Polvi lec #2 Flashcards
Can you visualize cell membranes using a light microscope? why or why not?
No, because the cell membrane is too small (5-10nm wide).
When were plasma membranes first observed? Using what?
They were first observed in the 1950s using an electron microscope
What are membranes composed of? How was this discovered?
lipids, Overton found this by dipping the plant root hairs into solution and found that they more readily took up nonpolar solutes
Membranes have how many layers? How was this found?
Membranes have two layers (bilayer) and this was found by Gorter and Grendel in 1925 which showed that lipids from a red blood cell could cover the cell twice.
Why did Gorter and Grendel use a red blood cell in their experiment?
Because they didn’t have any interior membranes, only one
What two things do membranes have?
lipids and proteins
What this the membrane bilayer composed of?
Phospholipids
Where do polar phosphatesbl face?
the membrane surface (where aqueous stuff is)
Where do nonpolar fatty acid tails face?
Into the interior of the membrane (so they don’t interact w polar water)
What does the lipid bilayer prevent?
Prevents random movement of substances in and out of the cell
What is the structure of fatty acids?
They are long unbranched hydrocarbon chains, have typically 14-20 carbons, can saturated or unsaturated
What are saturated fatty acids?
Lack double bonds
What are unsaturated fatty acids?
Has one or more double bonds
introduces a bending in the fatty acid
What kind of double bonds do naturally occurring fatty acids have?
cis
What do unsaturated fatty acids do to phosolipids packing?
The bend stops phospholipids from packing tightly
What are membrane lipids?
are lipids that make up the membrane
What are the three kinds of membrane lipids?
Phosphoglycerides
Sphingolipids
Cholesterol
Are all phosphoglycerides phospholipids?
yes
Are all sphingolipids phospholipids?
no only some
Most membrane phospholipids are what?
phosphoglycerides
What are the components of phosphoglycerides?
glycerol back bone, two fatty acid chains, a phosphate group, and an additonal group
What types of fatty acid chains do phosphoglycerides commonly have?
One unsaturated and one saturated fatty acid chain
What are the 5 different types of phosphoglycerides? What are they differentiated by?
Phosphatic acid
Phosphatidylcholine
Phosphatidylserine
Phosphatidyl-ethanolamine
Phosphatidylinositol
They are differentiated by their head groups
What the overall charge of phosphatidic acid?
Additional group is H, so negatively charged
What is the overall charge of phosphatidylcholine?
Has a choline additional group, is neutral
What is the overall charge of phosphatidylserine?
Has a serine additional group, is negatively charged
What is the overall charge of phosphatidyl-ethanolamine?
Has a ethanolamine additional group, is neutral
What is the overall charge of Phosphatidylinositol?
Has an inositol additional group, is negatively charged
What is a polar head group?
P group plus additional group
Are sphingolipids less or more abundant in membranes?
less
What is the structure of sphingolipids?
Built on a sphingosine spine, so has a polar head group and hydrophobic tail, the sphingosine is attached to a fatty acid, the polar head group can also attach to additional groups
What is the most basic example of a sphingolipid?
ceramide, made of just sphingosine and fatty acid
Sphingolipids are hydrophobic or hydrophillic?
Neither, they are amphipathic
What is sphingomyelin?
is a sphingolipid with a phosphorylcholine group attached, this makes it also a phospholipid
What has more longer and saturated fatty acid tails, sphingolipids or phosphoglycerides?
sphingolipids
What are the roles of sphingolipids?
signal transduction, membrane structure, and sensing
If the additional group to a sphingolipid is a carbohydrate. what is the molecule called?
A glycosphingolipid (in short a glycolipid)
What two types of glycolipids are there?
cerebrosides and gangliosides
What is a cerebroside?
a glycolipid where the carbohydrate additional group is a simple sugar (for ex galactose)
What is a ganglioside?
a glycolipid where the carbohydrate addition is a clusters of sugars that includes sialic acid
Membranes in the nervous system have a lot of what?
glycosphingolipids
What can alterations in glycolipid abundance result in?
neurological diseases
What is tay sachs disease? How does it connect to the neurological diseases we see when glycolipid abundance gets altered?
Is a deficiency of an enzyme that normally breaks down GM2 ganglioside, this causes excess GM2 buildup and impairs the function of nerve cells
Is cholesterol flexible? Why or why not?
No, because it has large carbon chains
How much of the plasma membrane lipid sin animal cells does cholesterol make?
50%
What is cholesterols structure?
Has a polar head group, and big carbon chains
Where is cholesterol oriented in the membrane?
oriented with small hydrophilic groups which face the membranes surface, rest of it is the fatty acid tails of phospholipids
What do cholesterols do the movement of fatty acid tails in phosphlipids?
slow it down cause it’s big and bulky
Are the lipids found on the two layers of membrane the same?
No, ratios of exoplasmic (facing outside) and cytosolic (facing inside) vary of each lipid
Which lipids are more exoplasmic?
sphingomyelin, phosphatidylcholine
Which lipids are more cytosolic?
phosphatidylserine
phosphatidylethanolamine
phosphatidylinositol
What lipids are equals parts cytosolic and exoplasmic?
cholesterol
What does membrane lipid asymmetry affect? give examples?
Asymmetry affects membrane permeability, surface charge, membrane shape, and stability
Phosphatidylethanolamine- promotes curvature of membrane
phosphatidylserine- has a negative charge which interacts with transmembrane proteins
Phosphatidylinositol- has roles in signal transduction
10% of membrane carbs are covalently linked to what?
lipids
50% of membrane carbs of covalently linked to what?
proteins
All membrane carbohydrates face what in the membrane?
the extracellular space, only outerleaflet has them
Do carbohydrates vary in diff cell types and tissues?
yes
What role do carbohydrates play, given an example?
play important roles as receptors, sorting membrane proteins, and cell recognition, theyre the ones that recognize blood type antigens
What can lipid composition determine?
the state of the membrane, it can help with protein interactions, and has role sin signal transduction
What is myeline sheath composed of?
multiple layers of plasma membrane with very little protein
