Chemistry Review for MLT ASCP or AMT

What is the most predominant buffer system in the body

Bicarbonate/carbonic acid

 

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

 

Glycogen is

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.

Define glycolysis
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 _____
Cholesterol
The turbid or milky appearance of serum after fat ingestion is caused by ___
chylomicron
What compound is a crucial intermediary in the metbolism of triglycerides to form energy

Acetyl-coenzyme A

 

 

______ is a breakdown

product of cholesterol used in the digestion

of dietary cholesterol

Bile
What substance is the precursor to all steroid hormones
cholesterol
The surfactant/albumin ratio is performed to assess _____
fetal lung maturity
VLDL primarily transports ___
triglycerides
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?
total CO2
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)

C

 

 

What is the anticoagulant of choice for blood gas analysis
heparin
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?

chloride

 

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

cardiac insufficiency.

 

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).

decreased

 

 

In “base excess” positive values represent ______

metabolic alkalosis

 

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

metabolic acidosis.

Classification of acid base disorders

 

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