Term
| Is pyruvate higher or lower in energy than glucose? Why? |
|
Definition
| Lower, because it is in a higher oxidation state |
|
|
Term
| What are the three functions of glycolisis? |
|
Definition
1. Make 2 net ATP
2. Make 2 NADH
3. Make metabolites that are AA precursors |
|
|
Term
| How does glucose get into a cell for glycolysis? |
|
Definition
| A GLUT protein is used for facilitated diffusion |
|
|
Term
|
Definition
| A glucose facilitated transporter that is responsible for insulin-regulated uptake of glucose into skeletal muscle and adipose tissue |
|
|
Term
| What three enzymes in glycolysis are irreversible and therefore regulated? |
|
Definition
1. Hexokinase aka Glucokinase
2. Phosphofructokinase-1
3. Pyruvate kinase |
|
|
Term
| About how many ATP are each NADH worth? |
|
Definition
|
|
Term
| In what way does hexokinase irreversibly start glycolysis? |
|
Definition
1. Once a phosphate is on glucose, it can't go back out the GLUT transporter
2. It consumes ATP to phosphorylate |
|
|
Term
|
Definition
| A form of hexokinase in the liver and β-cells of pancreas that has low affinity but high capacity |
|
|
Term
| How does glucokinase prevent hyperglycemia? |
|
Definition
| Because it has high capacity, it keeps up with glucose processing in the liver |
|
|
Term
| What effect does fructose-6-phosphate have on glucokinase, and why? |
|
Definition
| It inactivates and sequesters glucokinase, because fructose-6-phosphate is high during gluconeogenesis |
|
|
Term
| What does glucokinase do in β-cells of the pancreas? |
|
Definition
| It serves as a glucose sensor to help β-cells control insulin output |
|
|
Term
| What enzyme converts D-glucose to Glucose-6-phosphate? |
|
Definition
|
|
Term
| What enzyme converts glucose-6-phosphate to fructose-6-phosphate? |
|
Definition
|
|
Term
| What enzyme converts fructose-6-phosphate to fructose-1,6-bisphosphate? |
|
Definition
|
|
Term
| What enzyme regulates the most import control point/commitment step in glycolysis? |
|
Definition
|
|
Term
| Why is Phosphofructokinase-1 the most regulated and commitment step of glycolysis? |
|
Definition
| Fructose-1,6-bisphosphate is not used by other pathways |
|
|
Term
| What inhibits phosphofructokinase? |
|
Definition
| ATP (an energy-rich signal), citrate (a Krebs intermediate), and glucagon |
|
|
Term
| What activates phosphofructokinase? |
|
Definition
| AMP (allosterically), insulin (by pathway), fructose-2,6-bisphosphate |
|
|
Term
| Describe the pathway by which insulin activates phosphofructokinase |
|
Definition
1. High insulin decreases cAMP, reducing protein kinase A
2. This favors dephosphorlated PFK-2/FBP-2 complex
3. This formation (activated PFK-2) favors formation of fructose 2,6-bisphosphate
4. Fructose 2,6-bisphosphate activates phosphofructokinase
|
|
|
Term
| What enzyme converts fructose-1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate? |
|
Definition
|
|
Term
| What enzyme converts dihydroxyacetone phosphate to glyceraldehyde-3-phosphate? |
|
Definition
| Triose phosphate isomerase |
|
|
Term
| What enzyme converts glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate? |
|
Definition
| Glyceraldehyde-3-phosphate dehydrogenase |
|
|
Term
| How does Glyceraldehyde-3-phosphate dehydrogenase convert its substrate back to a diphosphate status without using ATP? |
|
Definition
| It couples the extraction of two electrons with the installation of a Pi |
|
|
Term
| How does arsenic poisoning inhibit glycolysis? |
|
Definition
| Arsenate enters glyceraldehyde-3-phosphate instead of a Pi, then this product is spontaneously hydrolyzed, producing 3-phosphoglycerate and bypassing substrate level ATP generation |
|
|
Term
| What enzyme converts 1,3-bisphosphoglycerate to 3-phosphoglycerate? |
|
Definition
|
|
Term
| Why do red blood cells sometimes bypass phosphoglycerate kinase? |
|
Definition
| They instead use mutase to produce 2,3-bisphosphoglycerate, an allosteric regulator of hemoglobin |
