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How many stages does glycolysis have?
2
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How many total reactions occur during glycolysis?
10
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What does glycolysis generally being with and end with?
Starts with glucose and ends with 2 molecules of pyruvate
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What occurs during stage one of glycolysis?
Glucose is phosphorylated and cleaved to form two G-3-P
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What occurs during stage two of gycolysis?
- Energy recaptured
- Oxidation-reduction-phosphorylation
- From this point on, there are two of each molecule
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What is pyruvate converted to in anaerobic organisms?
Anaerobic organisms convert pyruvate to waste product (lactate).
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What is pyruvate converted to in aerobic organisms?
- Aerobic organisms use oxygen as an electron accepter and convert pyruvate into CO2 and H2O (citric acid
- cycle/electron transport chain)?
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When is glycolysis activated and what is its general function?
- Activated when energy is needed
- Glucose is uses 2 ATP molecules to produce 2 pyruvates, 4 ATP (net gain of 2), and 2 NADH
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How is NAD+ used?
- NAD+ is used as an electron acceptor
- These electrons are used in the electron transport chain to make more ATP
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Net reaction:
D-Glucose + 2 ADP + 2 Pi + 2 NAD+ -->
2pyruvate + 2 ATP + 2 NADH + 2H+ + 2H2O
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-->2pyruvate + 2 ATP + 2 NADH + 2H+ + 2H2O
- D-Glucose + 2 ADP + 2 Pi + 2 NAD+
- Net gain
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Glucose is____ using ____ and requires ___to form___
- Phosphorylated
- Hexokinase, Mg2 or Glucokinase (GK)
- ATP
- Glucose-6-phosphate (G6P)
- Irreversible step
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__ converts glucose-6-phosphate to__
- Phosphoglucose isomerase (PGI)
- Fructose-6-phosphate
- Reversible rxn
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__catalyzes the __ of fructose-6-phosphate to__
- Phosphofructokinase-1(PFK-1), Mg2+
- Phosphorylation
- Fructose-1,6-bisphosphate
- Irreversible
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__ cleaves the fructose-1,6-bisphosphate to form __
- Aldolase
- Both dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
- Products used quickly
- End of 1st stage
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__ catalyzes the__ of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP)
- Triose phosphate isomerase
- Interconversion
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__ removes a__and adds __ to glyceraldehyde-3-phosphate to form__
- Glyceraldehyde-3-phosphate dehydrogenase
- Hydride ion (H:-)
- A phosphate
- Glycerate-1,3-bisphosphate
- Converts NAD+ to NADH and requires a molecule of inorganic phosphate
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___ catalyzes the production of __ from __and one of the phosphoryl groups on glycerate-1,3-bisphosphate leaving __
- Phosphoglycerate kinase
- ATP
- ADP
- Glycerate-3-phosphate or 3-phosphoglycerate
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__ interconverts 3-phosphoglycerate and __
- Phosphoglycerate mutase
- 2-phosphoglycerate
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__removes a molecule of __from glycerate-2-phosphate to form__
- Enolase
- Water
- Phosphoenolpyruvate
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__catalyzes the formation of __ using the__ from
phosphoenolpyruvate leaving__
- Pyruvate kinase
- ATP
- Phosphate
- Pyruvate
- Irreversible
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What is step 1 of glycolysis?
Phosphorylation of Glucose
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What is step 2 of glycolysis?
G6P to F6P
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What is step 3 of glycolysis?
Phosphorylation of F6P
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What is step 4 of glycolysis?
Cleavage of F1,6P
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What is step 5 of glycolysis?
Isomerization of DHAP to GAP
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What is step 6 of glycolysis?
Oxidation of GAP
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What is step 7 of glycolysis?
Phosphoryl group transfer
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What is step 8 of glycolysis?
Interconversion of 3PG to 2PG
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What is step 9 of glycolysis?
Dehydration of 2PG to form PEP
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What is step 10 of glycolysis?
Production of Pyruvate from PEP
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What happens when glucose and other 6 carbon sugars enter the cell?
- It is phosphorylated in the cytoplasm by enzymes called hexokinases
- Prevents the sugar from leaving the cell
- Irreversible
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What are Hexokinases I, II, and III inhibited by and how are they saturated?
