Question

MCAT Tutorial: Fatty Acid Metabolism & Storage

Answer 1

\({\bf{Basic~Properties:}}\)
- long carbon chains with high reducing potential.
- unsaturated fats have lower reducing potential than saturated due to the presence of C=C bonds which contain fewer electrons
- unsaturated fats store less energy

\({\bf{Metabolism:}}\)
two main methods: beta-oxidation and ketogenesis

Beta-Oxidation:
- fatty acids --> acetyl-CoA
- occurs ~the same time with gluceoneogenesis (fasting state)
- fatty acids are carried by lipoproteins into the bloodstream for use by organs
- the process of beta-oxidation occurs in mitochondria

steps:
- conversion to acyl-CoA by using 1 ATP
- transfer to mitochondrial matrix and conversion to acetyl-CoA (notice the difference between acyl and acetyl)
- also makes NADH and FADH2
- acetyl-CoA used in citric acid cycle
- glycerol backbone also used as intermediate in glycolysis

Ketogenesis:
- occurs in liver
- produces ketone bodies: acetone, acetoacetic acid, beta-hydroxylbutyrate
- each ketone body has C=O group that allows them to diffuse through membranes while still being uncharged
- provides alternative energy source
- not substrates for gluconeogenesis
- ketone bodies can be interconverted between acetyl-CoA and ketone bodies to provide for the citric acid cycle, or energy as needed

Answer 2

\({\bf{Storage~and~Release:}}\)
- storage: carried by lipoproteins and exocytosed as needed
- lipids are stored as tryglycerides which can be broken down into fatty acids by lipase

- chylomicron: a type of lipoprotein produced by the liver; has higher lipid: protein ratio
- liver converts chylomicrons to VLDLs and HDLs
> VLDLs move lipids through the bodyo
> HDLs transport "stray" fatty acids to the liver

- liver can also convert acetyl-CoA to fatty acids in cytosol (not mitochondria)

Answer 3

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 9th Edition ExamKracker's Biology 1 Prep book for the new MCAT