Eukaryotic Cells and Microorganisms Notes

Overview of Eukaryotes

Learning Outcomes:
- Understand the relation of bacterial, archaeal, and eukaryotic cells to their last common ancestor.
- Classify eukaryotic microorganisms as unicellular or multicellular.
- Explain the concept of endosymbiosis and its role in the evolution of eukaryotic cells.

Eukaryotic cells originated approximately 4 billion years ago.
All bacteria and eukaryotes descended from the last common ancestor (LCA):
- This ancestor was neither prokaryotic nor eukaryotic and led to the separate evolution of bacteria, archaea, and eukarya.
Organelles likely evolved from primitive cells that were engulfed by ancestral eukaryotic cells.

Eukaryotic organisms studied in microbiology:
- Protozoa: always unicellular.
- Fungi and Algae: can be unicellular or multicellular.
- Helminths: always multicellular, although they have unicellular egg or larval forms.

Common features found in all eukaryotic cells:
- Cytoplasmic membrane
- Nucleus
- Mitochondria
- Endoplasmic reticulum (ER)
- Golgi apparatus
- Vacuoles
- Cytoskeleton
- Glycocalyx
Additional structures found in some groups:
- Cell wall (in fungi and algae)
- Locomotor appendages (cilia and flagella)
- Chloroplasts

Key components of a generalized eukaryotic cell:
- Flagella: thicker (10x) and more complex than bacterial flagella; covered by a membrane extension.
- Cilia: similar to flagella but shorter and more numerous; function in feeding and filtering.
- Cell Wall: found in fungi and algae, made of chitin or cellulose, providing structural support.
- Cytoplasmic Membrane: bilayer of phospholipids; contains sterols and is selectively permeable.

The nucleus is the most prominent organelle, encapsulated by the nuclear envelope.
Contains nucleolus, where ribosomal RNA is synthesized.

Chromatin is the material constituting chromosomes, visible during mitosis.
Meiosis leads to the formation of sex cells.

Rough ER: has ribosomes; involved in protein processing.
Smooth ER: lacks ribosomes; responsible for lipid synthesis and detoxification.

Modifies and transports proteins; consists of stacked sacs that receive transitional vesicles from the ER.

Functions in energy production.
- Contains their own DNA and replicate independently of the cell.

Involved in photosynthesis; convert light energy into chemical energy, producing oxygen and organic nutrients.

Function in protein synthesis, located in the cytoplasm, on the rough ER, and within mitochondria and chloroplasts.
- Eukaryotic ribosome size is 80S (60S + 40S subunits).

Provides support and maintains cell shape; consists of actin filaments, intermediate filaments, and microtubules.

Consists of around 3-4 million species, separated into macroscopic (e.g., mushrooms) and microscopic (e.g., yeasts, molds).
- Nutritional sources are varied, including decomposing organic material and forming mutualistic relationships with plants.

Algae: photosynthetic organisms contributing significantly to ecosystems; possess chloroplasts with pigments.
Protozoa: diverse group, often found in various environments; some species are pathogenic to humans.

Describes flatworms (cestodes and trematodes) and roundworms (nematodes); their life cycles involve various hosts and routes of infection.