Advanced Biotechnology Study Guide: Cell Biology and Organelles

Introduction to Biotechnology and Cell Basics

  • Etymology and Definition of Biotechnology:

    • The term "biotechnology" is derived from two scientific terms: "biology" and "technology."
    • It involves the employment of biological resources to make human lives more convenient and comfortable.

  • Definition of the Cell:

    • The cell is define as the smallest, basic unit of life responsible for all life's processes.
    • Cells are considered the "building blocks" of all living beings, similar to bricks in a building.
    • Organisational Types:
      • Unicellular: Organisms made up of a single cell.
      • Multicellular: Organisms made up of many cells.

  • Cell Variety and Complexity:

    • Cells are complex units with components performing specialized functions (cell organelles).
    • They exhibit diverse shapes and sizes depending on their location and function in the body. Examples include:
      • White blood cells
      • Red blood cells
      • Bone cells
      • Nerve cells
      • Intestinal cells
      • Ovum
      • Sperm cell

Historical Milestones in Cell Biology

  • Anton Van Leeuwenhoek (1600s):

    • A Dutch scientist who was one of the first people to use a microscope to study nature.
    • He crafted powerful single-lens instruments to produce magnified images of small objects.
    • He was the first recorded person to observe tiny organisms in a drop of water.

  • Robert Hooke (1665):

    • An English physicist who used an early light microscope to examine thin slices of plant tissues.
    • Upon observing a slice of cork, he noted thousands of tiny chambers.
    • He coined the term "cells" because these chambers reminded him of a monastery's small rooms (cells).

  • The Development of Cell Theory:

    • Matthias Schleiden (1838): A German botanist who concluded that all plants are composed of cells.
    • Theodor Schwann (1839): A German scientist who concluded that all animals are composed of cells.
    • Rudolf Virchow (1855): A German physician who studied cell reproduction and summarized his research with the statement: "Where a cell exists, there must have been a pre-existing cell."

  • The Three Pillars of Cell Theory:

    1. All living species on Earth are composed of cells.
    2. The cell is the basic unit of life.
    3. All cells arise from pre-existing cells.

Classification of Cells: Prokaryotes vs. Eukaryotes

  • Prokaryotic Cells:

    • Etymology: Derived from the Greek words "pro" (before) and "karyon" (kernel), translating to "before nuclei."
    • Characteristics: These cells are generally smaller and simpler. They possess cell membranes and cytoplasm but lack a nucleus.

  • Eukaryotic Cells:

    • Etymology: Derived from the Greek words "eu" (true) and "karyon" (kernel), translating to "true nuclei."
    • Characteristics: These cells are larger and more complex. They contain a nucleus and dozens of other specialized structures called organelles.

  • Summary Comparison Table:

    • Type of Cell: Prokaryotes are always unicellular; Eukaryotes can be unicellular or multi-cellular.
    • Cell Size: Prokaryotes range from 0.1 μm0.1\,\mu m to 0.5 μm0.5\,\mu m in diameter; Eukaryotes range from 10 μm10\,\mu m to 100 μm100\,\mu m in diameter.
    • Cell Wall: Prokaryotes usually have a chemically complex wall. In Eukaryotes, plant cells have a wall while animal cells do not.
    • Nucleus: Absent in Prokaryotes; Present in Eukaryotes.
    • DNA Arrangement: Circular in Prokaryotes; Linear in Eukaryotes.
    • Organelles:
      • Mitochondria: Absent in Prokaryotes; Present in Eukaryotes.
      • Endoplasmic Reticulum: Absent in Prokaryotes; Present in Eukaryotes.
      • Lysosomes and Centrosomes: Absent in Prokaryotes; Present in Eukaryotes.
    • Ribosomes: Smaller and spherical in Prokaryotes; Larger and linear in Eukaryotes.
    • Cell Division: Through binary fission in Prokaryotes; Through mitosis in Eukaryotes.
    • Flagella: Smaller in size for Prokaryotes; Larger in size for Eukaryotes.
    • Reproduction: Asexual in Prokaryotes; Both asexual and sexual in Eukaryotes.
    • Examples: Bacteria and Archaea (Prokaryotes); Plant and Animal cells (Eukaryotes).

Anatomy of the Plant Cell

  • General Definition: Eukaryotic cells containing a true nucleus and specialized organelles for specific functions.

