15 Questions
What is the allosteric activator of PFK in eukaryotes?
Fructose-2,6-bisphosphate
What inhibits PFK-2 and stimulates fructose-2,6-bisphosphatase?
Pi (inorganic phosphate) and citrate
What activates pyruvate kinase, serving as an example of feed-forward regulation?
Fructose-1,6-bisphosphate
What is the result of increasing ATP concentration in terms of pyruvate kinase activity?
Increases Km for PEP
Under anaerobic conditions, glycolysis proceeds at higher rates than during aerobic conditions. What is this phenomenon called?
Pasteur Effect
What is the overall reaction of glycolysis?
Glucose + 2NAD+ + 2 ADP + 2Pi --> 2NADH + 2 pyruvates + 2ATP + 2H2O + 4H+
Which enzyme catalyzes the phosphorylation of glucose in the first reaction of glycolysis?
Hexokinase
What are the three possible fates for pyruvate after glycolysis?
Mitochondrial oxidation, reduction to lactate, decarboxylation to acetaldehyde
What strategy is employed in glycolysis to couple the subsequent hydrolysis of reactive substances to ATP synthesis?
Convert phosphorylated intermediates into compounds with high phosphate group-transfer potentials
What is the main purpose of the first phase of glycolysis?
To convert glucose to two G-3-P
What is the net ATP yield for glycolysis?
Two ATP and two very high energy phosphate intermediates
Which enzyme is responsible for phosphorylating glucose in β cells and is only active when glucose levels are high?
Glucokinase
What is the fate of NADH under anaerobic conditions?
It is oxidized to NAD+
Which enzyme is the committed step in glycolysis and is highly regulated?
Phosphofructokinase (PFK)
What regulates PFK-1 and is related to the energy status of the cell?
ATP, citrate, AMP, and fructose-2,6-bisphosphate
Study Notes
Glycolysis and Regulation
- Hexokinase and glucokinase are responsible for phosphorylating glucose in different tissues
- Hexokinase is the first step in glycolysis, with a large, negative ΔG
- Glucokinase acts as a glucose sensor in β cells and is only active when glucose levels are high
- Phosphofructokinase (PFK) is the committed step in glycolysis and is highly regulated
- The net ATP yield for glycolysis is two ATP, with two very high energy phosphate intermediates
- NADH's fate depends on aerobic or anaerobic conditions
- Pyruvate can be oxidized to Acetyl-CoA in aerobic conditions or reduced to lactate in anaerobic conditions
- Under anaerobic conditions, lactate is formed by lactate dehydrogenase to regenerate NAD+
- The Cori Cycle is important for recovery after intense activity and involves lactate accumulation and depletion of glycogen stores
- Alcohol fermentation is important for regenerating NAD+ under anaerobic conditions
- Regulation of hexose transporters and hexokinase is coordinated with other regulatory enzymes in glycolysis
- PFK-1 is regulated by ATP, citrate, AMP, and fructose-2,6-bisphosphate, and its regulation is related to the energy status of the cell.
Test your knowledge of glycolysis and its regulation with this quiz. Explore the roles of key enzymes, the ATP yield, and the fate of NADH in aerobic and anaerobic conditions. Delve into the regulation of hexokinase, phosphofructokinase, and other important aspects of glycolysis.
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