Carbohydrates Flashcards
Carbohydrates
The major food source and energy supply for the body and are stored primarily as liver and muscle glycogen.
Oligosaccharides
Chain containing 2 to 10 sugar units joined by glucosidic linkages
Polysaccharide
Chain containing greater than 10 sugars all joined by glycosidic linkages
Glycolysis
Metabolism of glucose molecule to pyruvate or lactate for production of energy.
Gluconeogenesis
Formation of glucose-6-phosphate from noncarbohydrate sources
Glycogenolysis
Breakdown of glycogen to glucose for use as energy
Glycogenesis
Conversion of glucose to glycogen for storage
Lipogenesis
Conversion of carbohydrates to fatty acids
Lipolysis
Decomposition of fat
Insulin
The primary hormone responsible for the entry of glucose into the cell.
Synthesis of insulin
Synthesized by the beta cells of islets of Langerhans in the pancreas; these cells detect an increase in body glucose, they release insulin.
When is insulin released?
When glucose levels are high.
Glucagon
The primary hormone responsible for increasing glucose levels.
Synthesis of glucagon
Synthesized by the alpha cells of the islets of Langethans in the pancreas and released during stress and fasting states. When these cells detect a decrease in body glucose, they release glucagon.
Epinephrine
Produced by the adrenal medulla, increases, plasma glucose by inhibiting insulin secretion, increasing glycogenolysis, and promoting lipolysis.
Glucocorticoids
Primarily cortisol, released from the adrenal cortex by stimulation by adrenocorticotropic hormone (ACTH), promote increase plasma glucose.
Growth Hormone
Increases plasma glucose by decreasing the entry of glucose into the cells and increasing glycolysis.
Thyroxine
Increases plasma glucose levels by increasing glyogenolysis, gluconeogeneis, and intestinal absorption of glucose.
Somatostatin
Produced by the gamma-cells fo the islets of Langerhans of the pancreas, increases plasma glucose levels by inhibition of insulin, glucagon, growth hormone, and other endocrine hormones.
Hyperglycemia
An increase in plasma glucose levels.
Diabetes mellitus
A group of metabolic diseases characterized by hyperglycemia resulting from defects of insulin secretion, insulin action, or both.
Type 1 diabetes
Characterized by inappropriate hyperglycemia primarily a result of pancreatic islet beta-cell destruction and a tendency to ketoacidosis.
Type 2 diabetes
Includes hyperglycemia cases that result from insulin resistance with an insulin secretory defect. An intermediate stage in which the fasting glucose in increased above normal limits but not the level of diabetes, has been names impaired fasting glucose.
Gestation diabetes mellitus (GDM)
Defined as any degree of glucose intolerance with onset or first recognition during pregnancy due to metabolic or hormonal changes.
Four methods of diagnosis of Diabetes Mellitus
(1) HbA1C greater than or equal to 6.5%, (2) fasting plasma glucose greater than or equal to 126 mg/dL, (3) and oral glucose tolerance test with a 2-hour post-load level greater than or equal to 200 mg/dL and, (4) symptoms of diabetes plus a random plasma glucose level greater than or equal to 200 mg/dL.
Results of hypoglycemia
Brain fuel deprivation, resulting in impaired judgment and behavior, seizures, comas, function brain failure, and death.
Severe hypoglycemia
Requires assistance to actively administer carbohydrates and glucagon or take other corrective actions.
Document symptomatic hypoglycemia
Symptoms of hypoglycemia
measured plasma glucose concentration <=70 mg/dL
Asymptomatic hypoglycemia
No symptoms of hypoglycemia
measured plasma glucose concentration <=70 mg/dL
Probably symptomatic hypoglycemia
Symptoms typical of hypoglycemia
No plasma glucose determination performed
Pseudohypoglycemia
Symptoms of hypoglycemia
Measured plasma glucose concentration >70 mg/dL but approaching that level
What method can glucose be measured?
Serum, plasma, or whole blood. Primarily serum or plasma.
Two most common methods for testing for glucose concentrations? Which is more accurate?
Glucose oxidase or hexokinase. Hexokinase more accurate.
Methodology for 2-hour postprandial test.
The patient drinks a standardized (75 g) glucose load and a glucose measurement is drawn 2 hours later. If that level is greater than or equal to 200 mg/dL and is confirmed on a subsequent day by either an increased random or fasting glucose level, the patient is diagnosed with diabetes.
Glycosylated hemoglobin
the term used to describe the formation of a hemoglobin compound produced when glucose (a reducing sugar) reacts with the amino group of hemoglobin (a protein).
Clinical significance of glycosylated hemoglobin
The glucose molecule attaches nonenzymatically to the hemoglobin molecule to form a ketoamine. The rate of formation is directly proportional to the plasma glucose concentrations. Because the average RBC lives ~120 days, the glycosylated hemoglobin level at any one time reflects that average blood glucose level over the previous 2 to 3 months.
For glycosylated hemoglobin measurement, what are the methods based on structural differences?
Immunoassays and affinity chromatography.
For glycosylated hemoglobin measurement, what are the methods based on charge differences?
Ion-exchange chromatography, electrophoresis, isoelectric focusing, and high-pressure liquid chromatography
Ketones
Bodies that are produced by the liver through metabolism of fatty acids to provide a ready energy source from stored lipids at times of low carbohydrate availability.
What are the three ketone bodies?
Acetone, acetoacetic acid, and 3-beta-hydroxybutyric acid
Ketonemia
The accumulation of ketones in blood
Ketonuria
The accumulation of ketones in urine
Two methods of ketone measurement
Nitroprusside and enzymatic
Albuminuira
Measurements that are useful to assist in diagnosis of diabetic kidney disease at an early stage and before the development of proteinuria.
Thyroxine
Secreted by the thyroid gland and its release is stimulated by TSH. It increases plasma glucose levels by increased glycogenolysis, increased gluconeogenesis, and increased intestinal absorption.
