Carbohydrates Flashcards
How are carbs classified?
Grouped into generic classifications based on the number of carbons in the molecule
What is a Monosaccharide, Dissaccharide, Oligosaccharide, Polysaccharide
mono - 1 carbon
Diss - 2 carbon
Oligo - 3-10 carbons
Poly - 10+ carbons
Are carbs reducing substances?
Yes, these carbs can reduce other compounds while themselves are oxidized (remember the Clinitest)
Define Glucose
Glucose is the primary source of energy for humans.
Can the nervous system store/concentrate carbs?
No
What are the 3 possible metabolic pathways for glucose?
- Embden-Meyerhof pathway (hexokinase starts)
- Hexose monophosphate pathway (HMP) (G-6-phosphate)
- Conversion to glycogen
What is the 1st step for all 3 metabolic pathways for glucose?
First step for all three pathways requires glucose to be converted to glucose-6-phosphate using the high-energy molecule, ATP.
Define gluconeogenesis
Conversion of amino acids by the liver and other specialized tissue, such as the kidney, to substrates that can be converted to glucose
Formation fo glucose-6-phosphate from noncarbohydrate sources
What happens in the Embden-Meyerhof pathway?
Starts with 2 ATP molecules and ends with 4
Takes place in Mitochondria
Hexokinase starts
Conversion of amino acids by the liver and other specialized tissue, such as the kidney, to substrates that can be converted to glucose-6-phoshate is called gluconeogenesis
In anaerobic conditions, like in muscles, by converting pyruvic acid to lactic acid.
What happens in the Hexose monophosphate pathway (HMP)
Detours from Embden-Meyerhof path by converting glucose-6-phosphate to 6-phosphogluconic acid
Produces NADPH which is important to cells lacking mitochondria, preservation of cellular membranes and enzymes
Conversion to glycogen
Occurs when cellular energy needs are met
Acts as energy storage
Define glycolysis
Metabolism of glucose molecule to pyruvate or lactate for production of energy
Define Glycogenesis
Conversion of glucose to glycogen for storage
Define Glycogenolysis
Breakdown of glycogen to glucose for use as energy
Define Lipogenesis
Conversion of carbohydrates to fatty acids
Define Lipolysis
Decomposition of fat
What are all involved in controlling the blood glucose concentrations within a narrow range?
Liver, pancreas, and other endocrine glands are all involved in controlling the blood glucose concentrations within a narrow range.
is the primary hormone responsible for the entry of glucose into the cell and therefore reducing blood glucose levels?
Insulin
What is the primary hormone responsible for increasing blood glucose levels
Glucagon (liver muscle)
What are the two hormones produced by the adrenal gland that affect carbohydrate metabolism?
Epinephrine
Glucocorticoids
What is Epinephrine?
Produced by the adrenal medulla, increases plasma glucose. (skeletal muscle)
What is Glucocorticoids?
Primarily cortisol, are released from the adrenal cortex on stimulation by adrenocorticotropic hormone (ACTH).
What is Diabetes Mellitus?
A group of metabolic diseases characterized by hyperglycemia (increase in glucose) resulting from defects in insulin secretion, insulin action, or both
What is Type 1 Diabetes Mellitus
B-cell destruction to absolute insulin deficiency and development of autoantibodies (includes latent autoimmune diabetes of adulthood)
“genetic”
Islet cell autoantibodies
Insulin autoantibodies
Glutamic acid decarboxylase autoantibodies
Tyrosine phosphatase IA-2 and IA-2B autoantibodies
5-10% of all cases
Commonly occurs in childhood with rapid onset
Tend to experience Ketoacidosis (buildup of ketones in blood)
Symptoms: Excessive thirst (polydipsia), increased food intake (polyphagia), excessive urination (polyuria), rapid weight loss, confusion, loss of consciousnesses
What is Type 2 Diabetes Mellitus
Insulin resistance with an insulin secretory defect (due to progressive loss of adequate B-cell insulin secretion)
Relative insulin deficiency due to insulin resistance
“Acquired”
Occurs due to insulin resistance combined with insulin secretory defect
Most common form of Diabetes Mellitus
Associated with obesity and lack of physical exercise
Tends to occur in adulthood
What is gestational diabetes?
Glucose intolerance during pregnancy diagnosed in the 2nd or 3rd trimester of pregnancy
What is is lab findings in Hyperglycemia?