|
|
Term
| What converts 3-phosphoglycerate to 2-phosphoglycerate? |
|
Definition
|
|
Term
| What enzyme converts 2-phosphoglycerate to phosphoenolpyruvate? |
|
Definition
| Enolase (dehydrates to form high energy phosphoenolpyruvate) |
|
|
Term
| What converts phosphoenolpyruvate to pyruvate? |
|
Definition
|
|
Term
| What are some activators of pyruvate kinase? |
|
Definition
Fructose-1,6-bisphosphate (feedforward regulation)
AMP |
|
|
Term
| What are some inhibitors of pyruvate kinase? |
|
Definition
|
|
Term
| Where do most of the rare genetic defects of glycolytic enzymes occur? |
|
Definition
Pyruvate kinase (PK deficiency disease)
4% in phosphoglucose isomerase |
|
|
Term
| Why are red blood cells in danger of hemolytic anemia? |
|
Definition
| They lack mitochondria and are thus highly dependent on glycolysis |
|
|
Term
| What does lactate dehydrogenase do? |
|
Definition
| Catalyzes formation of lactate from pyruvate, regenerates NAD+ |
|
|
Term
| What can circulatory collapse cause? |
|
Definition
| Global acidosis, which can be used as a measure of O2 debt |
|
|
Term
|
Definition
| The cycle by which lactate enters the bloodstream, is recovered by hepatocytes for gluconeogenesis, and then sent back to muscle |
|
|
Term
| What does pyruvate decarboxylase do? |
|
Definition
| In yeast, it anaerobically converts pyruvate to CO2 and Ethanol |
|
|
Term
| Why would yeast want to produce ethanol? |
|
Definition
| It may be beneficial as a poison to competitors |
|
|
Term
|
Definition
| Metabolism that results in no net oxidation or reduction of the nutrient |
|
|
Term
| Define the Pasteur effect |
|
Definition
| In low O2, cells consume higher levels of glucose (to make up for lack of oxidative phosphorylation) |
|
|
Term
| Define the Warburg effect |
|
Definition
| Tumor cells have a higher glycolytic rate than normal cells |
|
|
Term
| How long does allosteric activation/inhibition take? |
|
Definition
|
|
Term
| How long do hormones take to work? |
|
Definition
| If they are acting transcriptionally, hours to days |
|
|
Term
| Would diabetes cause high or low glycolytic activity? |
|
Definition
| Low- lots of sugar to the blood, and little insulin |
|
|
Term
| What is the ΔG for the entire reaction of glycolysis? |
|
Definition
| About -63kJ/mol, so the reaction would take place without enzymes, just much slower |
|
|
Term
| How can cancer cells be analyzed using glycolysis? |
|
Definition
| Radiography can observe injected flourescently labled flouro-2-glucose that becomes visible after hexokinase |
|
|
Term
| What areas of the body are naturally excessively glycolytic? |
|
Definition
| Brain, kidney, and bladder |
|
|
Term
| In what condition do hepatocytes need to be in before gluconeogenesis can occur? |
|
Definition
| Low glucose, but high amino acids and fatty acids |
|
|
Term
| What enzyme(s) bypass pyruvate kinase in gluconeogenesis? |
|
Definition
| Pyruvate carboxylase and PEP-carboxykinase |
|
|
Term
| What enzyme bypasses PFK-1 in gluconeogenesis? |
|
Definition
| fuctose 1,6-bisphosphatase |
|
|
Term
| What enzyme bypasses glucokinase in gluconeogenesis? |
|
Definition
|
|
Term
| What tissues are glucose dependent? |
|
Definition
| Brain, red blood cells, kidney medulla,s lens & cornea, testes, exercising muscle |
|
|
Term
|
Definition
| Anabolic process by which glucose is produced from precursors such as pyruvate, lactate, glycerol, and α-ketoacids |
|
|
Term
| Where does gluconeogenesis occur? |
|
Definition
| Liver, and to a lesser extent the kidney cortex |
|
|
Term
| How does pyruvate carboxylase add a carbon to pyruvate? |
|
Definition
| First, pyruvate carboxylase activates CO2 by attaching it to its biotin group. Then it transfers to CO2 to pyruvate, forming oxaloacetate. |
|
|
Term
| What enzyme converts pyruvate to oxaloacetate? |
|
Definition
|
|
Term
| What is an activator of pyruvate carboxylase? |
|
Definition
| Acetyl CoA, since it signifies lipolysis |
