Glycolysis/Gluconeogenesis Flashcards
What is the net reaction for glycolysis?
glucose + 2 ADP + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH
What reaction is occurring here?

Phosphorylation
What Enzyme is this?

Hexokinase
What molecule is this?

Glucose
What molecule is this?

Glucose 6-Phosphate
G-6P
What reaction is occuring here?

isomerization
What Enzyme catalyzes this reaction?

Phosphoglucose Isomerase
What molecule is this?

Glucose 6-Phosphate
G-6P
What molecule is this?

Fructose 6-phosphate
F-6P
What reaction is occuring here?

phosphorylation
What Enzyme is this?

Phosphofructokinase
What molecule is this?

Fructose 6-Phosphate
F-6P
What molecule is this?

Fructose 1, 6-Biphosphate
F-1,6BP
What reaction is occuring here?

Cleavage
What Enzyme is this?

Aldolase
What molecule is this?

Fructose 1, 6-Biphosphate
F-1,6BP
What molecule is this?

Dihydroxyacetone Phosphate
DHAP
What molecule is this?

Glyceraldehyde 3-Phosphate
GAP
What reaction is occuring here?

isomerization
What Enzyme is this?

Triose Phosphate Isomerase
What molecule is this?

Dihydroxyacetone Phosphate
DHAP
What molecule is this?

Glyceraldehyde 3-Phosphate
GAP
What reaction is occuring here?

oxidation and phosphorylation
What Enzyme is this?

GAP Dehydrogenase
What molecule is this?

Glyceraldehyde 3-Phosphate
GAP
What molecule is this?

1,3-Biphosphoglycerate
1,3-BPG
What reaction is occuring here?

Dephosphorylation
What Enzyme is this?

Phosphoglycerate Kinase
What molecule is this?

1,3-Biphosphoglycerate
1,3-BPG
What molecule is this?

3-Phosphoglycerate
3-PG
What reaction is occuring here?

Rearrangement
What Enzyme is this?

Phosphoglycerate Mutase
What molecule is this?

3-Phosphoglycerate
3-PG
What molecule is this?

2-Phosphoglycerate
2-PG
What reaction is occuring here?

Dehydration
What Enzyme is this?

Enolase
What molecule is this?

2-Phosphoglycerate
2-PG
What molecule is this?

Phosphenolpyruvate
What reaction is occuring here?

Dephosphorylation
What Enzyme catalyzes this reaction?

Pyruvate Kinase
What molecule is this?

Phosphenolpyruvate
What molecule is this?

Pyruvate
(enol form)
What molecule is this?

Pyruvate
Under what conditions does glycolysis occur?
Anaerobic
Pyruvate’s fate under _____ Conditions: NADH dump their e- into the Electron Transport Chain (ETC), where oxygen is the final e- acceptor. Pyruvate is further oxidized to acetyl-CoA by the Pyruvate Dehydrogenase Complex, and then enters into the Citric Acid Cycle
Aerobic
Pyruvate’s fate under ______ Conditions: ETC does not run and the NADH from glycolysis have nowhere to dump their e-, fermentation in yeast, reduced to lactate
Anaerobic
What are the 3 main enzymes that regulate glycolysis?
- Hexokinase
- Phosphofructokinase (most important)
- Pyruvate kinase
Where is the following true?
• Hexokinase:
– Regulated by feedback inhibition of its product (G-6-P)
– Allows glucose export from cell
• Phosphofructokinase:
– Regulated allosterically by ATP/AMP and pH
– ATP and low pH down-regulate glycolysis; AMP upregulates
• Pyruvate kinase:
– Allosterically regulated by ATP/ADP
– Inhibited by alanine (biosynthesis pathway)
– Stimulated through feed-forward mechanism by F-1,6-BP
Muscle
Where is the following true?
• Hexokinase:
– Regulated by feedback inhibition of its product (G-6-P)
– Hexokinase D functions only under high levels of glucose
– Provides G-6-P for glycogen synthesis
• Phosphofructokinase:
– Inhibited by citrate, an early intermediate of the TCA cycle
– Activated by fructose 2,6-bisphosphate (F-2,6-BP), an alternative product formed under high F-6-P levels
• Pyruvate kinase:
– Regulated through covalent modification via ATP phosphorylation of the enzyme
Liver
What reaction is occuring here?

carboxylation
What Enzyme is this?

Pyruvate Carboxylase
What molecule is this?

Pyruvate
What molecule is this?

Oxaloacetate
What reaction is occuring here?

decarboxylation and phosphorylation
What Enzyme catalyzes this reaction?

PEP Carboxykinase
What molecule is this?

oxaloacetate
What molecule is this?

