Concentration Gradient
the process of particles moving through a solution from an area with a higher # of particles to an area of a lower # of particles
Electrochemical Gradient
a gradient of electrochemical potential, usually for an ion that can move across a membrane.
What determines membrane potential?
the differences in ion concentration of the intracellular and extracellular fluids (potassium-sodium pump)
How is ion channel activity recorded?
patch clamp technique
Patch Clamp Technique
Technique used to record electrical currents through individual ion channels in cells.
Involves placing a glass pipette on the cell membrane and applying suction to form a tight seal
Allows for precise measurement of ion flow and can be used to study the effects of drugs on ion channels
Cell Attached (Patch Type)
almost never used
Whole Cell Patch Clamping
useful for recording ion channels in a cell
Inside Out Patch
inside of cell is out in both
Outside-Outside Patch
this is usually the valuable patch for recording a single ion channel after drug
Design an experiment to see if drug XYZ can increase voltage-gated calcium ion channel
starting mem. potential of ~ -60mV → then record current through all of the channcels
Find out if your drug affects a single Ca++ ion channel
drug is really lipophilic and gets inside the cell well → inside out patch
How is resting membrane potential maintained?
the sodium-potassium pump
What ions are prevalent on the inside of the cell
K+
What ions are prevalent on the outside of the cell
Cl-, Na+, Ca++
Sodium-Potassium ATPase
helps maintain equilibrium and membrane potential in cells
keep K+ high inside, this is what cells need at rest
why & what
maintain resting membrane potential
3 Na+ in → out
ATP hydrolysis → phosphorylation of pump
2 K+ out → in
What’s the best patch to use if you want to record currents from all of the ion channels in cell?
whole cell patch clamping
Voltage-Gated Ion Channels
takes an electrical change in the membrane potential to open
Ligand-Gated (extra or intracellular) Ion Channels
molecule acts as a key to open the door
Mechanically Gated Ion Channels
physically pull door open
What does the Nernst equation help a mathematically-minded electrophysiologist figure out before ever having to patch clamp a cell?
helps scientists figure out what the membrane potential of any membrane is
Uniporters Transporters
transport a single species of substrate across a cell membrane
Symporters Transporters
proteins that simultaneously transport two molecules across a membrane in the same direction
Antiporters Transporters
transport of two or more different molecules or ions across a phospholipid membrane
how many NADH are produced by glycolysis?
2 NADH
how many H+ are produced by glycolysis?
2 H+
how many CO2 are produced by glycolysis?
0 CO2
how many net ATP are produced by glycolysis?
2 net ATP
how many GTP are produced by glycolysis?
0 GTP
how many FADH2 are produced by glycolysis?
0 FADH2
how many pyruvates are produced by glycolysis?
2 pyruvates
how many NADH are produced between glycolysis & CAC?
2 NADH
how many H+ are produced between glycolysis & CAC?
2 H+
how many CO2 are produced between glycolysis & CAC?
2 CO2
how many net ATP are produced between glycolysis & CAC?
0 net ATP
how many GTP are produced between glycolysis & CAC?
0 GTP
how many FADH2 are produced between glycolysis & CAC?
0 FADH2
how many acetyl CoA are produced between glycolysis & CAC?
2 acetyle CoA
how many NADH are produced in CAC?
6 NADH
how many H+ are produced in CAC?
6 H+
how many CO2 are produced in CAC?
4 CO2
how many net ATP are produced in CAC?
0 net ATP
how many GTP are produced in CAC?
2 GTP
how many FAHD2 are produced in CAC?
2 FADH2
how many HS-CoA are produced in CAC?
2 HS-CoA
What was wrong with Patrick?
He had a single-base pair mutation that resulted in a lack of pyruvate dehydrogenase
Without this enzyme, his cells couldn't convert pyruvate into acetyl CoA, instead making more lactase, leading to lactic acid buildup
Why did this problem mean that he did not make ATP efficiently?
without pyruvate dehydrogenase, his cells couldn't continue with aerobic metabolism
without the enzyme, acetyl CoA couldn't be made, meaning the step between glycolysis and CAC didn't happen, and neither did the CAC and oxidative phosphorylation, meaning no ATP production
Why was he in pain?
He was in pain due to the lactic acid buildup in his cells (lactate acidosis)
The acidosis lead to hyperventilation, muscle pain & weakness, and abdominal pain & nausea
What treatments might have helped Patrick and why?
a high-fat, low-carbohydrate diet might have helped Patrick because fats skip through the portion of glycolysis that Patrick's cells couldn't undergo (they jumped directly to acetyl CoA, instead of having to go through glycolysis and be turned from pyruvate to acetyl CoA).
use dichloroacetate (DCA), which blocks the enzyme that converts PDH from active to inactive forms.
This says that Patrick had some of the enzyme and doctors would have kept what he had active - the "make the most of what you've got" strategy
Muscle Contractions Step 1
action potential zips down motor neuron
Muscle Contractions Step 2
at the terminal end of the axon, voltage gate Ca++ ion channels open
Muscle Contractions Step 3
the influx of calcium makes vesicles dock & dump out neurotransmitter → acetylcholine (Ach)
Muscle Contractions Step 4
Ach is received by receptors on muscle cell membrane AchR
Muscle Contractions Step 5
Whoosh Na+ rushes into the muscle cell through the nAchR channels
Muscle Contractions Step 6
zip action potential zooms down the muscle cell membrane down into t-tubules
Muscle Contractions Step 7
this makes ryanodine receptors on the sarcoplasmicreticulum (SR) organelle open
Muscle Contractions Step 8
Ca++ comes rushong out of the SR
Muscle Contractions Step 9
Ca++ binds to troponin
Muscle Contractions Step 10
making tropomyosin move out of the way of myosin/actin cross bridging sites
Muscle Contractions Step 11
ATP hydrolysis on myosin heads allows cross bridging & power-stroke for sliding filament contractions
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95% identity b/w the two rats
identity → identical DNA bases
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interleukin-8
tested in primates (1x/month injections)