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CHAPTER 1
INTRODUCTION: THE ORIGIN OF
LIFE
CONCEPTS:
1. Importance and Pioneers of Cell Biology
2. Characteristics of Cells and Cell Theory
3. Prokaryotes and Eukaryotes
4. Viruses, Virion, Viroids, and Prions
Introduction
• Cell Biology-The study of the life of the cell is
important because cells are the basic units of life:
• Cells Tissues  Organs Organ/Systems
Discovery of Cells
• Robert Hooke, Anton Van Leeuwenhoek
Basic Properties of Cells
• Can grow and reproduce in culture
• Undergo biochemical processes and are regulated
• Contain genetic materials and respond to stimuli
Cell Theory: Schleiden, Schwann and Virchow
Two fundamental classes of Cells
•Prokaryotes-all bacteria: Arose 3.5 billion years
ago, some are photosynthetic
•Eukaryotes- protists, fungi, plants and animals:
Arose 1.5 billion years ago
Characteristics of Prokaryotes vs Eukaryotes
•Complexity: simple (P), complex (E)
•Genetic Material: Located in Nucloid region (P),
Nucleus (E).
Characteristics of Prokaryotes vs Eukaryotes
•Cytoplasm: membrane-bound organelles and
cytoskeletal proteins (E), neither in prokaryotes, 70S
ribosomes (P) and 80S (E).
Subkingdoms of Prokaryotes:
Archaebacteria: Methanogens, Halophiles,
Thermoacidophiles
Eubacteria: mycoplasma, cyanobacteria, E.coli, etc.
• Viruses: Obligatory Parasites, Virion-viral particle
outside host. Origin: from host
• Genome
• Protein capsid surrounds genome
• Eukaryotic viruses have envolupes
• Infections: Lytic or Lysogenic (provirus)
• HIV: Lysogenic, budding, host may become
malignant.
• Other infectious agents: viroid (plants), prions
(animals)
• Overview of the Emergence of cells and
infectious agents
• (Prokaryotes) Archaebacteria Eubacteria 
mitochondrion and chloroplast  Eukaryotes
Viruses and other infectious agents