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55 Cards in this Set
- Front
- Back
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What are the sites of metabolism? |
- Mitochondria
- Cytoplasm - Both |
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Which processes take place in the mitochondria?
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- Fatty acid oxidation (β-oxidation)
- Acetyl-CoA production - TCA cycle - Oxidative Phosphorylation |
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Which processes take place in the cytosol?
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- Glycolysis
- Fatty acid synthesis - HMP shunt - Protein synthesis (RER) - Steroid synthesis (SER) - Cholesterol synthesis |
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Which processes take place in the mitochondria and cytosol?
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- Heme synthesis
- Urea cycle - Gluconeogenesis HUGs take TWO (ie, both) |
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What is the action of a "kinase"?
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Uses ATP to add high-energy phosphate group onto substrate (eg, phosphofructokinase)
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What is the action of a "phosphorylase"?
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Adds inorganic phosphate onto substrate WITHOUT using ATP (eg, glycogen phosphorylase)
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What is the action of a "phosphatase"?
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Removes phosphate group from substrate (eg, fructose-1,6-bisphosphatase)
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What is the action of a "dehydrogenase"?
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Catalyzes oxidation-reduction reactions (eg, pyruvate dehydrogenase)
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What is the action of a "carboxylase"?
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Transfers CO2 groups with the help of biotin (eg, pyruvate carboxylase)
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What is the rate determining enzyme and regulators of glycolysis?
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- Phosphofructokinase-1 (PFK-1)
- AMP (+) - Fructose-2,6-BP (+) - ATP (-) - Citrate (-) |
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What is the rate determining enzyme and regulators of gluconeogenesis?
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- Fructose-1,6-bisphosphatase
- ATP (+) - AMP (-) - Fructose-2,6-BP (-) |
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What is the rate determining enzyme and regulators of the TCA cycle?
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- Isocitrate Dehydrogenase
- ADP (+) - ATP (-) - NADH (-) |
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What is the rate determining enzyme and regulators of glycogen synthesis?
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- Glycogen synthase
- Glucose (+) - Insulin (+) - Epinephrine (-) - Glucagon (-) |
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What is the rate determining enzyme and regulators of glycogenolysis?
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- Glycogen phosphorylase
- AMP (+) - Epinephrine (+) - Glucagon (+) - Insulin (-) - ATP (-) |
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What is the rate determining enzyme and regulators of HMP Shunt?
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- Glucose-6-Phosphate Dehydrogenase (G6PD)
- NADP+ (+) - NADPH (-) |
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What is the rate determining enzyme and regulators of de novo pyrimidine synthesis?
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Carbamoyl phosphate synthetase II
(I is for the urea cycle) |
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What is the rate determining enzyme and regulators of de novo purine synthesis?
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- Glutamine-PRPP amidotransferase
- AMP (-) - IMP (-) - GMP (-) |
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What is the rate determining enzyme and regulators of the urea cycle?
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- Carbamoyl phosphate synthetase I
(II is for de novo pyrimidine synthesis) - N-acetylglutamate (+) - |
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What is the rate determining enzyme and regulators of fatty acid synthesis?
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- Acetyl-CoA carboxylase (ACC)
- Insulin (+) - Citrate (+) - Glucagon (-) - Palmitoyl-CoA (-) |
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What is the rate determining enzyme and regulators of fatty acid oxidation?
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- Carnitine acyltransferase I
- Malonyl-CoA (-) |
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What is the rate determining enzyme and regulators of ketogenesis?
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HMG-CoA Synthase
(reductase for cholesterol synthesis) |
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What is the rate determining enzyme and regulators of cholesterol synthesis?
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- HMG-Coa Reductase
(synthase for ketogenesis) - Insulin (+) - Thyroxine (+) - Glucagon (-) - Cholesterol (-) |
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What is the net gain of aerobic metabolism of glucose?
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Malate-Aspartate shuttle (heart and liver):
- Produces 32 ATP Glycerol-3-Phosphate shuttle (muscle): - Produces 30 ATP |
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What is the net gain of anaerobic metabolism of glucose?
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Anaerobic glycolysis:
- 2 net ATP / glucose molecule |
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What is the purpose of ATP?
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ATP hydrolysis can be coupled to energetically unfavorable reactions
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Which molecule carries phosphoryl groups in its activated form?
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ATP
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Which molecule carries electrons in its activated form?
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- NADH
- NADPH - FADH2 |
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Which molecule carries Acyl groups in its activated form?
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- Coenzyme A
- Lipoamide |
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Which molecule carries CO2 in its activated form?
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Biotin
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Which molecule carries 1-C units in its activated form?
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THF
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Which molecule carries CH3 groups in its activated form?
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SAM (S-adenosyl-methionine)
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Which molecule carries aldehydes in its activated form?
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TPP
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What are the universal electron acceptors?
