Flashcards in Lecture 15: Glycolysis & Pentose Phosphate Pathway Deck (84):
What 2 steps of glycolysis use ATP?
Steps 1 and 3
What 2 steps of glycolysis produce ATP?
Steps 7 and 10
Why is ATP used in steps 1 and 3 of glycolysis?
Because the free energy level of the beta-gamma bond of ATP is higher than the free energy of the phosphate linkages in G6P and F1,6BP (extra energy is heat)
Why is ATP produced in steps 7 and 10 of glycolysis?
Because the free energy level of the phosphate linkages in 1,3BPG and phosphoenolpyruvate is higher than the beta-gamma bond of ATP (extra energy is heat)
Glycolysis step 1 enzyme?
Glycolysis step 1: reversible or irreversible?
Glycolysis step 1: ΔG°'?
Large negative ΔG°' (-16.7 kJ/mol)
What is the main purpose of the 1st step of glycolysis?
Retain glucose in the cell
What is the 1st priming rxn of glycolysis?
Glycolysis step 2 enzyme?
Glycolysis step 2: reversible or irreversible?
Glycolysis step 2: ΔG°'?
Small positive ΔG°' (1.7 kJ/mol)
Glycolysis step 3 enzyme?
Which is the second priming step of glycolysis?
What is the first committed step of glycolysis?
Glycolysis step 2 reactant and product?
G6P --> F6P
Glycolysis step 3 reactant and product?
F6P --> F1,6BP
Glycolysis step 3: ΔG°'?
Large negative ΔG°' (-14.2 kJ/mol)
How is step 3 of glycolysis regulated?
- F2,6BP (feed-forward regulation)
- Citrate (feedback inhibition)
Explain how PFK-1 is regulated by F2,6BP.
F6P is high --> activates PFK-2 --> converts F-6P to F-2,6-BP --> stimulates PFK-1
What is citrate a marker of in inhibiting PFK-1?
FA synthesis because acetyl-CoA needs to be transported to the cytoplasm via the citrate shuttle, so if you have enough of it that means you have enough citrate for FA synthesis
Glycolysis step 4 enzyme?
Glycolysis step 4 reactant and product?
F1,6BP --> DHAP + GAP
Glycolysis step 4: ΔG°'?
Large positive ΔG°' (23.8 kJ/mol)
Glycolysis step 3: reversible or irreversible?
Glycolysis step 4: reversible or irreversible?
What does GAP stand for?
What does DHAP stand for?
What is DHAP a precursor for?
Glycolysis step 5 enzyme?
Triose Phosphate Isomerase (TPI)
Glycolysis step 5 reactant and product?
DHAP --> GAP
Glycolysis step 5: ΔG°'?
Small positive ΔG°' (7.5 kJ/mol)
Glycolysis step 5: reversible or irreversible?
What steps does the preparatory phase of glycolysis include?
How many GAP molecules produced per 1 glucose?
Glycolysis step 6 enzyme?
Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH)
Glycolysis step 6 reactants and products?
GAP + Pi + NAD+ --> 1,3-bisphosphoglycerate + NADH + H+
Glycolysis step 6: ΔG°'?
Small positive ΔG°' (6.3 kJ/mol)
Glycolysis step 6: reversible or irreversible?
What steps does the payoff phase of glycolysis include?
Explain how NADH is generated in step 6 of glycolysis? What is the rest of the energy used for?
The electrons on the aldehyde group of GAP are high in energy and are transferred to NAD+
Rest of energy used to form acyl-phosphate covalent bond that is very high in energy
Glycolysis step 7 enzyme?
Glycolysis step 7 reactants and products?
1,3BPG + ADP --> 3-phosphoglycerate + ATP
Glycolysis step 7: ΔG°'?
Large negative ΔG°' (-18.5 kJ/mol)
Glycolysis step 7: reversible or irreversible?
What bond in 1,3BPG is high in energy?
Acyl phosphate bond
How many ATP produced in step 7 of glycolysis per glucose?
Glycolysis step 8 enzyme?
Glycolysis step 8 reactants and products?
3-phosphoglycerate --> 2-phosphoglycerate
Glycolysis step 8: ΔG°'?
