Exam 3

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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* identity → identical DNA bases
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* tested in primates (1x/month injections)