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Cell theory basics

Tenets of cell theory
Original (Schleiden and Schwann)
  • All living things are made up of one or more cells
  • The cell is the basic unit of structure and organization in organisms
Refined by Rudolf Virchow:
  • All cells arise from other cells (Omnis cellula e cellua)
  • Normal physiology is the function of cellular physiology
  • Disease is the result of the disrupted physiology of cells
 
Interior anatomy of human cell
  • Nucleus (NEW-klee-us): Contains genetic material (DNA) and controls cell activities
    • Chromosomes: Thread-like structures made of DNA that contain genetic information made of DNA that contain genetic information
  • Cytoplasm (SAI-toh-plaz-uhm): Gel-like substance that fills the cell and holds organelles in place
  • Mitochondria (mai-toh-KON-dree-uh): Power plants of the cell that produce energy (ATP)
  • Endoplasmic Reticulum (en-doh-PLAZ-mik reh-TIK-yoo-lum): Rough ER (with ribosomes stuck to it) transports proteins, smooth ER transports lipids
  • Golgi Apparatus (GOHL-jee uh-puh-RAT-uhs) / Golgi Body: Packages and distributes cellular products
  • Lysosomes (LAI-soh-sohms): Contain digestive enzymes to break down waste materials
  • Ribosomes (RAI-boh-sohms): Synthesize proteins using genetic instructions
  • Cell Membrane (sel MEM-brayn): Controls what enters and exits the cell
  • Vacuoles (VAK-yoo-ohls): Store water, nutrients, and waste products
  • Peroxisome (puh-ROK-sih-sohm): Breaks down fatty acids and toxic substances
 
How does cell create protein
  1. Transcription occurs in the nucleus where DNA is used to create messenger RNA (mRNA)
  1. mRNA travels to ribosomes, which read the genetic code and assemble amino acids into proteins
  1. Proteins enter the Endoplasmic Reticulum (ER) for folding and modification
  1. The Golgi Apparatus receives proteins from the ER, packages them, and sends them to their final destination, which is either within the cell (for internal use) or outside the cell (for secretion to other parts of the body)
 
Mitochondria produce energy through cellular respiration:
  • Aerobic respiration occurs when oxygen is present and produces the most ATP (energy):
      • Glycolysis
      • Location: Cytoplasm
      • the breakdown of 1 molecule of glucose (a six-carbon sugar) into 2 molecules of pyruvate (a three-carbon compound).
      • Energy Production: produces a net gain of 2 ATP molecules and 2 NADH molecules (an electron carrier).
      • does not require oxygen and can occur in both aerobic (with oxygen) and anaerobic (without oxygen) conditions.
      Krebs Cycle (Citric Acid Cycle)
      • Location: Mitochondria
      • The pyruvate molecules are transported into the mitochondria, where they are converted into acetyl-CoA. Acetyl-CoA enters the Krebs cycle, a series of chemical reactions that further break down the molecules, releasing carbon dioxide as a waste product.
      • Energy Production: produces 2 ATP molecules per glucose molecule, as well as electron carriers NADH and FADH2.
      • Oxygen Requirement: yes.
      Electron Transport Chain (ETC)
      • Location: Inner mitochondrial membrane
      • The electron carriers NADH and FADH2 produced in glycolysis and the Krebs cycle donate electrons to the electron transport chain, a series of protein complexes that transfer electrons from one complex to another, leading to the production of a large amount of ATP.
      • Energy Production: The ETC produces the majority of ATP in cellular respiration, generating approximately 28-34 ATP molecules per glucose molecule.
      • Oxygen Requirement: requires oxygen as the final electron acceptor, forming water as a byproduct. This makes the ETC an aerobic process.
    • Produces 36-38 ATP molecules per glucose molecule
  • Anaerobic respiration (fermentation) occurs without oxygen:
    • Only uses glycolysis to break down glucose
    • Produces 2 ATP molecules per glucose molecule
    • Results in lactic acid buildup in muscles during intense exercise
aerobic and anaerobic exercises
  • Aerobic exercises (like jogging, swimming, cycling):
    • Sustained, moderate-intensity activities that use oxygen for energy production
    • Cells primarily use aerobic respiration, producing more ATP efficiently
  • Anaerobic exercises (like sprinting, weightlifting):
    • Short-duration, high-intensity activities that exceed oxygen supply
    • Cells switch to anaerobic respiration, leading to lactic acid buildup
    • Less efficient energy production but allows for quick bursts of power
 
Cell homeostasis
the maintenance of stable internal conditions within cells despite changes in the external environment, including
  • regulating pH levels
  • temperature
  • water content
  • and concentration of various substances
Cells achieve homeostasis through
  • active transport
  • osmosis
  • and feedback loops that help maintain optimal conditions for cellular functions
 
How do cells reproduce?
Cells reproduce through two main processes:
  • Mitosis (for body/somatic cells):
    • Divides one cell into two identical daughter cells
    • Important for growth, repair, and replacement of worn-out cells
      • Walther Flemming’s discovery on cell division
      In 1878, Walther Flemming made groundbreaking observations of chromosomes during cell division, becoming the first person to document the distribution of chromosomes during mitosis. He meticulously detailed the process using advanced microscopy techniques and biological staining methods, allowing him to see the thread-like structures of chromosomes. His work laid the foundation for our modern understanding of mitosis and chromosome behavior.
  • Meiosis (for reproductive cells):
    • Creates gametes (GAM-eets) (sperm or eggs) with half the chromosomes
    • Essential for sexual reproduction and genetic diversity
 
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