Glycogen

What are the two processes of carbohydrate metabolism related to glycogen in the liver and muscle?

Glycogenesis and Glycogenolysis.

Which tissues have an absolute requirement for blood glucose?

Brain and red blood cells (RBC).

What is the primary source of blood glucose between meals?

Liver glycogen.

Approximately how long does liver glycogen supply blood glucose?

About 3 hours.

What percentage of calories do glycogen stores provide in muscle?

1000 calories.

What is the amount of liver glycogen in a 70 kg adult?

75 grams.

Which transporter is responsible for glucose entry into the liver?

Glut-2 transporter.

What enzyme converts glucose to glucose-6-phosphate in the liver?

Glucokinase.

What role does glucokinase play in carbohydrate metabolism after a high carbohydrate meal?

Its activity increases.

What is the main function of glycogen synthase in glycogenesis?

To add more glucose molecules to glycogen.

What are the two types of enzymes involved in the breakdown of glycogen?

Glycogen phosphorylase and debranching enzyme.

What regulates the activity of glycogen phosphorylase?

Phosphorylation status and hormonal signals.

Which hormone activates glycogen synthase to promote glycogenesis?

Insulin.

What effect does glucagon have on glycogen metabolism?

It acts in opposition to insulin, stimulating glycogenolysis.

What is the role of AMP in glycogenolysis?

It activates phosphorylase kinase.

What activates glycogen phosphorylase during exercise?

Epinephrine via beta adrenergic receptors.

Which enzyme facilitates the conversion of glucose-6-phosphatase in the liver?

Glucose-6-phosphatase.

What initiates the glycogenolysis process in muscle?

Calcium ions and epinephrine.

Which enzyme is responsible for removing branches from glycogen?

Branching enzyme.

What is the function of phosphorylase kinase in glycogen metabolism?

It activates glycogen phosphorylase.

What does the enzyme phosphoglucomutase do in glycogenesis?

Converts glucose-6-phosphate to glucose-1-phosphate.

How does insulin affect glycogen phosphorylase?

Insulin inactivates glycogen phosphorylase.

What is the significance of glycogenin in glycogenesis?

It acts as a primer for glycogen synthesis.

What is the relationship between calcium ions and glycogenolysis?

Calcium ions activate phosphorylase kinase, promoting glycogenolysis.

What metabolic state stimulates gluconeogenesis in the liver?

Hypoglycemia.

Which hormone is released in response to stress and hypoglycemia?

Cortisol.

What is the effect of increased GTPase activity on glucagon action?

It inhibits the signaling pathway that promotes glycogenolysis.

What does the dephosphorylated form of glycogen synthase do?

It is more active than the phosphorylated form.

What is gluconeogenesis?

The process of synthesizing glucose from non-carbohydrate precursors.

Which fuel source is primarily tapped during prolonged exercise?

Glycogen.

What does a decrease in insulin levels influence regarding glycogen metabolism?

It leads to increased glycogenolysis.

How does adrenaline affect glycogen metabolism during the 'fight or flight' response?

It stimulates glycogenolysis to quickly release glucose.

What is the role of GLUT-4 in glucose metabolism?

It facilitates glucose uptake into muscle and adipose tissue.

What is one consequence of prolonged glycogenolysis during exercise?

Increased blood glucose levels for energy.

What is the typical composition of muscle glycogen storage?

250 grams.

How does glucagon affect liver glucose output?

Increases the output of glucose by promoting glycogen breakdown.

Which enzyme is responsible for converting glucose-1-phosphate to uridine diphosphate glucose?

UDPG pyrophosphorylase.

What are the main products of glycogenolysis?

Glucose-1-phosphate and free glucose.

What molecule is essential for insulin signaling in regulating metabolism?

Tyrosine kinase.

How does glucose exit the liver?

Via the Glut-2 transporter.

What effect does prolonged exercise have on hormone levels that regulate glycogenolysis?

Increased epinephrine and cortisol levels.

What is one action of cortisol in glycogen metabolism?

Promotes the conversion of glycogen to glucose.

Where does gluconeogenesis primarily occur?

In the liver.

What effect does high carbohydrate consumption have on glycogen storage?

Increases glycogen synthesis.

What is the primary function of glycogen stored in muscles?

To provide energy during immediate physical activity.

Overall, what is the primary goal of the glycogen metabolic pathways?

To maintain blood glucose levels during fasting and energy usage.