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Definition:- Carbohydrates may be defined as organic compounds occurring in foods and living tissues and including sugars, starch, and cellulose, composed of the elements C, H, and O. Carbohydrates are • A major source of energy from our diet. • Also called saccharides, which means “sugars.” Carbohydrates.

The importance Of carbohydrates Functions of Carbohydrates: 1 - Source of energy for living beings, e.g. glucose 2 - Storage form of energy, e.g. glycogen 3 - Serve as structural component, e.g. glycosaminoglycans in humans 4 - Non-digestable carbohydrates like cellulose, serve as dietary fibers 5 - Constituent of nucleic acids RNA and DNA, e.g. ribose and deoxyribose sugar 6 - Play a role in immunity and also involved in detoxification, e.g. glucuronic acid.

Classification of Carbohydrates Classification: According to no. of sugar units Monosaccharaides: 1 sugar unit : glucose, fructose which present mainly in fruits, galactose Disaccharides: 2 sugar units: lactose which known as sugar milk (galactose + glucose), maltose(glucose + glucose) Oligosaccharides: 3-9 units Polysaccharides: 10 or more units The suffix ose indicates that a molecule is a carbohydrate.

GLUCOSE • Physiologically and biomedically , glucose is the most important monosaccharide • It is called blood sugar • C6H12O6 • It is source of energy • It is can be stored in our body in form of glycogen.

• Glycogen is the major storage form of glucose mainly in the liver and muscle. • The concentration of liver glycogen (up to 6%) is greater than in muscle tissues (1%). • The synthesis( glycogenesis ) and degradation( glycogenolysis ) occur via different pathways. Glycogenesis and glycogenolysis are both cytosolic processes GLYCOGEN METABOLISM.

Glycogenesis Glycogenesis is the pathway for the formation of glycogen from glucose. This process requires energy, supplied by ATP and uridine triphosphate (UTP). It occurs in muscle and liver..

Glycogenolysis is the degradation of glycogen to glucose- 6-phosphate and glucose in muscle and liver respectively. Glycogenolysis is not the reverse of glycogenesis but is a separate pathway. Glycogenolysis.

In liver Following a meal, excess glucose is removed from the portal circulation and stored as glycogen by glycogenesis. Conversely, during fasting, blood glucose levels are maintained within the normal range by release of glucose from liver glycogen by glycogenolysis. In muscle The function of muscle glycogen is to act as a readily available source of glucose within the muscle itself during muscle contraction. The muscle cannot release glucose into the blood, because of the absence of glucose-6-phosphatase that hydrolyzes glucose 6-phosphate to glucose. Therefore, muscle glycogen stores are used exclusively by muscle. Significance of Glycogenolysis and Glycogenesis.

Glucose metabolism Glycolysis is the sequence of reactions that converts glucose into pyruvate in the presence of oxygen (aerobic) or lactate in the absence of oxygen (anaerobic) with the production of ATP. It is a unique pathway since it can utilize oxygen if available, or it can function in the total absence of oxygen Location Glycolysis is the major pathway for the utilization of glucose and is found in cytosol of all cells..

• Under aerobic condition pyruvate is taken up into mitochondria and after conversion to acetyl-CoA is oxidized to CO2 and H2 O by citric acid cycle with production of ATP. • Anaerobic Glycolysis • Tissues that function under hypoxic conditions produce lactate, e.g. exercising skeletal muscle and erythrocytes. • In erythrocytes even under aerobic conditions, glycolysis produce lactate because of absence of mitochondria..

Gluconeogenesis The synthesis of glucose from noncarbohydrate precursors is called gluconeogenesis Precursors for gluconeogenesis include: • Lactate • Glycerol • Glucogenic amino acids Location of Gluconeogenesis Gluconeogenesis occurs mainly in the cytosol. Liver is the major tissue for gluconeogenesis. During starvation, the kidney is also capable of making glucose by gluconeogenesis..

Diabetes mellitus • Diabetes mellitus is a group of diseases in which blood glucose levels are elevated. Diabetes is the most common disorder of carbohydrate metabolism • Diabetes is the leading cause of many complications as: • end-stage renal disease • non traumatic amputations, • blindness. • atherosclerotic disease. • deaths.

Pathophysiology • After carbohydrates digestion and absorption the blood glucose elevated which stimulates the pancreas to release insulin that facilitate glucose inertance inside the cells to use it as source of energy or in another metabolic processes • In diabetes mellitus, metabolism of all the main foodstuffs is altered. The basic effect on glucose metabolism is insulin deficiency or insulin resistance.

Classification • type 1 diabetes mellitus, which is caused by an absolute or near absolute deficiency of insulin, • represents approximately 10% of all cases of diabetes. • There usually is an autoimmune destruction of insulin- producing beta cells in the islets of the pancreas • type 2 diabetes mellitus, which is characterized by the presence of insulin resistance with an inadequate compensatory increase in insulin secretion which usually end with relative or absolute deficiency in insulin secretion. • Type 2 diabetes is the most common type of diabetes, affecting approximately 90% of cases. Many of them are obese.

 In addition, women who develop diabetes during their pregnancy are classified as having gestational diabetes.  Other specific types of diabetes..

Diagnosis of Diabetes Any of the followings tests is diagnostic to DM: • Fasting blood glucose ≥ 126 • Random blood glucose or 2 Hrs. post prandial blood glucose ≥ 200 mg/dl • HbA1c ≥ 6.5% To confirm the diagnosis repeat the same test in different day.

Glycated hemoglobin • Glycated hemoglobin (HbA1c) is the term used to describe the formation of a hemoglobin compound produced when glucose reacts with the globin part of hemoglobin. • HbA1c testing provides an index of average blood glucose levels over the past 2 to 4 months ( depending on RBC life span ) • Conditions associated with shortened red blood cell survival such as hemolysis and pregnancy will lower the HbA1c level ..