Clinical Chemistry II- Carbohydrates
Explain the procedure behind the 2hr PP test for glucose
-A FBS sample is taken -Patient ingests a high carbohydrate meal -Two hours after ingestion, another sample is taken
Ketones bodies have a composition of which compounds?
-Acetone -Acetoacetic Acid -Beta-hydroxybutyric Acid
What are the functions of carbohydrates? (5)
-Main source of energy -Stored for later use as energy -Component of other biological compounds (DNA/RNA) -Component of cell walls and exoskeletons -Linked to many proteins and lipids
What are the various methodologies of glucose testing?
-Metal Ion Reduction -Orthotoluidine -Glucose Oxidase and Hexokinase
There are three classifications of carbohydrates including:
-Monosaccharides -Oligosaccharides -Disaccharides
Explain the procedure for the GTT.
-Patient placed on high carbohydrate (150-300g/day) diet for 3 days -Report to lab fasting -Submit as urine and FBS sample -Urine screened for glucose -If pos, physician will be notified to determine continuance of testing -If neg, patient is given 100g glucose solution -Blood sample taken @ 30min, 1hr, 2hr, and 3hr points after ingestion
Symptoms of diabetes mellitus patient include:
-Polyuria -Increase in thirst, dehydration -Increased ketones in the urine -Increase rapid weight loss -Increase in blood glucose -Reduction of transport of glucose to muscle/tissue
What IS the function of ATP?
-Provides energy for molecule synthesis, muscle contraction, active transport of ions and molecules across cell membranes
What two things can effect the detection of glucose levels in testing? (2)
1) Not immediately separating cells and plasma/serum can falsely decrease glucose levels 2) Increased levels of ascorbic acid can also falsely decrease glucose results
During an FBS test for glucose how long does the patient need to fast before the sample is taken?
12 hours
The average renal threshold for glucose is:
180mg/dl
What is the net energy gain of Glycolysis?
2 ATP
Each revolution of the Kreb Cycle produces ___________, and consumes ________
2 mol CO2, 1 mol acetyl Co A
What is the hydrogen to oxygen ratio of a carbohydrate?
2:1, Same as water H20
For a Gestational Diabetes Screen, a blood glucose of ________ after consuming a high carbohydrate meal is indicative of gestational diabetes
>140 mg/dl
In all tissues, glucose is metabolized to produce what?
ATP
Which methodology of glucose testing can be used with both serum and urine samples?
All methodologies can be used with both serum and urine samples
Which form of carbohydrate is ingested: polysaccharide, oligosaccharide, or monosaccharide?
All of the carbohydrate forms are ingested
What is the most important enzyme of the digestion of carbohydrates?
Amylase
The major food supply and energy source for the body
Carbohydrates
Carbohydrates are composed of _________, _______, and _______
Carbon, Hydrogen, Oxygen
-Polysaccharide -Vegetable starch -Structural component of plant cells -Human cannot digest
Cellulose
-An uncommon condition caused by the insufficient production of ADH -Characterized by the kidneys inability to retain water -Results in constant diuresis of dilute urine, causing dehydration, hypernatremia, and hyperglycemia
Diabetes Insipidus
Disease caused by insulin deficiency, characterized by hyperglycemia and glycosuria
Diabetes Mellitus
Procedure resulting from abnormal production or utilization of insulin
Diabetes Mellitus
-Insulin dependent or juvenile onset diabetes -Early onset -Most severe type -If tested, blood insulin levels = severely decreased -Controlled by supplemental insulin
Diabetes Mellitus Type I
DKA resulting from gluconeogenesis is usually associated with which type of diabetes?
Diabetes Mellitus Type I
-Non-insulin dependent diabetes -Usually begins in middle age or afterward -Frequent in overweight individuals -Varying decrease in insulin production -Controlled by diet, oral medication, or small doses of insulin
Diabetes Mellitus Type II
HHNC is typically associated with which type of diabetes?
Diabetes Mellitus Type II
-Carbohydrates consisting of two monosaccharides bound together
Disaccharide
Carbohydrates typically enter the small intestine in which form?
Disaccharides
T or F. 2hr PP, is a diagnostic test.
