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Homework task HB2.18.1
Lesson reference: B2.18 Enzymes in industry
Enzymes in industry
Learning objectives:
 Understand why enzymes are used in industry.
 Consider some examples of using enzymes in industry.
 Evaluate the advantages and disadvantages of using enzymes in industry.
Suggested time:
30 minutes
Name: ________________________________ Date: ______________________
This homework task is all about applying your biology knowledge to a new
situation. Read the passage below and then answer the questions.
Making leather
 Leather is made from animal skins or hides. The hides have to be cured and
tanned to make them clean, flexible, and resistant to decay.
 The first stage is to cure the hides by immersing them in salt solution. This
removes water from the hides and prevents bacteria decomposing the
collagen protein in the hides.
 Then the hides are soaked in clean water to remove the salt and to rehydrate
them.
 The hides are then treated with a strong alkaline solution and some other
chemicals to remove the fats, alter the condition of the collagen proteins, and
remove the hairs. The hairs of the fur contain a protein called keratin. There
are many bonds between the sulfur groups of amino acids called cysteine.
 These bonds are hard to break. They make the protein structure very stable.
The chemicals added break these bonds and weaken the hairs, so they can be
scraped off the hide.
 Next, the pH of the hides is lowered, by adding salt and sulfuric acid.
 This neutralises the alkaline pH produced by the alkaline solution. Now
protease enzymes can be added to soften the leather.
 The leather is then soaked in a solution of tannins, aluminium salts, and egg
yolk. Tannins are obtained from plants, for example oak trees. They coat the
collagen so it is less water soluble and less susceptible to bacterial action. This
also makes the leather flexible. Finally the leather is waxed.
© Oxford University Press 2011
This document may have been altered from the original.
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A By what process is water removed form the hides when they are soaked in
strong salt solution?
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B Why do you think strong salt solution prevents bacteria from decomposing the
hides?
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C When the sulfur bonds between adjacent cysteine amino acids in the chain are
broken, what will happen to the structure of the keratin protein molecules?
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D Why does the pH have to be lowered before the protease enzymes are added
to the hides?
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E Why do you think coating the leather in tannins prevents bacterial action?
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© Oxford University Press 2011
This document may have been altered from the original.
171
F Until the 19th century, tanneries (where leather is made from animal skins)
used urine and dog or pigeon faeces to treat the hides. This practice had been
carried out since ancient times. Scientists now know that it was the protease
enzymes in the faeces that helped cure the hides.
i
Why are faeces a good source of protease enzymes?
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In Victorian times some children were employed to collect dog faeces from the
streets.
ii Why do you think dog faeces were used as opposed to horse faeces, which
would also have been readily available from the streets?
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G If you worked in a modern tannery and came across a new source of protease
enzymes, what investigations would you do to find out if these enzymes would
be suitable to use in making leather?
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© Oxford University Press 2011
This document may have been altered from the original.
172