Cellular Physiology Flashcards
What is disease? What two things are difficult to distinguish when the body tries to regulate function?
State of disrupted homeostasis.
The primary cause of disease vs the compensatory state.
What are the two types of control systems?
Controling within the organ (individual parts of it), and controling interrelations between organs throughout entire body.
Explain the example of hemoglobin as a control system.
Oxygen buffering function of hemoglobin: Hemoglobin + O2 (as blood passes through the lungs) and carries the oxygen to the rest of the body. HOWEVER, it dosnt release the oxygen if that part already has enough.
What does a higher than normal CO2 concentration do?
It excites the respiratory center, causing rapid and deep breathing to expel the Co2 from the body. This is a **negative feedback control. **
Negative Feedback Loop with aterial blood pressure example.
Where are the baroreceptors?
When the product of a reaction leads to a decrease in that reaction. Brings a system closer to a target of stability or homeostasis.
Arterial BP gets too HIGH: Stretch receptors/barorecetpors are stimulated, sending an afferent singal to the medulla which inhibits the vasomotor center–>decreased pumping and dilation of blood vessels to lower the blood pressure.
Arterial BP gets too LOW. Stretch receptros relax, allowing the vasocontrtor system to work, sends sympathetic singals –>constricts the blood vessels and makes the heart pump blood faster, raising the blood pressure.
Bifurcation of the carotid arteries in neck/aortic arch
Degree of Effectiveness of a control system
Gain= correction/error
Positive Feedback Loop
Maintains the direction of the stimulus/ causes more of the same. “Vicious cycle”
Positive Feedback Loop examples
-Blood clotting/clotting factors (although this is part of a larger negative feedback system, stopping of the bleeding and maintenance of the normal blood volume)
-Uterine contractions during birth, the power increases with each contraction signaled by the cervix’s stretch
-Action potentials: Na2+ leakage through channels
Feed-Forward Control
Responds to a measured disturbance in a pre-defined/anticipated way. “Prepares” for a change. The movements need to occur rapidly, so there is not enough time for the signals to happen in the moment, back and forth to the brain.
Example:thermostatically controlled room by installing a temperature sensor outside of the room, which would warn the thermostat about a drop in the outside temperature, so that it could start heating before this would affect the inside temperature
Example of Feed-Forward/Adapative control in Muscle Contractions
The muscle moves and the brain has to anazlye it and correct the movement if done ineffectively. Correction of the signal is sent to the muscle before the next movement is done. If further correction is necessary, the brain will repeat this process.
Feed-forward, like postive feedback, is within a negative deep back loop
What is adaptive control also known as?
Delayed negative feedback.
In G-Protein Coupled Receptors, when is the GDP inactive?
When the trimetric G protein is bound to GDP.
What happens when a hormone attaches to a receptor in the G-protein coupled recetor?
G protein is activated by the exchange of GDP for GTP.
What subunit of the GPCR does the transfer from GDP to GTP? What happens after?
The α subunit. The α subunit and the βγ subunits dissociate from one another.
What does the GTP bound α subunit do after the dissociation?
Activates the membrane effector protein adenylyl cyclase to catalyze conversion of ATP to cAMP.
There are Different subtypes of the alpha G protein subunit. Each have a different target protein. (You need to know 4.) First, **Gas vs Gai **
G-alphaS (Gas)= Stimulatory/Activation of Adenylyl cyclase, increasing cAMP, activates pKa–> phosphoylated proteins–>Cell Growth/Motility
G-alphaI (Gai)=Inhibitory/ Inactivation of Adenylyl Cyclase, decreases cAMP–> Cell Motiliy
G-alpha q (Gaq)
Causes PIP 2 to be cleaved by PLC to make IP3 and DAG . IP3 stimulates calcium release from the SR. DAG actives PKC.
PIP2:(Phosphatidylinositol Biphosphate)
PLC:(phospholipase C)
IP3:(Inositol trisphosphate)
DAG:(Diacylglycerol)
PKC: PKC (Protein Kinase C).
Ca2+= smooth muscle contraction
G-alpha T (Gat)
Common where?
G-protein acting via a Phosphodiesterase (PDE)–>reduction in cGMP–>GMP.
cGMP dependant channels close.
Photoreceptor Cells
What is intracellular fluids made of?
High K+, Higher PO₄³⁻ (phosphates) and proteins than extracellular.
Low Na2+ and Cl-.
What is extracellular fluids made of?
High Na2+ and Cl-.
Small amount of K+.
Active Transport
Requires input of energy because it’s against energy gradient, usually requires combination with carrier protien.
What is simple diffusion dependent on?
Amount of substance available, velocity of kinetic motion, number/sizes of openings in membrane.
Lipid Soluble Substances
O2, N2,CO2,Alcohol
These can diffuse directly through a lipid bilayer
Facilitated Diffusion
Requires interaction of a carrier protein that aids passage of the molecules or ions through the membrane by binding chemically with them and shuttling them through the membrane.
