How is fat used for energy?

[ilovemcat]

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I noticed this wasn't discussed much in my review book but:
1. How is fat stored for longterm use (what steps does it take to get into adipose tissue)?
2. How is stored fat utilized for energy?

 

[RogueUnicorn]

fatty acids packaged into lipoproteins are absorbed by the fat cells and made into triglycerides for storage.

stored fat gets used by cleaving off the fatty acids from the glycerol backbone. the glycerol can be made into glucose, and fatty acids are used two carbons at a time to make acetyl CoA, which feeds directly into the Krebs cycle. in times of starvation you can also use acetyl CoA to make ketone bodies

 

[ilovemcat]

fatty acids packaged into lipoproteins are absorbed by the fat cells and made into triglycerides for storage.

stored fat gets used by cleaving off the fatty acids from the glycerol backbone. the glycerol can be made into glucose, and fatty acids are used two carbons at a time to make acetyl CoA, which feeds directly into the Krebs cycle. in times of starvation you can also use acetyl CoA to make ketone bodies

That explains a lot, especially the second part. What review book did you use or do you just know this stuff? 🙂 Also, ketone bodies, what are they and what are they used for? Thanks for the reply.

 

[loveoforganic]

The basics of this should be covered in any review book, but the topic is covered in biochem.

 

[JFK90787]

I don't think you need to know what ketone bodies do. The things I remembered were that NADPH is made in fatty acid synthesis, ketone bodies are made from fatty acid breakdown. NADP+ can not be used in place on NAD+ for glycolysis/PDC/krebs.

I also remember hearing that the order of importance of breaking down macromolecule for energy went carbs > paroteins > fat, although I could never find a source for that.

 

[loveoforganic]

Should be carbs > fat > proteins.

 

[docelh]

I think NADPH is spent in fatty acid synthesis.

Interestingly, proteins have a two-phase behavior. Initially, some proteins are consumed before lipolysis goes full throttle. And then it becomes fats and finally protein then death of organism.

 

[PiBond]

I think NADPH is spent in fatty acid synthesis.

Interestingly, proteins have a two-phase behavior. Initially, some proteins are consumed before lipolysis goes full throttle. And then it becomes fats and finally protein then death of organism.

Word 👍. The nitrogen on the protein is toxic so it's only temporarily utilized before the body swithces to fats.

 

[RogueUnicorn]

That explains a lot, especially the second part. What review book did you use or do you just know this stuff? 🙂 Also, ketone bodies, what are they and what are they used for? Thanks for the reply.

just know it from classes. ketone bodies are used as an alternate fuel source, and in the absence of sugars are the only source for the brain

I think NADPH is spent in fatty acid synthesis.

Interestingly, proteins have a two-phase behavior. Initially, some proteins are consumed before lipolysis goes full throttle. And then it becomes fats and finally protein then death of organism.

correct on all counts sir.