- G6P and ATP
- At low [glucose]
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What is Hexokinase IV and mention other important fact?
- Also known as Glucokinase
- Only found in the liver, some cells of the intestines, pancreas, and brain;
- Requires higher [glucose] and is not inhibited by G6P
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What inhibits and what stimulates PFK-1?
- ATP
- AMP and F-2,6-bisphosphate
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What is Phosphofructokinase-2 (PFK-2)?
- A bifunctional enzyme
- Acts like a phosphatase (low blood sugar) or kinase (high blood).
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In response to glucagon (_), acts like a __to __and makes__which decreases__ and stimulates__
- Low blood sugar
- Phosphatase
- F-2,6-bP
- F-6-P
- Glycolysis
- Gluconeogeneis
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In response to insulin (_), acts like a __to __and makes__ by stimulating__activity and also stimulates __
- High blood sugar levels
- Kinase
- F6P
- F-1,6-bP
- PFK-1 (F-2,6-bp)
- Glycolysis
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Where is the first place energy is generated during glycolysis?
- During step 7 (Phosphoryl group transfer)-
- Phosphoglycerate kinase catalyzes the formation of ATP using one phosphate from glycerate-1,3-bisphosphate leaving glycerate-3-phosphate
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Where is the second place energy is generated during glycolysis?
- Step 10 (Production of Pyruvate from PEP)
- Pyruvate kinase catalyzes the formation of ATP using the phosphate from phosphoenolpyruvate leaving pyruvate
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Which steps are irreversible?
Steps 1,3, and 10
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What happens to pyruvate in anaerobic conditions?
- Anaerobic organisms convert pyruvate to waste product(s)
- Lactate formation (muscle cells)
- Ethanol formation (yeast)
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What happens to pyruvate in aerobic conditions?
Aerobic organisms use oxygen as an electron accepter and convert pyruvate into CO2 and H2O (citric acid cycle/electron transport chain)
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How is lactate formed?
Under anaerobic conditions (like during strenuous exercise), pyruvate is converted to lactate in muscle cells
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What is one of the main events during lactate formation?
- This reaction converts some of the NADH back to NAD+ allowing the cell to continue to make ATP via glycolysis
- Normally, the NAD+ would be regenerated during oxidative phosphorylation, but this is impeded by the lack of oxygen
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How is ethanol produced?
- Yeast and some bacteria can convert pyruvate to acetaldehyde and then to ethanol
- This involves the decarboxylation of pyruvate and the reduction of acetaldehyde
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How is the rate of glycolysis controlled?
Allosteric regulation of: hexokinase (1), PFK-1 (3), and pyruvate kinase (10)
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What is the inhibitor of hexokinase?
- Glucose-6-phosphate (product)
- ATP (distant product)
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What is the activator of PFK-1?
- Fructose-2,6-bisphosphate (signaling response to high glucose levels)
- AMP (ATP level sensor)
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What is the inhibitor of PFK-1?
- Citrate (citric acid cycle)
- ATP (distant product)
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What is the product of PFK-1?
Fructose-1,6-bisphosphate
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What is the activator of Pyruvate kinase?
- Fructose-1,6-bisphosphate (upstream precursor)
- AMP (ATP level sensor)
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What is the inhibitor of pyruvate kinase?
- Acetyl-CoA (citric acid cycle)
- ATP (product)
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What is the product of pyruvate kinase?
Pyruvate
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What is glucagon and how is it released?
- peptide hormone (29 amino acids) released by a-cells (pancreas) when blood glucose is low
- Activates the phosphatase of PFK-2 and thereby decreases the activity of PFK-1, slowing down glycolysis
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What is insulin and how is it released?
- Peptide hormone (51 amino acids) released by b-cells (pancreas) when blood glucose is high
- Activates the kinase of PFK-2 which increases the activity of PFK-1, increasing the rate of glycolysis
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What is released in response to high blood sugar?
Insulin
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What is released in response to low blood sugar?
Glucagon
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Where does gluconeogenesis primarily occur?
Liver
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Generally explain the steps of gluconeogenesis?
- The reverse of glycolysis with the exception of three key steps:
- Hexokinase, PFK-1, and pyruvate kinase
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Name the steps of gluconeogenesis:
- Synthesis of PEP
- Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
- Formation of glucose from glucose-6-phosphate
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