• The cell is the smallest structural and functional living unit
• Organismal depends on individual and collective cell function
• Biochemical activites of cells are dictated by their specific subcellular structures; Structures dictating function

• Over 200 different types of human cells
• Types differ in size, shape, subcellular components, and function 

• Biomolecular layer of lipids and proteins in a constantly changing fluid mosaic
• Plays a dynamic role in cellular activity 
• Seprates intracellular fluid (ICF) from extracellular fluid (ECF)
• 2 layers of Phospholipids and Fatty- acid tails

• 75% Phospholipids
• 5% Glycolipids- lipids with polar sugar groups on outer membrane surface
• 20% Cholesterol- increase membrane stability and fluidity  

• Intergral Proteins
• Peripheral Proteins 

• Firmly inserted into the membrane (most are transmembrane)
• Transport proteins (channels and carriers), enzymes, or receptors 

• Loosely attached to integral proteins
• Found on intracellular surface and on extracellular surface
• Enzymes, motor proteins, cell-to-cell links
• Provides support on intracellular surface 

1. Transport- things that are not lipid soluble
2. Receptors for signal transduction
3. Attachment to cytoskeletion and extracellular matrix
4. Enzymatic activity
5. intercellular joining
6. Cell-to-cell recognition 

• Passive- no energy
•    -Concentration gradient
• Active- ATP needed
•    -Pumping aganist concentration  

• A member protein exposed to the outside of the cell may have a binding site that fits with a specific chemical messanger.  

• Elements of the cytoskeleton (ICF) and the extracellular matrix may be anchored to the membrane protein.  

• A protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution.  

• Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions.  

• Some glycoproteins serve as ID tags that are specifically recognized by other cells. 

• No cellular energy (ATP) required
• Substance moves down its concentration gradient (high to low)

• Simple diffusion
• Carrier-mediated facilitated diffusion
• Channel-mediated facilitated
• Osmosis 

• Energy (ATP) required
• Occurs only in living cell membranes 

• Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through the phospholipid bilayer 

• Certain lipohobic molecules use proteins or channel protiens, both of which,
•   -Exibit specificity (selectivity)
•   -Are saturable; rate is determinded by number of carriers or channels
•   -Can be regulated in terms of activity and quantity

• Transmembrane integral proteins transport specific polar molecules
• Binding of substrate causes shape change in carrier 

• Leakage channels
•    -Always open
•    - Concentration gradeint
• Gated channels
•    -Controlled by chemical or electrical signals
•    -Closed at rest
•    -Chemical comes binds and opens 

• Movement of solvent (water) across a selectively permeable membrane
• Water diffuses through plasma membrane
• Concentration gradeint
• Determind by solute concentration

• The measure of total concentration of solute particles
• When solutions of different osmolarity are sperated by a membrane, osmosis occures intil equilibrium is reached 

• The ability of a solution to cause a cell to shrink or swell (solution compared to cytoplasm
•   -Isotonic, Hypertonic, Hypotonic 

• A solution with the same solute concentration as that of the cytosol 

• A solution having greater solute concentration than that of the cytosol 

• A solution having lesser solute concentration than that of cytosol 

• Size
• Solubility (lipid soluble)
• Change
• Constration gradient
• Protein channel
• Satration 

• Active transport
• Vesicular transport 

• Requires carrier proteins (solute pumps)
• Moves solutes against a concentration gradient

• Primary active Transport
• Secondary active transport 

• Energry from hydrolysis of ATP causes shape changes in transport protein so that bound solutes(Ions) are "pumped" across the membrane 

• Primary and Secondary Active Transport
• Maintains electrochemical gradients essential for functions of muscle and nerve tissues.

• Depends on an ion gradient created by primary active transport
• Energy stored in ionic gradients is used indirectly to drive transport of other solutes 

• Symport System
• Antiport System 

• Transport of large particles, macromolecules, and fluids across plasma membranes.
• Requires Cell energy (ATP) 

• Exocytosis
• Endocytosis
• Transcytosis
• Substance (vesicular) Trafficking 

• Resting Potential is -70mV
   
• Ranges from -50 to -100mV in different cells
• Results from diffusion and active transport of ions (mainly K+)  

Mantiance of RMP in Cell

(Potassium Soduim pump)

1. The Na+ - K+ pump continuously ejects Na+ (3) from cell and carries K+ (2) back in.
2. Some K+ continually diffuses down its concentration gradient out of cell through K+ leakage channels.
3. Membrane interior becomes negative (relative to exterior) because of large anions trapped inside cell
4. Eletrochemical gradient begins to attract K+ back into the cell
5. RMP is est. at the point where electrical gradient balances the K+ concentration gradient.
6. A steady state is maintained because the rate of active transport is equal to and depends on the rate of Na+ diffusion into cell