Chapter19R

Chapter19R - Chapter 19, page 1 BCH 4054 Fall 2000 Chapter...

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Unformatted text preview: Chapter 19, page 1 BCH 4054 Fall 2000 Chapter 19 Lecture Notes Slide 1 Chapter 19 Glycolysis Slide 2 Overview of Glycolysis aka The Embden-Meyerhoff Pathway First pathway discovered Common to almost all living cells Occurs in cytoplasm of Eukaryotes Overall reaction: Glucose + 2 NAD + + 2 ADP + 2 P i 2 Pyruvate + 2 NADH + 2 ATP aka = also known as Slide 3 Glycolysis Overview, cont. Ten reactions overall Same in all cells, but relative rates and regulation varies among species and even between tissues (i.e. liver and muscle). Intermediates all bound to phosphate Membrane impermeable Important in energy conversion to ATP Occurs in two stages (or phases) Chapter 19, page 2 Slide 4 Phases of Glycolysis Phase 1 Preparatory Phase Glucose converted to equilibrium mixture of triose phosphates Investment of 2 ATPs required Phase 2 Energy Yielding Phase Triose phosphates converted to pyruvate An oxidation step occurs Yield of 4 ATPs, two for each triose phosphate Slide 5 Reactions of Glycolysis (Summary) Overall Pathway (Figure 19.1) List of Enzymes (Table 19.1a) Energetics of Reactions (Table 19.1b) Intermediate structures, first phase (Figure 19.2) Slide 6 Phosphorylation of Glucose Energetics: Driven by ATP hydrolysis G o kJ/mol glucose + P i glucose-6-P + H 2 O 13.9 ATP + H 2 O ADP + P i-30.5 glucose +ATP glucose-6-P +ADP -16.7 At Q of cell, G can be much larger, -33.9 for erythrocytes, for example (Table 19.1b). The reaction is removed from equilibrium . (Review discussion of phosphate transfer energetics, Table 3.3, pp.67-69) Remember induced fit mechanism, Figure 15.1. Chapter 19, page 3 Slide 7 Hexokinase and Glucokinase Phosphorylation traps glucose in the cell. Figure 19.4 Transport systems vary. Some cells require insulin. Liver is freely permeable to glucose. Enzyme in most cells and organisms is hexokinase. Some isozymes exist. Muscle enzyme has Km = 0.1 mM. Liver has glucokinase, with Km = 10 mM. Hexokinases have a broad specificity as the name implies, phosphorylating a variety of hexoses. They are also inhibited by the product, glucose-6-phosphate, presumably a regulatory function that prevents further phosphorylation if there is no demand for the product. Glucokinase is specific for glucose and is not inhibited by glucose-6- phosphate. The Km of glucokinase is near the normal blood concentration, so that the enzyme becomes more active when blood glucose increases, such as after a meal. Slide 8 Phosphoglucoisomerase aka glucose phosphate isomerase and hexose phosphate isomerase Isomerization of an aldose and a ketose ....
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This note was uploaded on 11/27/2011 for the course BSC 5936 taught by Professor Staff during the Spring '08 term at FSU.

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Chapter19R - Chapter 19, page 1 BCH 4054 Fall 2000 Chapter...

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