What is Oxidative Phosphorylation?
Oxidative phosphorylation is a series of chemical reactions in which electrons are transferred, nutrients are metabolised and ATP is formed.
Brain Hypometabolism Hypothesis
The Brain Hypometabolism Hypothesis focuses on energy metabolism. More specifically the hypothesis states that
‘Energy hypometabolism in the brain leads to neuropathology‘
Human Metabolism by Frozen Man (CC BY 4.0)
What is Metabolism?
Metabolism can be defined as the chemical processes that occur in living organisms. There are three types of metabolic processes
(a) Generation of energy
(b) Generation of basic chemicals including fatty acids, amino acids and sugars
(c) Elimination of Nitrogen waste products
Glycolysis by Dr Thomas Shafee (CC BY 4.0)
Glycolysis is one of the key pathways for energy metabolism in the human body. In this metabolic pathway the molecule Glucose is converted into Pyruvate. This pathway generates energy in the form of ATP. This pathway however does not use oxygen although the products generated are metabolised using oxygen. This is relevant to the bigger picture of energy metabolism in the brain.
Acetyl CoA Space Filling Molecule by Benjah-bmm27 (Public Domain)
Acetyl Coenzyme A is an important molecule for many pathways involved in energy metabolism. Acetyl Coenzyme A is derived from
(a) Glucose via the Glycolysis pathway
(b) Amino acids via Acetoacetyl-CoA, Pyruvate and directly through multiple pathways
(c) Fatty acids via Beta-oxidation
Vitamin B5 is required for the synthesis of Acetyl CoA.
The Citric Acid Cycle
The Citric Acid Cycle (CC BY 3.0) by,
The Citric Acid Cycle is one of the main energy metabolism pathways in humans. Acetyl Co-A which is generated from other pathways is utilised in the Citric Acid Cycle. The Citric Acid Cycle has a number of properties
- Generation of energy in the form of ATP
- Generating NADH which is utilised in oxidative phosphorylation
- Citric Acid is regenerated
- Carbon Dioxide is produced
The Citric Acid Cycle takes place in the Mitochondria.
The Citric Acid Cycle is important for the discussion of the Brain Hypometabolism Hypothesis where we have already discussed the metabolism of Glucose.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook. Last update: 2014-02-24; version: 2.3.3. DOI of this term: https://doi.org/10.1351/goldbook.K03386. Accessed 8th May 2017.
White H1, Venkatesh B. Clinical review: ketones and brain injury. Crit Care. 2011 Apr 6;15(2):219. doi: 10.1186/cc10020.
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