Physio Ch 5 Membrane Dynamics

• -Fluid in two compartments are equal
• -expressed as amount of solute/vol.
• example: ECF and ICF fluids are equal

• -when solutes are unequal in two compartments
• example: ICF is high in K+ & proteins while ECF is high in  Na and Cl.

• -it is the solvent for all living matter
• -maintains osmotic equilibrium

• -diffusion of H2O (99% right)
• -water moving across a membrane/barrier in response to a solute concentration
• -water will stop moving when net movement is 0

-the applied pressure to oppose osmosis

• -osmolarity is the number of active particles in solution
• -expressed in osmoses per liter
• -osmol/L or OsM
• -
• -molarity is the number of active particles when started
• -mol/L x number of active particles/molecules
• -the concentration when started

-osmolaity-osmoles of solute/kg of water

• -used shen comparing two solutions
• isosmotic-refering to two solutions with the same osmolarity
• hyposmotic-one solution's osmolarity is lower than the other
• hyperosmotic-one solution's osmolarity is higher than the other

• -osmolarity is measuring active particle in a solution
• -tonicity is predicting where water will move
•  how will a cell react if placed in a specific      solution
• 

• penetrating-when solute particles (ions or particles) enter a cell
• nonpenetrating-when solute particles can't enter a cell
• functionally non penetrating-NaCl

• 1. if the cell has a high concentration of nonpenetrating solutes than the solution, water will move into the cell making the solution hypotonic
• 2. if the cell has a lower concentration of nonnpenetrating solutes than the solution, the water will move outside the cell making the solution hypertonic.
• 3. if both are the same, then the solution is isotonic.

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• -bulk flow refers to the movement of fluids in a compartment weather its liquid or gas
• -pressure gradients make fluid move from high to low pressure
• example: circulatory sys., heart pump and moves blood. Also the air flow of lungs.

• -size and lipid solubility 
• -O2, CO2, and move easily across the cell membrane 
• -ions, a large molecules like proteins move with more difficultly or not all
• -some require specific transport protein membranes(vesicles)

-Passive and active transport

• -passive transport does not require energy
• -active transport requires  energy(ATP)

• -simple diffusion
• -facilitated diffusion
• -primary active transport
• -secondary active transport(uses APT from primary)
• -endo-, exo-, and phagocytosis

the movement of molecules from a higher concentration to a lower concentration

• 1. Passive process
• 2. Molecule movement of higher to lower concentration 
• 3. net movement of molecules continues until concentration is equal
• 4. diffusion is faster over short distance and slower over long dist.
• 5. Diffusion is directly related to temperature
• 6. inversely related to size and weight
• 7. can occur in an open system or particles that separate two compartments

The rate diffusion depends on how permeable the membrane is to the diffusing molecules.

• -surface area
• -thickness of membrane
• -larger concentration gradient
• -solubility

Most of the molecules are either lipophobic or electrically charged, so they can't cross by simple diffusion.

• -mediated transport requires a membrane protein to enter
• -facilitated diffusion-does not require energy(ATP) to diffuse
• -active transport-requires ATP

• 1. maintain shape by connecting the cytoskeleton to the membrane. i.e. microvilli transporting epithelia
• 2. create cell junctions like gap and tight junctions that hold tissues together.
• 3. attach ECF matrix membrane fibers to ECF collagen and protein fibers.

• -membrane enzymes are active in metabolism and signal transfer.
• -intracellular enzymes transfer signals from ECF to cytoplasm

Receptors proteins can activate membrane enzymes, open and close chemically gated channels, and are active in receptor mediated endocytosis.

carrier and channel proteins

• 
• There are gated and open channels.

by the size of the pore and the electric charge of the amino acids that line it.

• -open channels are typically open with no regulation, also know as leak channels or pores
• -gated channels spend most of the time closed, they can be controlled chemically, mechanically, or by voltage.

• -chemically gated channels controlled by intracellular molecules or extracellular ligands that bind to the channel protein.
• -voltage-gated channels are controlled through the electrical state of the cell
• -mechanically gated channels respond to physical forces, like increased temperature or pressure

Na+, K+, ATPase, sodium potassium pump, Ca2+, H+, Glucose

• -uniport can only move one molecule
• -cotransporter refers to a carrier that moves more than one molecule
• -symport moves more than one molecule in the same direction
• -antiport moves more than one molecule in opposite directions

• Simple diffusion can directly cross the phosopholipid bilayer of a membrane.
• Facilitated diffusion is a mediated transport.
• Both are passive and move molecules down their concentration gradient.

• Sugars and amino acids
• GLUT transporters

Molecules moving against their gradient which requires a lot of energy. It creates a state of disequilibrium. Moving m In the sodium potassium pump, Na is getting pumped out while K is getting pumped in. In a neuron this would result in a neuron firing.

• -primary active transport also known as ATPase(enzyme)
• -secondary active transport uses ATP from primary active transport and usually is Na dependent

• 
• 

By using cotransporters molecule will piggy back with it.

The transporter(membrane protein) only allows a certain family of molecule through like GLUT.

Since transporters can move a family of molecules, the particular type that it wants could get beat out by a different molecule in the family.

• When one molecule prevents the needed molecule from binding to a transporter. 
• example: maltose and glucose are in the same family(disaccharides) but compete with each other for binding sites.

As the substrate concentration increases the rate of transport increases until to reaches a max like the check out stands at the super market.

Increase the number of carriers in the membrane.

phagocytosis and endocytosis

phagocytosis is the process of engulfing a bacteria or particle. A phagosome is the membrane bound vesicle that brings the particle to lyosomes.

• -in endocytosis the membrane indents
• -vesicles in endocytosis are much smaller
• -endocytosis is an essential process alway occurring while phagocytosis must be triggered.

Active process that can be nonselective or selective, sucks in water

• 1. Ligand binds to membrane receptor
• 2. Receptor-ligand move toward clathrin coated pit.
• 3. Endocytosis
• 4. vesicle losses clathrin coat(gets recycled)
• 5. receptor and ligand separate
• 6. Ligands go to lysosomes or Golgi for processing
• 7. Vesicle and receptors move towards membrane.
• 8. vesicle fuse to membrane(recycling of membrane.
• 9. Exocytosis.
• -clathrin is an indentation of the membrane where it is high in protein
• -endosome is the vesicle the ligands take when  there separated from the receptors.