24 Questions
During the hydration step of β-oxidation, what is added to the double bond at the beta carbon?
A -OH group
What molecule is used in the hydration step of β-oxidation?
H2O
How many acetyl-CoA molecules are produced from the breakdown of one C16 fat (palmitate)?
8
Which enzyme is involved in the acyl transfer step of β-oxidation?
Thiolase
What is the primary purpose of β-oxidation of fats?
To produce acetyl-CoA for the TCA cycle
In the third step of β-oxidation, what is the hydroxyl group converted into?
A carbonyl group
How much ATP is produced from the complete metabolism of one palmitate molecule?
106 ATP
How many β-oxidation cycles are needed to fully break down a C16 fat (palmitate)?
7
What is the net gain of ATP from glycolysis?
2 ATP
How many turns of the TCA cycle are required to completely oxidise one glucose molecule?
2 turns
What does dihydroxyacetone phosphate (DHAP) isomerize into during fat degradation?
Glyceraldehyde 3-phosphate
Which molecule is involved in the transport of fatty Acyl-CoA into the mitochondrial matrix?
Carnitine
During which step of $eta$-oxidation is a double bond formed between the alpha and beta carbons?
Dehydrogenation
What is the final product of the $eta$-oxidation pathway of fatty acids?
Acetyl-CoA
What are the main molecules produced during the $eta$-oxidation of Acetyl-CoA?
NADH and FADH2
What does the combination of fatty acid, CoA, and ATP produce?
Fatty Acyl-CoA
Where does fatty acid synthesis occur?
Cytosol
What is the enzyme responsible for converting acetyl-CoA to malonyl-CoA?
Acetyl-CoA carboxylase
How does acetyl-CoA get transported from the mitochondria to the cytosol?
As citrate
Which molecule is a product of the condensation step in fatty acid synthesis?
Acetyl group (2C)
Which step in fatty acid breakdown involves the production of NADH + H+?
Dehydrogenation
Which of the following is not a process in fatty acid synthesis?
Hydration
What is the main fate of carbon skeletons after the breakdown of amino acids?
Enter the TCA cycle
In amino acid catabolism, the amino group is converted into carbamoyl phosphate to enter which cycle?
Urea cycle
Study Notes
Fatty Acid Synthesis
- Fatty acid synthesis is not the reverse of fatty acid breakdown and involves different enzymes.
- It occurs in the cytosol, not the mitochondrial matrix.
- The process involves the conversion of acetyl-CoA to a 3-carbon malonyl CoA molecule, catalyzed by acetyl CoA-carboxylase.
- The malonyl CoA is then combined with acetyl groups in consecutive reactions to form a longer chain.
Fatty Acid Synthesis Summary
- Condensation: Acetyl CoA (2C) + malonyl CoA (3C) → Acetyl group (2C), CO2, NADPH + H+
- Reduction: NADP+, H2O
- Dehydration: NADPH + H+
- Reduction: NADP+, Saturated acyl group (lengthened by 2C)
Fatty Acid Breakdown
- Dehydrogenation: Palmitoyl-CoA → FADH2
- Hydration: H2O
- Dehydrogenation: NADH + H+
- Acyl transfer: Acyl-CoA + acetyl CoA (2C)
Fatty Acid Synthesis: Getting Acetyl CoA
- Problem: Acetyl CoA is in the mitochondria, but fatty acid synthesis occurs in the cytosol.
- Solution: Acetyl CoA is converted to citrate, which is transported out of the mitochondria and into the cytosol.
- Citrate is then converted back to acetyl CoA and oxaloacetate, allowing fatty acid synthesis to occur.
Breakdown of Amino Acids
- Amino acids are not stored as energy; instead, they are recycled as amino acids.
- Breakdown of amino acids:
- Carbon skeleton is used as intermediates in the TCA cycle to generate ATP.
- This process can also be used to make glucose.
Amino Acid Degradation and Nitrogen Excretion
- Amino acid catabolism: waste removal, catabolism, and recycling.
- Amino group is converted into carbamoylphosphate to enter the urea cycle.
- Carbon skeletons are converted into α-keto acids, which can enter the citric cycle and be used to make glucose or energy.
β-Oxidation of Fats
- Four-step process:
- Dehydrogenation: Make a double bond - FADH2
- Hydration: Make a hydroxyl (-OH)
- Dehydrogenation (again): Make a carbonyl from the hydroxyl - NADH
- Acyl transfer: Move unoxidized chain (acyl) to another CoA, leaving acetyl-CoA
Breakdown of Acyl-CoA
- Occurs inside the mitochondria.
- Acyl-CoA is attached to a carrier molecule called carnitine, generating fatty acyl-carnitine.
- Fatty acyl-carnitine is transported into the matrix via a specific transporter protein.
- Carnitine is removed, generating acyl-CoA.
Generating ATP through Electron Transport Chain
- 8 Acetyl-CoA → ca. 80 ATP
- 7 NADH → 7 x 4 ATP = 108 ATP
- 7 FADH2
- Used 2 ATP to generate fatty acyl CoA
- Total ATP generated: ca. 106 ATP
Learn about the process of fatty acid synthesis, its differences from fatty acid breakdown, and the enzymes involved. Discover how acetylCoA is converted to malonyl CoA in the cytosol.
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