1. Structure and function of cells and tissues

BTEC Level 3 Nationals in Applied Science: Cell Structure and Function Notes

Unit 1: Structure and Functions of Cells and Tissues

B1: Cell Structure and Function

  • Cell Theory:

    • Fundamental unit of structure, function, and organization in all living organisms.

  • Differentiation:

    • Process by which cells become specialized for specific functions.

  • Tissues:

    • Collections of similar specialized cells performing specific functions.

      • Types include epithelial, skeletal muscle, and nervous tissue.

  • Organs:

    • Collections of tissues performing specific physiological functions.

  • Organ Systems:

    • Groups of organs organized into systems (e.g., cardiovascular, respiratory, muscular, nervous systems).

  • Cell Organelles:

    • Prokaryotic Cells (e.g., bacterial cells):

      • Key structures include nucleoid, plasmids, 70S ribosomes, capsule, cell wall.

    • Eukaryotic Cells (plant and animal):

      • Structures include:

        • Plasma membrane

        • Cytoplasm

        • Nucleus, nucleolus

        • Endoplasmic reticulum (smooth and rough)

        • Golgi apparatus

        • Vesicles, lysosomes

        • Mitochondria, centriole, 80S ribosomes.

      • Plant-Specific Structures:

        • Cell wall, chloroplasts, vacuole, tonoplast, amyloplasts, plasmodesmata, pits.

  • Identification:

    • Recognize cell organelles using light microscopes and electron micrographs.

  • Light Microscopy:

    • Advantages and limitations of using light microscopes explored.

    • Understand how to calculate magnification using formulas (e.g., measured size = actual size × magnification).

B2: Cell Specialization

  • Examples of Specialised Cells:

    • Palisade Mesophyll Cells:

      • Major site of photosynthesis.

      • Features include cylindrical shape, close packing for gas exchange, thin cell walls for gas diffusion, large vacuole, chloroplast positioning to maximize light absorption, and cytoskeleton movement of chloroplasts.

    • Sperm and Egg Cells:

      • Sperm Cell:

        • Contains nucleus with 23 chromosomes, acrosome for penetrating egg membrane, numerous mitochondria for energy, a tail for motility.

      • Egg Cell:

        • Contains large cytoplasm for energy store, protective outer membrane, and corona radiata.

    • Root Hair Cells:

      • Large surface area for absorption, channels and proteins for ion movement, mitochondria for active transport, thin cell wall for easy diffusion.

    • White Blood Cells:

      • Involved in immunity; includes T cells and B cells which have specific structure-function relationships.

B3: Tissue Structure and Function

  • Epithelial Tissue:

    • Squamous Epithelium:

      • Alveolar epithelium role in gas exchange; affected by conditions like COPD:

        • Chronic Bronchitis:

          • Thickening of squamous epithelium, mucus overproduction.

        • Emphysema:

          • Damage to alveoli, reduced surface area for gas exchange.

    • Columnar Epithelium:

      • Goblet and ciliated cells in lungs protect against pathogens by trapping and moving them out.

    • Endothelial Tissue:

      • Lines blood vessels; critical for regulating blood flow and pressure, especially in atherosclerosis.

Muscular Tissue

  • Skeletal Muscle Fiber Structure:

    • Muscle fibers are multinucleated, striated, with specialized structures (myofibrils, sarcomeres).

  • Muscle Fiber Types:

    • Differences between fast and slow-twitch fibers regarding contraction rates, fatigue, and suitability for activities.

Nervous Tissue

  • Neurones:

    • Differences between myelinated and non-myelinated neurons.

    • Mechanism of nerve impulse conduction (action potential) through changes in membrane permeability and saltatory conduction.

Cell Organelles and Functions

  • Nucleus:

    • Contains genetic material and organizes cell activities.

  • Mitochondria:

    • Generate ATP; central to cellular respiration.

  • Endoplasmic Reticulum (ER):

    • Smooth ER synthesizes lipids; Rough ER with ribosomes synthesizes proteins.

  • Golgi Apparatus:

    • Modifies, packages proteins, and produces lysosomes.

  • Ribosomes:

    • Synthesize proteins, can be free in cytoplasm or associated with RER.

Additional Key Points

  • Prokaryotic vs Eukaryotic Cells:

    • Prokaryotic cells: smaller, no nucleus, usually unicellular.

    • Eukaryotic: larger, with membrane-bound organelles, can be multicellular.


Study Tips

  • Focus on understanding organelle structures and functions.

  • Be able to calculate magnifications and sizes based on images.

  • Practice identifying cell types and their specializations.

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