Cell structures and their functions

• Cell


  Basic living unit that determines the form and functions of the human body. Highly organized.
• Organelles


  Specialized structures within the cell.
• Nucleus


  Contains the genetic material and directs cell activities.
• Cytoplasm


  Holds the organelles.
• Plasma membrane


  Encloses the cytoplasm and forms the outer boundary of the cell.
• The number and type of organelles determine the cell's specific structure and function.
• Functions of the cell

  • Cell metabolism and energy use
  • Synthesis of molecules
  • Communication
  • Reproduction and inheritance
• Light microscope


  Uses light to produce an image. Adequate resolution to diagnose most conditions that cause changes in tissue structure.
• Electron microscope


  Uses beams of electrons to produce an image and can see objects smaller than a cell.
• Types of electron microscopes

  • Transmission electron microscope
  • Scanning electron microscope
  • Atomic force microscope
• Cell membrane


  Outermost component of a cell that separates intracellular and extracellular substances.
• Major types of molecules in the cell membrane

  • Phospholipids
  • Protein
  • Cholesterol
  • Carbohydrates
• Functions of the cell membrane

  • Support cell contents
  • Acts as selective permeable barrier
  • Plays a role in communication with cells
• Membrane potential


  Result of the cell's regulation of ion movement into and out of the cell.
• Fluid-mosaic model


  Describes the structure of the plasma membrane as neither rigid nor static in structure.
• Slight damage to the membrane can be repaired as the phospholipids tend to reassemble around damaged sites and close them.
• The fluid nature of the lipid bilayer also enables membranes to fuse with one another.
• Phospholipid


  Form double layer molecules with a polar head (attracted to water molecules) and a nonpolar tail (face one another in the interior).
• Cholesterol


  Gives added strength and stability to the membrane by limiting how much the phospholipids can move.
• Protein floats among the phospholipid molecules and carbohydrates may be bound to some protein molecules.
• Types of membrane proteins

  • Integral membrane proteins
  • Peripheral membrane proteins
• Marker molecules


  Cell surface molecules that allow cells to identify other cells or molecules.
• Glycoproteins


  Proteins with attached carbohydrates.
• Glycolipids


  Lipids with attached carbohydrates.
• Attachment proteins


  Integral proteins that allow cells to attach to other cells or extracellular molecules.
• Types of attachment proteins

  • Cadherins (cell to cell)
  • Integrins (cell to extracellular molecules)
• Transport proteins


  Allow ions or molecules to move from one side of the cell membrane to another.
• Characteristics of transport proteins

  • Specificity
  • Competition
  • Saturation
• Major classes of transport proteins

  • Channel proteins
  • Carrier proteins
  • ATP-powered pumps
• Leak ion channels


  Always open and responsible for cell membrane permeability to ions when at rest.
• Gated ion channels


  Open and close depending on certain conditions of the cell.
• Types of gated ion channels

  • Ligand-gated
  • Voltage-gated
• Cystic fibrosis is a genetic disorder that affects chloride ion channels.
• Carrier protein


  Integral membrane proteins that move ions or molecules from one side of the plasma membrane to the other.
• Types of carrier protein movement

  • Uniport
  • Symport (cotransport)
  • Antiport (counter transport)
• ATP-powered pumps


  Transport proteins that require cellular energy to move specific ions or molecules from one side of the plasma membrane to the other.
• Receptor proteins


  Membrane proteins or glycoproteins that have an exposed receptor site on the outer cell surface.
• Components of G protein complex

  • Alpha
  • Beta
  • Gamma
• Enzymes


  Catalyze chemical reactions on either the inner or outer surface of the cell membrane.
• Selectively permeable


  Allows only certain substances to pass through the cell membrane.