Homer

1
Homers Hair
Arrggh! Wheres my hair gone? Ohhh! Why wont it
grow faster? What is this hair stuff anyway?
2
Homers Hair Structure
The main component of hair is keratin. Keratins
are proteins made of long chains (polymers) of
amino acids. They account for approximately 85
of Homers hair with the remainder comprising
water, fats, vitamins and trace elements.

• Homers hair seen under an electron microscope.

Homers hair structure.
3
Homers Amino acids
Amino what? Where are they? Will they hurt me?
4
Homers Amino Acids
Amino-acids are small biomolecules. There are 16
different amino acids found in keratin.
Hydrogen
Carboxyl group
Amino group
Amino what? Where are they? Will they hurt me?
R group
5
Homers Amino Acids
So, how many do I need? Can I eat them? Mmmmmm
amino acids.
6
How many amino acids
does it take for 1 hair
to grow for 1 second?
7
Lets do the Calculation

• What shape is your hair Homer?
• Cubic Cylindrical
• OK we agree it is a cylinder. So we can work out
  a volume of hair grown per month using
• ?r2h
• For this we need to know the length of hair grown
  per month and the radius of a hair
• Choose a length (mm) 1 10 100
• Choose a radius (mm) 1 0.05 0.0001

8
Volume of Hair per month

• You grow about 10 mm of hair per month and the
  radius of one hair is about 0.05 mm (it takes
  about the width of 10 hairs is about 1 mm.
• Therefore the Volume of hair grown per month is
• ? x (0.05)2 x 10
• 0.0785 mm3

9
Mass of Hair

• We now need to transform this volume into a mass.
  What relates mass and volume?
• Refractive index Density Body Fat Index
• So we need to know the density of hair does it
  float or sink in water? Well it does a bit of
  both (surface tension is a problem) which
  suggests the density of hair is about the same as
  water which is 1 g/cm3 careful of the units
  Homer, convert it into g/mm3
• 1 g/cm3 0.001 g/mm3
• So the mass of hair grown per month is
• Mass density x volume
• 0.001 g/mm3 x 0.0785 mm3
• 0.000 0785 g

10
Mass per second

• OK so we know how much mass each hair puts on per
  month, but we need to know how much mass per
  second.
• How many seconds in a month Homer?
• About 30 days, 24 hrs per day, 60 minutes per
  hour, 60 seconds per minute
• 30 x 24 x 60 x 60 2592000 seconds per month
• Therefore
• Mass of hair per sec 0.000 0758 / 2592000
• 0.000 000 000 0302 g

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Moles
So now we have a mass of hair per second we need
to work out the number of molecules. To work out
the number of molecules we first need to work out
the number of moles. number of moles mass of
hair / RMM

• As you know Homer hair is made of keratin which
  is a protein made up of amino acids. To work out
  the number of moles of amino acids per second we
  need to know the relative molecular mass (RMM) of
  amino acids. As this is a rough calculation we
  will use the average RMM of 135 g/mole.

12
Moles to Molecules
OK Homer are you ready for this.

• Number of moles of amino acids
• 0. 000 000 000 0302 g
• 135 g/mole
• 0.000 000 000 000 224 moles

Not much Hey? Now to convert it into molecules
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Moles to Molecules
Avogadro was the first to work out how many
molecules were in a mole. He found that in one
mole there are 603 000 000 000 000 000 000 000
Molecules We now call this Avogadros Number

• 0.000 000 000 000 224 x 603 000 000 000 000
  000 000 000

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The Answer

• 135 000 000 000
• amino acids per second
• Thats
• 135 Billion

15
Homers donut tower
Which is a very large number Homer! If each
amino acid was a donut! Arrrrgggghhhh!Then you
could make a donut tower 4,375,000 km tall.
Enough to reach the moon 11 times!
16
Ok amino acids do your thing!