Laboratory Practices

Question 1

If mixing acids and water, which do you add first?

Answer 1

Always add acid to water.

Question 2

What does it mean when one solution is miscible with another?

Answer 2

That the first dissolves completely in the second, creating a uniform homogenous mixture.

Question 3

How often should you check that you are using the correct solution?

Answer 3

Twice. Once when you select it from the cabinet, and again just before use.

Question 4

In laboratory practice, what is a control?

Answer 4

A material with a known value of the substance that is to be tested.

Question 5

What are the definitions for in vivo, ex vivo, in situ and in vitro?

Answer 5

In vivo: cells within an intact living organism
Ex vivo: cells out of a living organism, but in natural conditions (skin explants)
In vitro: (in glass) cells cultured in test tubes or petri dishes
In situ: in the original place
Ex situ: out of the original place

Question 6

5 of the 7 base metric units are regularly used in chemistry: the meter, the kilogram, the second, the Kelvin, and the mole. What are their symbols, and what do they measure?

Answer 6

Meter, length, m; kilogram, mass, kg; second, time, s; Kelvin, temperature, K; mole, amount of a substance, m.

Question 7

What are the practical units of measurement for volume in medicine?

Answer 7

Cubic centimeter (cc or cm³), liters (L), and milliliters (mL).

Question 8

A millimeter is a distance of 10-³. What distance is a micrometer?

Answer 8

A micrometer (symbolized by the greek letter mu) represents a distance of 10-⁶.

Question 9

What is the difference between a micron and a micrometer?

Answer 9

There is no difference.

Question 10

If the formula for oxygen is O₂, what is the Formula for Carbon Dioxide?

Answer 10

CO₂

Question 11

The formula for water is H₂O (Dihydrogen Monoxide). What is the formula for Hydrogen Peroxide?

Answer 11

H₂O₂

Question 12

What is the formula for Methane?

Answer 12

CH₄

Question 13

What is the formula for Ammonia?

Answer 13

NH₃

Question 14

What part of a smear is read by the pathologist, and why?

Answer 14

The area just before the feathered end. There, the cells appear singly and are not too thick or distorted.

Question 15

What is a colloid?

Answer 15

A homogeneous mixture of small particles of one substance dispersed through another substance. This can be a gel, sol, or emulsion.

Question 16

What are some transport mediums and how are they used?

Answer 16

Normal saline, Michel’s solution, RPMI. These keep fresh tissue moist and stable either at room temperature or in a refrigerator for a few days until tests requiring fresh rather than fixed tissue can be performed.

Question 17

What is the pink stuff kept in the refrigerator for flow cytometry specimens?

Answer 17

RPMI. It is pink because of a pH indicator. It will turn yellow if contaminated.
RPMI stands for Roswell Park Memorial Institute. History can be found here:

https://karger.com/ocl/article-pdf/37/6/426/3270312/000225485.pdf