fatty acid synthesis Flashcards
(33 cards)
which is more unhealthy? trans or cis fat?
trans fat
Whats the role of fatty acids?
Fuel reserves
signal molecules
component of membrane lipids
Diet meets our needs for fats and lipids
humans have little need for FA synthesis
exceptionsL embryonic development
lactation
liver and adipose tiusses
essential fatty acids that humans cannot make
what are the 4 stages of fatty acid synthesis
- Preparatory step: Acetyl coA is transported in the form of citrate from the mitochondria to the cytoplasm (where FA synthesis occurs)
- Activation of acetyl coA to maloyl coA
- attachment to acyl carrier protien (ACP)
- elongation of fatty acids 2 carbons at time
How many NADPH is need to syntheissze palmitate (C16)? Where do they come from
8 will come from transferiing acetyl coA from mt -> cytoplasm
6 willl come from pentose phosphate pathway.
Does fatty acid syntehsis require ATP? Where does it come from?
Yes it does. It comes from glycolysis and oxidative phosphorylation.
What can we conclude about the resources of fatty acid synthesis?
its pulled from different metabalic pathways in different comparments
How is acetyl coA transproted from mt -> cytomaspm
acetyl coA leaves as citriate. for every moelcuel of acetyl coA transfered, 1 molecule of NADPH is generated , and 1 molecule of ATP is consumed.
Difference between NADPH and NADH
NADH is consumed in biosynthetic reactions, whereas NADH is generated in energy yielding reactions
What is ACP
it carries activated carbon groups.
functions in fatty acid syntheiss
What happens before the elongation phase of fatty acid synthesis?
Acetyl coA and malonyl coA react with scaffold protien called ACP -> forming acetyl ACP and malonyl ACP
What are the steps in fatyt acid syntheiss
1) condensation: KS
(involves decarboyxlation of malonyl-ACP and formation of beta-ketobutyrul ACP
2) reduction: KR
uses 1 NADPH -> NADP+
3) dehydration: DH
4) reduction: ER
uses 1 NADPH -> NADP+
Whats added to the fatty acid chain as it elongates
malonyl ACP (this is the building block)
but the first substrate is acetyl coA
Whats the last step in fatty acid syntheiss
thioesterase. remove the fatty acid chain from ACP
From Acetyl coA to palmitate what do you need
7 molonyl coA + 14 NADPH
(so 7 ATP and 14 NADPH)
Difference between omega 6 and omega 3
omega 6: (18c) promotes inflammation (double bond between 6-7)
omega 3 (18c) : reduces inflammation (double bond betwene 3-4)
humans lakc the enzymes to synthasez the FAs
When will the liver make TAGs from fatty acids?
- When glucose levels are high
- Acetyl coA is plentiful
- fatty acids are scarce
carbon substrates for fatty acid synthesis is primarily derived from dietary carbohydrates
How is this regulated: how is the conversion of citrate -> acetyl coA to allow acetyl coA to transport into the cytoplasm ?
If cells need energy -> TCA cycle runs. If cells dont need energy -> citrate is exported.
To syntehsize palmitic acid, how many times does the conversion and transport of acetyl coA need to happen?
8 times
What is consumed/produced for every molecule of Acetyl coA thats transported from the mitochondira to the cytoplasm?
1 ATP is consumed, and 1 NADHPH is produced
Citrate breaks down into acetyl coA and oxaloaxetate, how does the oxaoloacetate get back into the mitochondria?
Oxaloacetate is reduced to malate -> malate turns to pyruvate nad pyruvsate moves back in
What are the steps for fatty acid syntheis?
Prior: acetyl coA is transfered from the mitochondria into the cytoplasm (uses 1 ATP, produces 1 NADHP)
Activcation of Acetyl coA to Malonyl coA (requires 1 ATP)
ACP tranfer: Acetyl coA, malonyl coA -> acetyl ACP and malonyl ACP
Ekgonation.
1. KS (Acetyl ACP + malonyl ACP)
2. KR (reducase, uses 1 NADPH)
3. HD (dehydratase)
4. ER (uses 1 NADPH)
Finally, thioesterase releases the fatty acid from ACP
Synthesis of palmitate requires how many NADHP?
14
Which enzymes act as a ruler and is highly specific?
Thioesterase (mark 16 C)
and AD
