Cell Biochem: Chapter 8: Lipids and Membranes

intrinsic proteins (integral proteins)

Proteins of the cell-surface membrane that completely span the phospholipid bilayer from one side to the other.

extrinsic proteins (peripheral)

Proteins that are weakly bound to membranes via intermolecular forces of attraction

How does a higher temperature affect the fludity of a biological membrane?

at higher temperatures the fluidity is decreased

triacylglycerol definition

fats and oils found in animals or plants - the acyl group (R-CO- groups) of 3 fatty acids are esterified to the three hydroxyl groups of glycerol

saturated fatty acid definition

fatty acid with no double bonds and with tails containing many hydrogens

unsaturated fatty acid definition

fatty acids with double bonds

amphipathic definition

having both a hydrophilic region and a hydrophobic region

Are lipids hydrophobic or hydrophilic?

hydrophobic

Describe the fluid mosaic model of membrane structure.

integral membrane proteins (blue) float in a sea of lipids and can move laterally but cannot undergo transverse movement (flip-flop). The gold structures are the carbohydrate chains of glycolipids and glycoproteins

beta-barrel

interior is polar and allows water and small polar molecules to pass through the membrane

What type of lipid is cholesterol?

isoprenoid

lipid defintion

predominantly hydrophobic molecules that can be esterified but cannot form polymers that make up the physical structure of the membrane

glycoprotein definition

proteins which contain oligosaccharide chains covalently attached to amino acid side-chains.

Do saturated or unsaturated fatty acids increase fluidity of the membrane?

saturated fatty acids have no double bonds in their hydrocarbon chain and the maximum amount of hydrogens so saturated fatty acids make the membrane less fluid and increase the strength of the membrane

is cholesterol found in biological membranes?

yes, they are found in biological membranes

What are fatty acids made up of?

- carboxylic acid (head) - hydrocarbon chain (tail)

structure of glycerophospholipids

Contains glycerol as a backbone - Esterified to two fatty acids - Third position of a phosphate which in turn in linked to a nitrogen-containing base (polar/hydrophilic head group)

structure of Triacyclglycerol

Fatty acids linked to one glycerol

lipid bilayer definition

Made of two layers of lipid molecules and form a barrier around all cells that are impermeable to ions and other solutes

sphingomyelin definition

a long chain sphingoid base backbone (predominantly sphingosine), a fatty acid, and a phosphocholine head group.

Glycerophospholipid defintion

a major lipid that contains a glycerol backbone with fatty acyl groups esterified at positions 1 and 2 and a phosphate derivative, called a head group, esterified at position 3

Fatty acids: a. are long chain hydrocarbons with a polar head group and nonpolar tail b. are not usually found as part of triacylglycerols c. are abundant in biological membranes d. are always esterified e. all of the above

a. are long chain hydrocarbons with a polar head group and nonpolar tail

In biological membranes, a. transverse diffusion of lipids is thermodynamically unfavorable, because a solvated polar head would have to pass through a hydrophobic interior b. lateral diffusion of lipids occurs very infrequently c. the upper leaflet and lower leaflet are always identical d. sphingolipids are not often found e. none of the above

a. transverse diffusion of lipids is thermodynamically unfavorable, because a solvated polar head would have to pass through a hydrophobic interior

does cholesterol have amphiphilic or amphipathic character?

amphiphilic character

which of the following lipids is commonly found in cell membranes? a. C16 fatty acids b. phosphatidylcholine c. retinol d. ubiquinone e. triacylglycerol

b. phosphatidylcholine

which of the following can form a lipid bilayer? a. fatty acids b. triacylglycerols c. glycerophospholipids d. isoprenoids e. all of the above

c. glycerophospholipids

What is the function of cholesterol in biological membranes

cholesterol maintains the fluidity of the biological membrane by acting as a buffer, preventing lower temperatures from inhibiting membrane fluidity and preventing higher temperatures from increasing fluidity

Structure of sphingolipids

contains sphingosine as a backbone - derived from serine and palmitate - the attatchment of a second acyl group and a phosphocholine head yields a sphingomyelin

Cholesterol is: a. an isprenoid lipid b. found in bilogical membranes c. a metabolic precursor of the steroid hormones estrogen and testosterone d. has amphilic character e. all of the above

e. all of the above

Lipids: a. predominately hydrophobic molecules that can be esterified but cannot form polymers b. are biological molecules that are soluable in nonpolar solvents and poorly soluable in water c. make up about 50% of biological membranes d. perform a variety of biological functions e. all of the above

e. all of the above

the fluidity of a biological membrane depends on: a. the length of its lipids b. the degree of saturation of its lipids c. the presence of cholesterol d. temperature e. all of the above

e. all of the above

translocase definition

enzymes that assist cells with moving certain lipids between leaflets

common saturated fatty acids

lauric, myristic, palmitic, stearic, arachidic, lignoceric acids

What 2 things each make up 50% of the biological membrane?

lipids and proteins

Structure of isoprenoids

lipids constructed from a 5-carbon unit with the same carbon skeleton as isoprene

isoprenoid definition

lipids that are constructed from 5-carbon units with the same carbon skeleton as isoprene

members of fatty acids

long chain carboxylic acids (like palmitate, stearate, oleate, and linoleate) lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, palmitoletic acid, oleic acid, linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachildonic acid, EPA, DHA

fatty acid definition

long-chain carboxylic acids that can contain up to 24 carbons but mostly are C16 or C18

Are lipids in a more fluid membrane longer or shorter?

membranes containing lipids with longer fatty acid tails are less fluid than membranes containing lipids with shorter fatty acid tails

sphingolipid definition

membranes that contain amphipathic lipids

transverse diffusion (flip-flop) definition

movement from one leaflet to another

are fatty acids found in abundance in the biological membrane?

no, they are important components of the phospholipids that form phospholipid bilyarers

common unsaturated fatty acids

palmitoleic, oleic, linoleic (alpha and gamma), arachidonic, EPA and DHA acids

melting point definition

the temperature of transition from an ordered crystalline state to a mroe fluid state

are lipids soluable in non polar solvents or polar solvents

they are soluable in nonpolar solvents

In what lipid are fatty acids found in?

triacylglycerols