Lecture Notes: Cellular Organelles and Structures

Overview

• Cells contain various organelles and structures.
• These are categorized into four themes:
  1. Genetic Control: Nucleus and ribosomes.
  2. Endomembrane System: Membranes producing, polishing, packaging, and shipping cellular products.
  3. Energy Processing: Mitochondria, chloroplasts, peroxisomes.
  4. Structural Support and Communication: Structural roles, movement, communication.

Genetic Control

Nucleus

• Contains most of the DNA in eukaryotic cells.
• Structure:
  • Membrane-bound organelle with a unique double membrane called the nuclear envelope.
  • Composed of two phospholipid bilayers, making it a double membrane.
  • Includes nuclear pores for molecule transport.
  • Supported by the nuclear lamina, a protein layer that maintains its shape.
• Contents:
  • DNA organized into chromosomes.
  • Chromosomes consist of a long DNA molecule wound around histone proteins forming chromatin.
  • Nucleolus:
    • Dense region responsible for synthesis of ribosomal RNA (rRNA).

Ribosomes

• Not organelles: Composed of proteins and rRNA.
• Essential for protein synthesis.
• Types:
  • Free Ribosomes: Float in the cytosol, produce proteins for internal use.
  • Bound Ribosomes: Attached to membranes; located on the nuclear envelope and the endoplasmic reticulum.
    • Produce proteins for export or membrane insertion.
• Structure: Consist of two subunits (large and small).

Key Takeaways

• Understanding cellular structures is crucial for grasping cellular function.
• Each organelle has a specific role and is organized in a unique way to support cellular life.