  • Main Structures and Organelles:

    • Cell Wall: A rigid outer covering located outside the cell membrane that protects and shapes the cell. It allows water, oxygen, and CO2CO_2 to pass through.
    • Cell (Plasma) Membrane: A thin, semi-permeable membrane that encloses the cytoplasm.
    • Nucleus: Membrane-bound structure containing hereditary information (DNADNA).
      • Nucleolus: Structure inside the nucleus for ribosome synthesis.
      • Nuclear Envelope: A double-membrane layer with thousands of nuclear pores to regulate material movement.
    • Cytoskeleton: A network of protein filaments for shape and support.
      • Microtubules: Hollow rods of protein; vital for chromosome movement in mitosis/meiosis and cytosol movement.
      • Microfilaments: Long, thin fibers for movement and support; narrower than microtubules.
    • Cytoplasm: Gel-like substance containing water, enzymes, salts, and organelles.
    • Ribosomes: Responsible for protein assembly; found free in cytoplasm or on the rough ER.
    • Endoplasmic Reticulum (ER): Network of membranes.
      • Rough ER: Contains ribosomes; synthesizes proteins.
      • Smooth ER: No ribosomes; synthesizes lipids.
    • Golgi Complex: Manages manufacturing, storing, and shipping cellular products like proteins.
    • Lysosome: Known as "suicidal bags"; hold digestive enzymes for waste disposal and digesting worn-out organelles.
    • Vacuole: Occupies approximately 30%30\% of a mature plant cell's volume. Included is the Tonoplast (membrane surrounding the central vacuole). It sustains turgid pressure against the cell wall.
    • Chloroplast: Site of photosynthesis; contains chlorophyll (green pigment) to absorb sunlight.
    • Mitochondria: Generates energy via respiration, converting glucose and oxygen to ATPATP.
    • Peroxisomes: Single membrane-bound structures producing hydrogen peroxide (H2O2H_2O_2) as a byproduct; involved in photorespiration.
    • Plasmodesmata: Pores/channels in cell walls that allow signal communication and molecule passage between cells.

Anatomy of the Animal Cell

  • General Definition: Eukaryotic cell lacking a cell wall, featuring a membrane-bound nucleus and varied shapes (flat, oval, rod-shaped, spherical, concave, or rectangular).

  • Distinct Animal Cell Characteristics:

    • Plasma Membrane: Regulates molecule entry/exit to maintain homeostasis.
    • Nucleus: Usually found at the center; controls cell activities and metabolisms.
    • Endoplasmic Reticulum: Physically connected to the nuclear membrane.
      • Rough ER: Transports proteins/lipids into cristae to be sent to Golgi bodies or the cell membrane.
      • Smooth ER: Synthesizes cholesterol and phospholipids for new membranes.
    • Golgi Apparatus: Sorts modified proteins/lipids in the trans-Golgi network for delivery to lysosomes or exocytosis.
    • Lysosomes: Acidic environment; site for nutrient digestion, excretion, and cell renewal.
    • Centriole: Distinctly found in animal cells. Replicate themselves; made of 99 microtubule bundles; assist in organizing cell division.
    • Vacuoles: Fluid-filled organelles storing food, water, carbohydrates (sugars), and waste.
    • Peroxisome: Common micro-bodies that perform lipid metabolism and chemical detoxification (neutralizing substances like alcohol by producing H2O2H_2O_2).
    • Endosome: Membrane-bound organelles involved in the folding of the plasma membrane. They remove waste via endocytic processes like exocytosis and phagocytosis.
    • Cilia and Flagella: Locomotive projections. Flagella allow sperm to swim. Cilia help move fluids/particles (e.g., mucus in the nostrils) past immobile cells.

The Bacterial Cell

  • General Characteristics: Prokaryotes lacking membrane-bound organelles and a defined nucleus. DNA is a single closed circle located in a region called the nucleoid.

  • Classifications of Bacteria:

    • By Oxygen Requirement:
      1. Aerobic: Require oxygen to live.
      2. Anaerobic: Cannot tolerate oxygen.
      3. Facultative Anaerobes: Prefer oxygen but can survive without it.
    • By Energy Acquisition:
      1. Heterotrophs: Consume and break down complex organic compounds (includes fermentation/respiration).
      2. Autotrophs: Create their own energy via light or chemical reactions.

  • Bacterial Structures:

    • Capsule: Third protective layer made of polysaccharides; prevents desiccation and protects against phagocytosis.
    • Cell Wall: Rigid wall made of peptidoglycan (protein-sugar molecule); prevents bursting from osmotic pressure and anchors appendages.
    • Cytoplasmic Membrane: Asymmetric, dynamic phospholipid/protein bilayer.
    • Flagella: Structures providing propeller-like motion to move toward nutrients/light or away from toxins.
    • Pili: Hairlike projections for attachment to surfaces (teeth, rocks, intestines).
      • Conjugation: Specialized pili used to exchange plasmid DNA between bacteria.
    • Ribosomes: Smaller than eukaryotic ribosomes and always free-standing (never bound to ER).
    • Plasmid: Small, auxiliary circular DNA that replicates independently; often carries genes for antibiotic resistance.