Cells

• Cells are the basic fundamental unit of ALL living organisms
• Cells contain the machineries needed to maintain life
• Cells are the basic physiological (functions) and morphological (structures) unit of life
• Cellula


  Basic fundamental unit of ALL living organisms
• Why study cells

  • Cells make up tissues, organs, and bodies
  • Cells do all the work of life
• The work of life

  • Breathe (gas exchange)
  • Eat (take in & digest food)
  • Make energy (ATP)
  • Build molecules (Macromolecules)
  • Remove wastes
  • Control internal conditions (homeostasis)
  • Respond to external environment
  • Build more cells (GRRD)
• ATP


  • Make energy
  • Need energy for all activities
  • Need to clean up waste produced while making energy
  • Make proteins - proteins do all the work in a cell, so we need lots of them
  • Make more cells - for growth and to replace damaged or diseased cells
• Our organelles do all the jobs of cells
• Cytologists


  • Robert Brown - discovered the presence of nucleus within the cells
  • Félix Dujardin - discovered the sarcode - a life substance containing gelatinous fluid
  • Johannes Purkinje - coined the term protoplasm – living material within the cell (nucleus, cytoplasm, and other organelles)
  • Rudolf Albert von Kölliker – coined the term cytoplasm (semisolid-semiliquid substance inside the cell) from protoplasm
• Cell Theory

  • All organisms are made up of one or more cells
  • The cell is the basic unit of structure and function of all organisms
  • All cells come only from preexisting cells
• Key roles and function of a cell

  • The energy of organisms is formed in the cell (ATP)
  • Organism can be made of one or more cells (Prokaryotic and Eukaryotic)
  • DNA replication and division (Cell Division)
  • An organism carrying certain chemical composition of cells is the same with the species where it belongs (Exclusivity)
  • The activities in an organism are dependent on the activities done by the cells (Function)
• Cell


  The basic unit of life, from which larger structures such as tissue and organs are made
• Unicellular organisms


  Consist of just a single cell
• Multicellular organisms


  Consist of many cells - humans are made from an estimated 50 trillion cells
• Cell size


  • Most plant and animal cells are between 0.025 µm and 60 µm in size - around half the diameter of a human hair - and too small to see without a microscope
  • The largest cell in the human body is the female egg cell, (ovum) at around 1,000 µm in diameter
  • The smallest human cell is the sperm cell – the head is around 5 µm long
• Most plants and animals are multicellular
• The human body is made up of around 200 different types of cell, all working together
• Most cells are specialized, meaning that each type of cell has a specific structure and function
• All cells with a nucleus contain the same genes, but different cells activate different genes so they only produce the proteins they need
• All cells have certain common features and structures called organelles
• Prokaryotic cells


  • Lack a membrane-bound nucleus
  • Structurally smaller and simpler than eukaryotic cells (which have a nucleus)
• Prokaryotic cells are placed in two taxonomic domains

  • Bacteria
  • Archaea
• Archaea live in extreme habitats
• Domains are structurally similar but biochemically different
• Structure of bacteria


  • Extremely small - 1–1.5 μm wide and 2–6 μm long
  • Occur in three basic shapes: spherical coccus, rod-shaped bacillus, and spiral spirillum (if rigid) or spirochete (if flexible)
• Cell envelope of bacteria

  • Plasma membrane - lipid bilayer with imbedded and peripheral protein
  • Cell wall - maintains the shape of the cell and is strengthened by peptidoglycan
  • Glycocalyx - layer of polysaccharides on the outside of the cell wall
• Cytoplasm of bacteria


  • Semifluid solution bounded by plasma membrane, containing water, inorganic and organic molecules, and enzymes
  • Nucleoid is a region that contains the single, circular DNA molecule
  • Plasmids are small accessory (extra chromosomal) rings of DNA
• Appendages of bacteria


  • Flagella – Provide motility
  • Fimbriae – small, bristle-like fibers that sprout from the cell surface
  • Sex pili – rigid tubular structures used to pass DNA from cell to cell
• Eukaryotic cells


  • Domain Eukarya includes: Protists, Fungi, Plants, Animals
  • Cells contain: Membrane-bound nucleus that houses DNA, Specialized organelles, Plasma membrane
  • Much larger than prokaryotic cells
  • Some cells (e.g., plant cells) have a cell wall
• Eukaryotic cells are compartmentalized
• Eukaryotic cells contain small structures called organelles that perform specific functions
• Two classes of organelles in eukaryotic cells

  • Endomembrane system: Organelles that communicate with one another via membrane channels and small vesicles
  • Energy related organelles: Mitochondria & chloroplasts - Basically independent & self-sufficient
• Organelles do the work of cells and keep the cell alive
• Cells need power to fuel daily life and growth
• Organelles that help cells make energy

  • Cell membrane
  • Lysosomes
  • Vacuoles & vesicles
  • Mitochondria
• Cell membrane


  Separates cell from outside, controls what enters or leaves cell, recognizes signals from other cells
• Cytoplasm


  Jelly-like fluid that fills a cell, made up of mostly water and salt, contains molecules such as enzymes, where most metabolic reactions take place
• Vacuoles & Vesicles


  Move material around cell, provide storage for food, water, and waste
• Lysosomes


  Digest food, clean up and recycle broken organelles
• Mitochondria


  Make ATP energy from cellular respiration (sugar + O2 → ATP)