Question

1. Name a pancreatic hormone that stimulates gluconeogenesis and activates glycolysis.

2. Fructose 2,6-bisphosphate has what effects on glycolysis and gluconeogenesis?

	A.	Enhances glycolysis only.
	B.	Enhances gluconeogenesis only/
	C.	Inhibits glycolysis only
	D.	Inhibits gluconeogenesis only.
	E.	Enhances glycolysis/inhibits gluconeogenesis
	F.	Inhibits glycolysis/enhances gluconeogenesis

3. Under actual cellular conditions, how many strongly exergonic reactions take place in glycolysis?

4. The name of the cofactors that carries CO2 (carbon dioxide) in most biological reactions is:

Answer 1

High sugar levels stimulate the pancreas to produce insulin, which enhances the entry of glucose into the cell and increases the production of the critical glycolysis enzymes. These actions stimulate glycolysis and lower blood glucose levels.

1. Gluconeogenesis occurs in the liver and kidneys. Gluconeogenesis supplies the needs for plasma glucose between meals. Gluconeogenesis is stimulated by the diabetogenic hormones such as glucagon secreted by the pancreas.

2. e. Enhances glycolysis/inhibits gluconeogenesis

Fructose-2,6-bisphosphate functions as a potent allosteric activator of PFK1, a rate-limiting enzyme of glycolysis. It also regulates the activity of fructose 1,6-bisphosphatase which controls gluconeogenesis. Elevated expression of Fru-2,6-P₂ levels in the liver allosterically activates phosphofructokinase 1 by increasing the enzyme’s affinity for fructose 6-phosphate, while decreasing its affinity for inhibitory ATP and citrate. Thus an increase in fructose 2,6-bisphosphate stimulates the activity of phosphofructokinase, increases glycogen synthesis and inhibits gluconeogenesis.

3. In glycolysis, there are three highly exergonic steps (steps 1,3,10). These are also regulatory steps which include the enzymes hexokinase, phosphofructokinase, and pyruvate kinase. Thus these exergonic reactions occur only in the forward direction and are not reversible.

The first step in glycolysis is the conversion of D-glucose into glucose-6-phosphate. The enzyme that catalyzes this reaction is hexokinase.

step3- Phosphofructokinase, with magnesium as a cofactor, changes fructose 6-phosphate into fructose 1,6-bisphosphate.

The enzyme pyruvate kinase transfers a P from phosphoenolpyruvate (PEP) to ADP to form pyruvic acid and ATP Result in step 10.

4. Biotin- the  role of biotin is to serve as an enzymic cofactor required for the transfer of carbon dioxide.