Lecture 9 - Fatty Acid Metabolism II Flashcards
what is fatty acid anabolism (i.e: biosynthesis)?
fatty acid anabolism is essentially the reverse of fatty acid catabolism (i.e: beta-oxidation)
what sort of process is fatty acid anabolism?
fatty acid anabolism is a two step process: preparation of precursor malonyl-CoA & acyl-ACP followed by elongation of fatty acid by fatty acid synthase
what are the starting materials for fatty acid anabolism?
the starting materials are:
(1) unit added is malonyl-CoA instead of acetyl-CoA (bB-oxidation)
(2) chain reaction starts from acyl-CoA and malonyl-CoA
where does fatty acid catabolism take place?
fatty acid catabolism takes place in the mitochondria
where does fatty acid anabolism take place?
fatty acid anabolism takes place in the cytoplasm
what is the primary electron donor in fatty acid anabolism?
NADPH is the primary electron donor in fatty acid anabolism
fatty biosynthesis - step one - carboxylation:
(1) fatty acid synthesis starts by carboxylation of acetyl-CoA to malonyl-CoA by acetylene-CoA carboxylase enzyme [this step requires 1 ATP for every malonyl-CoA synthesised
substrates of fatty acid synthase are:
substrates of fatty acid synthase are: acetyl-CoA, malonyl-CoA and NADPH
what is mamillian fatty acid synthase encoded by?
a singular gene
structure of fatty acid synthase:
a single polypeptide chain with three domains and 7 catalytic sites makes a homodimer
what is required for the fatty acid synthase reaction?
a significant amount of NADPH is required
how many fatty acids are synthesised simultaneously?
2 fatty acids are synthesised simultaneously
where does fatty acid biosynthesis take place?
fatty acid biosynthesis takes place in the cytosol
the cytosolic pathway leads to:
the synthesis of saturated fatty acids, with the main product being the 16-carbon fatty acid palmitate
elongation reactions are catalysed by enzymes located on:
the cytosolic face of the endoplasmic reticulum membrane - malonyl CoA acts as the donor
what reactions also occur at the ER membrane? reduction
reactions also occur at the ER membrane to produce unsaturated fatty acids
what odes fatty acid elongation require?
fatty acid elongation requires acid elongase
where does fatty acid elongation occur?
fatty acid elongation occurs on the ER
Very long chain FA produced in the _____ which increases rapidly during __________ producing the FA required for ____________production
(1) Brain
(2) myelination
(3) sphingolipid
where in the body does fatty acid biosynthesis take place?
pathways are present in: the liver, brain and kidney cells
what is fatty acid biosynthesis regulated and activated by?
fatty acid biosynthesis is regulated by hormones and are activated in mammary glands during and post pregnancy
when is the fatty acid biosynthesis pathway likely to occur?
the pathway is used in conditions of excess energy in particular carbohydrate intake
Under a condition in which citrate accumulates more than the capacity of TCA cycle to process, citrate moves to the cytoplasm
how does excess citrate from the TCA cycle allow for aided fatty acid biosynthesis?
•Citrate is digested down to acetyl-CoA and oxaloacetate.
•Oxaloacetate returns to mitochondria as pyruvate
•The conversion of oxaloacetate to malate then pyruvate provides the NADPH pool required for FA anabolism (biosynthesis)
what is needed to produce the variety of fatty acids:
•Additional enzymes and reactions are needed to produce the variety of fatty acids
Elongation reactions are catalysed by enzymes located on the:
cytosolic face of the endoplasmic reticulum membrane. Malonyl CoA acts as the donor
the cytosolic pathway leads to:
the synthesis of SATURATED fatty acids, with the main product being the 16 carbon fatty acid, palmitate
how are fatty acids transported?
fatty acids are transported in a form of neutral fats that are either monoacylglycerol (MAG), or diacylglycerol (DAG) or triacylglycerol (TAG)
what about palmitate allows it allows it to be activated by ATP/AMP and to be acyl-CoA before attached to a glycerol:
the reactive carboxyl group of palmitate
what about glycerol becomes activated when fatty acids are attached?
glycerol has 3 hydroxyl groups where activated fatty acids are attached
what is glycerol synthesised from?
fatty acids are synthesised from DHAP and Glycerol-3-phosphate (G-3-P)
G-3-P comes from:
dihydroxyacetone phosphate (DHAP) – glycolysis
fatty acids are stored as neutral fats in the body in three forms:
•Monoacylglycerol (MAG)
•Diacylglycerol (DAG)
•Triacylglycerol (TAG)
