Multiple Choice Quiz

Multiple choice quiz of 20 questions.
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Digestion is the breakdown of large particles of
food into smaller, more soluble molecules that can be absorbed
into the body.

Digestion happens inside the gut, and relies on enzymes.

Enzymes pass out into the gut, where they catalyse
the breakdown of food molecules.

Different enzymes

Different enzymes catalyse different digestion reactions.

Enzymes and their reactions catalysed

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Enzyme Reaction color="#000099">catalysed
amylase starch to sugars
protease proteins to amino acids
lipase fatty acids to glycerol

Different parts of the gut produce different enzymes. This is
shown in the table below:

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Where produced
salivary glands, small intestine, pancreas
pancreas, stomach, small intestine
pancreas, small intestine

Overall, this means that:

        Amylase catalyses the
breakdown of starch into sugars in the mouth and small intestine.

        Proteases catalyse the
breakdown of proteins into amino acids in the stomach and small

        Lipases catalyse the
breakdown of fats and oils into fatty acids and glycerol in the
small intestine.

Different enzymes work best at different pH values. The digestive
enzymes are a good example of this.

The stomach

The stomach produces hydrochloric acid which helps to begin
digestion. Tjhis acid kills many harmful microorganisms that might
have been swallowed along with the food. The enzymes in the
stomach work best in acidic conditions - in other words,
at a low pH.

The small intestine

After the stomach, food travels to the small intestine. There, the
enzymes work best in alkaline conditions. But the food is
acidic after being in the stomach. A substance called bile
neutralises the acid to provide the alkaline conditions needed in
the small intestine.

Naming enzymes

The names of the different types of enzymes usually end in the
letters -ase. Three of the most common enzymes with
their chemical actions are:

  • lipase - breaks down fats
  • protease - breaks down proteins
  • carbohydrase - breaks down carbohydrates
Uses of Enzymes in the home

Enzymes allow certain processes to be carried out at normal
temperatures and pressures, thereby reducing the amount of energy
and expensive equipment needed.

Below are some common enzyme uses you should be familiar with.

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used, together with protease, in biological
detergents to break down the substances in stains into
smaller, water soluble substances
used to pre-digest proteins during the
manufacture of baby foods
used to convert starch syrup, which is
relatively cheap, into sugar syrup, which is more valuable
- for example, as an ingredient in sports drinks
used to convert glucose syrup into fructose
syrup. Fructose is sweeter than glucose, so it can be used
in smaller amounts in slimming foods