Fatty Acid Oxidation
Calculate the P/O ratio for the aerobic catabolism of stearate
(C=18). Show all work in a table such as we have used in class. KEY
synthesis of ketone bodies starting with glucose (assume that
the organism goes from well fed to starving during this synthesis).
Your discussion should include the most likely tissues involved.
- How many acetoacetate molecules could be synthesized from
four initial glucose molecules (assume all processes take place
in a single cell).
- Would glucose be used to make ketone bodies directly? Why
or why not?
- Is it more likely that fat is made first, then used to make
- Determine the energy available from these acetoacetate molecules
in ATP equivalents:
- Create a table as we have done in class, considering only
the acetoacetate molecules themselves.
- Does the answer in (1) gives a good estimate of the energy
actually used by the organism? As a check try making a table
following the path for making and using the acetoacetates. As
a simplification, include only the major carbon flux pathways
in your table (e.g. glycolysis, beta-oxidation, fatty acid biosynthesis,
- Is this Table a reasonable approximation? Why or why not?
From the Final Exam Study Guide:
beta-Oxidation of Fatty Acids:
- What is the first step?
- Where does it take place?
- What is the energy product of this step?
- What are oxidizing agents for beta-oxidation?
- "Mainline Sequence."
- How are AcCoA groups cleaved off? (Claisen cleavage.)
- How many turns of beta-oxidation to convert a fatty acid to AcCoA?
- Where do the reactions of beta-oxidation take place?
- Which step controls the rate?
- Would you say that the breakdown of short chain fatty acids is uncontrolled? Explain.
- Be able to calculate energy yield from the complete or partial oxidation of a given fatty acid.
- What are "ketone bodies?"
- Know reactions by which ketone bodies are synthesized and
- What are the starting materials?
- What is the first reaction?
- What kind of reaction is this? (compare to the Citrate synthase
- how is CoASh removed?
- In which tissues are ketone bodies synthesised?
- beta-hydroxybutyrate vs. acetoacetate.
- Under what conditions will "ketone bodies" be formed
(instead of complete oxidation of acetyl).
- answer: High [ATP] with continued breakdown of FA's, therefore
need to form ketone bodies to recycle CoA.
- Ketone Use
- In which tissues are ketone bodies utilized?
- What is the source of CoA in acetoacetate degradation?
- Does this cost energy?
- What do we mean by the statement: "ketone bodies give
the liver overall control of fatty acid metabolism?"
©R A Paselk
Last modified 20 April 2011