Ion Channel Structure + 2 examples
Tetrameric structure: consists of four identical protein subunits surrounding a central pore with pore loops that form a narrow selectivity filter lined with carbonyl oxygens
K+ Ion Channel: K comes in with bound water and gets “dehydrated” by the carbonyl oxygens, allowing its passage. Na+ are smaller, so these carbonyl oxygens are too far apart to interact with them, leaving them outside of the cell.
Na+ Ion Channel: Inner surface of channel=negatively charged amino acids which can pull small dehydrated sodium ions into these channels.
There is alot more K in the cell than Na.
Two types of gated channels
1.Voltage
2.Chemical
Voltage Gated
Conformation of gate changes due to a change in the electrical potential across the cell membrane.
Usually its more positive IN the cell, more negative OUT.
Example: Na/K Pump. 3 Na out, 2 K in to fix equilibrium of too much Na entering cell.
NA/K pump Graph
Just take a look.
Chemical Gated Channel
Binding of a ligand–>conformational change
Example: Acetylcholine Channel
Channels conduct current in an all-or-nothing fashion./ Average Current Flow
At specific voltage potentials, a channel may either be in the open or closed state.
At in b/t the max and min voltages, gates tend to snap open and closed intermittently= average current flow.
GLUT4
Glucose transporter sensitive to changes in insulin level. A **facilitated **diffuser.
Name two things that use facilitated diffusion.
Glucose and Amino Acids
What is unique about facilitated diffusion’s rate?
Rate of diffusion approaches a Vmax and it levels off. The rate at which molecules can be transported by this mechanism can never be greater than the rate at which the carrier protein molecule can undergo change back and forth between its two states.
(Simple diffusion is linearly proportionate with concentration of diffusing subtance).
Osmosis
Water’s net movement; Water moves towards the higher concentration of solute.
Osmotic Pressure
Amount of pressure required to stop osmosis.
# of particles (molar concentration) per unit volume of fluid.
Bigger partiples=slower velocity.
Osmotic pressure calculation
Osmolarity vs Osmolality
Osmolarity: osmoles of solute particles /liter of solution
* more practical in physiology. *Volume *mol/L *depends on temp/pressure
Osmolality: osmoles solute particles/ solvent aka kg of water
*mass *osmol/L *dosnt depend on temp/pressure
Osmole: used to express the concentration of solution in terms of numbers of particles
1 g of molecular weight NaCl dissociates into 2 ions, so its 2 osmoles.
Glucose can’t dissociate so its 1 osmole.
What is the normal osmolality of intracellular and extracellular fluids?
300 milliosomoles per kg of water
How much pressure will 1 osmole per liter create?
19,300 mmg osmotic pressure
(although may be lower).
Calculation for the amount of energy required to move against concentration gradient?
logarithm of the degree of substance concentration
100-fold concentration requires **twice **as much energy as 10-fold concentration.
Primary vs Secondary active transport?
Primary: energy needed is derived DIRECTLY from the breakdown of ATP or other high-energy phosphate compound.
Secondary or “Co-transport/Counter transport”: Energy is derived secondarily from energy that’s been *stored *in the form of ionic concentration differences across a cell membrane created originally by primary active transport.
What does the sodium potassium pump maintain?
The negative electrical voltage across the membrane (3 Na out, 2 K in)
What enzyme is associated with the Na/K pump?
adenosine triphosphatase (ATPase)
In order to pump 3 Nas out and 2 Ks in, what happens to ATP?
It turns into ADP + Pi via the cleavage of the ATPase
What if we need ATP?
3 Na in, 2 K out. Reverse it.
What is the Na/K pump protective against?
Cell volume swelling
(due to the large amount of negatively charged proteins and other organic compounds that can’t escape the cell, these compounds that attract positive ions will cause osmosis into the cell)
What kind of transporter is the Calcium Pump? Function?
Primary active transporter.
Calcium Pump:Maintains a low concentration of Calcium ions in the cell. One pump puts Ca out of the cell, another into an organelle like the sacroplasmic reticulum (SR).
What kind of transporter is the hydrogen Pump? Function?
Transports H+ at cortical collecting ducts in kidneys for excretion in urine to eliminate excess.
What fact provides energy for the Sodium-Glucose Co-Transport?
Sodium ions are high on the outside and low on the inside. Once Na+ and Glucose both attach, they are co-transported into the cell.
Where is the sodium-glucose co- transport important?
Intestinal tract and Renal Tubules in Kidneys
Secondary active
Example of a secondary active counter transporter?
Sodium-Calcium/Hydrogen Counter-Transpor.
Transport is occurring in opposite directions.
Energy is again given from the Na+ moving in, moving Ca2+ or H+ out.