Small positive ΔG°' (4.4 kJ/mol)
Glycolysis step 8: reversible or irreversible?
Glycolysis step 9 enzyme?
Glycolysis step 9 reactants and products?
2-phosphoglycerate --> phosphoenolpyruvate + H2O
Glycolysis step 9: ΔG°'?
Small positive ΔG°' (7.5 kJ/mol)
Glycolysis step 9: reversible or irreversible?
Glycolysis step 10 enzyme?
Glycolysis step 10 reactants and products?
Phosphoenolpyruvate + ADP --> pyruvate + ATP
Glycolysis step 10: ΔG°'?
Large negative ΔG°' (-31.4 kJ/mol)
Glycolysis step 10: reversible or irreversible?
What is the net reaction of the oxidation of 1 glucose through glycolysis?
1 glucose + 2 ATP + 2 NAD+ --> 2 pyruvate + 4 ATP + 2 NADH + 2 H+ + 2 H2O
What are the 2 ways of regenerating NAD+ for step 6 of glycolysis? Which one is fastest?
1. Aerobically in mito
2. Anaerobically in cytosol = fermentation (FASTEST)
Describe the aerobic regeneration of NAD+ in the mito. Equation?
2 NADH + 2 H+ + O2 --> 2 NAD+ +2 H2O
NADH needs a carrier to enter the mito matrix so this step is slow
Describe the anaerobic regeneration of NAD+ in the cytosol = fermentation. Equation?
Pyruvate --> L-lactate by lactate dehydrogenase
Where can fermentation occur?
Muscles, RBCs, and other tissues
What is the pentose phosphate pathway?
It's the pathway taken by G6P if glycolysis is inhibited to generate 2 NADPH and ribose-5-phosphate
What is ribose-5-phosphate created by the PPP used for?
1. De novo ATP synthesis
2. Nucleotide synthesis
What is NADPH created by the PPP used for?
1. Biosynthesis of FAs and sterols
2. Converts GSSG to 2GSH
What are the 2 phases of the PPP and what happens in each?
1. Oxidative: generation of 2 NADPH and ribose-5-phosphate (CO2 leaves)
2. Nonoxidative: ribulose-5-phosphate regenerates G6P
What are the 2 enzymes of the PPP that generate NADPH?
1. G6P dehydrogenase (G6PD)
2. 6-phosphogluconate dehydrogenase
What is the purpose of NADPH converting GSSG to 2GSH?
Protect the body from oxidizing agents:
Small amount of O2 in cells is converted to ROS (superoxide radicals, hydrogen peroxide, and hydroxyl free radicals) and gluthathione peroxidase can convert these to water by using the reducing power of GSH (which is converted back to GSSG)
How is GSSG converted to 2GSH?
Gluthatione reductase use NADPH's reducing power
What does GSH stand for? Does it have disulfide bonds?
No disulfide bonds
What does GSSG stand for? Does it have disulfide bonds?
1 disulfide bond
What is favism? Symptoms? Treatment?
Condition caused by lack of G6PD enzyme and foods that have divicine (like fava beans): too many ROS in RBCs and no NADPH to protect the body
Symptoms: anemia, diarrhea, respiratory problems, can be lethal
Treatment: avoid oxidizing agents in diet
Describe the nonoxidative phase of the PPP. What 2 enzymes are used?
Six 5-carbon molecules are converted to five 6-carbon
molecules, thus regenerating glucose 6-phosphate.
Which steps of glycolysis are irreversible?
1, 3, and 10
Other than 1,3BPG and phosphoenolpyruvate, what other molecule has a phosphate linkage that is higher in energy than ATP's?
Which produces ATP the fastest: glycolysis or ETC?
What is the definition of fermentation?
Generating ATP from a metabolic fuel without net oxidation of the fuel
Which organs have the enzyme PFK2?
Why do patients with favism not have a ribose-5-phosphate caused deficiency in nucleotides?
Because nucleotides can be obtained in the diet
What are 2 important glycolytic intermediates does the nonoxidative phase of the PPP generate?
Does the PPP involve the oxidation of glucose?