Catabolism of FA Flashcards
what 3 functions does cholesterol serve?
1) membrane structure
2) precursor for bile acids
3) precursor for steroid hormones
what is esterification?
addition of FA to glycerol to form an ester bond
-Formation of fat
explain the structure of a FA
carboxyl group (polar head)
non-polar HC tail
-amphipathic molecule
-can be saturated or unsaturated
what 2 configurations can a FA be found in? which one is the most common and there fore assumed?
trans and cis
-cis is the most common and the db is assumed to be cis unless otherwise stated
how many carbons do you expect short chain, medium chain and long chain FA to have?
short chain <6C
Medium 6-12
long 13-21* primary focus
very long >22
How is the type of omega fat determined?
by the number of carbons away that the first db is from the methyl end
what is conjugation?
1 single bond between each db
how many C is palmatate? what type of FA is it? what is its common name?
16C
-saturated FA
-palmitic acid
what 2 major factors affect MP? which one causing more of an effect?
1) length
2) saturation
-saturation drops MP more (more dramatic affect)
how does increasing length and saturation affect MP of a FA?
longer chains- increases MP
more unsaturation - lower MP
what is a triacylglycerol?
3 fatty acid esters of glycerol
what are white fat cells? what are their primary functions?
Adipocytes
1) storage of fat for energy
2) hormone production
what hormone is released from adipocytes to regulate appetite?
leptin
What is the storage and breakdown of FAT known as
synthesis of TAGs from FA- esterification
Breakdown of TAGs to form FA- lipolysis
What is the synthesis and breakdown of FA known as?
synthesis of FA - FAS
breakdown of FA -beta oxidation
what deterines the amount of fat stored in the body?
1) the rate of the breakdown and synthesis of TAGs
2) fat consumption
what is the affect of glucagon in adipocytes in regards to TAG regulation? what target enzyme does PKA phosphorylate as a result of this signal? what effect does this have on the enzyme?
glucagon stimulates breakdown of TAGs
-hormone-sensitive lipase is phosphorylated, which activates the enzyme
what is the role of hormone sensitive lipase?
1) breaks down the first FA from TAGs to form diacylglycerol
2) Breaks down the 2nd FA from DAG to form monoacylglycerol
what enzyme is needed to convert monoacylglycerol into glycerol + FFA?
monoacylglycerol lipase
what is the most important lipase responsible for breaking down TAGs into diacylglycerols?
Adipose triglyceride lipase
(ATGL)
what happens to majority of the FA produced from the breakdown of TAGs (lipolysis)? what happens to the glycerol?
-majority of the TAGs are released into the blood
-all of the glycerol is released into the blood
what does adrenaline and epinephrine signal in adipocytes?
fight or flight
-energy is needed, stimulates the same pathway as glucagon
what is the function of perilipin? how does phosphorylation / dephosphorylation affect its activity? what phosphorylates it?
unphosphorylated perilipin coats lipid droplets, shielding them from hormone sensitive lipase
-when phosphorylated by PKA it is activated and undergoes conformational changes; the change in structure allows the lipase to access the lipid droplet and break it down
what FA can readily diffuse across the plasma membrane? how is this possible given given the charge of FA at physiological pH?
short / medium chain
-at pH 7 FA are deprotonated and carry a (-), however, once in contact with the membrane they pick up a H+ and can diffuse across
what 2 signals stimiulate FA transporters onto the plasma membrane?
1) insulin
2) contraction
-increases [AMP] –> increases [AMPK]–> stimulates increase in transporter
what transporter do FA transporters act like?
GLUT 4
How are FA transported?
bound to albumin
what bond in coA allows us to form a high energy bond…in turn allowing us to create alot of enegry?
HS group
explain the steps in FA activation? what enzyme catalyzes this rxn? what is needed to activate the FA? how many high energy bonds are in this rxn? what are they)
1) FA attached to a phosphate group which releases pyrophosphatase, creating a mixed anhydride (high energy)
2) attachement of coA and release of AMP to form Acyl-coA
3) pyrophosphatase is then converted to inorgancic phosphate by inorganic pyrophosphatase
- creates energy to drive the rxn forward
-fatty acyl-coA synthetase
-3 types of high energy bonds (phosphoanhydride, mixed anhydride, thioester)
are LCFA , MCFA, and SCFA activated differently?
yes, LCFA are activated in the cytosol and MCFA / SCFA can diffuse across the membrane and are activated in the matrix
how many ATP moleucles are required to activate FA? explain why?
2
- Adenylate kinase is needed to reconvert AMP back to ATP to be used in the reaction
list all the enzymes involed in FA activation?
1) thiokinased (FA acyl-coA synthetase)
2) inorganic pyrophosphatase
3) Adenylate kinase
4) ATP synthase
explain the steps in the transfer of activated FA into the mitochondria? what types of FA are transported across this transporter?
1) acyl group transferred to carnitine using carnitine acyl/palmitoyl transferase I (CAT1)
-breaking thioester and forming ester bond
2) carnitine acyl group is taken across IMM with carnitine carrier protein (Carnitine transferase)
3) in the matrix carnitine acyl / palmitoyl transferase II transfers acyl group back to coA
-breaks ester bond
4) free carntine is taken back out
- transfers free FA and LCFA
what type of transporter is carnitine carrier protien (carnitine transferase)?
antiporter
