Metabolism of Carbohydrates
Metabolism of Carbohydrates
Metabolism of Carbohydrates
(Nurs MC 2)
METABOLISM OF CARBOHYDRATES
1. General Principles of Metabolism
2. Concentration of Sugar in the Blood
3. Source of Energy
4. Glycogenesis (report)
5. Glycogenolysis
6. Glycogen Storage Diseases
7. Glycolysis
8. Cori Cycle and Lactic Acid Pathway
9. Citric Acid Cycle
10. The Role of B-Vitamins in Citric Acid Cycle
11. Electron Transport Chain and Oxidative Phosphorylation
12. Gluconeogenesis
13. Hormones Involved in Regulating Blood Sugar
GLYCOGENESIS
GLYCOGEN METABOLISM: Glycogen, Glycogen Synthesis, and Glycogen Breakdown
A constant source of blood glucose is an absolute requirement for human life.
Glucose is the greatly preferred energy source for the brain and the required energy
source for cells with few or no mitochondria such as mature red blood cells.
In a subsequent reaction, the UDP produced in Step 3 is converted back to UTP, which
can then react with another glucose 1-phosphate (Step 2). The conversion reaction requires ATP.
Adding a single glucose unit to a growing glycogen chain requires the investment of two
ATP molecules: one in the formation of glucose 6-phosphate and one in the regeneration of UTP.
Location of Glycogenesis
Glycogenesis takes place in the cytoplasm of cells in the muscle, liver, and
adipose tissue.
Steps of Glycogenesis
Glycogenesis is a multistep process that takes place primarily in the liver and
muscle cells, although other tissues also contribute to glycogen synthesis. The
following steps outline the process of glycogenesis:
1. Glucose Uptake
In this step, glucose molecules from the bloodstream are transported into
the liver or muscle cells through glucose transporters, such as GLUT2 in the
liver and GLUT4 in muscle cells.
This facilitated diffusion process ensures an adequate supply of glucose for
glycogen synthesis within the cells.
Reaction: Glucose + ATP → Glucose-6-Phosphate + ADP (Catalyzed by
hexokinase)
2. Conversion to Glucose-6-Phosphate (G6P)
Once inside the cell, glucose is converted to glucose-6-phosphate (G6P)
through a phosphorylation reaction.
The enzyme hexokinase or glucokinase catalyzes this reaction, using ATP as a
phosphate donor.
The conversion of glucose to G6P traps glucose within the cell and makes it
more reactive for further metabolic processes.
Reactions: Glucose + ATP → Glucose-6-Phosphate + ADP (Hexokinase
or Glucokinase)
3. Isomerization to Glucose-1-Phosphate (G1P)
In this step, the G6P isomerizes to glucose-1-phosphate (G1P).
BIOCHEMISTRY
(Nurs MC 2)
Calcium Ions
Additionally, calcium ions are crucial for controlling glycogen metabolism.
Glycogen phosphorylase is activated and glycogen breakdown is promoted
by elevated intracellular calcium concentrations, which are frequently
brought on by muscular tension.
This is accomplished by calcium ions binding to calmodulin, which activates
the CaMK protein kinase.
Phosphorylase kinase is then phosphorylated and activated by CaMK, which
in turn phosphorylates and activates glycogen phosphorylase.