Regulated glycolytic reactions are not at equilibrium in the cell

1. Regulated glycolytic reactions are not at equilibrium in the cell Regulation points Regulation points

2. Rate-limiting steps are regulated: reactions in the pathway that operate away from equilibrium are regulated. At these reaction steps there is a build-up of substrates because the substrates are not converted to products fast enough. Typically these reactions are regulated. DG < 0 B C DG ~ 0 C D

3. Regulation of Glycolysis Inhibitors Activators Hexokinase Glucose 6-phosphate ADP, AMP, Fructose 2,6P ATP, citrate, PEP Phosphofructokinase ATP Pyruvate kinase CITRIC ACID CYCLE (ATP, citrate)

4. Regulatory Enzymes: exhibit decreased or increased activity in response to certain signals. Allosteric regulation: the enzymes activity is regulated through reversible, noncovalent binding of a small molecule regulator (an allosteric modulator).

6. The Fates of Glucose Glycogen Pentose Phosphate Pathway Gluconeogenesis Glycolysis Lactate (anaerobic) Citric acid cycle (aerobic)

7. Gluconeogenesis: Synthesis of glucose from non-hexose precursors (lactate, fatty acids and amino acids) lactate Chapter 20. Figure 20-2

8. Pentose Phosphate Pathway Glycolysis Pentose Phosphate Pathway (a) Produces NADPH, a reducing agent needed for anabolic reactions. (b) Pentose type sugars. Required for the production nucleic acids

9. Glycogen Synthesis Glycogen Breakdown Glucose Glycogen Glucose Glycogen Breakdown R

10. Glycogen Synthesis Glycogen Breakdown Glucose Glycogen Glucose Glycogen Synthesis R Chapter 20. Figure 20-12

11. The liver is the central control point for regulating blood glucose levels Heavy activity in muscle consumes muscle glycogen Muscle glycogen reserves are rebuilt during times of less intense activity Gluconeogenesis in liver converts lactate to glucose Suggested Reading: Chapter 23 869-884

12. The liver is the central control point for regulating blood glucose levels Brain Liver glycogen Muscle tissue glycogen rest Dietary and intrinsic carbohydrates, proteins, and lipids glucose glucose active lactate lactate It’s critical that blood glucose levels are maintained within a defined concentration range.

13. Low Blood Glucose: (Hungry. Several hours after eating) Increase glycogen break down Increased gluconeogenesis

15. Low Blood Glucose: (Panic reaction) Epinephrine (aka Adrenaline) mediates the fight or flight response Effects similar to glucagon. It mobilizes glucose from glycogen. In contrast, it also promotes glucose catabolism in muscle tissue (for production of ATP for activity).

16. Glucagon/Epinephrine control of glycogen synthesis/degradation

17. Signal cascade initiated by epinephrine Optional reading Page 449-454

18. Signal cascade initiated by epinephrine

19. Glucagon control of glycolysis/gluconeogenesis (the fructose 2,6-bisphosphatate connection) Glucogon controls the production of fructose 2,6-bisphosphatate

20. High Blood Glucose: Insulin lowers blood glucose levels