Exam 1 Review Phys
What is the Na+ equilibrium potential?
+60 mV
What are desmosomes?
-"spot rivets" that anchor together two adjacent but non-touching cells
What is the osmolarity of a typical human cell?
-0.3 osm
What is the osmolarity of 1 molar glucose solution?
-1 osmolar
What is the osmolarity of 1 molar NaCl solution?
-2 osmolar
What os the osmolarity of 1 molar CaCl2 solution?
-3 osmolar
What percentage of the body's water is found in the ECF?
-33%
What is the normal human body temperature?
-37 degrees celsius, 98.6 farenheit
What percentage of the body's water is found in the ICF?
-67%
A typical neuron at rest is sitting at a membrane potential of?
-70 mV
What is the K+ equilibrium potential?
-94 mV
What are the two sources of energy for active transport?
-ATP -ionic concentration gradient
What is an agonist?
-Chemical messenger that binds to a receptor that it does not normally work with -Produces the same response within the cell that the normal chemical messenger would.
In facilitated diffusion, what is the affinity of the binding site?
-It is the same when exposed to either the outside or the inside of the cell -the carrier protein takes the conformation in which solute binding site is exposed to the region of higher concentration.
Which ion is the primary determinant of resting membrane potential? Why?
-K+. -the membrane is much more permeable to K+ (20 to 30 times) -because there are a greater number of leak channels for K+, and the membrane is much more permeable to K+ (the hydration shells of K+ are much smaller than those of Na+)
What is it?
-NET FLUX = ΔC * A * P
What maintains the concentration gradient necessary for the proper functioning of the SGLT?
-Na+/K+ pump
What is it equal to?
-PARTITION COEFFICIENT = lipid solubility/water solubility
What is osmolarity?
-a measure of the total solute concentration given in terms of the number of particles per liter of solution. Expressed in osmoles/liter (or Osm)
What is positive feedback?
-a mechanism of response in which a stimulus initiates reactions that increase the stimulus--amplifies an initial change
What is negative feedback?
-a mechanism of response in which a stimulus initiates reactions that reduce the stimulus--opposes an initial change
What is this facilitated diffusion mediated by?
-a passive glucose transport of the GLUT family of proteins
Where is this pump found?
-at the basolateral membrane -this keeps the intracelllular Na+ concentration low
What are tight junctions?
-at tight junctions, adjacent cells bind firmly with each other at points of direct contact to seal off the passageway between two cells
Why is the sodium and glucose transporter necessary?
-because the body wants to transfer glucose from the intestinal and kidney lumen into the intestinal and kidney cells -however, concentration of glucose is high within the intestinal and kidney cells, and is low within the intestinal and kidney lumen -as such, glucose needs to be moved against its concentration gradient
What molecules cannot easily cross the cell membrane?
-hydrophilic/polar molecules -this includes large macromolecules, as well as charged molecules and ions
What molecules can easily cross the cell membrane?
-hydrophobic/non-polar molecules -this includes non-charged molecules, as well as small polar molecules such as water
Where is the body's thermostat located?
-in the hypothalamus
Where is the sodium and glucose cotransporter fround? What type of transporter is it?
-in the luminal membrane of the kidneys and the small intestine -secondary active transport co-transporter (symporter)
What is the result of an increase in A?
-increase in the net flux/net rate of diffusion
What is the result of an increase in P?
-increase in the net flux/net rate of diffusion
What is the result of an increase in ΔC?
-increase in the net flux/net rate of diffusion
What factor do hydration shells have on the size of ions?
-increase the size of ions
What is the effect of increasing the concentration gradient on osmotic pressure?
-increases osmotic pressure. By increasing the concentration gradient, you increase the amount of solute relative to water. This means that there is now a higher concentration gradient for water.
What effect does temperature have on permeability, and therefore on net flux/net diffusion?
-increases permeability -increases the rate of net flux/net diffusion
How does the body increase heat at the onset of a fever? How does the body "break" the fever?
-initiates shivering -promotes skin vasoconstriction -(both conserve heat which rapidly drive the temperature upward)
Concentration gradient for Na+
-inward
Electrical gradient for K+
-inward
Electrical gradient for Na+
-inward
Electrochemical gradient for Na+
-inward
What does this mean in terms of diffusion across the plasma membrane?
-it is more difficult for sodium to cross the plasma membrane
How is active transport different from passive transport?
-it requires energy
What are the two types of protein/ion channels that exist?
-leak channel: pores are always open -gated ion channel: door opens and closes in response to some signal
What are gap junctions?
-link the cytoplasm of one cell to the cytoplasm of another so that small molecules can pass from one side to another
What is homeostasis?
-maintenance of the body's internal environment
Walk through G-protein coupled receptors...
