Flashcards in Exam 1 Deck (74):
When bonds are being broken, is the delta G positive or negative?
When biosynthesis is occurring is delta G positive or negative?
If Delta G is negative, then Delta H must be ____ compared to Delta S * T.
What is the equation for Delta G standard at equilibrium?
Delta G Standard = -RTLnKeq
If the concentration of products is greater than the concentration of reactions, is Delta G positive or negative?
If the concentration of reactants is greater than the concentration of products will delta G be positive or negative?
If Keq is greater than 1, will Delta G be positive or negative?
What is the primary indicator of the magnitude of Delta G?
Concentration of Products and Reactants
If 2 reactions are coupled, the Delta G’s are _____
If 2 reactions are coupled, the Keq values are ______.
Why is ATP so popular for energy?
ATP is a stable molecule in solution and requires an enzyme to break its bonds
How does the cell drive the energetically unfavorable reaction of ADP + Pi -> ATP?
Maintain equilibrium far to the left to increase the magnitude of Delta G
What is the name of the intermediate that undergoes tautomerization in glycolysis to create a stable product?
Phosphoenolpyruvate -> Pyruvate (enol) -> Pyruvate (keto)
Why is Pyruvate in the enol form tautomerized to Pyruvate in the keto form?
Carbonyl bond (C=O) is more stable than the enol bond (C-OH)
Which intermediates undergo resonance?
Acetyl-CoA -> Acetic acid -> Acetate
1,3 BPG -> 3PG acid -> 3PG
Phosphocreatine -> Creatine
What is the term for the molecule that loses electrons in redox reactions?
What is the term for the electron donor in a redox reaction?
Reductant or reducing agent
What is the term for the molecule that gains electrons in redox reactions?
What is the name for the electron acceptor in a redox reaction?
Oxidant or Oxidizing Agent
What is the term for enzymes that catalyze oxidation reactions?
What is the predominant cofactors in dehydrogenase reactions?
What are the primary derivatives of Niacin?
NAD+ and NADP+
Why do alcoholics develop niacin/B3 deficiencies?
Alcohol damages intestinal lining and prevents proper absorption of niacin
What are the 3 most regulated steps of glycolysis?
1, 3, 10
True or False: Any hexose can enter glycolysis as long as it is phosphorylated?
False. Only glucose can enter glycolysis, all other hexoses need to be converted to glucose or enter a different pathway.
What are the 4 kinase enzymes involved in glycolysis??
What are the 3 isomerases involved in glycolysis?
Triose Phosphate Isomerase
What is the name and role of the aldolase in glycolysis?
Fructose 1,6 Bisphosphate Aldolase separates a 6 carbon fructose into 2, 3 carbon sugars.
What is the name and role of the dehydrogenase enzyme in glycolysis?
Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH)
Oxidize G3P and Reduce NAD+ to create 1,3-bisphosphglycerate and NADH
What is the role of the enolase of glycolysis?
Convert 2-phosphoglycerate into an energetically favorable substrate, phosphoenolpyruvate, for step 10.
If there is a defect with Hexokinase, what substrates would accumulate and what products would be lacking?
Glucose would accumulate
All substrates would be lacking
How many hexokinase isozymes are there?
Where is hexokinase IV expressed, exclusively?
Liver & Pancreatic Beta Cells
When does Glucokinase activate and when does it deactivate?
It activates at higher glucose concentrations and does not have product inhibition so will continue until concentrations decrease.
What type of symptoms would you expect a patient with a glucokinase defect to present with?
Symptoms similar to diabetes, high levels of thirst, frequent urination. But no hormonal defects in insulin/glucagon expression.
If phosphoglucose isomerase is not working properly what substrate would you expect to accumulate and what products would you expect to be lacking?
Glucose 6-Phosphate would accumulate, it would not revert back to glucose because that reaction is not energetically favorable.
Downstream, fructose-6-phosphate and all related products of energy would be lacking
What is the primary role of phosphoglucose isomerase?
Convert an Aldose to a Ketose, so that phosphate groups can be transferred to a terminal OH
What is the most regulated enzyme of glycolysis?
If there is an over-abundance of ATP, what will happen to PFK-1?
If there is an abundance of AMP, what will happen to PFK-1
What is the strongest regulator of PFK-1?
