Glycolysis/ Gluconeogenesis and regulation

Question 1

redox balancing is important for glycolysis because…

Answer 1

Redox balancing relates to the relative amount of NAD+ and NADH in the cell. Remember that reaction 6 is very sensitive to the ratio of NAD+/NADH. Redox balancing involves pyruvate in all cells.

Question 2

Pyruvate in anaerobic conditions

Answer 2

Creates lactic acid in animal cells (ethanol in bacteria/yeast). converts NADH to NAD+, only creates 2 ATP per glucose molecule.

Question 3

Pyruvate in aerobic conditions

Answer 3

there is plenty of NAD+, so aerobic cells convert pyruvate to acetyl-CoA for oxidation in the citric acid cycle.aerobic metabolism of glucose generates 38 ATPs per glucose.

Question 4

Galactose

Answer 4

can enter glycolysis by being converted to galactose-1phosphate followed by converstion (ultimately) to glucose-1-phosphate and subsequently to glucose-6-phosphate, which is a glycolysis intermediate.

Question 5

Lactase

Answer 5

Enzyme necessary for lactose breakdown to glucose and galactose.

Question 6

3 enzymes that regulate glycolysis

Answer 6

hexokinase, PFK, and pyruvate kinase.

Question 7

PFK

Answer 7

is very unusual in being negatively regulated by a molecule (ATP) that is also a substrate. This is possible because the enzyme has an allosteric binding site for ATP in addition to the substrate binding site and the Km for the allosteric site is higher than the substrate binding site.

Question 8

Gluconeogenesis

Answer 8

accomplishes the reverse of glycolysis - synthesis of glucose from pyruvate using four different enzymes to replace three energetically unfavorable reactions in glycolysis for a total of 11 reaction.

Question 9

The primary gluconeogenic organs of the body

Answer 9

the liver and part of the kidney. does not occur in all tissues of the body.

Question 10

The enzymes unique to gluconeogenesis

Answer 10

Pyruvate Carboxylase and PEP carboxykinase (PEPCK) instead of Pyruvate Kinase of glycolysis, Fructose 1,6 Bisphosphatase (F1,6BPase) instead of Phosphofructokinase (PFK) from glycolysis, and Glucose-6-phosphatase (G6Pase) instead of Hexokinase from glycolysis.

Question 11

Futile cycles

Answer 11

generate heat, but that is the only product they make. anabolic and catabolic pathways occurring at the same time and place.

Question 12

Pyruvate carboxylase regulation

Answer 12

inhibited by ADP (low energy indicator) and activated by acetyl-CoA (high energy indicator)

Question 13

PEPCK is mostly regulated by

Answer 13

whether or not the enzyme is synthesized, but ADP (low energy indicator) can inhibit the enzyme.

Question 14

Overall, regulation of glycolysis and gluconeogenesis

Answer 14

occurs mostly allosterically using molecules that are indicative of the energy state of the cell. Molecules indicating high cellular energy (like ATP) favor gluconeogenesis and inhibit glycolysis, but molecular indicating low energy (like ADP or AMP) favor glycolysis and inhibit gluconeogenesis.

Question 15

The Cori Cycle

Answer 15

a cycle of the body where the liver supplies glucose to muscles when needed. This occurs, for example, during heavy exercise when muscles are using oxygen faster than it can be delivered. When this happens, muscles start to make lactate and export it into the blood stream. Lactate travels to the liver where it is converted to pyruvate and then to glucose. The glucose is exported to the book and is taken up the by muscles.