-messenger binds to a receptor -alpha subunit of the g-protein releases GDP and picks up GTP -alpha subunit disengages from the heterotrimeric protein, slides down the plasma membrane -the alpha subunit activates a downstream target, which is either an ion channel or an effector protein (enzyme).
Are negative feedback systems or positive more common?
-negative feedback system -roughly 90% of all systems are based on negative feedback
Is passage of materials through carrier proteins governed by Fick's Law?
-no it is not -the reason being is that the carrier protein has to undergo a confirmational change (in molecular structure) to open to one side or another at a time
How is cAMP formed?
-one molecule of ATP is hydrolyzed twice to form cyclic adenosine mono phosphate
Concentration gradient for K+
-outward
Electrochemical gradient for K+
-outward
How does the body respond to an increase in blood glucose levels?
-pancreas secretes insulin -liver cell, adipose tissue, and skeletal muscles take up glucose -blood glucose levels fall
How does the body respond to a decrease in blood glucose levels?
-pancrease secretes glucagon -liver cells and adipose cells release glycogen -blood glucose levels rise
What is P?
-permeability
What is the most abundant cation in the ICF?
-potassium
Where are they found?
-primarily found in sheets of epithelial tissue
What are the two types of ACTIVE transport?
-primary active transport -secondary active transport
Which transfer solutes from low to high concentration?
-primary active transport -secondary active transport
What two types of signals + receptors activate enzymes?
-receptor is an enzyme -receptor is separate from an ion channel, but is coupled to it via a G protein
What two types of signals + receptors open ion channels?
-receptor is an ion channel -receptor is separate from an ion channel, but is coupled to it via a G protein
What is endogenous pyrogen?
-released by macrophages in response to microbial invasion -triggers release of prostoglandins
What is their role?
-role is to allow communication between the cells -the small diameter of the tunnel permits small, water-soluble particles to pass between the connected cells -precludes passage of large molecules -ions and small molecules can be exchanged without ever entering the ECF
What is their role?
-seal off the paracellular pathway -compartmentalize the membrane -create membrane asymmetry
What steps does the body take in an effort to conserve heat?
-shivering (produces heat) -vasoconstriction (blood is directed away from the skin to the center of the body) -goosebumps (non-adaptive, do not have an effect) -voluntary, heat producing actions
What are the two main types of membrane transport?
-simple diffusion -mediated transport/assisted transport
Why doesn't the skeletal muscle respond to glucagon?
-skeletal muscle will always hold onto glucose -requires glucose for energy
How does the body "break" the fever?
-skin vasodilation -sweating -(results in heat loss)
What is the most abundant cation in the ECF?
-sodium
Which 2 types of leak channels are present in the membranes of all body cells?
-sodium and potassium channels -sodium moves into the cell -potassium moves out of the cell
What are the ramifications of this in terms of hydration shells?
-sodium has a larger hydration shell than potassium
How does the diffusion of surface charges across sodium ions and across potassium ions compare?
-sodium is smaller so it has a more concentrated surface charge -potassium is larger so it has a more diffuse surface charge
Describe the movement that takes place through the SGLT?
-sodium moves from high concentration within the intestinal or kidney lumen to low concentration within the intestinal or kidney cells -at the same time, glucose moves from low concentration within the intestinal/kidney lumen to high concentration within the intestinal or kidney cells
What are the hydrated ionic radii of sodium and potassium?
-sodium's hydrated ionic radius is equal to 3.5 A -potassium's hydrated ionic radius is equal to 2.3 A
What is A?
-surface area -denotes the number of physical locations across which things can move -does not appreciably change on a day-to-day basis
What steps does the body take to increase heat loss?
-sweating (sweating produces evaporative cooling) -skin vasodilation (blood is routed to the skin for cooling through convection) -decreased muscle tone -decreased voluntary exercise
What are the 2 types of secondary active transport?
-symport/co-transport -antiport/counter-transport
What specifically does the liver do in response to the insulin signal?
-takes glucose monomers and makes glycogen -(glycogen is the storage form of glucose)
What does a high partition coefficient indicated?
-that a material is very lipid soluble and can therefore more easily cross the cell membrane
What is the internal environment synonymous with?
-the ECF
What is the body's internal environment?
-the ECF -the world that the cells live in
What is the primary challenge encountered with facilitated diffusion?
-the carrier protein can easily become saturated
What does it mean if the membrane is sitting at equilibrium for an ion?
-the chemical driving force is equal to the electrical driving force -net movement of the ion is zero
What are the size of hydration shells related to?
-the diffusion of surface charges across an ion
What is osmotic pressure?
-the driving force of water/the force at which water hits the membrane when diffusing from low solute to high solute
What are the two fluid compartments of the ECF?
-the interstitial fluid, which surrounds all cells except for blood cells -the plasma, which surround all blood cells
What does a partition coefficient indicated?
-the lipid solubility of a given substance
What is osmosis?