_____ insulin
_____ Glucose in plasma and urine
_____ Urine SG
_____ Serum and urine osmolality
_____ Blood and urine pH (acidosis)
Electrolyte imbalance
Are there Ketones in serum and urine? (Ketonemia and Ketonuria)
Decreased or absent insulin
Increased Glucose in plasma and urine
Increased Urine SG
Increased Serum and urine osmolality
Decreased Blood and urine pH (acidosis)
Electrolyte imbalance
Are there Ketones in serum and urine? (Ketonemia and Ketonuria)
Impaired fasting glucose or Prediabetes
When fasting glucose is elevated but not to diabetic levels
Criteria for Testing:
- Habitually inactive
- Family History of Diabetes Mellitus
- At risk minority populations
- History of Gestational Diabetes (diabetes from pregnancy)
- Hypertension (high blood pressure)
- Low HDL cholesterol (good cholesterol)
- High Triglycerides (fat)
- Glycosylated Hemoglobin A1c ≥ 5.7
- History of glucose intolerance
- Insulin resistance
Gestational Diabetes Mellitus
Any degree of glucose intolerance that occurs in the 2nd or 3rd trimester of pregnancy
Can lead to severe hypoglycemia of baby when umbilical cord is cut
Women who meet the criteria below in their prenatal visit should be diagnosed with Diabetes Mellitus not Gestational Diabetes Mellitus
Pathophysiology of Diabetes Mellitus (symptoms)
Excessive thirst (polydipsia)
Increased food intake (polyphagia)
Excessive urination (polyuria)
Rapid weight loss
Confusion
Loss of consciousnesses
Glycosuria
Diabetic Keto Acidosis
Hyperkalemia from the displacement of Potassium
Heart Disease
Stroke
Pancretatits (inflammation)
Criteria for Diagnosis of Diabetes Mellitus
Normal glucose = 74 - 100 mg/dL
Impaired fasting glucose = 100 - 125 mg/dL
Provisional diabetes diagnosis = > 126 mg/dL
Criteria for the Testing and Diagnosis of Gestational Diabetes Mellitus
Plasma glucose decreases as hours of test increases
One step:
Fasting plasma glucose = > 92 mg/dL
1-h plasma gl = >180 mg/dL
2-h plasma gl = >153 mg/dL
Two step:
Fasting plasma glucose = > 95 mg/dL
1-h plasma gl = > 180 mg/dL
2-h plasma gl = > 155 mg/dL
3-h plasma gl = > 140 mg/dL
Hypoglycemia
Involves decreased plasma glucose levels and can have many causes—some are transient and relatively insignificant, but others can be life threatening
Level 1 (glucose alert value) = < 70 mg/dL
Level 2 (clinically significant hypoglycemia) = < 54 mg/dL
Level 3 (severe hypoglycemia) = No specific glucose threshold….below range
Methods of glucose measurement
Serum (no anticoagulant), plasma, or whole blood
Hexokinase method measured at 340 nm (wavelength being isolated)
Sample integrity
Sample must be separated, serum/plasma poured off and refrigerated within 1 hour to maintain specimen integrity
Use serum or Plasma from lithium/sodium heparin or sodium flouride
Fasting blood glucose levels are to be collected after 8-10 hours of fasting, no more than 16 hours
Falsely increased by reducing agents
Hemolyzed and Icteric (yellow) samples may by falsely decreased
Glucose Tolerance Testing
Purpose is to evaluate how the body reacts to glucose
Procedure begins with a fasting glucose level
Patient orally consumes a 75 g glucose solution
2 hours later another glucose level
If the 2 hour glucose result is >200 mg/dL the patient is diagnosed with Diabetes Mellitus
Glucose level is drawn every hour for evaluation of pregnant women
Normal glu tolerance = < 140 mg/dL
Impaired glu tolerance = 140 - 199 mg/dL
Provisional diabetes diagnosis = > 200 mg/dL
Glycosylated Hemoglobin
Defined as the formation of a hemoglobin compound when glucose (a reducing sugar) reacts with the amino group of hemoglobin
Rate of formation is directly proportional to plasma glucose levels over 3 months
HbA1c is most commonly measured glycosylated Hemoglobin
Normal range is 4.0% - 6.0% (< 5.7% < 39 mmol/mol)
Uses EDTA whole blood sample
Ketones
Produced by the liver through metabolism of fatty acids to provide a ready energy source from stored lipids at times of low carbohydrate availability
Albuminuria
An early sign that diabetic kidney disease is occurring is an increase in urinary albumin.
Islet Autoantibody, Insulin Testing, and C-Peptide Testing
Presence of autoantibodies to the β-islet cells of the pancreas is characteristic of type 1 diabetes.