Overview of Cell Organelles

Aug 17, 2024

Cell Organelles Overview

Definition and Types

  • Organelles: Structures within a cell that perform specific functions.
    • Membrane-bound organelles: Have their own membrane, facilitating compartmentalization for specific functions.
    • Non-membrane-bound organelles: Do not have a membrane.

Importance in Biology

  • Drawing and identifying organelles is crucial, especially under light and electron microscopes.
  • Knowledge of each organelle's structure and function is essential.

The Nucleus

Structure

  • Double Membrane Organelle:
    • Nuclear Pores: Allow material exchange.
    • Nucleolus: Site of ribosome production.
    • Chromatin: Linear DNA wrapped around histone proteins.
    • Double Helix: Too small to be seen with light or electron microscopes.

Microscopy

  • Light Microscope: Produces color images; offers limited detail.
  • Electron Microscope: Produces black and white images; high resolution (0.5 nm) revealing detailed structures.

Functions

  • Genetic Information: Contains chromatin.
  • Transcription Site: For protein synthesis.
  • Ribosome Production: Via the nucleolus.

Endoplasmic Reticulum (ER)

Types and Structure

  • Rough ER (RER): Studded with 80S ribosomes; may be connected to the nucleus; synthesizes and transports proteins.
  • Smooth ER (SER): Lacks ribosomes; involved in lipid and steroid synthesis and transport.
  • Single Membrane Organelles: Have a fluid-filled space known as cisternae.

Microscopy

  • Not visible under light microscopes due to small size and thin membranes.
  • Visible under electron microscopes.

Functions

  • Smooth ER: Synthesizes and transports lipids and steroids (e.g., triglycerides, oestrogen).
  • Rough ER: Ribosomes synthesize proteins; transports proteins via vesicles.

Golgi Apparatus

Structure

  • Single Membrane Organelle: Fluid-filled space arranged in stacks (cisternae), surrounded by vesicles.
  • Resembles pancakes or Wi-Fi signals.

Microscopy

  • Visible under electron microscopes; not visible under light microscopes.

Functions

  • Lysosome Production.
  • Protein Modification and Packaging: Combines carbohydrates with proteins to form glycoproteins (e.g., antibodies, mucus).
  • Hydrolytic Enzymes: Packaged into lysosomes.

Future Topics

  • Histone Proteins: To be covered in Chapter 5.
  • Nuclear Pores: Discussed further in Chapter 6.
  • Protein Synthesis and Transport: Detailed in future chapters.