly known as germs or microbes, found everywhere in nature.

• Microorganism Types:

  • Viruses
  • Bacteria
  • Fungi

Viruses

• Definition:

  • Smallest organisms, located on the boundary between living and nonliving entities. They are complex chemical entities, nonliving outside the cell, but become a living entity when infecting a cell.

  • Obligate parasites, smallest disease-causing particles, only visible under high magnification electron microscopes, requiring significant magnification (e.g., ~250,000x).

  • Size: 10 to 300 nanometers (can be observed at around 30,000x magnification).

• Structure:

  • Protein coat: Protects the genetic material from digestive enzymes, defines shape and size, and determines host cell attachment.
  • Genetic material (DNA or RNA): Used for viral replication inside host cells. Viruses use host cells' machinery.

• Functions:

  • Protein coat: Protects the nucleic acid from degradation by enzymes and determines structure/interactions with host cells.

• Viruses and Cells: Viruses are not considered cells because they lack essential cell components like cytoplasm, nucleus, cellular organelles, and a cell membrane.

• Viral Reproduction: Viruses rely on host cell ribosomes for the production of viral proteins.

• Viral Shapes:

  • Spherical (e.g., influenza virus, 0.1 µm diameter, RNA)
  • Rod-shaped (e.g., tobacco mosaic virus, 0.3 µm, RNA)
  • Complex (e.g., bacteriophages, 0.3 µm, DNA)

• Viral Reproduction Mechanisms:

  • Attachment: Virus attaches to a host cell (bacterial cell).
  • Penetration: Virus injects its DNA/RNA into the host cell.
  • Replication: The virus's nucleic acid commandeers the host cell's systems to create new viral components.

• Assembly: Newly assembled viruses are released from the host cell, often causing cell lysis (bursting).

• Viral Properties: Exhibit no biological activity outside a host cell (no feeding, breathing, excretion, growth, or reproduction). Intracellularly, viruses exploit host cell mechanisms.

Bacteria

• Definition:

  • Unicellular prokaryotic microorganisms larger than viruses, generally 0.01 mm long. Visible under a light microscope. Found in almost all terrestrial environments.

• Structure:

  • Cell wall: Rigid structure (protein, sugars, fats), maintains shape, protects cell contents, and facilitates cell division.
  • Cell membrane: Controls substance passage. Site of respiration and energy production (lacking mitochondria in their structure).
  • Capsule: Slimy coating protects from phagocytosis (white blood cells), facilitates adherence and disease.
  • Cytoplasm: Contains single circular DNA (bacterial chromosome) and plasmids (small DNA rings carrying genetic information). Also stores glycogen and fats.
  • Ribosomes: sites for protein synthesis.
  • Flagella: Some bacteria possess flagella for movement. Most are non-motile.

• Bacterial Classification by Shape: Cocci (spherical), bacilli (rod-shaped), spiral, vibrio.

• Bacterial Classification by Nutrition: Saprophytes (decomposers), parasites (obtain nutrients from living organisms), autotrophs (produce their own food).

• Bacterial Reproduction: Binary fission. Under unfavorable conditions, bacteria form dormant endospores, a resistant protective layer.

Fungi

• Definition:

  • Eukaryotic microorganisms; can be unicellular (like yeast) or multicellular (like molds, mushrooms). Some are visible to the naked eye; others require a microscope.

• Structure:

  • Some fungi are composed of spherical cells adapted for growth in liquid media (e.g., yeast).
  • Yeast cells: Single, round, or oval, encased in a complex carbohydrate cell wall (chitin). Cytoplasm with stored nutrients (glycogen), a true nucleus (with a nuclear membrane), and a large vacuole.

• Fungi Classification by Nutrition: Saprophytes (decomposers), parasites (obtain nutrients from living organisms).

• Fungi Reproduction: Through spores. Some also reproduce asexually (like yeast via budding).

• Methods of Digestion: Fungi digest food outside their cells, then absorb the digested materials. Secreted enzymes break down complex organic molecules in the environment.

Biotechnology

• Definition: The large-scale, industrial use of biological processes (especially of microorganisms) to generate products and services. (Developed in the 1970s).

• Applications: Food production, antibiotic production, single-cell protein (SCP) production, enzyme production, waste water treatment, and more.

• Importance: Economical, cost-effective, and environmentally friendly.

• Note: This is a detailed summary of Microbiology topics. Further details and examples are provided in the supplemental material.