-the net diffusion of water down its own concentration gradient/diffusion of water from low solute to high solute
What is the primary variable then that controls the movement of passages through carrier proteins?
-the number of carrier proteins available -as the number of carrier proteins increases, net movement of molecules increases -if the number of carrier proteins were to decrease, the net movement of molecules would decrease as well
What is hydrostatic pressure?
-the pressure exerted by standing, or stationary, fluid on an object--in our case the membrane -note that the greater the amount of fluid, the greater the hydrostatic pressure
What is net flux?
-the rate of diffusion of a substance across a membrane
What are the factors that effect permeability?
-the size of the substance -the partition coefficient -the temperature -membrane thickness
What is convection?
-the transfer of heat energy by air currents -cool air warmed by the body through conduction rises and is replaced by more cool air -creates "convection currents"
What is radiation?
-the transfer of heat energy from a warmer object to a cooler object -in the form of electromagnetic waves or heat waves. -whether the body loses or gains heat by radiation depends on the differences in temperature between the skin surface and the environment.
What is conduction?
-the transfer of heat from a warmer to a cooler object that is in direct contact with the warmer one -heat is transferred through the movement of the thermal energy from molecule to adjacent molecule.
What is responsible for generating and maintaining membrane potential?
-the unequal distribution of ions between the ICF and ECF and their selective movement through the plasma membrane. -the ions primarily responsible for the generation of the resting membrane potential are Na+, K+ and A-.
Does an electrical or chemical gradient exist for an ion if it is at equilibrium potential?
-there still might be an electrical gradient or a chemical gradient but there is no more movement because it is opposed by a chemical gradient or an electrical gradient that is exactly equal to it
What do pumps and facilitated diffusion carriers have in common?
-they both involve a conformational change that is important in the mechanics of how the molecule is transported across the membrane
What is Fick's Law used for?
-to describe the rate of net diffusion of a substance across a membrane
What is their role?
-to provide tensile strength -to allow for cells to be subjected to lots of mechanical distortion without tearing apart
What is the most abundant molecule found in both the ECF and the ICF?
-water
What is osmotic equilibrium?
-when osmotic pressure exactly counterbalances hydrostatic pressure.
Do carrier proteins transport materials with or against their concentration gradient?
-with their concentration gradient
Is the majority of your total body water found in the ICF or the ECF?
-within the ICF
Does the ion exhibit any movement?
-yes it does -it moves into and out of the cell at equal rates
What are they made of?
-zipper-like structures called occludins
Why do substances transported through facilitated diffusion require a carrier protein?
1. Molecules are polar so cannot diffuse readily through the cell membrane 2. Molecules are too large for ion channels
Explain the mechanics of the Na+/K+ pump, an example of prmary active transport
1. Pump has 3 high-affinity sites for Na+ and 2 low-affinity sites for K+ when exposed to the ECF 2. When 3 Na+ from ICF bind to the pump, it splits ATP into ADP plus phosphate; phosphate group binds to pump 3. Phosphorylation causes pump to change conformation so that Na+ binding sites are exposed to the opposite side of membrane and 3 Na+ are released to ECF as affinity of Na+ binding sites greatly decreases 4.Change in shape exposes pump's binding sites for K+ to ECF, increases affinity of sites 5.When 2 K+ from the ECF bind to the pump, it releases phosphate group. Dephosphorylation causes pump to revert to original confirmation. 6. 2 K+ are released to ICF. Affinity of Na+ binding sites greatly increases, returning to step 1.
What occurs during antiport?
1. Solute and Na+ move through the membrane in opposite directions 2. Na+ moving down its concentration gradient 3. Solute moving uphill against its concentration gradient
What occurs during symport?
1. Solute and Na+ move through the membrane in the same direction 2. Na+ moving down its concentration gradient 3. Solute moving uphill against its concentration gradient
What are the components of a feedback loop?
1. deviation in controlled variable (acts as the stimulus) 2. sensor (monitors the magnitude of the controlled variable) 3. integrator/control center (compares the sensor's input with the set point and determines appropriate response) 4. effector (the component of the control system commanded to bring about the appropriate response to oppose a deviation from the set point)
Explain the basic physiology of a fever. What are the role of pyrogens? Macrophages? Prostaglandins? Hypothalamus?
-body detects an infection or inflammation -macrophages release endogenous pyrogen -endogenous pyrogen trigger the release of prostaglandins -prostaglandins increase the hypothalamic set point -increase in set point triggers the initiation of the cold response -initiation of cold response results in increase in heat production, decrease in heath loss -this establishes a new set point
Once it is inside the intestinal/kidney cell, how is glucose transported out of the cell?
-by facilitated diffusion down its concentration gradient across the basolateral membrane
How can rates of transport be increased then?
-by increasing the number of pumps/carrier proteins
Are ion channels unidirectional or bidirectional?