Phosphenolpyruvate
PEP
What reaction is occuring here?

dephosphorylation
What Enzyme is this?

Fructose-1,6-biphosphatase
What molecule is this?

Fructose-1,6-biphosphate
F-1,6-BP
What molecule is this?

Fructose-6-phosphate
What reaction is occuring here?

dephosphorylation
What Enzyme is this?

Glucose-6-phosphatase
What molecule is this?

Glucose-6-phosphate
What molecule is this?

Glucose
What is the net yield of ATP from glucose in glycolysis?
2
What is pyruvate’s fate under aerobic conditions? Anaerobic conditions?
- Under aerobic conditions the NADH formed dump their e- into the ETC (where oxygen is the final e- acceptor).
- Under anaerobic conditions i.e. low or no oxygen, ETC does not run and NADH from glycolysis has nowhere to dump their e- (and thus cannot regenerate NAD+ which is in limited supply)
Reaction occurs best in anaerobic conditions.
What is kinetics? Allosterism? Compartmentalization?
- Control the amount of enzyme (kinetics)
- Control their catalytic activity (allosterism)
- Control accessibility of substrates (compartmentalization)
How is glycolysis regulated in muscle?
- In muscle, phosphofructokinase is regulated by ATP/AMP and pH. Classic allosterism
- ATP and pH down-regulate glycolysis and AMP upregulates.
- Hexokinase is regulated by classic feedback inhibition by its product (G-6-P). Allows G export from cell.
- Pyruvate kinase is also regulated by ATP/ADP allosterism and inhibited by alanine (biosynthesis pathway) and is stimulated through a feed forward mechanism by F-1,6-BP.
How is glycolysis regulated in the liver?
In the liver, there is little ATP or pH
flux as seen in muscle (thus these are not regulators of PFK) . Citrate is a biomolecule in the CAC pathway that can cross the mitochondria and signal a high state of energy (thus it will downregulate glycolysis in liver)
Why does a CO2 group get temporarily added on to pyruvate only to be taken off?
Pyruvate carboxylase is a mitochondrial enzyme thus, oxaloacetate must be transported from mitochondria to cytoplasm for gluconeogenesis to continue.
How is blood glucose related to glycolysis and glyconeogenesis?
- Blood [Glucose] high = glycolysis
- Blood [Glucose] low = gluconeogenesis
–Irrespective of physical activity level and cellular energy demand. Remember, this is liver.
Hexokinase activation
Feedback inhibition but also enzymatic isoforms of low level activity
Phosphofructokinase activation
M = muscle; L = Liver
(M): Inhibited by high ATP levels; Activated by high AMP levels
(M): Inhibited by low pH (acid)
(L): inhibited by citrate
Pyruvate Kinase activation
Activated by F-1,6-BP in a feed forward mechanism
Inhibited by ATP; activated by ADP
Inhibited by alanine
Activated by epinephrine; inhibited by glucagon in signal transduction via phosphorylation
Pyruvate Carboxylase activation
Activated by glucagon; inhibited by insulin
Activated by Acetyl CoA; inhibited by CoA
F-1,6-bisphosphatase activation
Citrate enhances
AMP inhibits
What is oxaloacetate reduced to for transport across the mitochondrial membrane?
Malate
Where does Conversion of G-6-P to glucose occur?
Only in the ER of liver cells, where glucose 6-phosphatase is found
What is consumed during gluconeogenesis?
4 ATP, 2 GTP, and 2 NADH
What other non-carbohydrate precursors can be converted into glucose?
Lactate: from muscle following strenuous exercise enters as pyruvate
Amino acids (alanine): transamination product of pyruvate enters as pyruvate
Glycerol: from triacylglycerol breakdown enters as DHAP
Where does the regulation of gluconeogenesis and glycolysis occur?
The liver
Which two steps of glycolosis use ATP?
Glucose to G-6P via hexokinase
F-6P to F-1,6-BP via phosphofructokinase
Which two steps of glycolosis produce ATP?
1,3-BPG to 3-PG via phosphoglycerate kinase
PEP to Pyruvate via pyruvate kinase
Which step of glycolosis produces NADH?
GAP to 1,3-BPG via GAP dehydrogenase
Which step of glycolysis releases H2O?
2-PG to PEP via enolase
What molecule is this?

Pyruvate
What enzyme is this?

Pyruvate Carboxylase
What molecule is this?

Oxaloacetate
What enzyme is this?

Phosphoenolpyruvate Carboxykinase
What molecule is this?

Phospenolpyruvate (PEP)
What molecule is this?

Malate
What enzyme is this?

Malate dehydrogenase
What molecule is this?

Oxaloacetate