Module 8: Lipid Metabolism Flashcards
omega-3 three fatty acids
healthy fats
our body does not produce these types of fatty acids
get from oily fish (salmon)
What are the different fates for acetyl CoA?
- amino acids –>pr-
- pyruvate
- ketone bodies
- cholesterol
- fatty acids –> triacylglycerols or membrane lipids
How is fat stored in the body?
fats are stored in the body in the form of triacylglycerols
fat stores are found in our adipose tissue in specialized cells called “adipocytes”
Triacylglyercol
made up of three fatty acids which have been esterified with glycerol
Lipase
releases the free fatty acids from the glycerol moiety by hydrolyzing the ester bonds
When is lipase stimulated and what occurs?
At rest/when glucose levels low, glucagon stimulates the lipase to breakdown fats to provide energy
occurs through beta oxidation
also generates NADH and FADH2 and acetylCoA
What happens to products (fatty acids and glycerol) of Triacylglycerol Breakdown?
Fatty acids leave the adipose tissue and enter the bloodstream to be delivered to the tissues (can be carried thru blood when bound to albumin which keeps FAs soluble)
Fatty acids will be taken up by liver and muscle and broken down by beta oxidation
Glycerol leaves the adipose tissue to be taken up by liver, which is where gluconeogenesis will occur and convert it to glucose
Activation Of Fatty Acids
attach a long chain hydrocarbon of a fatty acid to coenzyme A
catalyzed by acylCoA synthetase
occurs in cytosol
acylCoA now ready to be transported into the mitochondrial matrix
Beta Oxidation Of Fatty Acids
carbons removed from fatty acids 2 at a time adjacent to beta carbon (cleavage of C-C bond produce acetylCoA)
produces 1 NADH & 1 FADH2 per round
No ATP produced directly
acetylCoA –>enters CAC for further oxidation to CO2
NADH&FADH2 –>donate e- to ETC and generate ATP thru OxPhos
Ketone Bodies:
When it is used
Pathway
Once carbohydrate reserves are used up from fasting/starvation, liver has the ability to convert fats to ketone bodies
Our bodies are able to produce the following ketone bodies: acetone, acetoacetate, and beta-hydroxybutyrate
ketone bodies produced in liver–>enter bloodstream–>taken up by brain–>broken down into acetylCoA–>CAC–>produce energy
How does Fatty Acid Biosynthesis occur?
Where do the materials come from?
Two carbons (originating from acetylCoA) are added one at a time to an elongating fatty acyl chain
- When glucose not needed/for glycogen stores, acetylCoA does not enter CAC but instead diverted to fat synthesis
- Electrons come from reducing NADPH to NADP+
- Tricarboxylate transport system must move acetylCoA out of the mitochondrial matrix into the cytosol
Process of Fatty Acid Synthesis in Cytosol
describe fatty acid synthase & elongase
FA synthesis catalyzed by fatty acid synthase, which takes 8 acetylCoA molecules and condense them (similar to beta oxidation but in reverse) and synthesize the 16-carbon fatty acid called palmitate
Consumes NADPH instead of NADH/FADH2
1 ATP consumed per round of acetylCoA addition to elongating fatty acid
Elongases/desaturases: make longer chain fatty acids and create double bonds in unsaturated fatty acids
Fatty Acid Metabolism: High Glucose
Under conditions when glucose is high, insulin is released, which activates fat synthesis in the liver and simultaneously inhibits fat breakdown in adipose tissue
Fatty Acid Metabolism: Low glucose
Under conditions when glucose levels are low, glucagon is released, which stimulate fat breakdown by stimulating the lipase in adipose tissue
fats are broken down to acetylCoA and used for energy OR
during periods of extended fasting or starvation, the acetylCoA can be diverted to ketone body synthesis
Cholesterol Synthesis
AcetylCoA–>HMG-CoA -(HMG-CoA reductase)->Mevalonate–>….–>Cholesterol
