Chapter 4, Part A: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Types of Cells

Prokaryotes

• Definition: Derived from Greek "pre-nucleus"; do not have a nucleus.
• Examples: Bacteria, Archaea.
• Characteristics:
  • Single circular chromosome.
  • No histones or organelles.
  • Cell walls: Bacteria (peptidoglycan), Archaea (pseudomurine).
  • Reproduction: Binary fission.

Eukaryotes

• Definition: Derived from Greek "true nucleus"; have a nucleus.
• Examples: Plants, animals, protists, fungi.
• Characteristics:
  • Paired chromosomes in nucleus.
  • Histones present.
  • Organelles present, such as mitochondria, endoplasmic reticulum, etc.
  • Cell walls in some (polysaccharides like cellulose or chitin).
  • Reproduction: Mitosis.

Cell Structures

Eukaryotic Cells

• Types: Plant and animal cells.
• Shared Structures: Nucleus, endoplasmic reticulum, mitochondria, plasma membranes.
• Unique Features:
  • Plant cells: Chloroplasts, cellulose cell wall.
  • Animal cells: Some have flagella, e.g., sperm cells.

External Structures

• Flagella: Long, whip-like for locomotion.
• Cilia: Short, numerous for moving substances.
• Microtubules: Composed of tubulin, arranged in a "9+2" array.

Cell Walls

• Prokaryotes: Made of peptidoglycan or pseudomurine.
• Eukaryotes: Carbohydrates/polysaccharides like cellulose or chitin.

Glycocalyx

• Description: Sugar coat on cell surface.
• Function: Attachment and cell recognition.

Cell Membrane

• Structure: Phospholipid bilayer with embedded proteins.
• Differentiation: Eukaryotic membranes contain cholesterol.

Cell Organelles

Nucleus

• Feature: Double membrane, stores DNA.
• DNA Packaging: Histones form chromatin.

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes for protein synthesis.
• Smooth ER: Lipid synthesis.

Golgi Complex

• Function: Modifies, sorts, and packages proteins.

Lysosomes

• Description: Vesicles containing digestive enzymes.

Vacuoles

• Function: Storage and maintaining cell shape.

Mitochondria

• Function: ATP synthesis through cellular respiration.

Chloroplasts

• Function: Photosynthesis in plants and algae.

Peroxisomes

• Function: Oxidize fatty acids, destroy hydrogen peroxide.

Centrosomes

• Role: Cell division, forming mitotic spindle.

Prokaryotic Cell Features

Size and Shape

• Size: Smaller than eukaryotic cells, 0.2-2 µm.
• Shapes:
  • Bacillus (rod-shaped)
  • Coccus (spherical)
  • Spiral (vibrio, spirillum, spirochetes)

Flagella

• Structure: Filament, hook, and basal body.

Pili and Fimbriae

• Fimbriae: Attachment.
• Pili: Motility and DNA transfer.

Cell Wall

• Description: Peptidoglycan layer provides structure.
• Types:
  • Gram-positive: Thick peptidoglycan, teichoic acids.
  • Gram-negative: Thin peptidoglycan, additional outer membrane.

Movement and Function

Flagella and Cilia

• Use: Locomotion and moving substances.
• Prokaryotic Flagella: Allows movement toward/away from stimuli.

Endocytosis in Eukaryotes

• Types:
  • Phagocytosis: "Cell eating"
  • Pinocytosis: "Cell drinking"

Cytoplasm and Cytoskeleton

• Cytoplasm: Fluid inside cells.
• Cytoskeleton: Provides shape, supports cytoplasmic streaming.

Ribosomes

• Prokaryotic: 70S, smaller.
• Eukaryotic: 80S, larger; can be membrane-bound or free.

Pathogenicity

• Cell Wall Composition: Influences treatment of infections.

This concludes the chapter section on cell types and their structures, covering both prokaryotic and eukaryotic cells, their features, and functions.