2. A cell is the basic, living, structural and
functional unit of the body.
Cell Theory:
the building blocks of all plants and
animals
all cells come from the division of
preexisting cells
cells are the smallest units that perform
all vital physiological functions
each cell maintains homeostasis at the
cellular level.
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3. • Cells are measured in micrometers.
• Cells vary in size and shape.
• Shape is determined by function.
• Two types of cells:
– Sex cells
– Somatic (body) cells
• Cells are surrounded by extracellular fluid,
which is called interstitial fluid in most
tissues
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6. Every Eukaryotic cell has three main parts:
Plasma (cell) membrane - separates inside of
cell from external environment.
Nucleus – organelle that contains the cell’s
DNA and is surrounded by a double
membrane.
Cytoplasm – everything from the nuclear
membrane to the plasma membrane
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7. Cytoplasm refers to cytosol plus organelles
and inclusions.
cytosol - contains proteins, enzymes,
nutrients, ions, and other small molecules
organelles - highly organized structures with
characteristic shapes that are specialized
for specific cellular activities.
inclusions - are temporary structures in the
cytoplasm that contain secretions and
storage products of the cell.
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9. Plasma membrane
• Physical isolation
• Regulation of exchange with the
environment
• Sensitivity to the environment
– Signal transduction
• Structural support
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10. Most of the surface area of the cell membrane
is made of phospholipid, but accounts for
only 42% of the weight of the membrane.
Proteins – important in many functions
Also find glycolipids and cholesterol.
Phosphoslipid is an amphipathic molecule –
phosphate heads on the outside and inside,
and fatty acid tails in the middle.
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12. Membrane is fluid
- fatty acid tails are unsaturated
The membrane is selectively
permeable – it allows fat soluble
substances to pass through (such as
steroid hormones) and some other
small, uncharged molecules.
Cholesterol is a large molecule, and
helps to stabilize the membrane.
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13. Membrane carbohydrates
• 3-5 % of membrane
• Proteoglycans, glycoproteins and
glycolipids
• Gylcocalyx
– Lubrication and protection
– Anchoring and locomotion
– Specificity in binding
– Recognition
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14. Fluid mosaic model - proteins float like
icebergs in a sea of phospholipids.
Proteins can be integral proteins – go all
the way through the membrane, or may be
peripheral proteins -bound to the inside or
outside membrane.
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18. Intercelluar junctions
Tight junctions – membranes of adjacent
cells bound together by occludins and
claudins formingAn impermeable junction.
• Desmosomes are protein “spot welds” in
skin and cardiac muscle:
– plaques, linker protein filaments, and
thicker filaments across inside of cell
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19. Intercellular junctions
• Gap junctions are tubular channels
(connexons) that connect the cytoplasm
of one cell with that of another.
– Ions, simple sugars and other small
molecules
• Cellular Adhesion Molecules help cells
form
• temporary attachments to other cells.
CAMs
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23. Membrane Physiology
• Cell membrane function:
– Cellular communication
– Establish an electrochemical gradient
– Are selectively permeable
• Lipids
• Size
• Electrical charge
• Presence of channels and transporters
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24. Movement of materials
• Passive processes:
– Depend on concentration and kinetic energy
– Do not require energy
– Move substances from an area of high
concentration to an area of low concentration
• Down a concentration gradient
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25. Diffusion
• Rate depends on:
– Temperature
– Gradient size
– Distance
– Molecule size
– Electrical forces
• Reaches equilibrium or
• Physiological steady state
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28. • Simple diffusion
• Channel mediated diffusion
– 0.8 nm
– Size and charge
– Interaction between ion and channel walls
Rate limited by number of suitable channels
- Na, K, Cl pass through membranes at a rate
comparable to simple diffusion
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29. Osmosis
• Movement of WATER through a
selectively permeable membrane
• Moves according to the conc. of water
• Osmotic pressure
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31. Tonicity
• Concentration of one solution relative to
another ( conc. in cytoplasm)
• Isotonic – equal concentrations
– 0.9 % NaCl or 5% glucose soln.
• Hypertonic – more concentrated
• Hypotonic – less concentrated
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39. Filtration
-a type of bulk flow where the
movement of water and dissolved
substances across a membrane
is due to gravity or hydrostatic
pressure (water pressure).
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42. Active Transport
• Depends on the use of energy (ATP)
• Moves substances up a concentration
gradient (up hill)
• These systems are often called “pumps”
– Na+ / K+ pump - Na/K ATPase
– Others carry Ca++, Mg++, I-, Cl- and Fe++
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43. Active transport
• Countertransport
– Exchange pump
• Cotransport or symport
– Move two different substances in same direction
– One down a conc. Gradient
– Use of energy to pump one substance back out
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