Anatomy Chapter 2: Cells - The Living Units

Introduction

• Presented by Dr. Mark Kahn
• Focus on cells as the fundamental living units

Historical Contributions

• Robert Hooke (1600s): First observed plant cells with a primitive microscope
• Matthias Schladen & Theodor Schwann (1830s): Asserted that all living things are composed of cells
• Rudolf Virchow: Proposed that cells arise from pre-existing cells, challenging spontaneous generation theory

Basic Characteristics of Cells

• Smallest living units in the body
• Perform essential functions (nutrient uptake, waste disposal, replication)

Cell Components

1. Plasma Membrane

   • Outer boundary, separates intracellular from extracellular fluid
   • Structure: Fluid mosaic model, lipid bilayer with integral and peripheral proteins
   • Functions: Barrier, selective permeability, receptor activity

2. Cytoplasm

   • Contains organelles and cytosol

3. Nucleus

   • Control center; contains DNA, directs cellular activities

Plasma Membrane

• Structure:
  • Lipid bilayer with hydrophilic heads and hydrophobic tails
  • Integral and peripheral proteins, glycocalyx
• Functions:
  • Receptor activity, selective permeability
• Transport Mechanisms:
  • Simple diffusion, osmosis, facilitated diffusion, active transport

Types of Membrane Transport

1. Simple Diffusion & Osmosis
   • High to low concentration, no energy required
2. Facilitated Diffusion
   • Movement via integral proteins
3. Active Transport
   • Against concentration gradient, requires ATP

Endocytosis and Exocytosis

• Endocytosis: Entry of substances
  • Phagocytosis: Cell eating
  • Pinocytosis: Cell drinking
  • Receptor-mediated endocytosis: Specific molecule uptake
• Exocytosis: Exit of substances

Organelles and Functions

• Ribosomes: Protein synthesis
• Endoplasmic Reticulum (ER):
  • Rough ER (with ribosomes): Protein synthesis
  • Smooth ER (no ribosomes): Lipid synthesis
• Golgi Apparatus: Protein sorting and shipping
• Lysosomes: Digestion of unwanted substances
• Mitochondria: ATP production, energy source
  • Contains maternal DNA
• Peroxisomes: Detoxification, breakdown of fatty acids

Cytoskeleton

• Provides structural support
• Composed of microtubules, microfilaments, and intermediate filaments

Centrosomes and Centrioles

• Involved in cell division and formation of cilia

Nucleus

• Structure: Contains nucleolus, chromatin, nuclear envelope
• DNA: Double helix, directs protein synthesis
• Chromatin and Chromosomes: DNA organization

Cell Life Cycle

• Interphase:
  • G1 Phase: Cell growth
  • S Phase: DNA replication
  • G2 Phase: Preparation for division

Mitosis (Cell Division)

1. Prophase: Chromatin condenses into chromosomes
2. Metaphase: Chromosomes align at the metaphase plate
3. Anaphase: Sister chromatids separate
4. Telophase: Nuclear membranes reform
5. Cytokinesis: Division of cytoplasm, final separation into daughter cells

Conclusion

• Understanding cellular structures and processes is crucial for comprehending body functions and treatment of diseases such as cancer.