CHEM 1516 Biochem II Abby's Notes Part II

CHEM 1516 Biochem II Abby's Notes Part II - Biochem II...

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Biochem II Notes PART 2 I. Gluconeogenesis (GNG) A. General Info 1. Gluconeogenesis is the key metabolic pathway for homeostasis and survival. a. Literally means “Glucose new create”. b. Increases blood glucose level. Essentially Glycolysis backwards. c. Links the Catabolic and Anabolic Pathways for many molecules d. Highly regulated (Complex regulation) e. A cell cannot perform both Glycolysis and Gluconeogenesis at the same time! (It would be pointless). They are reciprocally regulated. 2. Glucose a. Brain, muscles, and RBCs need a constant supply of ATP (medulla of b. Sources of Glucose 1) Diet 2) Glycogen (Glycogenolysis) usually a 10-18 hour supply stored in liver 3) Gluconeogenesis (GNG) 4) Remember; FAT CANNOT GO TO CHO!! (Neither can nucleic acids) 3. GNG keeps glucose levels from falling to dangerously low levels → (cell death). Hormone is Glucagon. (vs. Insulin, which ↓s blood sugar) a. GNG is especially important for the BRAIN b/c the Brain cannot use fatty acids, it can only use glucose and ketone bodies to make ATP. b. Muscle can (likes to) utilize fatty acids for ATP. 4. GNG a. Takes pyruvate to glucose (or Glucose 6-Phosphate) b. Is Irreversible! Takes a lot of ATP. c. Happens in the cytoplasm ! (Mostly) d. Glucose is synthesized from non-CHO precursors (PROTEIN) e. The LIVER is the main site for GNG (90%) Kidney handles ~10% (more during prolonged starvation. NOT IN MUSCLE. f. GNG is activated by depletion of glycogen reserves (ie; low blood sugar). - GNG is full blown after 24 hours of fasting. B. Metabolic Overview 1. Glycogen → via glycogenolysis → Glucose → via glycolysis → Pyruvate 2. Pyruvate → via gluconeogenesis → Glucose → via glycogenesis → Glycogen 3. A dynamic equilibrium exists a. glycogen (storage), b. glycolysis (energy production) c. other pathways (like pentose phosphates) 4. Count the Carbons
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a. In Glycolysis, 6 carbons are divided by 2, giving you two 3-carbon molecules. b. Gluconeogenesis: 3 + 3 = 6 5. Pyruvate for GNG comes from protein precursors. 6. Glucogenic compounds (those that can be turned into glucose) a. Lactic Acid = Lactate via Cori Cycle b. Pyruvate. Pyruvate can come from. .. 1) Lactic Acid back to pyruvate, 3) Other TCA intermediates which go to OAA, which can be converted to pyruvate c. Glycerol (an Alcohol) from lipids/triglycerides to DHAP (see lipid metabolism) d. Acetyl CoA is Ketogenic. It does NOT/ CANNOT go to Glucose. Fat cannot go to CHO! 7. Liver is special a. The Liver buffers the level of glucose in the blood. b. Glucose 6-Phos goes to glucose with Glucose 6 Phosphatase , which is only found in the liver. c.
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CHEM 1516 Biochem II Abby's Notes Part II - Biochem II...

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