The Cell

• Cell Theory:

  • A cell is the smallest unit of life
  • Cells make up living things, from unicellular to multicellular organisms
  • New cells can arise only from preexisting cells
• Two basic types of cells:

  Prokaryotic cells:

  • Structurally simpler and smaller than eukaryotic cells
  • Limited to bacteria and archaea
  • Surrounded by a cell wall
  • Does not have membrane-bound organelles
• Eukaryotic cells:

  • Found in plants, animals, and other organisms
  • Contains organelles that carry out specific functions
  • Membrane-bound organelles like ER and mitochondria are unique to eukaryotic cells
• Plasma Membrane:

  • Thin outer covering of the cell
  • Controls what comes in and out of the cell
  • Hydrophilic heads interact with extracellular fluid, while hydrophobic tails hold the membrane together
• Movement across the Plasma Membrane:

  • Simple diffusion: high to low concentration
  • Facilitated diffusion: high to low concentration with the aid of a membrane protein
  • Osmosis: movement of water molecules from high to low concentration
  • Active transport: moves substances from low to high concentration with the help of a carrier protein and energy
• Endocytosis:

  • Movement of large substances into the cell
  • Involves the plasma membrane engulfing the substance to be ingested and forming a vesicle
• Organelles:

  Nucleus:

  • Contains genetic information
  • Nuclear envelope separates it from the cytoplasm
  • Nucleolus produces rRNA
• ER (Endoplasmic Reticulum):

  • Rough ER has ribosomes and modifies proteins
  • Smooth ER modifies drugs to make them more water-soluble
• Golgi Complex:

  • Protein processing and packing center
• Lysosomes:

  • Contains digestive enzymes
  • Break down materials from outside the cell
• Mitochondria:

  • Powerhouse of the cell
• Cytoskeleton:

  • Network of interlinking protein filaments in the cytoplasm
  • Includes microfilaments, intermediate filaments, and microtubules
• Cellular Respiration:

  • Oxygen-requiring pathway with four phases: Glycolysis, Transition Reaction, Citric Acid Cycle, Electron Transport Chain
• Fermentation:

  • Breakdown of glucose without oxygen
  • Lactic Acid Fermentation happens during exercise
• Cell Size and Microscopy:

  • Cells vary in size but cannot exceed the volume that can be nourished by materials passing through the surface membrane
  • Surface-to-volume ratio decreases as cells get larger
• Microtubules:

  • Made of the protein tubulin
  • Responsible for the structure and movement of cilia and flagella
• Issues in glycolysis can cause diseases like diabetes and genetic diseases