CHAPTER 2 - 2.1-2.2

Overview of Cells

  • Cells: Smallest living units in the body.

  • Essential functions of cells:

    • Obtain nutrients.

    • Make necessary molecules.

    • Dispose of wastes.

    • Maintain shape.

    • Replicate.

  • Organelles: Subunits of cells responsible for specific functions.

Cell Components

  • Three main components of a cell:

    • Plasma Membrane: Outer boundary of the cell.

    • Cytoplasm: Bulk of the cell containing organelles, surrounds the nucleus.

    • Nucleus: Controls cellular activities and transmits genetic information.

Internal Structures of the Cell

  • Ribosomes: Required for protein synthesis, located throughout cell.

  • Rough Endoplasmic Reticulum (Rough ER): Surrounds nucleus, has embedded ribosomes for protein synthesis.

  • Golgi Apparatus: Packaging and shipping division, shaped like pancakes next to rough ER.

  • Peroxisomes: Round structures acting as toxic waste removal.

  • Cytoskeletal Elements: Include microtubules and intermediate filaments.

  • Centrosome Matrix & Centrioles: Surround centrioles, assist in forming cilia, flagella, and mitotic spindle.

  • Lysosomes: Contain digestive enzymes, act as demolition crew.

  • Mitochondria: Power plants of the cell, produce ATP.

  • Smooth Endoplasmic Reticulum (Smooth ER): Lacks ribosomes, involved in lipid synthesis.

  • Nucleolus: Site of ribosome subunit assembly within nucleus.

Plasma Membrane

  • Definition: Defines the boundary of the cell, separates intracellular from extracellular fluid.

  • Structure: Made of a phospholipid bilayer, contains:

    • Phospholipids

    • Cholesterol

    • Integral and peripheral proteins

    • Glycocalyx (sugar coat from carbohydrates)

  • Fluid Mosaic Model: Describes the plasma membrane as fluid and composed of diverse molecules.

Membrane Transport Mechanisms

  • Types of Transport:

    • Simple Diffusion: Movement from high to low concentration.

    • Osmosis: Diffusion of water across a membrane.

    • Facilitated Diffusion: Movement through integral membrane proteins.

    • Active Transport: Movement against concentration gradient; requires energy.

  • Endocytosis Types:

    • Phagocytosis: Engulfing large particles (cell eating).

    • Pinocytosis: Uptaking liquid droplets (cell drinking).

    • Receptor-Mediated Endocytosis: Specific intake of substances through receptor proteins.

  • Exocytosis: Release of substances from the cell via vesicle fusion with the plasma membrane.

Summary

  • Key concepts covered:

    • Basic cell structure and organelles.

    • Functionality of the plasma membrane and transport mechanisms.

  • Next steps: Continue learning about cells in upcoming lab exercises.