## Learning Outcomes

After completing this module, you should be able to:

- do some basic conversions, most importantly between milli, micro, nano, etc.
- understand how micropipettes (also referred to as pipette, pipetman, micropipette, etc.) work and which pipette is ideal to use for any given volume that you want to dispense

## The metric system

How well do you know your metric vocabulary? Below are a list of prefixes used in

the metric system, arranged in order of size. It is a very good idea to familiarise yourself with them as they are the most commonly used notation for many experimental measurements and in daily life!!

trillions |
billions |
millions |
thousands |
hundreds |
tens |

tera 10 ^{12} |
mega 10 ^{6} |
hecto 10 ^{2} |
deca 10 ^{1} |

tenths |
hundredths |
thousandths |
millionths |
billionths |
trillionths |

deci 0.110 ^{-1} |
centi 0.0110 ^{-2} |
pico 0.00000000000110 ^{-12} |

You already familiarised yourself with the metric system? That’s great. Try these questions below to apply that knowledge.

### Metric Quiz

To make this interactive, turn on javascript!

NOTE: Do NOT put commas in your numbers — the program is not smart enough to understand them!

**The brain of an elephant can weigh up to 7.5 kilograms. **

What is this in grams?

*g*

**Homo sapiens have a brain volume of about 1350 ml. **

How much is this in litres?

* l*

**A mouse brain weighs about 400 milligrams. **

What is this in micrograms?

*µg*

**Prokaryotic ribosomes can have a diameter as small as 20 nm.. **

How many micrometres is this?

*µm*

**A mitochondrion averages 0.5 micrometres across. **

How much is this in nanometres?

*nm*

**Commander Spock identifies a new strain of bacteria which averages 17.83 micrometres. **

How many nanometres is this?

*nm*

**The nerve cell running the length of a giraffe’s neck can measure up to 3100 millimetres. **

How much is this in metres?

*m*

in micrometres?

*µm*

## If you need to brush up…

The easiest way to convert metric measurements is to move the decimal place.

Remember that metric vocabulary? It went like this:

tera – giga – mega – kilo – no prefix – milli – micro – nano – pico

Every time you move to the right on this list, the unit gets smaller (by 3 decimal places), so you need more of them to compensate (move the decimal 3 places to the right).

For example, an ostrich egg can be up to 0.12 metres. What if you need to convert this to millimetres? Since millimetres are smaller than metres, you will need more of them to cover the egg. So, move the decimal 3 places to the right:

To convert to a larger unit, you need to move the decimal place to the left. For example, a microtubule is 25 nm in diameter. To convert the microtubule length to micrometres, you need to move the decimal 3 places to the left (so that there will be fewer micrometres than nanometres). So,

If you need to convert between two prefixes that are not next to each other (i.e., milli to nano), just add up all the decimal places (in this case, 6 decimal places to the right).

For example, a human egg is 0.1 millimetres in diameter. So, in nanometres, this is:

To summarise, remember that the SMALLER the unit, the MORE of them you need to make the same measurement, so move the decimal in the appropriate direction.