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