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.