Question

11. Providing at least three appropriate examples, describe mechanisms that biological systems use to avoid futile cycles (opposing reactions occurring at the same time

A futile cycle occurs when two metabolic pathways run simultaneously in opposite directions and have no net effect other than to dissipate energy in the form of heat.

1. if glycolysis and gluconeogenesis were to be active at the same time, glucose would be converted to pyruvate by glycolysis and then converted back to glucose by gluconeogenesis, with an overall consumption of ATP.

2. hydrolysis of ATP without any useful metabolic work being done. Clearly, if these two reactions were allowed to proceed simultaneously at a high rate in the same cell, a large amount of chemical energy would be dissipated as heat.

other examples?

12.Describe the reciprocal regulation of glycogenolysis and glycogenesis, highlighting the major hormonal differences. [5]

Just need a short 2-3 sentence answer thanks!

Answer 1

11. In our cycle one macromolecules is synthesized and degraded but these two process are regulated in that way . At a time either synthesis takes place or degradation.

For example

a) regulation of fatty acid synthesis of degradation regulated in such a way that at a time either degradation take place or synthesis of fat.

This is regulated by, regulating their key enzyme.

Fatty acid degrade by Hormone sensitive lipase this is inhibited by malonyl CoA ( formed during Fatty acid synthesis)

Hormones also regulate body process reciprocal way ,

Insulin -- activate Fatty acid synthesis, while inhibit degradation

glucagon- inhits fatty acid synthesis, while activate degradation.

b) regulation of glycolysis and gluconeogenesis by fructose 2,6 bis phosphate.

This 2,6 fructose bis phosphate formed by fructose by PFK 2 enzyme. This F2,6 BP also regulate both pathway.

F2,6 BP -- activate glycolysis

F2,6 BP - inhibits gluconeogenesis.

C) synthesis and degradation of keton bodies

These two process are also regulate by hormones reciprocally.

12) glycogenolysis- degradation of glycogen, glycogen phosphorylase enzyme

Glycogensis- synthesis of glycogen, glycogen synthase enzyme.

Hormone insulin promte glycogen synthesis by activating glycogen synthase enzyme, and inhibits degradation by inhibiting glycogen phosphorylase.

Glucagon and Epinephrine and norepinephrine cause reverse , activate glycogen phosphorylase and promote glycogenolysis, while inhibit glycogen synthesis by inhibiting glycogen synthase