Lec 3: Cells I

• Cell


  Smallest living units in Biology

  
• What are the two basic cell functions?

  1) They carry out all chemical activities needed to sustain life.

  2) Basic structural and functional unit of living organisms.
• What are the 3 main parts of the cell?

  plasma membrane, cytoplasm with organelles, nucleus

  
• Plasma Membrane


  Cell membrane divides the intracellular and extracellular environments

  
• Membrane Potential


  Produces a charge difference across the membrane by regulation of intracellular and extracellular ion concentrations.

  
• 3 Major Components of a Phospholipid Bilayer (Plasma Membrane)

  Phospholipids, Proteins, Cholesterol

  
• Phospholipid Bilayer


  Double bilayer of phospholipids with embedded proteins

  
• Fluid Mosaic Model


  Membrane is neither rigid nor static in structure but instead highly flexible and can change its shape and composition through time.

  ; How the cell membrane looks and functions.

  
• Phospholipid heads are:

  Phospholipid tails are:

  Heads: Hydrophilic, they face the water in the interior and exterior of the cell.

  Tails: Hydrophobic, they face each other on the interior of the membrane.

  
• Phospholipid function


  Makes up the cell membrane, can keep some substances from flowing directly through membrane.

  -Lipid soluble substances can get through (some hormones, drugs, etc.) while other substances cannot.

  
• Integral (transmembrane) proteins


  Protein under the bilayer

  
• Peripheral Proteins


  Proteins inscribed in the bilayer

  
• Proteins function


  Function as transport channels, receptors for signal transduction, attachment to cytoskeleton and extracellular matrix (ECM), enzymatic activity, intercellular joining, cell-cell recognition, etc.

  
• Function of Cholesterol in Plasma Membrane

  Stabilizes membrane, the amount determines how fluid the membrane will be.

  
• Selective Permeability


  Some substances can cross more easily than others
• 3 Requirements for Selective Permeability

  Small, hydrophobic, not charged.

  
• Exception to Selective Permeability


  Water
• Membrane Transport


  Movement of substances into and out of the cell

  
• Simple Diffusion


  Movement from High to Low concentration

  No energy

  Solutes are lipid-soluble materials and small enough to pass through membrane pores

  
• Facilitated Difussion


  Movements from High to Low concentration

  No energy

  Requires transport protein (pump)

  
• Facilitated Diffusion Characteristics


  -Specificity for a single type of molecule

  -Competition among molecules of similar shape

  -Saturation- rate of transport limited to number of available transport proteins.

  
• Active Transport


  Moves from Low to High concentration

  Requires ATP (energy)

  Requires Transport Protein (pump)

  
• Vesicular Transport


  Transport ofLARGEparticles and macromolecules across plasma membranes

  
• Vesicle


  A membrane bound sac that contains materials involved in transport of the cell.

  
• Endocytosis


  Bulk or large molecule transport goingINTOcell

  
• 3 types of Endocytosis

  Phagocytosis, Pinocytosis, Receptor-Mediated Endocytosis

  
• Phagocytosis


  Cell eating (Like Pacman)

  ex) White blood cells engulf invaders or cell debris and take into the cell

  
• Pinocytosis


  Cell Drinking

  
• Receptor Mediate Endocytosis


  When protein receptor are active on the surface, the membrane takes in substances from the outside

  
• Exocytosis


  Bulk or large molecule transport out of the cell

  
• Osmosis


  Diffusion of water across a selectively permeable membrane

  Affected by Osmolarity

  
• 3 types of Osmosis

  hypertonic, hypotonic, isotonic

  
• Osmolarity


  Total concentration of all solute particles in a solution

  
• Hypotonic


  Lowsolute concentration compared to human body plasma compartment

  
• Hypertonic


  Highsolute concentration compared to human body plasma compartment

  
• Isotonic


  Same/equalsolute concentration compared to human body plasma compartment

  
• What way does water go in Osmosis

  From Hypotonic to Hypertonic

  
  

  *Large volume changes caused by water movement disrupt normal cell function

  
• Cytoplasm


  Fluid matrix like jello (cytosol) with embedded Organelle structures

  
• Organelle


  Small separate, membrane-bound structures within the cell with distinct functions

  
• Mitochondria


  *ATP Synthesis

  -Provides all energy for cellular work

  -Number will increase in cell when energy requirements increase

  -Small amount of mitochondrial DNA is present