Lecture Notes: Chapter 3 - The Cell

Introduction

• Video lecture by Dr. Hinky.
• Chapter 3 focuses on the cell, particularly prokaryotic cells.
• Future video to cover eukaryotic cells and microbes in Chapter 5.

Early Cell Theory and History

• Spontaneous Generation: Early belief that life could arise from non-living matter.
  • Examples: Frogs appearing in water, maggots on meat.
• Francesco Redi: Disproved spontaneous generation with meat jar experiment.
• Louis Pasteur: Disproved spontaneous generation conclusively.
  • Swan neck flask experiment demonstrated biogenesis (life arises from existing life).

Development of Cell Theory

• Robert Hook: Coined the term "cell" in the 1600s after observing cork.
• Matthias Schleiden & Theodor Schwann: Developed early cell theory; plants and animals are made of cells.
• Modern Cell Theory: All cells arise from other cells; cells are the fundamental units of life.

Endosymbiotic Theory

• Proposed by Lynn Margulis in the 1960s.
• Eukaryotic cells may have evolved from prokaryotic cells through symbiosis.
  • Mitochondria and Chloroplasts: Resemble bacteria, have their own DNA.
  • Theory widely accepted after further evidence.

Germ Theory of Disease

• Ignaz Semmelweis: Advocated hand washing to prevent childbed fever.
• John Snow: Mapped cholera outbreaks, linked to contaminated water sources; father of epidemiology.
• Louis Pasteur & Robert Koch: Established microbes responsible for disease.
  • Koch's postulates: Four steps to link microbe to disease.
• Joseph Lister: Developed aseptic techniques in surgery.

Classification of Cells

• Domains: Bacteria, Archaea, Eukaryotes (Protista, Fungi, Plants, Animals).
• Prokaryotes: Simple, single-celled, no membrane-bound organelles.
  • Bacteria: Cell wall with peptidoglycan.
• Eukaryotes: Complex, with nucleus and organelles.

Prokaryotic Cell Structures

• Cell Membrane: All cells have a plasma membrane.
• Cell Wall: Provides shape, made of peptidoglycan in bacteria.
• Cytoplasm and Ribosomes: Present in all cells, site of protein synthesis.
• Nucleoid Region: Area where DNA is concentrated.

Additional Structures in Prokaryotes

• Flagella: Used for movement.
• Pili and Fimbriae: Used for attachment and genetic exchange.
• Glycocalyx: Capsule or slime layer, aids in evasion of immune system and biofilm formation.

Types of Bacterial Cell Wall

• Gram-Positive: Thick peptidoglycan layer.
• Gram-Negative: Thin peptidoglycan layer, outer membrane with lipopolysaccharides.

Endospores

• Endospores: Dormant, resistant structures formed under stress.
  • Important for survival of bacteria in harsh conditions.

Summary

• Continued exploration and understanding of cell structures and theories.
• Video to follow on eukaryotic cells and microbial eukaryotes.