01:694:301 Lecture Notes - Lecture 17: Acetyl-Coa, Thiamine Pyrophosphate, Oxidative Decarboxylation

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Chapter 17‘The Citric Acid Cycle
The Citric Acid Cycle (CAC) is strongly oxidative, in contrast to glycolysis which is anaerobic
o Also known as the
‘tricarboxylic acid cycle
or ‘
Kreb’s cycle’
o CAC takes place in the mitochondrial matrix of eukaryotic cells—whereas glycolysis occurs
in the cytoplasm
o Process starts with complete oxidation of glucose derivatives to CO2
! Final common pathway oxidation of fuel molecules – carbs, fatty acids, aa
! Most fuels enter CAC as acetyl CoA
o Most ATP provided is from the
aerobic
processing of glucose " CAC
! Function of CAC is to
harvest high energy electrons
from these carbon fuels
! Removes e- from acetyl CoA and uses e- " NADH and FADH2
o The immediate products of the CAC are reduced cofactors (NADH and FADH2),
which then feed electrons into oxidative phosphorylation, yielding much ATP
o **OAA is an important glucose precursor
The CAC is connected with glycolysis via the pyruvate DH complex
o Under anaerobic conditions, PYR " ethanol or lactate
o Under aerobic conditions " PYR transported to mitochondria " acetyl CoA
! There is oxidatively decarboxylated by PYR DH complex
o Large highly integrated complex of 3 enzymes
KNOW the 3 enzymes, cofactors, and the mechanism shown in class for PYR DH complex
o The cofactors, which are prosthetic groups are TPP (thiamine pyrophosphate), lipoic acid
(lipoamide), FAD; CoA and NAD+ are cofactors that serve as substrates
o Refer to notes for full mechanism
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