Lecture notes
Glycolysis
A summary of the lectures on glycolysis and the role of ATP and NAD+ in this.
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All chemical reactions involved inRole of NADH Catabolic pathways
maintaining the living state of the
Transfers electrons away from food Stage I – digestion and hydrolysis.
cells and the organism.
sources, for it to be used in Breaking down of complex
We breakdown a variety of energy-
anabolism molecules
rich nutrients – carbohydrates, lipids
NAD+ and NADP+ are the major Stage II- conversion. Breaking
and proteins- and catabolise them
electron acceptors in biological down 2-,3-carbon compounds and
to a few, energy-poor end products
systems. Oxidation of fuel molecules acetyl CoA
– CO2, H2O, NH3, and release ATP,
results in the transfer of electrons to Stage III- oxidation. Oxidation of
NADH and e-. These are used in
the terminal electron acceptor, O2, acetyl CoA via citric acid cycle and
anabolic reactions, converting small
via carriers. electron flow to O2 via NADH
precursor molecules – amino acids,
carriers.
sugars and fatty acids, into a wide
variety of complex molecules. Metabolism E.g. glucose can be stored as
glycogen, converted to nucleotides
ATP is the currency of free energy in Glycolysis and can be used to generate ATP.
biological systems. A free energy Net outcome: 2 pyruvate, 2 ATP, 2 Its catabolism accounts for 80% of
donor in anabolism/biosynthesis, NADH. Free energy released = 197 carbohydrate catabolism.
mechanical work/movement and KJ/mol. Glycolysis
active molecular transport. 3 stages:
Under typical cellular conditions ATP Stage I : investment phase
' - Glucose receives a Pi group from
∆ G ° =−7.3 Kcal /mol meaning
that it has a high phosphoryl ATP – irreversible
transfer potential. - Glucose-6-phosphate isomerised
This value is around the midpoint - Fructose-6-phosphate
meaning ATP can easily lose or gain phosphorylated = rate-limiting
phosphate groups. We have step
reservoirs of high-potential
phosphoryl groups in the body. Stage II: Energy investment Cont.
- Fructose-1,6-bisphosphate is
ADP and NAD+ regeneration cleaved into two, 3-carbon
ATP utilised in reactions -> ADP. molecules that are isomers.
NAD+ regenerated via either lactate - Glyceraldehyde 3-phosphate is
dehydrogenase (anaerobic) or on the direct path of glycolysis.
oxidative phosphorylation (aerobic) - Dihydroxyacetone phosphate is
isomerised to glyceraldehyde-3-
Control of metabolism phosphate, generating two
Controlled by controlling selected molecule for subsequent steps
enzymes – saves time and effort
Stage III: Energy generation step
Control irreversible enzymes, - Generation of phosphorylated
enzymes at the start of a pathway or 1,3-bisphosphoglycerate via
branchpoint and rate-limiting oxidation of the aldehyde group
enzymes e.g phosphofructokinase. (NADH reduced)
- Phosphoryl group transfer from
Enzymes are controlled by altering 1,3-bisphoshoglucerate. (ATP
their levels of synthesis (slow) or generation)
altering their activity (fast). E.g - Phosphoryl group is shifted from
insulin turns on glucose metabolism the 3 carbon to the 2 carbon Aerobic conditions
whilst glucagon turns off glucose position. Pyruvate -> Krebs -> ETC
metabolism. - Dehydration of 2- Anaerobic conditions
Obesity phosphoglycerate elevates the Pyruvate is converted to lactic acid –
Predisposes us to diabetes type II transfer potential. causes muscle fatigue & cramp &b
through regulatory substances - Phosphoryl group transfer from less ATP produces. O2 not final
produced by adipose tissue which phosphoenolpyruvate. (ATP electron acceptor
can cause insulin resistance -> generation) Anaerobic conditions in yeast
hyperglycaemia. Pyruvate is converted to ethanal
(+CO2) -> ethanol . Non-reversible.
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