Eukaryotic Microorganisms

• Unicellular eukaryotic microorganisms include protozoa such as Plasmodium (malaria-causing) and yeast like Saccharomyces cerevisiae (used in baking and brewing).
• Multicellular eukaryotic microorganisms include fungi (molds) consisting of hyphae networks and helminths (parasitic worms) like tapeworms and ascarids.

Eukaryotic Microorganisms with Cell Walls

• Fungi have cell walls made of chitin, like Aspergillus.
• Algae have cell walls made of cellulose, such as Chlorella, but are not human pathogens.
• Some protists, like diatoms, have cell walls made of silica and are not human pathogens.

Eukaryotic vs. Bacterial Cytoplasmic Membranes - Similarities

• Both eukaryotic and bacterial membranes have a phospholipid bilayer.
• Both membrane types contain proteins for transport and signaling.

Eukaryotic vs. Bacterial Cytoplasmic Membranes - Differences

• Eukaryotic membranes contain sterols (e.g., cholesterol) for stability.
• Bacterial membranes lack sterols but have other ring-composed lipids as stabilizers.
• Eukaryotic membranes contain lipid rafts for signaling.
• Bacterial cell walls have core structures of peptidoglycan (PDG) in Gram-positive and Gram-negative bacteria.

Exceptions to Bacterial Cell Walls

• Mycoplasma lack a peptidoglycan layer and cell wall, incorporating host-acquired sterols into their membranes for stability.
• Mycobacteria have a peptidoglycan layer uniquely embedded in a waxy, lipid-rich acid-fast cell wall with mycolic acids, such as Mycobacterium tuberculosis.

Main Structural Components of a Nucleus

• Nuclear envelope: A double membrane surrounding the nucleus with nuclear pores for material exchange.
• Nucleolus: Site where ribosomal RNA (rRNA) is synthesized and ribosomes are assembled.
• Chromatin: A combination of DNA and proteins that forms chromosomes during cell division preparation.

Function of the Mitochondrion

• Energy production: The mitochondrion is responsible for aerobic respiration, producing ATP through oxidative phosphorylation.
• Apoptosis: Mitochondria release enzymes that activate cell death pathways, playing a key role in programmed cell death.
• Calcium storage: Mitochondria help regulate cellular calcium levels.

Importance of Ribosomes

• Ribosomes are responsible for protein synthesis by translating mRNA into polypeptides.
• Eukaryotic ribosomes (80S, with 60S and 40S subunits) are larger than bacterial ribosomes (70S, with 50S and 30S subunits).

Three General Features of Fungal Anatomy

• Hyphae: Thread-like structures forming the body of multicellular fungi (molds).
• Mycelium: The network of hyphae that makes up the fungal body.
• Spores: Reproductive cells that develop into new organisms.

Heterotroph, Saprobe, and Parasite

• Heterotroph: Organisms rely on external organic carbon sources for energy (e.g., fungi, protozoa).
• Saprobe: Organisms decompose dead organic material (e.g., molds).
• Parasite: Organisms live on/in a host, obtaining nutrients at the host's expense (e.g., Giardia, Plasmodium).

Fungal Spore Formation

• Sexual reproduction: Spores form after the fusion of two genetically distinct cells.
• Asexual reproduction: Spores form via mitosis (e.g., conidia in molds).

Detrimental and Beneficial Activities of Fungi

• Infections: Fungi causes infections like athlete’s foot (Tinea) and candidiasis (Candida albicans).
• Toxin production: Molds produce mycotoxins (e.g., aflatoxins) that contaminate crops and cause health issues.
• Antibiotics: Penicillin is derived from the mold Penicillium.
• Food production: Yeasts like Saccharomyces cerevisiae are used in baking and brewing.
• Cyst Stage in Protozoa: A cyst is a dormant, protective stage in protozoa that helps them survive harsh conditions and facilitates transmission between hosts.

Examples of Protozoan Diseases

• Amoebas (e.g., Entamoeba histolytica) causes amoebic dysentery.
• Flagellates (e.g., Giardia lamblia) causes giardiasis.
• Ciliates (e.g., Balantidium coli) causes balantidiasis.
• Sporozoans (e.g., Plasmodium species) cause malaria.

Two Major Groups of Helminths

• Flatworms include cestodes (tapeworms-segmented body) and trematodes (flukes-unsegmented body).
• Roundworms (Nematodes) include hookworms, pinworms, and ascarids.

Genome vs. Gene

• Genome: The complete set of genetic material (DNA) in an organism.
• Gene: A segment of DNA that codes for a specific protein or RNA molecule.

Genotype vs. Phenotype

• Genotype: The genetic makeup of an organism, including all its alleles.
• Phenotype: The physical expression of the genotype, such as traits like eye color.

Bacterial DNA Replication

• Initiation: Occurs at the origin of replication (Ori C).
• Elongation: DNA polymerase is used
• Termination: Occurs when replication reaches the end of the DNA copying.

The Central Dogma of Biology

• The central dogma describes the flow of genetic information: DNA → RNA (Transcription) and RNA → Protein (Translation).

Transcription Steps

• Initiation: RNA polymerase binds to the promoter region of DNA.
• Elongation: RNA polymerase synthesizes mRNA using one strand of DNA as a template.
• Termination: RNA polymerase reaches a stop signal, with mRNA released.

RNA Types Involved in Translation

• mRNA (messenger RNA): Carries genetic information from DNA to ribosomes.
• tRNA (transfer RNA): Transports amino acids to the ribosome during protein synthesis.
• rRNA (ribosomal RNA): Forms the ribosomes' core and catalyzes protein synthesis.

Antibiotics Targeting Transcription and Translation

• Rifampin: Inhibits RNA polymerase in bacteria, preventing transcription.
• Tetracycline: Binds to bacterial ribosomes, inhibiting translation.

Horizontal Gene Transfer in Bacteria

• Transformation: Uptake of naked DNA from the environment.
• Transduction: Transfer of DNA via bacteriophages (viruses that infect bacteria).
• Conjugation: Direct transfer of DNA between bacteria via a sex pilus.

Additional Key Terms

• Endosymbiosis (endosymbiont theory): The theory that mitochondria and chloroplasts originated from a eukaryotic cell engulfing a prokaryotic cell.
• Organelles: Specialized structures within eukaryotic cells (e.g., mitochondria, Golgi apparatus).
• Helminths: Parasitic worms.
• Cilia and Flagella: Structures used for movement in eukaryotic cells.
• Glycocalyx: It is a carbohydrate-rich layer surrounding some eukaryotic cells, particularly in epithelial tissues playing a key role in cell-cell recognition, adhesion, protection, and signaling, and in some cells, such as those lining the intestines or blood vessels, it helps regulate interactions with the extracellular environment.
• Extracellular Matrix (ECM): A complex network of proteins (e.g., collagen, elastin, fibronectin) and polysaccharides secreted by eukaryotic cells which provides structural support.
• Sterols: Lipids found in eukaryotic membranes that provide rigidity.
• Phagosome: A vesicle formed when a cell engulfs material for digestion.

Hyphae

• Thread-like, tubular structures that make up the body (mycelium) of fungi.
• They are essential for growth, nutrient absorption, and reproduction, and are classified based on their structure and function.
• Septate Hyphae – Have cross-walls (septa) that divide the hyphae into individual cells, though they often have pores for cytoplasmic flow.
• Mycoses: Fungal infections that affect humans and animals, that range from superficial to systemic, depending on the type of fungus and the immune status of the host.