DLA #4: Membrane Structure and Transport Flashcards
Lipid Rafts are:
Dynamic assemblies of lipids and proteins
Lipid Rafts play a role in:
Signal transduction and virus infections
Planar lipid rafts are:
- formed by cholesterol, glycolipids and sphingomyelin
- they are short lived
Caveola are
- Also lipid rafts
- Form invagination of the pm
- Long lived -Stabilized by caveolins
Explain what happens to fatty acid tails when exposed to a cold environment. What homeostatic response occurs
- Fatty acid tails stiffen up
- Cholesterol will intercalate itself b/w phospholipids and increase membrane fluidity.
Explain what happens to fatty acid tails when exposed to a hot environment. What homeostatic response occurs
- Fatty acid tails begin to loosen up and become more fluid.
- Cholesterol will use its steroid ring system to decrease fluidity.
What are lipoproteins
Proteins that transport nonpolar lipids through the blood/lymph.
Describe the characteristic traits of a lipoprotein
- Hydrophobic core
- Hydrophillic shell.
- Transfers TAG and cholesteryl ester.
How do membranes inside the cell regulate fluidity
Membranes inside the cell DO NOT have cholesterol.
Therefore, regulation of fluidity is based upon the fatty acid composition of that membrane.
Passive transport through a membrane includes:
1) Simple Diffusion (Moves down gradient through pm)
2) Faciliated DIffusion (Moves down gradient through a channel/transporter)
Cell w/in out body take in Glucose via:
Glucose Transporters aka GLUT
(multiple in body for select area)
GLUT is a good example of what type of diffusion
Faciliated.
List out the high affinity GLUT transporters:
GLUT-1, GLUT-3, GLUT-4
List out the low affinity transporters
-GLUT-2 and GLUT-5
During normal or lower blood glucose levels in general circulation we expect
-GLUT-1 and GLUT-3 to be working at a constant rate
GLUT-1 is found in
RBC’s, BBB and Kidneys
GLUT-3 is found in:
Neurons and the brain
What is hereditary GLUT-1 deficiency
- form of metabolic encephalopathy
- as infants develop growth of brain and skull is slowed
- Symptoms include:
- Epileptic-Seizures
- Ataxia
- Delayed psychomotor development
- Movement disorder
- Speech Disorder
***Symptoms become more prevalent w/ age
What is a way in which we can evaluate if someone has GLUT-1 Deficiency
Taking a sample of the RBC’s
What is really unique about GLUT-2:
Its a TWO way transporter.
Where are GLUT-2 transporters usually found:
1) Intestinal Mucousal cells => Glucose gets transferred via GLUT-2 into the portal vein
2) Hepatocytes => Liver is the glucose banks. It both stores glucose during levels of high glucose in circulation and gives off stored glucose during fasting. It can even make new glucose during serious starvation. Therefor we expect a two way GLUT portal to be available.
3) Pancreatic B-cells => Beta cells have GLUT - 2 in order to test the amount of glucose in general circulation and determine if release of insulin is necessary.
4) Renal tubular cells. => In the renal syste, both reasorption and secretion of glucose occurs. Therefore, a two way portal is needed. Not only that, kidneys do very little gluconeogensis, therefore we expect the kidney’s to also have GLUT-2.
Explain a little more about why GLUT-2 is used to measure glucose levels in regards to B-cell functioning:
GLUT-2 is used by Beta cells of the pancreas to “taste” glucose levels in the general circulation.
These GLUT-2 are so important b/c the pancreas needs to know when it’s the right time to release insulin for uptake of glucose into our adipose and skeletal tissue cells.
****Document attached goes even more in depth
Where is GLUT-4 found and what is its function
- Adipose
- Skeletal
- Heart
What signals can cause a cell to release GLUT-4
- High levels of Glucose in general circulation
- ALSO, during vigorous excercise
Where is GLUT-5 and function
- GLUT-5 is the “fructose transporter”
- Transports fructose from the lumen of the intestinal mucousa through hepatic portal.
- GLUT-5 is also found in seminal vesicles
Fructose supplies energy to the sperm.
Define Primary Active transport
Transport that requires ATP in order to move a substance against its concentration gradient.
Give a poster child example of primary active transport
Na+/K+ - Atpase (sodium-potassium pump) found on pm
How does the sodium-potassium work.
Pumping of 3 Na+ out of cell and 2 K+ into cell.
Keep in mind this requires ATP and we are moving against the concentration gradient.
Define/explain secondary active transport
A transporter that is dependent upon the concentration gradient generated by a primary active transporter.
Typically we see this coupled to a sodium-potassium pump
What is SGLT-1 and what does it do
SGLT-1 is a Secondary active transporter (symporter).
SGLT-1 bring in either Na+ - Glucose or Na+ - Galactose into the intestinal mucousal cell.
What is SGLT-2 and what does it do
SGLT-2 is a Secondary Active Transport (symporter).
Also Is dependent upon sodium-potassium Atpase
SGLT-2 is found in the kidney and its job is to transport Na+ -Glucose for reuptake
What type of inhibitors are used in the treatmen of diabetes and why.
SGLT-2 inhibitors
Rather than re-uptaking glucose back into the blood stream and jeapordize a diabetics blood sugar, SGLT-2 inhibitors can allow the patient to excrete out glucose instead.
What are ATP Binding Cassette (ABC) transporters
- They are a form of active transport
- Pumping of molecules from the cytosol to the extracellular space occur
- Requires ATP
- Solutes transported tend to be lipid compounds:
- Bile
- Cholesterol
- Bilirubin
Describe CFTR:
- Voltage-gated ion channels that faciliates the movement of chloride.
- Considered a “special” type of ABC transporter
- Chloride flow with gradient like a channel rather than a pump
- Mainly present in epithelial cells on the luminal membrane
- Pancreatic ducts
- Airway ducts
-
Reproductive ducts
- Mnemonic: “CFTR on PAR”
Describe Cystic Fibrosis
- Disease with which there is a deficiency in CFTR.
- Known in infants as “salty baby syndrome”
- Patient will have:
- Poor Growth
- Low weight
- Lung infection
- Pancreatis
- Male infertitility
- Steatorrhea (oily-foul stool)
What unique property does CFTR ONLY have in the epithelial cells of the skin.
- The CFTR can re-open and bring back Cl- from the the ecs back into the cytosol.
- Done in order to salvage sweat for future cooling