F. 2hr PP is NOT a diagnostic test, it is a screening test
T or F: a gestational diabetes screen of >140 mg/dl is definitive for gestational diabetes
F. Indicative or screen of gestational diabetes but not definitive or diagnostic
Glucose test that screens patients for abnormalities in their carbohydrate metabolism process by taking a venous blood sample after a patient has been fasting
Fasting Blood Sugar (FBS)
Monosaccharide commonly found in fruits
Fructose
What is a key enzyme in the phosphogluconate pathway, as it catalyzes the initial step of the pathway and helps to protect the red cell against oxidizing agents?
G-6-PD
Monosaccharide that is the chief component of lactose, which provides the sugar in milk
Galactose
Glucose test that is performed on pregnant women who are in their 24-28 weeks of gestation
Gestational Diabetes Screening
Gluconeogenesis is controlled by which hormone?
Glucagon
Glycogenolysis is regulated by which hormone?
Glucagon
Hormone secreted by the pancreas that raises blood glucose levels
Glucagon
Two important hormones that take part in the regulation of blood glucose levels include:
Glucagon and Insulin
Long term regulation of blood glucose levels in a fasting state is maintained by:
Gluconeogenesis
The formation of glucose from noncarbohydrate sources such as amino acids, glycerol, or fatty acids; the process of forming "new" glucose from protein (amino acids) and lipids (glycerol).
Gluconeogenesis
Monosaccharide that provides the main energy source for all body cells (cellular energy)
Glucose
Methodology of Glucose: -Third Generation Testing -High levels of sensitivity, specificity, and precision
Glucose Oxidase and Hexokinase
What is the preferred method of glucose testing to date?
Glucose Oxidase and Hexokinase
This test is a diagnostic test for glucose, and is used to confirm any abnormal finding in either the FBS, or the 2hr PP as both of these are screening tests.
Glucose Tolerance Test (GTT)
-Polysaccharide -Animal Starch -Consists of up to 1,000 glucose molecules -Primary source is meat and dairy products
Glycogen
The storage form of glucose
Glycogen
Process of converting glucose into glycogen. Explain.
Glycogenesis. This process is controlled by the pancreatic hormone insulin. Stimulates cells to take up glucose from the blood and convert it to glycogen, the storage form of glucose
Process involving the breakdown of glycogen into glucose. Explain.
Glycogenolysis. This process is controlled by the hormone glucagon, who's principle action is to raise glucose levels by initiating the conversion of glycogen to glucose
Active skeletal and cardiac muscle require large amounts of ATP, and this demand is met through a process called ________ in which glucose is converted to pyruvic acid, lactic acid (by products), and ATP (energy)
Glycolysis
Four processes of carbohydrate metabolism that help regulate glucose levels include:
Glycolysis Glycogenesis Glycogenolysis Gluconeogenesis
Glucose in the urine resulting when serum concentrations reach the "threshold" value, excess glucose will be excreted in the urine
Glycosuria
Increased blood glucose
Hyperglycemia
What are the two life threatening complications of diabetes?
Hyperglycemic, Hyperosmolar, Nonketonic Coma (HHNC) and Diabetic Ketoacidosis (DKA)
This condition is caused by an over production or excess of insulin due to a tumor of the pancreas, or an overdose of insulin given to a diabetic patient
Hyperinsulinism
Decreased blood glucose
Hypoglycemia
Hyperinsulinism is a condition that causes _________.
Hypoglycemia
When testing for glucose, when must serum/plasma be separated from RBCs? Why?
Immediately as the RBCs will continue to metabolize the glucose that is in the specimen, falsely decreasing results
Where does digestion of carbohydrates begin? Explain.
In the mouth, as the salivary glands secrete amylase which begins the breakdown of complex carbs
Hormone produced by the pancreas that promotes glycogenesis resulting in a decreased blood glucose level
Insulin
What pancreatic hormone is most important concerning the regulation of Glycogenesis?
Insulin
As gluconeogenesis forms new glucose from protein and lipids, what is the metabolic end-product of lipid and/or protein metabolism?
