University:
Amherst College
Course:
CHEM 330 | Biochemical Principles of Life at the Molecular Level
Academic year:

2023
Views:

15

Pages:

10
Author:

Summer Roman

BioChem 330 - Course Outline • Metabolism and Bioenergetics (II) – ENZYME CATALYSIS: • kinetic constants kcat, Km • Catalytic strategies, the serine proteases – CATABOLISM (breakdown) • Carbohydrates – – – – Glycolysis Tricarboxylic Acid Cycle Electron Transport Chemiosmosis and ATPase • Fatty acids and amino acids BioChem 330 Nov 8, 2011 • Linkage of cytosolic events (glycolysis) to mitochondrial events (tricarboxylic acid cycle -‐ TCA) in the digesFon of carbohydrates • The linker: pyruvate dehydrogenase What’s happening to the substrate? • ..in the pyruvate dehydrogenase complex – Conversion of pyruvate to Acetyl CoA and CO2 • Unlike acFon of LDH, there is no regeneraFon of NAD+ for glycolysis • No going back • … then in the Krebs cycle – ConverFng acetylCoA to 2 CO2 – The Cycle: origin and properFes A Bed&me Story by PLW Curly: Type: ? MoFlity a specialty Meets... Mo Eubacterium Mo is eaten by Curly!! Electron transport to acceptor (O2) 1. 2. 3. 4. Protozoa Fungi Plants & Animals Curly/Mo Jrs I & II • Curly And now... – Cytoplasm – Glycolysis • Mo – Mitochondria... ..where, for our purposes... The Coupling Machinery is Complex • Pyruvate -‐> Acetyl CoA – (OxidaFve DecarboxylaFon) – CH3-‐CO-‐CO2-‐ + NAD+ + CoA-‐SH -‐> CH3-‐CO-‐S-‐CoA + NADH + CO2 – ΔGo’ = -‐ 8 kcal/mole • Catalyzed by pyruvate dehydrogenase complex – E1 (24 α2β2 tetramers), E2 (8 α3 trimers ), and E3 (6 αβ dimers) • “Stoichiometric” cofactors – NAD+ – CoA-‐SH • “CatalyFc” cofactors – Thiamine pyrophosphate – Lipoic Acid (fajy acid) – FAD How it starts... • First the E1 bound TPP (related to vitamin B1, absence of which causes beriberi) …does some carbanion chemistry on pyruvate... … and now the “aldehyde” gets oxidized by running into oxidized lipoate on E2... “AcFve aldehyde” …and then the dramaFc wrap-‐up is trapped by the CoA This thioester While the electrons from substrate stay with the lipoamide and ... ….go ﬁrst to a bound FAD ….and ﬁnally end up in a NADH mobile e-‐ carrier The components of which can be broken down into... • THE ENZYMES: • E1: pyruvate dehydrogenase • E2: Dihydrolipoyl transacetylase • E3: Dihydrolipoyl dehydrogenase All of which occurs in a factory which is enormous... • Located in the matrix of the mitochondrion and larger than ribosomes

BioChem 330 - Course Outline Metabolism and Bioenergetics (II) Part 1

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