Lecture 10: lipid structure, properties, and signaling

why dont cells want to add saturated acids at 10 degrees celcius?

b/c the membrane would become a solid and at 10 degrees celcius we need to to be a liquid

what is found inside a membrane?

endoplasmic reticulum nuclear membrane mitochondria secretory granule * All 4 of these have their own membranes

where would cholesterol be found in an animal cell?

in the phospholipid bilayer (has hydrophobic head and hydrophillic head)

Which of the following statements is CORRECT? An E. coli cell grown at 30 degrees will have a lower percentage of unsaturated fatty acids in its membrane than one grown at 20 degrees C . An E. coli cell will have the same percentage of unsaturated fatty acids in its membrane when grown at 20 degrees or 30 degrees C. An E. coli cell grown at 30 degrees C will have a higher percentage of unsaturated fatty acids in its membrane than one grown at 20 degrees C.

An E. coli cell grown at 30 degrees will have a lower percentage of unsaturated fatty acids in its membrane than one grown at 20 degrees C . the higher the temperature the more saturated fatty acids you have and the lower the temperature the more unsaturated fatty acids you have

what vitamin can cholesterol be converted to?

Vitamin D

inner and outer layers of lipids in the plasma membrane dont mix true or false?

true

Vitamin D is derived from cholesterol. True False

true. vitamin D is made in the skin upon exposure to UV light

between uncatalyzed transbilayer ("flip flop") diffusion and uncatalyzed lateral diffusion which one is slow?

uncatalyzed transbilayer is very slow (can even take up to days)and thermodynamically unfavorable b/c you would have to pass polar groups through the hydrophobic tails

if a cell is grown at 10 degrees celcius what type of fatty acids will be most abundant in the lipids of the membrane?

unsaturated fatty acids (oleic)

Steroids are derived from arachidonic acid. True False

false

The percentage of the glycerophospholipid phosphatidylserine is the same in the inner layer of the phospholipid bilayer as in the outer layer of the phospholipid bilayer. True False

false it is hydrophobic on the inside and hydrophillic on the outside

what biological responses are controlled by prostaglandins?

-inflammatory response -pain and fever -blood pressure/clotting -regulates sleep and wake cycle -control of reproductive function, including induction of labor ex) aspirin works by inhibiting the enzyme prostaglandin synthase

what is the purpose of membranes?

-membranes are critical for cell function (life) -they provide compartments and allow redirection of the energy flow into useful metabolic processes * you cant organize cells without a membrane

what are the compartments to membrane structure and function?

1. selective 2. barriers to diffusion 3. origin of active transport 4. organization of complex reactions 5.signal transduction (binding a hormone to a receptor)

Approximately how long would it take for a lipid to diffuse all the way around the outer bilayer of an E. coli cell? a. 1 sec b.1 hour c. 1 day

a. 1 sec this is known as lateral diffusion

what should you do to increase fluidity in the membrane?

add more unsaturated fatty acids and allow the cells to divide

which fatty acid is cleaved from the lipids to make a prostaglandin?

arachidonic acid (20-carbon fatty acid) from glcerophospholipid

how and why are liposomes formed?

bilayers wrap around to form continuous, spherical particles so there are no exposed hydrophobic surfaces -they have polar heads on the outside -they have hydrophobic tails on the inside -in the center its filled with a bunch of polar head called the aqueous cavity

how do cells control membrane fluidity?

by regulating the lipid content of the bilayer

steroid nucleus are derived from steroids which are derived from ___________________

cholesterol

different membranes have (same/different) lipid concentrations

different

how much energy is needed to create a liposome?

forming a bilayer is energetically favorable so no energy is needed to create a liposome

what kind of lipids is used to make prostaglandins?

glycerophospholipids

signaling molecules that enter into the bloodstream leads to an...

inflammatory response

what is the treatment/cure for rickets?

irradiating foods with UV light could cure the disease rickets

what does detergent do when inserted into the integral protein?

is disrupts the membranes aliphatic tail and polar head group the integral protein is a hydrophobic domain which is coated with detergent

how do cells maintain a balance in the fluidity of their membranes?

regulate the lipids content (unsaturated and saturated) bilayer

what is the function of vitamin D once it is converted into a hormone?

regulation of calcium uptake in the bone

when looking at a cholesterol molecule, what part is the steroid nucleus?

the 4 rings

how do lipids form bilayers?

they self-aggregate to spontaneously form bilayers

uncatalyzed lateral diffusion * look in lecture notes to see image

very fast you just move to the right you dont have to pass through anything you just move across towards the right