Ketone Bodies
Glucose + Galactose = _________; principle carbohydrate found in _______
Lactose, milk
Glucose + Glucose = __________, prinicple carbohydrate found in _________
Maltose, plants
Methodology of Glucose: -First Generation testing -Based on the ability of carbohydrate molecules to reduce certain metals -Popular method: Cupric sulfate reduction -Major disadvantage: lack of specificity because it detects ALL reducing sugars, not just glucose
Metal Ion Reduction
-Basic or "simple" sugars -Cannot be broken down any further -Building blocks for larger, more complex carbohydrates
Monosaccharides
Abosorption of carbohydrates takes place in which form?
Monosaccharides
All other carbohydrates are formed by combining two or more of what?
Monosaccharides
How long is the time frame of the GTT?
Most commonly a 3-hour GTT but may be extended up to 4 or 5 hours if hypoglycemia is suspected
How does digestion of carbohydrates take place in the stomach? Explain.
No digestion of carbohydrates takes place in the stomach due to the acidic pH of gastric juices which actually stops the action of amylase. However, this is where protein is broken down thus, releasing more carbohydrates from the ingested food.
Absorption of carbohydrates back into the blood is very selective. What carbohydrates can be found in the blood of normal individuals? Which cannot?
Normal- Monosaccharides, Disaccharides Abnormal- Oligosaccharides, Polysaccharides
-Carbohydrates consisting of two to ten monosaccharides bound together -Normally named using numeric prefix (trisaccharide, tetrasaccharide)
Oligosaccharides
Methodology of Glucose: -Second Generation Testing -Metal reduction test using Ortholuidine -Offers less interference and better reproducibility than first generation testing -Not specific for glucose
Orthotoluidine
An alternate method of glucose metabolism in which carbon dioxide and pentoses are produced by glucose oxidation, and also serving as a mechanism for synthesis and disposal of pentoses
Phosphogluconate Pathway
-Carbohydrates that are large molecules consisting of 11 or more monosaccharides -Referred to as "complex carbohydrates"
Polysaccharides
The maximum amount of substance that can be maintained in the blood stream prior to being excreted in the urine
Renal Threshold
What would happen to an individual that is deficient in G6PD when exposed to oxidizing agents?
Resulting in hemolytic anemia
Examples of Disaccharides include:
Sucrose, Lactose, Maltose
Glucose + Fructose = ___________; also known as "_______"
Sucrose, table sugar
T or F: GTT is diagnostic for glucose metabolism disorders such as diabetes mellitus
True
T or F: Glucose can also be measured in CSF and urine.
True
Glucose test that is a screening procedure, normally for diabetes mellitus.
Two-Hour Post Prandial (2hr PP)
Diabetes Mellitus can be divided into two major clinical categories including:
Type I and Type II
DKA most often occurs as a complication of the __________ and has mortality rate of approx. _____, while HHNC occurs most often in an older population with _______ and has a mortality rate of ______.
Type I diabetic, 10%, type II diabetes, 50%
What differences are seen between HHNC and DKA?
While it is not exactly clear why one patient develops HHNC and another develops DKA, in HHNC: serum osmolarity is higher, glucose is almost always >800mg/dl, and the patient tends to be older
In the mouth amylase breaks down ingested starch and glycogen (polysaccharides) into _______ and ______.
dextrin and maltose (disaccharides)
When monosaccharides are absorbed and taken to the liver, they can then be converted into:
glycogen; keto acids, amino acids, proteins; fat
Non-fasting states of regulation of blood glucose levels are maintained by:
hormones
Short term regulation of blood glucose levels in a fasting state is maintained by:
liver glycogen stores
After the disaccharides enter the small intestine they are further broken down into ______ by _________ such as ______ and _________
monosaccharides, enzymes, amylase, maltase
In a 2 hr PP, blood glucose values of a normal individual will:
return back to fasting level (70-115 mg/dl)
Carbohydrates belong to the _________ family, and is ended with which suffix?
saccharide, "ose"
Where does more carbohydrate (monosaccharide) absorption take place? At which rate?
small intestine, @ a constant rate
In a case of diabetes mellitus, plasma (blood) glucose levels are often _________. Explain.
so elevated that it exceeds the renal threshold (approx. 160 mg/dl) -This results in spillage of glucose into the urine, a condition known as glucosuria
The cyclic metabolic mechanism by which complete oxidation of acetyl Co A begins
the Kreb Cycle, read over 3-9
