Monday, October 4, 2010




  • The cytoskeleton is a network of fibers extending throughout the cytoplasm and it helps to hold the cells shape together.
  • They are the "muscles" for movement.
  • The three types are microfilaments, intermediate filaments, and microtubules.


  • Helical rods made out of a globular protein called actin.
  • These help the cell move and change their shape.
  • Actin and other fibers work together to make muscles contract.

Intermediate Filaments

  • These are ropelike fiberous proteins.
  • They have reinforced rods to bear tension and they anchor organelles.


  • Straight, hollow tubes that are made of globular proteins. They are called tubulins.
  • Globular molecules are like small marbles.
  • They make themselves longer by adding tubulin subunits to one end.
  • Their functions are providing shape, tracks for organelles to move within teh cytoplasm, they guide the movement of chromosomes during cell division, and move the cilia and flagella.


  • Shorter than flagella and they are more numerous.
  • Propel protists; single celled organisms.
  • Can be damaged by smoking and line the respiratory tract.
  • The cilia push debri up and out of the body.


  • A type of transport.
  • Propel sperm, other animals, and protists.

Microtubule Structure

  • Microtubules form a 9 + 2 arrangement which means that there are 9 doubles of microtubules forming a ring around one double.
  • These make up one cilia or one flagella
  • To move the cilia or flagella, a motor protein called dyneins is needed. It grabs ontioo an adjacent microtubule doublet.
  • These structures are flexible.
  • Basal bodies and centrioles have identical structures.
  • Basal bodies are anchor cilia or flagella in the cytoplasm.

Plasma Membrane

Membranes of the Cell

  • Plasma Membrane - cell's outer membrane (Cell Membrane)
  • Endomembranes - smooth and rough endoplasmic reticulum, golgi, vacuole, and lysosome (only these internal oragnelles can break apart)
  • Membranous envelopes - nucleus, chloroplast, and mitochodria (have 2 membranes)

Membrane Features

  • Semi-permeable - allow some substances to pass through, but blocks the passage of other substances. (only small things can go through)
  • Membranes enclose and maintain the specific chemical environment.
  • Every membrane carries out its specific functions.

Membrane Structure

  • Two layer membrane called phospholipid bilayer.
  • Made of proteins and lipids
  • Contains two fatty acids instead of three (hydrophobic)
  • Contains a phosphate group in the place of the third fatty acid (hydrophilic)

Membranes and Proteins

  • Specific proteins are inserted into the phosolipid bilayer to:
  1. Attach to the cytoskeleton
  2. Talk to other cells
  3. Enzyme Activity
  4. Transporting passively and actively
  5. Two cells holding each other, intercellular joining
  6. Cell-cell recognition


  • Membranes are not rigid.
  • Protiens move freely on the membrane and do not just stay in one spot.
  • This is called the fluid mosaic model.

Diffusion and Osmosis

  • In diffusion, the molecules move.
  • In osmosis, the water moves.
  • Diffusion: the tendency of molecules to move from a high concentration to a low concentration until equilibrium is reached.
  • Equilibrium is when the conecentration of either side it equal.

Passive Transport

  • Diffusion across a membrane.
  • Cell does not use any energy for diffusion.
  • Selectively permeable membrane.
  • Water, O2, and CO2 go through the membrane because they are small.


  • Osmosis: passive transport of water across a semi-permeable membrane.
  • Solute = what is dissolved.
  • Solvent = what the solute is dissolved in.
  • Water moves across the membrane, not the solute.


  • High concentration of solute and lower for solvent.
  • Hyper = above.
  • Plasmolysis = losing water.
  • Cells will shrivel up if there is not enough water.


  • High concentration of solvent and lower for solute.
  • Hypo = below.
  • Lysing = bursting of a cell.
  • Good for plant cells.


  • Everything is equal.
  • Isos = equal.
  • Animal cells like this, but plant cells do not.

Effect on living animal cells

  • Osmoregulation - control of water balance.
  • Animals must use this to survive.
  • Blood cells love this.

Effect on living plant cells

  • Most plants thrive in a hypotonic environment when the vacuole is full.
  • Plants become wilted in a isotonic environment.

Posted on 10/4/2010

Next Scribe: Katie B.

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