Metabolism Flashcards
Catabolism vs anabolism
Catabolism= Capture- energetically favorable oxidation of substrates and capture of energy as ATP, GTP, and reduced cofactors (NADPH, NADH, FADH2)
Anabolism= Assembly- energetically unfavorable reactions that require energy to produce various substances our bodies need
CO2 is formed by 3 reactions, NADH forms 2.5 ATP, FADH2 forms 1.5 ATP
Carbs enter as glucose or fructose, lipids enter as acetyl CoA, you make ATP and GTP directly via substrate level phosphorylation
Gluconeogenisis starts in the TCA cycle and is regulated by ATP, NADH, and TCA substrates
Proteins become AAs and enter the TCA
High energy molecules used in Metabolism
high energy molecules: ATP, GTP, NADH, FADH2, and NADPH
NADH and FADH2 are used in electron transport and oxidative phosphorylation (catabolic) and generate 2.5 ATP and 1.5 ATP
Anabolic pathways use ATP and NADPH
Producing these high energy molecules
CAtabolism is a - dGo and Anabolism is a positive dGo
To make ATP you need a molecule thats even more unstable than ATP (such as phosphoenolpyruvate)
ATP and PEP dont go back down to a more stable form bc of a high activation energy to transition state (ipsofacto they dont readily convert to P unless an enzyme is there)
Making of ATP
The coupling of the two half reactions in an enzymes active site provides the means of storing energy (work) in the form of ATP and the remaining energy comes off as heat (breakdown PEP-> pyruvate, and ADP-> ATP)
Hydrolysis of phsophoenolpyruvate PEP, is highly favorable, due to electrostatic repulsion within the reactant molecule is relieved, both products (pyruvate and phosphate) are stabilized via resonance (tautomerization)
Pyruvate undergoes further solvation by h20
Hydrolysis of ATP is not as favorable as PEP
yB phosphate anhydride bond of ATP are v high energy, negative charges repulse (like PEP), release of first P has resonance and is solvated (like PEP), but there is no resonance with ADP (so ADP is not as stable as pyruvate)
when aB bond is split (-10.9) pyrophosphate is made and the two phosphates between beta and gamma are split (-7.3) via pyrophosphatase
Energy charge
Energy utilizing path: use 3.3 kcal/mol to phosphorylate glucose, 4 of heat is derived
HEXOKINASE
Energy yielding: 7.3 work is done to make ATP, 7.4 of heat
PYRUVATE KINASE
the enzymes keep water out of active sites so that some ATP energy is converted into work instead of diectly hydrolized
Energy charge: energy yielding molecules over the total amount of adenine nucleotides
typical charge of .8/.9 ish
Adenylate kinase maintains the ratios of ATP:ADP:AMP
Energy charge= ([ATP] +.5[ADP])/ [ATP}+ [ADP] + [AMP]
a 2400 calorie diet~ 3400 mM of ATP made each day in average cell
Phosphocreatine
high energy molecule used in skeletal muscle to provide quick way to produce more ATP
creatine kinase: converts creatine to phosphocreatine using ATP
Phosphocreatine has a high energy phosphate bond, it can act like PEP and power the production of ADP to ATP
Roles of NADH and NADPH
high energy electrons in the form of hydride ions (H-) are captured by NAD+ forming NADH
Reoxidation of NADH by O2 in mito yields 2.5 ATP
NADP+ also accepts H- to form NADPH have biosynthetic and antioxidant defense system roles rather than ATP formation
Role of FADH2
can capture one or two high energy electrons by FAD forming FADH or FADH2
FADH2 is oxidized by O2 in mito to yield 1.5 ATP
role Coenzyme A thioesters
Acetyl- CoA is a central metabolic intermediate and a high energy species that transfers acetyl groups to other molecules.
General properties of metabolic pathways
Pathways occur in discreet chemical steps each catalyzed by an enzyme
Most steps are reversible
Entry and exit of pathway is controlled by enzymes catalyzing irreversible reactions, entry enzymes are commited steps and are tightly regulated (allosterically)
Pathways sharing common intermediates have a branch point
Short term regulation is acheived by activators and inhibitors (effectors)
Long term reg is done thru gene induction and protein turnover (enzyme degredation)
Regulation of Metabolic Pathways
Catabolic and Anabolic pathways share many intermediates, tight regulation prevents futile cycling Futile cycling (breaking down a substrate that we are using enrgy to make)
Charged or large molecules require specific transporters
Catabolic and anabolic paths are segregated into different cellular compartments
Intracellular location of major enzymes and metabolic processes
Cytoplasm: glycolysis and gluconeogenisis, hexose monophosphate shunt, glycogenisis and glycogenolysis, fatty acid synthesisi
Mito: gluconeogenisis, TCA FA oxidation, urea cycle, ETC , AA synthesis and degredation
ER: G6Pase
