Chemistry Review for MLT ASCP or AMT
|What is the most predominant buffer system in the body|
Because of its high concentration in blood,
the bicarbonate/carbonic acid pair is the most
important buffer system in the blood.
This buffer system is also effective in the lungs and in the kidneys in helping to regulate body pH. The other buffers that also function to help maintain body pH are the phosphate, protein, and hemoglobin buffer systems. The acetate buffer system is not used by the body to regulate pH.
|What is the storage form of glucose? Where is it stored|
Storage form of glucose is glycogen
found in a variety of animal tissues, particularly
in the liver, and provides the storage form for
carbohydrates in the body. When energy requirements warrant it, glycogen may be broken down to glucose by a series of phosphorylating and related enzymes.
|Conversion of glucose into lactate or pyruvate|
|Is the glucose concentration in fasting whole blood higher or lower than the concentration in plasma or serum?|
|The glucose concentration in whole blood is lower than in serum or plasma|
|Describe the hexokinase method for determining glucose levels|
The hexokinase method for quantifying glucose
uses two coupled enzymatic reactions.
In the first reaction, which is catalyzed by hexokinase, glucose is phosphorylated by adenosine triphosphate, forming glucose-6-phosphate and adenosine diphosphate.
In the second reaction, glucose-6-phosphate dehydrogenase (derived from yeast) catalyzes the oxidation of glucose-6-
phosphate and the reduction of nicotinamideadenine dinucleotide phosphate. The amount of reduced NADPH formed is proportional to the glucose concentration in the sample. Thus, the greater the absorbance reading of NADPH at 340 nm, the greater is the glucose concentration.
If bacterial G-6-PD is used, the cofactor is NAD+ with the production of NADH.
|Bile acids that are synthesized in the liver are derived from _____|
|The turbid or milky appearance of serum after fat ingestion is caused by ___|
|What compound is a crucial intermediary in the metbolism of triglycerides to form energy|
______ is a breakdown
product of cholesterol used in the digestion
of dietary cholesterol
|What substance is the precursor to all steroid hormones|
|The surfactant/albumin ratio is performed to assess _____|
|fetal lung maturity|
|VLDL primarily transports ___|
|What does an increase in serum enzyme levels indicate?|
|tissue damage and necrosis|
|The measurement of the pressure of dissolved CO2 (PCO2) in the blood is most closely associated with what substance?|
Carbonic acid (H2CO3)
|What is the term that describes the sum of carbonic acid and bicarbonate in plasma?|
|To maintain a pH of 7.4 in plasma, it is necessary to maintain what ratio of bicarbonate to carbonic acid?|
|20:1 ration of bicarb to carbonic acid|
Which of the following characterizes respiratory acidosis?
a. Excess of bicarbonate
b. deficit of bicarbonate
c. excess of dissolved carbon dioxide (pco2)
d. deficit of dissolved carbon dioxide (pco2)
|What is the anticoagulant of choice for blood gas analysis|
|If a specimen is left exposed to air, what changes will occur?|
PO2 and pH will increase; PCO2 will decrease
When a blood specimen is drawn for gas
analysis, it is important to avoid exposure of the
specimen to air because of the differences in the partial pressures of carbon dioxide and oxygen in air and in blood. The PCO2 in blood is much greater than the PCO2 in air. Hence on exposure of blood to air, the total CO2 and the PCO2 both decrease, causing an increase in pH. Similarly, the PO2 of air is much greater than that of blood, thus, the blood PO2 increases on exposure to air.
|How would blood gas parameters change if a SEALED specimen is left at room temp for 2 or more hours|
PO2 decreases; PCO2 increases; pH decreases
Glycolysis and other oxidative metabolic processes will continue in vitro by red blood cells when a whole blood specimen is left standing at room temperature. Oxygen is consumed during these processes, resulting in a decrease in PO2 levels. A decrease of 3-12 mm Hg/hr at 37°C has been observed for blood specimens exhibiting normal pO2 ranges. This rate of decrease is accelerated with elevated PO2 levels. Additionally, carbon dioxide is produced as a result of continued metabolism. An increase in pCO2 levels of approximately 5 mm Hg/hr at 37°C has been demonstrated. The increased production of carbonic acid and lactic acid during glycolysis contributes to the decrease in blood pH.
|In order to maitain electrical neutrality in the red blood cel, bicarbonate leaves the red blood cell and enters the plasma through an exchange mechanism with what electrolyte?|
The red blood cell membrane is permeable to
both bicarbonate and chloride ions. Chloride ions participate in buffering the blood by diffusing out of or into the red blood cells to compensate for the ionic change that occurs when bicarbonate enters or leaves the red blood cell. This is called the chloride shift.
|Excessive vomiting causes (respiratory/metabolic) (acidosis/alkalosis).|
|Excessive vomiting causes metabolic alkalosis|
|What is a compensatory mechanism in respiratory acidosis?|
Increased Na+/H+ exchange by the kidneys
Respiratory acidosis is a disturbance in acid base balance that is caused by the retention of
CO2 by the lungs.
This imbalance is associated with such conditions as bronchopneumonia, pulmonary
emphysema, pulmonary fibrosis, and
Respiratory acidosis is characterized by a primary excess in physically dissolved CO2, which is quantified by measuring the blood PCO2 level.
The primary problem leading to an increase in the PCO2 level is hypoventilation. This retention of CO2 alters the normal 20:1 ratio of cHCO3/PCO2, causing a decrease in blood pH level.
In respiratory acidosis, because the initial defect is associated with the lungs, the kidneys respond as the major compensatory system. The production of ammonia, the exchange of Na+ for H+ with the excretion of H+, and the reabsorption of bicarbonate are all increased in the kidneys to compensate for the malfunction of the lungs. In cases where the defect is not within the respiratory center, the excess of pCO2 in the blood can actually have a stimulatory effect on the center, causing an increase in the respiration rate. Thus compensation can also occur through CO2 elimination by the lungs.
|In partially compensated respiratory alkalosis, renal reabsorption of HCO3 is (increased/decreased).|
|In “base excess” positive values represent ______|
Base excess is a measure of the nonrespiratory
buffers of the blood. They are hemoglobin, serum protein, phosphate, and bicarbonate. Therefore, base excess reflects an abnormality in the buffer base concentration.
Bicarbonate has the greatest influence on base excess, which is an indicator of metabolic function. The normal range for base excess is ±2.5 mmol/L.
A quick estimation of base excess is to subtract the average “normal” reference bicarbonate level set by the laboratory from the measured bicarbonate level
(if laboratory reference bicarbonate = 25 and patient’s bicarbonate = 30, then base excess = (30 — 25) = + 5; if patient’s bicarbonate = 20, then base excess = (20 — 25) = —5).
As demonstrated, a positive base excess is associated with metabolic alkalosis, and a negative base excess is associated with
Classification of acid base disorders