Cell Theory and Eukaryotic Cells

Cell Theory

• All organisms are made of cells
• Cells are the basic functional unit of life
• Cells come from pre-existing cells
• Cells carry genetic information (DNA)

Eukaryotic Cells

• Nucleus: Double-layered envelope containing DNA; Nucleolus synthesizes rRNA
• Mitochondria: Outer membrane, intermembrane space, inner membrane, matrix; Proton-motive force: pumps H+ from matrix to intermembrane space; Apoptosis via cytochrome C release from ETC
• Lysosomes: Autolysis via release of hydrolytic enzymes from cells
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded ribosomes and translates secreted proteins
  • Smooth ER: Lipid synthesis, detoxification, and protein transport
• Golgi apparatus: Modifies materials from the ER
• Peroxisomes: H₂O₂ production to break down VLCFAs; assists in phospholipid synthesis and the pentose phosphate pathway
• Cytoskeleton:
  • Microfilaments (actin rods): Protection, muscle contraction (with myosin), cleavage furrow
  • Microtubules (tubulin tubes): Motor protein pathway (kinesis and dynein), centrioles, cilia (cell movement), and flagella (overall cell movement); 9+2 structure found only in eukaryotes
  • Intermediate filaments (keratin, desmin, vimentin, lamins): Cell-cell adhesion, maintains cytoskeleton, cell rigidity, anchors organelles
• Types of Tissues:
  • Epithelial: Lines body cavities and forms parenchyma (squamous, cuboidal, columnar, simple, pseudostratified, stratified);
  • Connective: Supports body and forms stroma (secretes collagen/elastin to form ECM)

Prokaryotic Cells

• Structure: Cocci (spheres), bacilli (rods), spirilla (spiral); Single circular chromosome in nucleoid; Envelope (cell wall and plasma membrane)
• O₂ Requirements: Obligate aerobes (require oxygen), facultative anaerobes (use oxygen or not), microaerophiles (tolerate low oxygen), aerotolerant anaerobes (tolerate oxygen), obligate anaerobes (die in oxygen)
• Recombination: Transformation (acquire genes from environment), conjugation (transfer genetic material between bacteria), transduction (acquire genes from viruses)
• Growth Stages: Lag phase, Log phase, Stationary phase, Death phase

Viruses

• Virions (nucleocapsids):
  • DNA viruses (DNA genome, host machinery): dsDNA (double-stranded DNA), SSDNA (single-stranded DNA)
  • RNA viruses (RNA genome, own machinery): dsRNA (double-stranded), ssRNA(+) (single-stranded positive-sense), ssRNA(-) (single-stranded negative-sense)
• Retroviruses: Two copies of ssRNA, reverse transcriptase (RNA to cDNA); Life cycle (bacteriophages only)

Cell Cycle

• Interphase: G₁, S, and G₂ (pre-synthetic gap, DNA synthesis, and post-synthetic gap, respectively) preparing cells for mitosis
• Mitosis (PMAT): Processes that separate duplicated chromosomes and divide cytoplasm into daughter cells (prophase, metaphase, anaphase, and telophase)
• Checkpoints: G₁/S, G₂/M, M/A: Ensure the cell's ready for the process, repair damaged cells, and detect environmental problems

Meiosis

• Reductional division that produces four haploid offspring cells from one diploid parent cell; The process involves two rounds of division. Prophase I (Synapsis, Crossover), Metaphase I, Anaphase I (Disjunction), Telophase I, Meiosis II

Reproductive Processes

• Male Anatomy: SEVE(N) UP (Seminiferous tubules, Epididymis, Vas deferens, Ejaculatory duct, (N) Urethra, Penis); Sertoli and Leydig cells; Spermatogenesis: spermatogonia→1° spermatocyte→2° spermatocyte→spermatid→spermatozoa
• Female Anatomy: Ovaries, Fallopian tubes, Uterus, Vagina, Ovulation, Oogenesis (Oogonia-1° oocyte-2° oocyte and polar body), Fertilization, and Implantation

Early Development

• Fertilization, cleavage, blastulation, implantation (implantation of blastocyst into uterine wall)