Glycolysis, Beta Oxidation, Krebs Cycle

• What does NAD+ do when oxidising a carbohydrate?

  Form a double bond between the carbon and oxygen
• What does FAD do when oxidising a carbon chain?

  Form a double bond between carbons
• Why is it called beta oxidation?

  All chemical rearrangements occur on the beta (second) carbon
• The alpha carbon of a fatty acid is attached to the functional group
• How are FAs transported in the blood?

  Loose association with albumin
• How do FAs enter the cytoplasm?

  Passive diffusion
• Why are FAs transported by albumin in the blood?


  To stop them from acting like soap
• What negates the hydrophobicity of FAs in the cytoplasm?

  FA binding protein
• What traps the FA in the cytoplasm?


  Esterification to CoA
• What does the esterification of FAs to CoA require?

  ATP dephosphorylation to AMP and fatty acyl CoA synthetase
• How is FA-CoA transported into the mitochondria?

  Carnitine replaces the CoA
• How is the CoA of FA-CoA displaced by carnitine?

  Carnitine acyltransferase
• Once in the mitochondria, carnitine acyl-transferase 2 swaps the carnitine back to CoA
• FAD performs the first H/e- stripping event of beta oxidation
• In the first H/e- stripping event of beta oxidation:

  1. Reduction of FAD forms a carbon double bond
  2. The bond is hydrated by addition of water to form an -OH group
• NAD+ performs the second H/e- stripping event of beta oxidation
• In the second H/e- stripping event of beta oxidation:

  1. Reduction of NAD+ causes double bond formation between carbon and oxygen
  2. CoA breaks two carbons off the molecule to form acetyl CoA
• Each round of beta oxidation gives:

  • 1 acetyl CoA
  • 1 NADH
  • 1 FADH2
• Where does glycolysis occur?

  In the cytoplasm of all tissues
• Does glycolysis require oxygen?

  No
• GLUT-1: present on all cells all the time
• GLUT-4: present on insulin sensitive tissues (muscle and adipose)
• GLUT-2: present on blood glucose regulating tissues all the time (liver and pancreas)
• Early glycolysis = investment phase
• Early glycolysis

  1. Phosphate added to glucose to trap within cell
  2. Energy is invested to produce a symmetrical sugar with two phosphates
  3. Sugar splits into two 3-carbon sugar phosphate
• Late glycolysis = return phase
• late glycolysis

  1. A phosphate is added to the 3-carbon sugar phosphate and oxidised with NAD
  2. Substrate level phosphorylation
  3. Rearrangement to form two pyruvate molecules
• Pyruvate from glycolysis can be:

  1. Oxidised by NAD+ into acetyl CoA to enter the Kreb's Cycle
  2. Reduced by NADH into lactate to be recycled to glucose
• What is the substrate of the Kreb's cycle?

  acetyl CoA
• Where does the Kreb's Cycle occur?

  Entirely in the mitochondria
• What is the carrier molecule for the Kreb's Cycle?

  Oxaloacetate
• When Acetyl-CoA joins with oxaloacetate, it becomes citrate (6C)
• NAD and FAD oxidise in the Kreb's cycle to reproduce the carrier molecule