Lipids 3 COPY Flashcards
Where do we get fatty acids?
Diet Synthesis from excess carbohydrates, fat and protein components (acetyl co a)
Where does fatty acid synthesis occur?
Liver, lactating mammary gland, adipose tissue
What is fatty acid synthesised from ?
Acetyl co a
What chemicals are needed for FA synthesis?
NADPH and ATP and acetyl co a
Where does fatty acid synthesis take place?
Cytosol
Where is acetly co a formed?
In the mitochondria
How does the acetyl co a pass over the mitochondrial membrane into the cytosol?
Via the citrate shuttle, occurs when citrate concentration in the mitochondria is high. Citrate molecule passes over the mitochondrial matrix
Oxaloacetate plus citrate synthase plus acetyl co a =
Citrate
Citrate plus citrate lyase =
Acetyl co a plus oxaloacetate
Oxaloacetate plus NAD plus malate dehydrogenase=
Malate
Malate plus malate enzyme =
Pyruvate + NADPH
Pyruvate (crosses membrane) plus pyruvate carboxylase =
Oxaloacetate
What enzymes are involved in the synthesis of fatty acids?
Acetyl co a carboxylase (activation / regulation)Fatty acid synthase (multifunctional enzyme)
What is the product of fatty acid synthesis?
Palmitic acid
What enzyme is needed for the formation of malonyl co a ?
Acetyl CoA Carboxylase, committed step in fatty acid synthesis, c-c bond requires much energy supplied indirectly by synthesising malonyl co a
What is the regulatory enzyme?
ACC - Acetyl CoA Carboxylase
How is ACC activated?
By citrate, indicates that Glucose levels are high so makes FA
What de-activates ACC?
Palmitoyl CoA (when enough fatty acid is made)
Insulin?
High levels of plasma insulin cause the dephosphorylation of acetly co a phosphorylase thus promoting the formation of malonyl-CoA from acetyl-CoA, and consequently the conversion of carbohydrates into fatty acids
Glucagon and epinephrine?
Deactivates, glucagon (made in the pancreas) causes the liver to break down glycogen to glucose, therefore is present during low levels of glucose, so no fatty acid synthesis is taking place at this time. Epinephrine is adrenaline - released into the blood during starvation and exercise cause the phosphorylation of acetyl CoA phosphorylase, inhibiting lipogenesis in favour of fatty acid oxidation via beta-oxidation.
What is the overall reaction for palmitate?
8 acetyl CoA + 14 NADPH + 14H+ +7ATP -> Palmitate (C16) + 8CoA + 14 NADP+ 7ADP +7Pi + 7H2O
During elongation which enzyme is responsible for producing Aceto-Acetyl ACP?
Acyl Malonyl ACP
What are the three main reactions involved with fatty acid synthesis (opposite to degradation)?
Reduction, dehydration reduction
What is used instead of NADH and FADH2?
NADPH
What is the function of Malonyl CoA?
Provides 2 carbons to a fatty acid and commits them to fatty acid synthesis, used to produce palmityl ACP. Malonyl-CoA is formed by carboxylating acetyl-CoA using the enzyme acetyl-CoA carboxylase
What is the function of the thioesterase?
Cleaves palmityl CoA from the ACP molecule
What is linked to the ACP (acyl carrier protein)?
The intermediates in fatty acid synthesis
How does ACP act on the growing chain?
Holds it and moves it round all the different enzymes. The pantothenate arm moves the intermediates from one site to the next
What is significant about the fatty acid synthase enzymes?
They are multifunctional (seven of them)
What are the two sources of NADPH?
Pentose phosphate produces 6NADPHMalic enzyme reaction that converts malate to pyruvate 8NADPH
Where does further modification of palmitate and dietary fatty acids take place? (Unsaturation, branching and elongation)
Mitochondria and ER
Can fatty acids be synthesised?
No but are required to make other lipids (eicosanoids) fatty acids with 20-carbon unsaturated fatty acids. omega 3 and 6
What happens to the fatty acid that is synthesised in the body?
Converted into triacyglycerol, which is converted into VLDL which then forms adipose tissue
What is the starting material for the synthesis of steroids?
Cholesterol
How many rings do steroids have?
4
Where can you find cholesterol in the body?
Cell membrane
What is cholesterol the precursor for?
Bile acidsVitamin DSterol hormones
What is cholesterol derived from?
Acetyl CoA
What is the effect of statins?
Stops the body making cholesterol, lowers plasma cholesterol beneficial for preventing heart attacks and strokes. Can raise liver acids and give you muscle cramps. Lower LDL levels
What are eicosanoids precursors to?
Prostoglandins, thromboxanes, and leukotrines
What are the functions of eicosanoids?
Regulate: - Inflammatory response- Pain and fever (prostaglandins)- Blood clotting induction (thromboxane)- Leukotrines
What does aspirin stop the synthesis of?
Prostoglandines, often associated with pain
What are thromboxanes associated with?
The clotting of blood
What are leukotrines responsible for?
The closing up of airways in the lung in asthma, leukotrine antagonists used to help with asthma
What might the prostoglandin anologue be used for?
Labour induction
COX is an enzyme for?
Production of prostoglandins
Why does aspirin have an anti-inflammatory and fever reducing property due to?
COX 1 enzyme and prostoglandin synthesis
What else does aspirin inhibit?
Thromboxanes