|
|
Term
| What can happen to oxaloacetate after pyruvate carboxylase generates it? |
|
Definition
| It can be used as a TCA cycle intermediate or it can be converted to phospholenolpyruvate |
|
|
Term
| What enzyme converts oxaloacetate to phospholenolpyruvate? |
|
Definition
|
|
Term
| Where does gluconeogenesis take place in a cell? |
|
Definition
| Pyruvate to oxaloacetate takes place in the mitochondria, then oxaloacetate is converted to Malate to get into the cytosol |
|
|
Term
| What sort of energy investment does PEP carboxykinase require? |
|
Definition
|
|
Term
| How does glucagon discourage phosphoenolpyruvate from a glycolytic fate? |
|
Definition
| Glucagon inactivates pyruvate kinase by causing its phosphorylation |
|
|
Term
| What enzyme converts fructose-1,6-bisphosphate to fructose-6-phosphate? |
|
Definition
| Fructose-1,6-bisphosphatase |
|
|
Term
| What are some activators of fructose 1,6-bisphosphatase? |
|
Definition
|
|
Term
| What are some inhibitors of fructose 1,6-bisphosphatase? |
|
Definition
| AMP, fructose-2,6-bisphosphate |
|
|
Term
| Describe the pathway by which high glucagon activates fructose-1,6-bisphosphatase |
|
Definition
1. High glucagon causes increased cAMP and therefore increased protein kinase A
2. This leads to phosphorylation of the PFK-2/FBP-2 complex, FBP-2 is active
3. fructose 2,6-bisphosphatase production is impeded
4. fructose 2,6-bisphosphatase normally inhibits fructose-1,6-bisphosphatase, therefore F(1,6)BPase is now activated
|
|
|
Term
| What enzyme transfers glucose-6-phosphate into the lumen of the ER? |
|
Definition
| Glucose 6-phosphate translocase |
|
|
Term
| What enzyme converts glucose-6-phosphate to D-glucose? |
|
Definition
|
|
Term
| Where is glucose-6-phosphatase found? |
|
Definition
| It is compartmentalized inside the ER lumen of the liver and kidney |
|
|
Term
| How does D-glucose get out of the ER lumen and back into the bloodstream after gluconeogenesis? |
|
Definition
| Glucose transporters T2 (on lumen) and GLUT2 (on plasma membrane) transport it |
|
|
Term
| What does a deficiency of Glucose 6-phosphatase cause? |
|
Definition
| Type 1a glycogen storage disease and severe fasting hypoglycemia |
|
|
Term
| What is the energy cost to form a glucose from 2 pyruvates? |
|
Definition
| 6 ATP equivalents, and oxidation of 2 NADH (about 5 ATP) |
|
|
Term
| What is the ΔG of gluconeogenesis? |
|
Definition
| -17kJ/mol (with all of the ATP expense) |
|
|
Term
| Describe the energy charge concept |
|
Definition
| A concept that represents availability of ATP to sustain homeostatic functions. For example, ATP can be formed from two ADPs if needed by use of adenylate kinase. |
|
|
Term
|
Definition
| An enzyme that forms ATP (and AMP) from 2ADPs, and vice versa with no energy change |
|
|
Term
| Define nucleoside diphosphate kinase |
|
Definition
| An enzyme that can introconvert various nucleoside triphosphates to create NTPs needed for their respective enzymes |
|
|
Term
| What products does ethanol consumption lead to? |
|
Definition
|
|
Term
| How can ethanol consumption lead to hypoglycemia? |
|
Definition
| The excess NADH produced from ethanol oxidation can lead to the reduction of pyruvate and oxaloacetate, limiting their availability for gluconeogenesis |
|
|
Term
| How can ethanol consumption lead to lactic acidosis and hyperuricemia? |
|
Definition
The NADH generated from ethanol oxidation can cause pyruvate to be reduced to lactate, causing lactic acidosis
Hyperuricemia can result if lactate competes with urate for kidney excretion |
|
|
Term
|
Definition
| An inhibitor of alcohol dehydrogenase, it is a "learning experience" deterrent for alcohol consumption because accumulation of acetaldehyde can lead to flushing, tachycardia, hyperventilation, nausea |
|
|
Term
| What enzyme catalyzes the oxidation of ethanol to acetate? |
|
Definition
|
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