Eukaryotic

Eukaryotic Cell Structure and Function

• Cell Membrane

  • Basic structure of the cell, responsible for regulating what enters and exits.

• Nuclear Membrane

  • Composed of two membranes with pores that allow transport and communication.

• Nucleus

  • Contains nucleoplasm where chromosomes are found.

  • Nucleolus:

  • Site for rRNA synthesis and ribosome assembly.

• Eukaryotic Organelles

  • Rough Endoplasmic Reticulum (RER) with ribosomes: Synthesizes and processes proteins.

  • Smooth Endoplasmic Reticulum (SER): Functions in lipid synthesis and detoxification.

  • Golgi Complex:

  • Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

  • Mitochondrion:

  • Powerhouse of the cell, site for ATP production.

  • Chloroplasts:

  • Present in plants and algae, conducts photosynthesis.

  • Lysosome:

  • Contains enzymes for intracellular digestion.

  • Peroxisome:

  • Contains enzymes for oxidative reactions.

Comparative Microbiology

• Prokaryotes vs. Eukaryotes

  • Prokaryotes: Simple cells without a nucleus, e.g., Bacteria and Archaea.

  • Eukaryotes: More complex cells with a nucleus, e.g., Plants, Animals, Fungi, and Protists.

  • Characteristics:

  • Eukaryotic cells have membrane-bound organelles unlike prokaryotic cells.

  • Eukaryotic ribosomes are larger (80S) compared to prokaryotic (70S).

Origin of Eukaryotic Cells

• Endosymbiosis Theory:

  • Eukaryotic cells originated via prokaryotic cells engulfing other prokaryotes that became permanent residents (e.g., mitochondria and chloroplasts).

  • Membrane infolding also contributed to organelle development (e.g., ER and nuclear envelope).

Cell Structures and Functions

• Cytoskeleton:

  • Composed of microtubules, microfilaments, and intermediate filaments involved in cell shape, support, and movement.

• Locomotor Appendages:

  • Flagella:

  • Thicker (10X) than prokaryotic flagella; composed of a 9+2 arrangement of microtubules.

  • Functions in cell motility, can push or pull cells.

  • Cilia:

  • Shorter than flagella, numerous per cell, used for movement and feeding in protozoa and animal cells.

Glycocalyx

• Composition and Function:

  • Composed of polysaccharides, serves in protection, attachment, and communication.

• Cell Wall:

  • Provides structural integrity.

  • Fungi: Thick layer made of chitin.

  • Algae: Variable chemical composition including celluloses and pectins.

Endoplasmic Reticulum (ER)

• Rough ER:

  • Studded with ribosomes, synthesizes proteins for export.

• Smooth ER:

  • Lacks ribosomes, involved in lipid synthesis and storage, detoxification.

Golgi Apparatus

• Structure and Function:

  • Stacks of flattened sacs (cisternae) modify, package, and distribute cell products.

Mitochondria

• Structure:

  • Double membrane with inner folds (cristae), contains ribosomes and circular DNA.

• Function:

  • Site of aerobic respiration, energy production (ATP).

Chloroplasts

• Photosynthesis:

  • Converts light energy to chemical energy. Contains thylakoids (site of light reactions) and stroma (site of calvin cycle).

Fungi Characteristics and Classifications

• Kingdom Fungi:

  • Majority are unicellular or colonial; significant roles in decomposition and nutrient cycling.

  • Cell walls composed mainly of chitin.

  • Divided into macroscopic (molds) and microscopic (yeasts).

• Reproduction:

  • Asexual reproduction through sporulation; sexual reproduction with two hyphal strains forming zygospores, ascospores, or basidiospores.

Fungal Pathogenicity and Human Infections

• Types of Infections:

  • Superficial (e.g., Tinea) - outer layer of skin.

  • Systemic infections (deep tissue invasion) - Coccidioidomycosis, Histoplasmosis.

• Mycoses:

  • Can be life-threatening for immunocompromised patients.

Summary of Human Pathogenic Fungi

• Detail infections and causative fungi (e.g., Candidiasis - Candida albicans).

• Disease severity is determined by the extent of tissue involvement and the patient's immune status.

Fungal Intoxications

• Types:

  • Ergot poisoning (Claviceps purpurea), Aflatoxin production by Aspergillus flavus.

  • Ethanol production from fermentation (Saccharomyces cerevisiae).

This thorough documentation captures structural characteristics, functions, comparisons between eukaryotic and prokaryotic cells, detailed organelle functions, origins of eukaryotic cells, classifications of fungi, and implications of fungal infections.