biochem lipids

what regulates lipolysis

hormonal mechanisms: insulin, gluacagon, epinephrine, cortisol , coordination of CH, lipid and protein metabolism

biosynthesis in liver first step

acetyl coa → malonyl coa

-happen in cytosol

-use enzyme acetyl coa carboxylase

-use biotin vitB7 as cofactor

what is the commitment enzyme for biosynthesis in liver

acetyl coa carboxylase

biosynthesis in liver second step

malonyl coa→ fatty acid

-happen in cytosol

-use enzyme fatty acid synthase

-use NADPH as cofactor

carnitine shuttle

transports long fatty acid chains into mitochondria for catabolism

what inhibits the carnitine shuttle and prevents synthesis and breakdown simultaneously

malonyl coa

where does ketogenesis happen during fasting and starvation

liver

what can the liver make but cant use

ketone bodies

what is the main ketone body exported during catabolism

beta-hydroxybutyrate

if there are excess nutrients in the body

-high malonyl coa

-carnitine shuttle inhibited

-fatty acid stay in cytosol and synthesis happens

if there is fasting or starvation occuring

-low malonyl coa

-carnitine shuttle activated

-fatty acid enter mitochondria and beta oxidation happens

long fatty acid chain would go to

carnitine shuttle

short/medium fatty acid chain would go

and diffuse

very long fatty acid chains would go to

peroxisome

beta oxidation occurs ___________ and is entirely _________

mitochondria, oxidative

what do odd chain fatty acids produce and what vitamin is needed

produce propionyl coa and needs vitamin b12

excess of acetyl coa in liver leads to

ketogenesis

methylmalonyl coa aciduria caused by deficiency in _______, accumulates _________

vitamin b12, propionyl coa

fat malabsorption is missing ________, accumulates _________

bile salts/lipases, unabsorbed fats

diabetic ketoacidosis missing __________, accumulates ________

insulin deficiency, excess ketone bodies

zellweger syndrome

peroxisome biogenesis disorder that leads to multiorgan disorder and early death

acetyl coa carboxylase requires presence of ________ for polymerization to its active form

citrate

acetyl coa carboxylase is regulated by

phosphorylation-dephosphorylation mechanism and hormonally

first stage of biosynthesis and storage of fatty acids

precursor malonyl coa

second stage of biosynthesis and storage of fatty acids

elongation of fatty acid

elongation of fatty acid takes place in

cytosol

what enzyme contribute to elongation of fatty acid

fatty acid synthase

starting material for fatty acid synthesis and elongation

fatty acid synthesis staring point = acetyl coa + malonyl coa

elongation starting point = existing fatty acid + malonyl coa

end product for fatty acid synthesis and elongation

fatty acid synthesis staring point = palmitate (16C)

elongation starting point = longer fatty acids (18-24C)

elongation of fatty acids also called

macrolipogenesis

how does elongation of fatty acids occur

1. Elongation adds 2 carbons at a time using Malonyl-CoA

2. Done by Fatty Acid Synthase — a dimer with 7 enzymes in 3 domains

3. Has a flexible arm that moves the chain between enzyme domains

4. Can produce fatty acids up to 22-24 carbons lons

step 1 of elongation of fatty acids

acetyl coa→ malonyl coa, product is malonyl coa (commitment step)

step 2 of elongation of fatty acids

malonyl coa → palmitate, product is palmitate (16C, the first product made)

step 3 of elongation of fatty acids

palmitate → longer fatty acid, 18-24 carbon fatty acids (second product made, final)

lipases hydrolyze ____, by releasing 1 fatty acids at a time, yielding ____ and _____

TAG, DAG, glycerol

glycerol is converted to dihydroxyacetone phosphate by catalyzed

glycerol kinase (1st) and glycerol phosphate dehydrogenase (2nd)

process of glycerol converted to dihydroxyacetone phosphate

glycerol kinase glycerol phosphate dehydrogenase

glycerol —→ glycerol 3p -—→ dihydroxyacetone phosphate

first step of catabolism is

activation of fatty acid to their coa derivative by using ATP as energy source (using fatty acyl coa synthase also known as fatty acid thiokinase)

once fatty acid reaches acyl coa form its

fully activated

fatty acids are never free roaming without being binded to

albumin in the plasma (direct to tissues needing energy) or lipoproteins (to adipose for storage or tissue for energy)

liver uses fatty acids as source of energy for

gluconeogenesis

excess acetyl coa accumulates during

fasting/starvation

during starvation brain converts to using __________ for more than 50% of its energy metabolism

ketone bodies

during starvation the brain uses ketone bodies sparing ______ thus reducing degradation of muscle protein for ___________

glucose, gluconeogenesis

fatty acids are stored as

TAGs

TAGs are produced from

glycerol 3P

fatty acids are an immediate

source of energy

2 carbons at a time released from carboxyl end of fatty acid result in

acetyl coa, fadh2, nadh

synthesis of fatty acids and TAG called ______ and happens in ________

lipogenesis, cytosol

degradation of triglycerides is called _______ and catabolism of fatty acids happens by ______ and are entirely _______

lipolysis, b-oxidation, oxidative

end product of acetyl coenzyme a in muscle

metabolized by TCA and oxidative phosphorylation → produces ATP

end product of acetyl coenzyme a in liver

used to synthesize keton bodies (ketogenesis) then exported to other tissues

regulation of fat metabolism by

-involvement of insulin, glucagon, epinephrine, cortisol

-rate of lipolysis in adipose tissue