BIO 306- ch 12
how to make a cell membrane from fatty acids?
1. an anchor/platform is needed to hold the fatty acids. three-carbon compound glycerol is used to attach the fatty acids 2. addition of a polar or hydrophilic molecule
RBS life span
120 days
Cardiolipin (diphosphatidylglycerol)
A double phospholipid linked by glycerol. it has a net charge of -2 and an inverted cone shape
Glycolipids
Membrane carbohydrates that are covalently bonded to lipids. the covalent bond is a glyosidic bond
Are membranes symmetrical?
No, they are asymmetrical
Where are glycolipids found?
On the surface of Eukaryotic all plasma membranes found in the monolayer facing away from the cytosol Sugar groups attached to proteins
sialic acid
Responsible for the force that repels RBCs from each other.
unsaturated fatty acid
a fatty acid whose hydrocarbon chain contains one or more double bonds (monounsaturated or polyunsaturated)
monoglyceride
a glycerol molecule with one fatty acid attached
What is sphingomyelin?
a phospholipid found in membranes that are not derived from glycerol. The headgroup is phosphocholine.
what are phospholipids composed of?
a platform (glycerol or sphingosine), fatty acids, a phosphate, and an alcohol.
cholesterol is
a steroid that is modified on one end of the attachment of a fatty acid chain and at the other end by a hydroxyl group
what does a sphingosine consist of?
amino alcohol that contains a long , unsaturated hydrocarbon chain
what is the ratio of lipids and proteins in membranes
between 1:4 to 4:1
what is the thickness of membranes?
between 6 nM (60 A) and 10 nM (100 A)
how are fatty acids linked to glycerol?
by ester bonds formed by the removal of water. forms a C=O bond
How are the four blood types determined?
by the oligosaccharide which attaches to a specific glycolipid on the surface of the RBC, which acts as an antigen
what is the job of glycolipids?
cell-cell communication ad immune response
Macrophages
cells specialized in the detection and removal of damaged, dying cells. they hunt for PS exposure on outer layer of the membrane.
what could be the head group of a phospholipid?
choline, serine, inositol, etc...
fatty acids
consist of hydrogen-bearing carbons that have a methyl group at once end and a carboxylic acid at the other end. they may be saturated or unsaturated.
cerebroside
contains a single sugar residue either glucose or galactose.
Phosphoglycerides
derived from phosphatidate by the formation of an ester bond between the phosphate and alcohol.
what causes the asymmetry in plasma membrane?
different distribution of lipids across the membrane
How does cholesterol affect fatty acid chains?
disrupts the tight packing
do fatty acids contain an odd or even number of carbon atoms?
even, with 16 and 18 being the most common
Phosphatidylserine (PS)
found on the inner layer of membrane, flips to outside during apoptosis. serves as the "eat me" signal!
Triglycerides
glycerol and three fatty acids attached
What does a fat molecule consist of?
glycerol backbone and three fatty acid chains
What are lipids made of?
glycerol backbone and two fatty acid chains
what do phosphatidates consist of?
glycerol backbone, fatty acids on C1 and C2, and a phosphate on C3.
diglyceride
glycerol with two fatty acids attached
saturated fatty acids
have the maximum number of hydrogen atoms possible and no double bonds
lipid rafts
highly dynamic complexes formed between cholesterol and specific lipids. they may concentrate in defines regions of the membrane
trans unsaturated fatty acids
hydrogen atoms are bonded to carbon atoms on opposite sides of a double bond. these are man-made and linked to cardiovascular diseases
cis unsaturated fatty acid
hydrogen atoms are bonded to carbon atoms on the SAME SIDE of a double bond in a fatty acid carbon chain which causes a kink in the chain
are triglycerides hydrophilic or hydrophobic? why?
hydrophobic because fatty acids are hydrocarbons which are nonpolar and not attracted to water
How does cholesterol affect membrane fluidity?
it acts as a bidirectional regulator. -at high temps, it stabilizes membrane and raises MP -at low temps, it intercalates between phospholipids and prevents them from clustering and stiffening
what does the melting temperature depend on?
length of fatty acids and degree of cis unsaturation
why are membranes non-covalently assembled?
lipids cannot form covalent bonds
What are fatty acids?
long chains of carbon and hydrogen- hydrocarbons
where is cardiolipin often found
membranes of bacteria, archaea, and the inner membranes of mitochondria
what are the three common types of membrane lipids
phospholipids, glycolipids, cholesterol
what does cholesterol form complexes with
sphingolipids, glycolipids, and some GPI-anchored proteins
how are fatty acid carbons numbered?
start at the carboxyl terminal carbon atom. they can also be numbered from the methyl carbon atom which is called the omega (w) carbon
Glycosphingolipids
subgroup of glycolipids based on sphingolipids. they are mostly found on nervous tissue and are responsible for cell signaling.
What are glycolipids?
sugar containing lipids derived from sphingosine
melting temperature
temperature at which a membrane transitions from being highly ordered to very fluid
where are the sugar attached to in glycolipids?
the head/ R group. this is because sugars are hydrophilic
how does cholesterol get imbedded into the membrane
the hydroxyl group interacts with the phospholipid head group. since it is very hydrophobic, it is packed in with the fatty acid chains
what are choloestrols?
they are constructed from a steroid nucleus, they modulate membrane fluidity
why do pathogens use lipid rafts
to enter the cell