Physio Ch 5 Membrane Dynamics
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What is osmotic equilibrium? How does it arise?
- -Fluid in two compartments are equal
- -expressed as amount of solute/vol.
- example: ECF and ICF fluids are equal
What is chemical disequilibrium? Give some examples of specific solutes that exist in a state of chemical disequilibrium in your body.
- -when solutes are unequal in two compartments
- example: ICF is high in K+ & proteins while ECF is high in Na and Cl.
Why is water movement such an important aspect of physiology?
- -it is the solvent for all living matter
- -maintains osmotic equilibrium
Define and describe osmosis.
- -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
What is osmotic pressure?
-the applied pressure to oppose osmosis
How does osmolarity differ from molarity?
- -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
-osmoles of solute/kg of water
Distinguish between the terms isosmotic, hyposmotic, and hyperosmotic.
- -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
Contrast osmolarity and tonicity.
- -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
Contrast penetrating and nonpenetrating solutes. What does it mean when a solute is considered "functionally nonpenetrating?
- penetrating-when solute particles (ions or particles) enter a cell
- nonpenetrating-when solute particles can't enter a cell
- functionally non penetrating-NaCl
What are the rules for predicting tonicity?
- 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.
How can a solution be isosmotic and hypotonic?
What is bulk flow? Give examples in the body.
- -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.
What qualities of a cell membrane contribute to its permeability? Give examples of substances that typically are permeable and impermeable to human cell membrane.
- -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)
What two properties of a molecule determine whether it can diffuse across a membrane?
-Passive and active transport
What is the difference between passive and active transport?
- -passive transport does not require energy
- -active transport requires energy(ATP)
What are the different ways a molecule can move across a membrane?
- -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
List seven properties of diffusion.
- 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
Define simple diffusion. Beyond the seven properties, what additional properties influence rate of diffusion?
The rate diffusion depends on how permeable the membrane is to the diffusing molecules.
What factors influence membrane permeability?
- -surface area
- -thickness of membrane
- -larger concentration gradient
Why is simple diffusion not an option for most molecules in our body?
Most of the molecules are either lipophobic or electrically charged, so they can't cross by simple diffusion.
Differentiate between mediated transport, facilitated diffusion, and active transport.
- -mediated transport requires a membrane protein to enter
- -facilitated diffusion-does not require energy(ATP) to diffuse
- -active transport-requires ATP
What are the three major roles of structural proteins? Fig 5.8
- 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.
What are membrane enzymes? How are they different in function from intracellular enzymes?
- -membrane enzymes are active in metabolism and signal transfer.
- -intracellular enzymes transfer signals from ECF to cytoplasm
Describe membrane receptor proteins.
Receptors proteins can activate membrane enzymes, open and close chemically gated channels, and are active in receptor mediated endocytosis.
The current classification scheme recognizes two types of transporters:____and _____.
carrier and channel proteins
Describe and draw a typical protein channel. What type of molecules pass through channel proteins? Give examples of channel proteins.
- There are gated and open channels.
What factors determine the channel protein's specificity?
by the size of the pore and the electric charge of the amino acids that line it.
Distinguish between an open and gated channel.
- -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.
List three types of gated channels and indicate the stimulus that opens each type.
- -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
Give examples of molecules that might cross a membrane by using a carrier protein.
Na+, K+, ATPase, sodium potassium pump, Ca2+, H+, Glucose
Define the following terms: uniport carriers, cotransporters, symport carriers, and anti port carriers.
- -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
Compare and contrast facilitated diffusion and simple diffusion.
- 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.
Give example of molecules that might cross a membrane by facilitated diffusion.
- Sugars and amino acids
- GLUT transporters
What is active transport? What does it accomplish? Why does it require the input of energy?
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.
Distinguish between primary active transport and secondary active transport.
- -primary active transport also known as ATPase(enzyme)
- -secondary active transport uses ATP from primary active transport and usually is Na dependent
Diagram the structure and mechanism of the Na+-K+-ATPase as an example of primary active transport.
How is the relativity high extracellular Na+ used to drive transport of other molecule against their concentration gradient across a membrane?
By using cotransporters molecule will piggy back with it.
Give examples of how specificity applies to carrier-mediated transport.
The transporter(membrane protein) only allows a certain family of molecule through like GLUT.
How does competition relate to specificity?
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.
Give an example of competitive inhibition.
- 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.
Describe how the principle of saturation applies to carrier-mediated transport. Included a description of transport maximum.
As the substrate concentration increases the rate of transport increases until to reaches a max like the check out stands at the super market.
How can cells increase their transport capacity and avoid saturation?
Increase the number of carriers in the membrane.
The two primary modes of vesicular transport are _____ and _____.
phagocytosis and endocytosis
Describe the process of phagocytosis. What is a phagosome?
phagocytosis is the process of engulfing a bacteria or particle. A phagosome is the membrane bound vesicle that brings the particle to lyosomes.
How does endocytosis differ from phagocytosis?
- -in endocytosis the membrane indents
- -vesicles in endocytosis are much smaller
- -endocytosis is an essential process alway occurring while phagocytosis must be triggered.
What is pinocytosis?
Active process that can be nonselective or selective, sucks in water
Explain the process of receptor-mediated endocytosis. What role does clathrin play? What is an endosome?
- 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.
Describe the movement of glucose across a transporting epithelial cell. Include in your diagram all membrane proteins ions, and directionality of transport.
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