Glossary of Cell Membrane and Membrane Transport

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What are the 3 functions of the Cell membrane?
1. To selectively impede molecules from passing in/out of the cell.

2. To detect chemical signals from cells

3. To anchor the cell to other cells and the extracellular matrix.
What is contained in the lipid bilayer?
-double layer of lipids
what kinds of lipids are in the cell membrane?
-phospholipids mostly
what does amphipathic refer to?
the charged/uncharged regions of the phospholipids
what are intrinsic and extrinsic proteins?
intrinsic - protein spans the membrane

extrinsic - protein is on one side or the other of the membrane, or partway through.
what 4 things are membranes permeable to?
-carbon dioxide
what things are impermeable to membranes without protein carriers?
what is diffusion?
net movement of molecules down their gradient as a result of random thermal motion
what is brownian motion?
continuous random thermal motion
what is the driving force for diffusion?
concentration gradient
what is Fick's law?
J = PA(C1-C2)

Flux = permeability x area x conc. diff
what is included in the permeability constant?
-size of molecule
-solubility of molecule in the membrane.
-membrane thickness
How is flux decreased in
in emph: smoking decreases SA of alveoli, net diff decreases. further, CO2 perm constant is higher than O2, so its more difficult for O2 to diffuse into blood.

Pneumo: o2 has to cross 2 cell membranes AND a layer of fluid; increased thickness decreases O2 diffusion
what's the most typical type of secondary active transport?
how is the higher intracellular protein concentration established?
by coupling movement of negaitvely charged proteins with sodium secondary act. trans.
How does glucose in the gut get into circulation?
via a Na+/glucose cotransporter
what is vant hoff's law about/
osmotic pressure

pi = nRTC
if a patient in an emergency needs fluid volume replacement, what type of IV would you give, and why?
normal saline - isotonic to the intravascular fluid.

Patients in emergent situations will lose fluid from the intravascular space.
giving normal saline keeps the ECF isotonic to the IV space, prevent loss.
To replace normal fluid losses from a person in the hospital, what type of IV do you give, and why?
a hyposmotic IV fluid - 1/2 NS.

this hypotonic fluid has a lower solute conc than cells, and a higher H2O conc. so water will flow into cells and replace fluid lost.
what is ascites?
abnormal buildup of fluid in the abdomen, due to an inability to pass water from the interstitial fluid to the blood capillaries.
what can ascites be caused by?
-Cirrhosis of the liver
-Increased permeability of peritoneal capillaries
-decreased colloid osmotic pressure
how does cirrhosis cause ascites?
the liver causes increased pressure on the portal vein, so fluid leaks out and builds up in the abdomne.
how does decreased colloid osmotic pressure cause ascites?
Albumin proteins in the vascular space cause oncotic pressure. when their production is decreased, lower oncotic pressure decreases pull of water from interstitial space to vascular
what is pitting edema?
accumulation of extra isf in tissues
2 causes of pitting edema
1. fluid overload
2. heart failure
what in plain language is central pontine myelinolysis?
breakdown in the myelin of the white matter in the mid pons
what happens in acute hyponatremia?
trauma to brain makes the body fluid hypotonic and hyposmotic to the brain.

brain cells SWELL

because of brain injury, Na regulation is inhibited, Na is lost, and cerebral edema occurs.
what is chronic hyponatremia?
1. Cerebral Edema has resulted from Na regulation problems and increased H2O conc. of extra cell fluid.
2. ICfluid increases, increasing Hydrostatic pressure. Not enough room in brain, so fluid goes to CSF.
3. As time goes by, brain cells adapt by losing solutes but then are HYPOSMOTIC to the ECF, so they swell and fluid leaves hte brain too
Is adaptation in chronic hyponatremia good?
well, yes, because it makes the cerebral edema correct itself when fluid leaves the brain.

But when you try to fix it later, it's harder.
How is chronic hyponatremia that has self-regulated itself treated?
by giving very careful amounts of solute.
what happens to a patient w/ chronic hyponatremia if you infuse too much solute?
the plasma in their blood will be hypertonic/hyperosmotic to the cells, because the cells had adapted to being hypotonic to the ECF in order to decrease edema. now the cells will shrink and cause osmotic demyelination

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