If there is an over-abundance of citrate, what will happen to PFK-1?
If there were a malfunction with PFK-1 what substrate would you expect to accumulate, and what product would you expect to be lacking?
G6P and F6P would accumulate due to the readily reversible reaction of phosphoglucose isomerase.
Glycolysis would never pass F1,6P and into the energy harvest phase.
What is the product of F6P and PFK-1?
What is the role of Fructose 1,6 bisphosphate aldolase?
Separate F1,6P into DHAP and G3P for energy harvest.
If there is a malfunction with F1,6P Aldolase, what substrates would accumulate and what products would you expect to be lacking?
F1,6P would accumulate because F6P->F1,6P is the first irreversible reaction of Glycolysis.
You would not be able to enter energy harvest.
Given the large, positive delta G for the F1,6P Aldolase reaction, how does this reaction proceed?
The concentration of reactants is much higher than concentration of products, driving the reaction towards equilibrium. The previous reaction is irreversible and the next reaction is very fast.
What is the role of Triose Phosphate Isomerase in glycolysis?
Convert DHAP to G3P to be used as a substrate for G3P DH
If there is a failure in TPI what products will accumulate, and what substrates will be lacking?
F1,6P Aldolase is reversible with high concentrations of DHAP, but PFK-1 is not, so F1,6BP and DHAP would accumulate.
50% of the products from F1,6P Aldolase will continue through glycolysis which will slow down energy harvest.
What is the role of GAPDH in glycolysis?
Reduce NAD+ and oxidize G3P to form an acrylic phosphate instead of a carbonyl group.
What step of glycolysis would be most directly inhibited by ethanol fermentation, and why?
Step 6, Glyceraldehyde 3-Phosphate Dehydrogenase because NAD+ in the cytoplasm is required, but ethanol fermentation also requires NAD+ and will outcompete glycolysis for NAD+.
What is the product of GAPDH?
1,3 BPG and NADH
What is the term for a transfer of a phosphorylation group of a substrate onto ADP?
Substrate level phosphorylation
What is the role of phosphoglycerate kinase in glycolysis?
Removing a phosphate group from 1,3BPG and adding it to ADP.
If Steps 6 & 7 are coupled together to make a strongly negative Delta G, what bioenergetics concept is this an example of? What would be the reaction intermediate?
What is the function of Phosphoglycerate Mutase in glycolysis?
Create an energetically favorable substrate for the next step of glycolysis
What is the substrate and product of the phosphoglycerate Mutase reaction?
3-phosphoglycerate -> 2-phosphoglycerate
What is the function of the enolase in glycolysis?
Create an energetically favorable substrate for the final step of glycolysis
What is the purpose of converting 2PG to PEP in glycolysis?
The enol form of Pyruvate is less stable than the keto form, so PEP will increase the potential energy to transfer the phosphate to ADP
What is the function of Pyruvate kinase?
To convert phosphoenolpyruvate into the enol form of Pyruvate, which will spontaneously tautomerize into the keto form of Pyruvate and ATP.
What is the reaction intermediate of step 10 of glycolysis?
Enol form of Pyruvate
Where does the oxidation of non-glucose sugars occur?
What is the first enzyme in the fructolysis pathway?
Fructokinase and ATP
What is the enzyme that separates Fructose 1-Phosphate into its products?
What are the substrates of the F1P + Aldolase B reaction?
Glyceraldehyde and DHAP
What enzyme is used to convert Glyceraldehyde into G3P?
What causes regulated enzymes in coupled reactions to generate a large effect on delta G from small changes in products or reactants?
Multiplicity of Keq in coupled reactions
What is the term for the state where cells die due to a decrease in reaction rates for reactions that use ATP?
As ATP decreases the magnitude of free energy ______.
Why is AMP a strong allosteric stimulant of glycolysis?
As ADP accumulates, adenylate kinases generate AMP and ATP
What is the net yield of glycolysis reactions per glucose?
2 ATP and 2 NADH
Aerobic respiration in the mitochondria produces more/less ATP than glycolysis anaerobically.
Under what conditions will cellular localization and sequestration occur in glycolysis?
When glucagon is high, due to steps #3 & #10 shutting down, concentrations of F6P will increase. These increased concentrations of F6P will bind to glucokinase and move the enzyme to the nucleus where it cannot access the substrate (glucose)