Fuel Oxidation and ATP generation Flashcards
What’s the point of ATP
ATP contains “high energy” phosphate bonds we use that energy to: -muscle contraction -active ion transport -biosynthesis -detoxificaion -thermogenesis
(ΔG) for a reaction
free energy change depends on temperature and on the concentration of the products and the substrates when the rxn is at equilibrium
What does ΔG>0 mean?
at equilibrium the reactants are favored, so it needs external help to proceed
ATP hydrolysis coupled to change in transporter conformation. Costs energy to move ions against electrochemical gradient.
Transport work: Na+/K+ -ATPase
*ATP hydrolysis coupled to change in protein conformation.
Mechanical work: muscle contraction
ATP hydrolysis coupled to change in enzyme conformation.
Synthesis (work): asparagine synthetase -ATP activating the enzyme
only type that ATP physically participates in the reaction itself (adds a phosphate to the reactant.
Biochemical work: glucose to G6P (its phosphorylation, so the enzymes will be kinases)
Molecules with phosphate or thioester linkage have high energy bonds, so?
We can cleave these to release a lot of energy (couple it to rxn we want to drive forward!)
What fuels can we get the most energy from?
**FA least oxidizes relative to number of carbons. glucose is the worst- most oxidized
Name 2 electron carriers that capture energy from oxidized fuels, and what is used to synthesize each?
NAD+ - made via niacin FAD+ - made via riboflavin *buzz word: dehydrogenase reactions
name 2 metabolic byproducts of fuel oxidation and ATP generation
-H20 (formed when oxygen molecules - the final electron acceptors of cellular resp. - take up protons) -CO2 (TCA cycle)
What is another term for glycolysis?
anaerobic metabolism -doesnt require oxygen or mitochondria -reducing pyruvate to lactic acid regenerates the electron carriers -takes place in cytosol -RBCs, WBCs, Kidney medulla, eye tissue -skeletal muscle (white fibers!)
What is another term for oxidative phosphorylation?
aerobic metabolism -takes place in mitochondria -requires mitochondria and oxygen -skeletal muscle (red fibers), most tissues of the body
Products of glycolysis
-2ATP -Lactic ACID -NAD+ -FAD+
Products of oxidative phosphorylation
-28 ATP -o2 (final electron acceptor)
Glycolysis investment phase
a
What are the 2 regulated steps in the investment phase of glycolysis, and why are they regulated?
conversion of glucose to G6P (currency of cell!) -*hexokinase is the enzyme that accomplishes phosphorylation conversion of fructose 6 phosphate to fructose 1,6 bisphosphate -*phosphofructokinase enzyme -they are regulated because they require ATP (phosphorylation), dont want to run the step and waste energy if they are not needed.
result of investment phase
Converted 1 glucose into 2 trioses Used 2 ATP ΔG′° = -51 kJ/mol – why is this negative? -Giving off energy because of ATP hydrolysis
What are the 2 regulated steps in the payoff phase of glycolysis, and why are they regulated?
conversion of 1,3-Bisphospho-glycerate to 3-Phospho-glycerate is regulated (bc it requires ATP!) -enzyme: phosphoglycerokinase conversion of Phosphoenol-pyruvate (PEP) to Pyruvate is regulated (bc it requires ATP!) -enzym: *pyruvate kinase
result of payoff phase
2 trioses into 2 pyruvate molecules Make 4 ATP, net of 2 ATP 2 NAD+ are reduced (NAD+ + H:- NADH) Oxidation of glucose!
when you see a dehydrogenase enzyme, what does that tell you?
electron carrier are being reduced!
So what is the point of glycolysis?
-for cells that cant do aerobic metabolism, the purpose is to generate the 4 ATP (Only net of 2 ATP tho) (and of course regenerate your electron carriers) *BUT for cells capable of aerobic metabolism, Glycolysis produces: PYRUVATE and NADH
What does the Malate shuttle do?
delivers electrons to the mitochondria
Regarding the enzymes involved in the steps of glycolysis that require energy, how do we regulate those enzymes?
Substrate availability [enzymes] *Allosteric regulation Covalent modification of enzyme
examples of molecules that stimulate glycolysis?
-things in high concentration when energy is depleted will stimulate glycolysis ↑ [AMP]* ↑ [fructose-2,6-bisP] ↑ [fructose-1,6-bisP]