Eukaryote Cell

  • Eukaryote Cell Structure

    • Eukaryotic cells are characterized by the presence of a nucleus and membrane-bound organelles.

    • Size Comparison:

    • Eukaryotic Cells: Approximately 10 - 100 μm

    • Prokaryotic Cells: Approximately 0.2 - 10 μm

  • Differences between Prokaryotic and Eukaryotic Cells

    • Nucleus:

    • Prokaryotic: DNA in nucleoid, no nuclear membrane.

    • Eukaryotic: DNA contained within a nucleus with double membrane.

    • Organelles:

    • Prokaryotic: No membrane-bound organelles.

    • Eukaryotic: Contains organelles such as mitochondria and Golgi apparatus.

    • DNA Structure:

    • Prokaryotic: Circular and naked DNA.

    • Eukaryotic: Linear DNA associated with histone proteins.

    • Ribosomes:

    • Prokaryotic: Smaller (70s) ribosomes.

    • Eukaryotic: Larger (80s) ribosomes.

    • Cell Wall Composition:

    • Prokaryotic: Cell wall with peptidoglycan.

    • Eukaryotic: Plant cells have cellulose walls; fungal cells have chitin walls.

    • Division:

    • Prokaryotic: Division by binary fission.

    • Eukaryotic: Division by binary fission, mitosis, or meiosis.

  • Common Eukaryotic Cell Structures

    • Nucleus, Rough ER, Smooth ER, Golgi Apparatus, Lysosome, Mitochondrion, Free Ribosomes, Chloroplasts, Vacuole, Vesicles, Centrioles, Cytoskeleton, Cilia, Flagella, Cell Wall, Cell Membrane, Microvilli.

  • Detailed Look at Specific Organelles

    • Nucleus:

    • Contains DNA, stores information for protein synthesis through transcription and translation.

    • Contains nucleolus where ribosome subunits are made.

    • Double membrane with pores separates gene transcription from translation.

    • Ribosomes:

    • Catalyze polypeptide synthesis (translation).

    • Composed of two subunits made of proteins and ribosomal RNA (rRNA).

    • Free ribosomes: Synthesize polypeptides for use within the cell.

    • Bound ribosomes: Attached to rough ER, produce secretory or membrane proteins.

    • Endoplasmic Reticulum (ER):

    • Rough ER (RER):

      • Series of interconnected membranes with bound ribosomes involved in polypeptide synthesis.

      • Continuous with nuclear envelope.

    • Smooth ER (SER):

      • Lacks ribosomes; involved in lipid synthesis, notably phospholipids and cholesterol.

    • Golgi Apparatus:

    • Modifies, sorts, and packages proteins into vesicles for transport or secretion.

    • Lysosomes:

    • Contains enzymes to digest large molecules and recycle cellular components.

    • Functions in immune defense by digesting pathogens.

    • Mitochondria:

    • Powerhouse of the cell, site of ATP production via aerobic respiration.

    • Modified through endosymbiosis.

    • Chloroplasts:

    • Site of photosynthesis converting light energy, water, and carbon dioxide into glucose.

    • Contains chlorophyll pigments; also evolved through endosymbiosis.

    • Central Vacuoles:

    • Large organelles in plant cells that help maintain turgor pressure and store materials.

    • Cytoskeleton:

    • A network of fibers providing structure and enabling movement and division of cells.

    • Composed of microtubules, actin filaments, and intermediate filaments.

    • Centrioles:

    • Organize microtubules during cell division; absent in most fungi and vascular plants.

    • Cilia and Flagella:

    • Extensions aiding cell movement formed from centrioles; cilia are short and numerous, while flagella are longer and fewer.

  • Differences between Animal, Fungi, and Plant Cells

    • Plastids:

    • Plant cells have plastids (chloroplasts) for photosynthesis; absent in animal and fungi cells.

    • Cell Wall:

    • Present in plant cells (cellulose) and fungi cells (chitin), absent in animal cells.

    • Vacuoles:

    • Animal cells: Small, temporary.

    • Fungi cells: Large, permanent.

    • Plant cells: Central vacuole for turgor pressure.

    • Centrioles:

    • Present in animal cells, absent in most fungi and flowering plants.

    • Cilia and Flagella:

    • Present in many animal cells, absent in most fungi; differ in plant male gametes.

  • Eukaryotic Domain (Eukaryota)

    • Includes all organisms with eukaryotic cells, such as animals, plants, fungi, and many unicellular organisms.

Microscopy skills are essential for observing cell structures and functions across various types of specimens. Key techniques and concepts include the following:

  1. Types of Microscopes

    • Light Microscope: Uses visible light to magnify images of specimens.

    • Electron Microscope: Uses electrons for higher magnification and resolution; suitable for observing very small structures.

  2. Microscope Magnification

    • Magnification refers to the enlargement of the specimen image, typically expressed as a ratio (e.g., 100x indicates the specimen appears 100 times larger).

    • Total magnification is calculated by multiplying the eyepiece lens magnification by the objective lens magnification (e.g., 10x eyepiece and 40x objective = 400x total magnification).

  3. Resolution and Contrast

    • Resolution: The ability to distinguish two close objects as separate; it determines the clarity of the image.

    • Contrast: Increases the visibility of structures; can be enhanced using stains or special techniques.

  4. Sample Preparation Techniques

    • Fixation: Preserving cellular structures by using chemicals.

    • Staining: Applying dyes to enhance contrast; specific stains can highlight certain organelles or structures.

    • Mounting: Creating a thin layer for observation; involves placing a cover slip on the sample.

  5. Focusing Techniques

    • Start with the lowest magnification to locate the specimen, then gradually switch to higher magnifications for detailed observation.

    • Use fine and coarse focus knobs to achieve a clear image.

By mastering these microscopy skills and understanding magnification principles, one can effectively observe and analyze cellular structures in both eukaryotic and prokaryotic cells, enhancing overall biological studies.