Cell Biology

 

 

http://occawlonline.pearsoned.com/bookbind/pubbooks/ehapplace/chapter3/deluxe.html

 

 

Click the topic for notes on this page:

 
Prokaryotic_Cells Structure_of_the_Cell_Membrane Energy_and_Biology
Eukaryotes Cell_Transport Enzymes
Eukaryotic_Cell_Parts    

 

 

 

 

 

 

 

 

 

 

Prokaryotic Cells

  1. Bacteria & Archaebacteria

  2. Small, relatively simple structure

  3. DNA not enclosed in nucleus

 

 

 

 

 

 

Eukaryotes

 

  1. •Single cells (protists) or multicellular organisms

  2. •DNA contained in nucleus

  3. •Contain organelles:  Specialized structures with specific functions in the cell

  4. •Animal and plant cells have some differences!

 

 

Animal Cell

Plant Cell

 

Eukaryotic Cell Parts

 

Nucleus: The Headquarters

 

  1. •DNA protected within membrane-bound nucleus

    •Control center – information contained in DNA

  2. Chromatin = DNA wrapped with protein

  3. •Many cell organelles are connected through a network of membranes within cell

    •Endomembrane system is a collection of membranous organelles that manufactures and distributes cell products

Smooth Endoplasmic Reticulum (ER): Production of Lipids

  1. •Smooth ER

  2. Synthesizes lipids

  3. Processes toxins and drugs in liver cells

Rough Endoplasmic Reticulum: Production of Proteins

•Ribosomes on the surface of the rough ER •produce proteins that are:

  1. •     released from cell (secreted) 

  2. •     inserted into membranes or

  3. •     transported in vesicles to other organelles

 

Golgi apparatus: Packaging & Shipping (UPS)

  1. The Golgi apparatus finishes, sorts and ships cell products

  2. Stacks of membranous sacs receive and modify ER products then ship them to other organelles or the cell surface

     

    Lysosomes: Clean-up Crew

    1. •Lysosomes breakdown materials in cell

    2. •Sacs of enzymes that digest food, macromolecules and damaged cell parts

    3. •Lysosomes in white blood cells destroy bacteria

      Lysosomes also recycle damaged organelles

       

      Lysosomal Storage Diseases

      •Abnormal enzymes in lysosomes cannot break down large molecules -->

      •Build up toxic levels in cell

      •Damage nerves, liver, other organs

      •>40 Lysosomal storage diseases

      •Due to defective gene coding for the enzyme

      •(examples:  Tay Sachs, Gaucher, etc.)

       

       

       

      Vacuoles: Storage

      Vacuoles function in the general maintenance of the cell

      •Plant cells contain a large central vacuole which has lysosomal and storage functions

      •Some protists have contractile vacuoles that pump out excess water

       

      The various organelles of the endomembrane system are interconnected structurally and functionally

 

 

 

 

See Textbook Website or CD for animation of protein synthesis in endomembrane system.

 

 

 

 

Energy Converting Organelles

Chloroplasts: Solar converters

•Chloroplasts convert solar energy (sunlight) to chemical energy (sugars)

•Found in plants and some protists

 

Mitochondria: Powerhouse of the Cell

Mitochondria harvest chemical energy from food

 

 

 

 

 

 

 

Cytoskeleton and Related Structures
 

Cytoskeleton: Network of protein fibers

  1. The cell’s internal skeleton helps organize its structure and activities

  2. Cilia and flagella move when microtubules bend

    •Eukaryotic cilia and flagella on the surface of some cells allow movement

     

     

    CELL SURFACES AND JUNCTIONS

    1. Cell surfaces protect, support, and join cells

    2. •Cells interact with their environments and each other via their surfaces.

    3. •Animal cells are embedded in an extracellular matrix which binds cells together in tissues

    4. •Plant cells are supported by rigid cell walls made largely of cellulose and connect by connecting channels

      •called plasmodesmata.

 

 

 

 

 

 

 

 

 

 

 

Structure of the Cell Membrane

 

 
Structure Function
Phospholipid bilayer Basic structure of cell membrane; phospholipids arranged with hydrophilic phosphate heads in contact with cytoplasm and extracellular matrix; lipid tails align to form a hydrophobic interior
Cholesterol Allows membrane to be flexible
Transport Proteins Act as channels or gates to regulate what enters and exits the cell.
Receptor & Signal Proteins Mechanism by which cell interior communicates with environment
Glycoproteins Used for identification (e.g., blood type)
 
   
   
   

Cell Transport

 

 
Diffusion  
Diffusion works by:

nDifference in concentration of molecules

nMolecules move from high concentration --> low concentration

n

Continue to move until the molecules are evenly distributed

n
 
Diffusion across a selectively permeable membrane

nMembrane will allow some molecules into cell by simple diffusion

nSmall, nonpolar molecules

nGases (CO2, O2) n(some water)

 

Passive transport in cells

Substances move from high concentration --> low concentration

Does not require Energy

Includes

simple diffusion (small nonpolar molecules & gases)

facilitated diffusion (some ions, sugars, amino acids)

osmosis (water)

 

Osmosis = diffusion of water across a selectively permeable membrane

water crosses membrane, but solute dissolved in water does not because it is too large or too polar

   
  • Water moves from area of high water concentration to low water concentration
  • Water moves from area of low solute concentration to high solute concentration

 

 

 

 

 
No change in the amount of water in the cell in isotonic solution Water flows into cells from hypotonic solution Water flows out of cells in hypertonic solution    
 
   
Facilitated Diffusion

High concentration --> low concentration

No energy required

Special proteins help substance cross the cell membrane by creating channels in the membrane

Carrier protein in membrane changes shape as a specific molecule binds, allowing molecule to enter the cell.

 

 

 
 
   
Why is passive transport important?
nDiffusion
nOxygen to body cells
nCO2 waste removed
nOsmosis
nRemoves toxins and waste from blood
nRegulates blood pressure and volume
nFacilitated diffusion
nNutrients from food enter body
nCells get supplies they need
nCommunication between cells

 

 

Active Transport

n       Cell needs something that is not abundant
(low concentration)

n       Transport molecules from
low concentration high concentration

n       Like pedaling a bike uphill – molecules move against concentration gradient

n       Requires ENERGY (ATP)

 

Click to see Sodium Potassium Pump (with sound effects!)

n       Na+ pumped out of the cell

n       K+ pumped into the cell

n       ATP involved

n       Used in nerve cells to create an electrical charge that is used by nerve cells to communicate

 

Endocytosis

n       Cell takes in particles or solutes by forming vesicles which surround substance

n       Pinocytosis –Cell drinking

n       Phagocytosis – Cell eating

Pinocytosis

n  Membrane folds in, trapping liquid in vesicle.

n  Vesicle pinches off, enters cell.

n  Energy required.

n  Click here to see Pinocytosis

Phagocytosis – cell eating

n  Pseudopods (false feet) surround particle to form a vesicles

n  Vesicle is taken into cell

n  Click here to see Phagocytosis

 

 

Exocytosis

n       Vesicle with cell products or waste moves to cell membrane.

n       Vesicle fuses with cell membrane.

n       Contents of vesicle released from cell.

 

Comparison of Passive and Active Transport

Passive Transport

Active Transport

No energy required

Energy required

High --> Low concentration

Low --> High concentration

Nonpolar molecules            

Polar molecules

Small molecules                                               

Large molecules                    

Gases

Particles                                       

 

 

 

Energy and Biology

 

 

 

 

 

 

 

 

 

Enzymes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mitosis video

Shoe mitosis