cell structure

• Cells are the building blocks of all living things
• Tissues are groups of cells that are similar in structure and function e.g. muscle cells (myocytes), liver cells, (hepatocytes)
• Plasma membrane

  • Barrier for cell contents
  • Double phospholipid layer (phospholipid bilayer)
  • Hydrophilic heads (polar, water-loving)
  • Hydrophobic tails (non-polar, water-hating)
  • Also contains proteins, cholesterol, and glycoproteins
  • SELECTIVELY PERMEABLE
• Cytoplasm

  • The material outside the nucleus and inside the plasma membrane
  • Contains cytosol (fluid) and organelles ("little organs")
• Nucleus

  • Control center of the cell
  • Contains genetic material (DNA)
  • Surrounded by a nuclear envelope that has nuclear pores
• Mitochondria

  • "Powerhouses" of the cell
  • Provides ATP for cellular energy
  • Inner and outer membrane with cristae (folds)
• Ribosomes

  • Protein builders or the protein synthesizers of the cell
  • Can be free in the cytoplasm or part of rough endoplasmic reticulum
• Endoplasmic Reticulum

  • Rough endoplasmic reticulum (has ribosomes) - Synthesizes proteins
  • Smooth endoplasmic reticulum - Role in lipid metabolism and detoxification of drugs
• Golgi apparatus

  • Modifies and packages proteins
• Lysosomes

  • Contain hydrolytic enzymes that work as the cells digestive system
• Centrioles

  • Important during cell division (mitosis & meiosis)
• Cell projections

  • Cilia - power stroke in one direction. Located in respiratory tract and uterine tubes. Many per cell.
  • Flagella – move cell in a wave-like motion. Only found in spermatozoa. One per cell.
  • Microvilli – cylindrical shaped extensions. Increase surface area. Found in digestive tract. Many per cell.
• Fluid compartments

  • Intracellular – inside the cell
  • Interstitial – between the cells
  • Intravascular – inside the blood vessels
  • Extracellular – outside the cell (interstitial + intravascular)
• Molecules that need to move around the body

  • Ions
  • Water
  • Nutrients
  • Waste products
  • Proteins
  • Macromolecules
• Osmosis

  Movement of water across a semi-permeable membrane (from high to low concentration)
• Osmotic pressure

  The pressure needed to stop osmosis across a semi-permeable membrane
• Osmolality

  The number of moles of solute per kilogram of solvent i.e. the concentration of solute
• Isotonic

  A solution that has the same solute concentration as cells and blood (290 mOsm/L)
• Hypotonic

  A solution with lower solute concentration than cells and blood
• Hypertonic

  A solution with higher solute concentration than cells and blood
• How molecules move between fluid compartments

  1. Passive transport (no energy needed) - Diffusion, Facilitated diffusion

  2. Active transport (energy needed ATP) - e.g. Na+/K+ being pumped across cell membrane
• Diffusion


  Particles tend to distribute themselves evenly within a solution, from high concentration to low concentration, or down a concentration gradient
• Facilitated diffusion

  Substances require a protein carrier for passive transport, transports lipid-insoluble and large substances
• Active transport

  Substances are transported that are unable to pass by diffusion, ATP is used for transport
• Vesicular transport

  1. Exocytosis e.g. hormones

  2. Endocytosis - Phagocytosis "cell eating", Pinocytosis "cell drinking", Bacterial phagocytosis by macrophage