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- Nicotinamides (NAD+ from vitamin B3, NADP+)
- Flavin nucleotides (FAD+ from vitamin B2) |
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What is the typical function of NAD+?
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Used in catabolic processes to carry reducing equivalents away as NADH
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What is the typical function of NADPH?
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- Used in anabolic processes (steroid and fatty acid synthesis) as a supply of reducing equivalents
- Respiratory burst - P-450 - Glutathione reductase |
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How is NADPH produced?
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HMP Shunt
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What is the first step of glycolysis?
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Phosphorylation of glucose → glucose-6-phosphate
- Hexokinase or Glucokinase depending on the tissue |
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What is the action and location of Hexokinase vs Glucokinase?
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Hexokinase
- Ubiquitous (everywhere) - High affinity (↓ Km) - Low capacity (↓ Vmax) - Uninduced by insulin - Feedback inhibition by glucose-6P (product) Glucokinase: - Liver and β cells of pancreas - Low affinity (↑ Km) - High capacity (↑ Vmax) - GLUcokinase is a GLUtton, it has a high Vmax because it cannot be satisfied - Induced by insulin - Feedback inhibition by fructose-6P |
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How do Hexokinase and Glucokinase compare in location?
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- Hexokinase: ubiquitous (everywhere)
- Glucokinase: liver and β cells of pancreas |
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How do Hexokinase and Glucokinase compare in affinity for glucose?
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- Hexokinase: high affinity (↓ Km)
- Glucokinase: low affinity (↑ Km) |
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How do Hexokinase and Glucokinase compare in capacity / Vmax?
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- Hexokinase: low capacity (↓ Vmax)
- Glucokinase: high capacity (↑ Vmax) * GLUcokinase is a GLUtton, it has a high Vmax because it cannot be satisfied |
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How do Hexokinase and Glucokinase compare in their response to insulin?
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- Hexokinase: uninduced by insulin
- Glucokinase: induced by insulin |
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What happens to Hexokinase / Glucokinase at low glucose concentrations?
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Hexokinase sequesters glucose in the tissue at high glucose concentrations
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What happens to Hexokinase / Glucokinase at high glucose concentrations?
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Excess glucose is stored in the liver (phosphorylation of glucose by hexokinase or glucokinase is the first step of glycogen synthesis in liver)
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What is the net effect of glycolysis?
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Glucose + 2 Pi + 2 ADP + 2 NAD+ →
2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O |
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How many ATP / NADH are produced by glycolysis of a single glucose molecule?
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- 2 ATP
- 2 NADH |
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Which steps of glycolyis require ATP?
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- Glucose → Glucose-6P (by hexokinase/ubiquitous or glucokinase/liver)
- Fructose-6P → Fructose-1,6-BP (by phosphofructokinase-1) = rate-limiting step |
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Which steps of glycolyis produce ATP?
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Each produce 2 for 1 molecule of glucose:
- 1,3-BPG → 3-PG (by phosphoglycerate kinase) - Phosphoenolpyruvate (PEP) → Pyruvate (by pyruvate kinase) |
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What regulates hexokinaae and glucokinase (1st step that requires ATP)?
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- Hexokinase: inhibited by glucose-6P
- Glucokinase: inhibited by fructose-6P |
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What regulates phosphofructokinase-1 (2nd step that requires ATP)?
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Inhibited by:
- ATP - Citrate Stimulated by: - AMP - Fructose-2,6-BP |
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What regulates pyruvate kinase (step that produces ATP)?
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Inhibited by:
- ATP - Alanine Stimulated by: Fructose-1,6-BP |
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How is sugar metabolism regulated during the FASTING state?
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- ↑ Glucagon →
- ↑ cAMP → - ↑ Protein Kinase A → - ↑ FBPase-2 (Fructose Bisphosphatase-2), - ↓ PFK-2 (Phosphofructokinase-2), LESS GLYCOLYSIS |
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How is sugar metabolism regulated during the FED state?
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- ↑ Insulin →
- ↓ cAMP → - ↓ Protein Kinase A → - ↓ FBPase-2 (Fructose Bisphosphatase-2), - ↑ PFK-2 (Phosphofructokinase-2), MORE GLYCOLYSIS |
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Which enzyme involved in sugar metabolism is activated by ↑ PKA? Implications?
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FBPase-2 (Fructose Bisphosphatase-2)
- Converts Fructose-2,6-Bisphosphate → Fructose-6-Phosphate Occurs during fasting state: - ↓ GLYCOLYSIS - ↑ GLUCONEOGENESIS |
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Which enzyme involved in sugar metabolism is active when there is ↓ PKA? Implications?
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PFK-2 (Phosphofructokinase-2)
- Converts Fructose-6-Phosphate → Fructose-2,6-Bisphosphate Occurs during fed state: - ↑ GLYCOLYSIS - ↓ GLUCONEOGENESIS |