-can be both -monovalent cation channels allow monovalent cations to pass through bidirectionally
What are prostoglandins?
-chemical mediators that act directly on the hypothalamus during fever production -raise set point -release triggered by endogenous pyrogen
What is an antagonist?
-chemical messenger that binds to a receptor that it does not normally work with -shuts down the normal biological response.
What is ΔC?
-concentration gradient -the difference in concentration of a substance between two adjacent areas
What is molarity?
-concentration measured by the number of moles of solute per liter of solvent. Expressed in moles/liter.
What are they made of?
-connexons, which are made up of six protein subunits arranged in a hollow tube-like structure
What is evaporation?
-conversion of a liquid such as sweat into a gaseous vapor -process requires heat, which is absorbed from the skin
What effect does membrane thickness and distance have on net flux/diffusion?
-decreases permeability -decreases the rate of net flux/net diffusion --> take home message is that diffusion takes a long time, especially over long distances!!
What are the two types of simple diffusion?
-diffusion through a lipid bilayer -diffusion through a protein/ion channel
Of all the membrane transport mechanisms, which require membrane proteins?
-diffusion through a protein/ion channel -facilitated diffusion -primary active transport -secondary active transport -->diffusion through the lipid bilayer does not require a membrane protein
Of all the membrane transport mechanisms, which are specific for a particular solute?
-diffusion through a protein/ion channel -facilitated diffusion -primary active transport -secondary active transport -->diffusion through the lipid bilayer is non-specific
What is the difference between diffusion through a protein/ion channel and facilitated diffusion?
-diffusion through a protein/ion channel requires a channel protein; facilitated diffusion requires a carrier protein -protein/ion channels are always open to both the ECF and the ICF, even if closed by a gate; carrier protein has to undergo a conformational change to open to one side or the other -only ions can diffuse through a protein/ion channel; small polar molecules such as glucose and amino acids are transported across the membrane by carrier proteins -diffusion through a protein/ion channel is considerably faster than facilitated diffusion
Of all the membrane transport mechanisms, which transfer solutes from high to low concentration?
-diffusion through lipid bilayer -diffusion through protein/ion channels -facilitated diffusion
What are the three types of PASSIVE transport?
-diffusion through lipid bilayer (simple diffusion) -diffusion through protein/ion channel (simple diffusion) -facilitated diffusion (mediated transport)
What are the three signals that can open a gated channel?
-electrical/voltage signals -chemical/ligand signals -mechanical signals
What is hyperglycemia?
-elevated blood glucose levels, usually associated with diabetes
Where are they found?
-especially abundant in cardiac muscle and smooth muscle
Of all membrane transport mechanisms, which face a limit to the number of molecules that can be transported per unit per time?
-facilitated diffusion -primary active transport -secondary active transport
Describe the cAMP second messenger system
-first messenger arrives, binds with G protein coupled receptor -alpha subunit drops GDP, picks up GTP -alpha subunit slides down the plasma membrane and activates adenylyl cyclase -adenylyl cyclase activates protein kinase A -protein kinase A phosphorylates another protein that produces a cellular response
Where are they found?
-found in tissues that are stretch and subjected to lots of mechanical distortion -including the heart, female uterus, and skin cells
What is a hydration shell?
-group of water molecules that orient themselves around an ion
What is the objective of the body making a fever?
-has a beneficial role in fighting infection
What is a hypertonic solution?
-has a higher concentration of nonpenetrating solutes as the cell -when a cell si placed in the solution, water leaves the cell by osmosis -this causes the cell to shrink or crenate
What is a hypotonic solution?
-has a lower concentration of nonpenetrating solutes as the cell -when a cell is placed in the solution, water enters the cell by osmosis -this causes the cell to swell, and potentially to lyse
What is an isotonic solution?
-has the same concentration of nonpenetrating solutes as the cell -when a cell is placed in the solution, there is no change in cell size
Describe the PIP-2 messenger system
1. first messenger binds with G-protein coupled receptor 2. alpha subunit drops GDP and picks up GTP 3. alpha subunit activates phospholipase C 4. phospholipase C converts PIP2 to DAG and IP3 5a. DAG remains in the plasma membrane and activates protein kinase C. protein kinase C takes ATP and phosphorylates proteins. produces a cellular response 5b. IP3 attaches to receptor in an ion channel that sits in the endoplasmic reticulum. IP3 triggers release of calcium from the ER. Ca binds to calcium-binding proteins in the cytoplasm, creates calcium-calmodulin complex. calcium-calmodulin complex phosphorylates a protein kinase.
What are they made of?
1. plaques, which are dense cytoplasmic thickenings found on the inner surface of each of the two adjacent cells 2. cadherins, strong glycoprotein filaments that extend across the space between the two cells 3. intermediate filaments, which anchor the plaques on the inside of each cell