The document summarizes carbohydrate digestion. It states that salivary amylase in the mouth begins breaking down starch into maltose. In the small intestine, pancreatic amylase further breaks down starch and maltase breaks down maltose into glucose. The small intestine also secretes sucrase and lactase to break down sucrose into glucose and fructose and lactose into glucose and galactose, respectively. Lactose intolerance occurs when people lack sufficient lactase as adults to digest lactose from milk.

1. What’s
wrong with
this?
Monosaccharides are sweet tasting, insoluble
substances, e.g. glucose. To test for this
non-reducing sugar you carry out the Benedict’s
test where a red precipitate of copper sulphate is
produced if the sugar is present.
Disaccharides are when two monosaccharides are
linked by a glucose bond, this happens due to a
condensation reaction where a molecule of water
is added. E.g. glucose linked with fructose forms
maltose.
Polysaccharides are when many
monosaccharides are linked, e.g. glucose. To test
for this add iodine and a blue-black colour
indicates a polysaccharide.
Can you spot the 7
mistakes in this
answer? Underline
and then correct at
the side of the text.

2. Carbohydrate
digestion
Objective: To understand in detail
how carbohydrates are digested.
Outcomes:
~ Identify specific carbohydrases and
describe how they hydrolyse
polysaccharides into their
monosaccharides.
~ Explain how lactose intolerance
occurs.
Sunday, 28 September 2014
Keywords
Amylase
Maltase
Sucrase
Lactase

3. Mouth & salivary glands
Physical digestion
Chemical digestion  salivary
amylase is produced.
Starch  maltose
Also in saliva are mineral salts to
provide neutral conditions for
this enzyme.

4. Stomach
Acidic conditions so amylase is
denatured.

5. Small intestine
Chyme mixed with pancreatic
juice.
Pancreatic amylase.
Hydrolyses starch to maltose.
Maltase is secreted which
hydrolyses maltose to glucose.

6. Sucrose?
Small intestine
secretes sucrase.
Hydrolyses sucrose
into glucose and
fructose.
Lactose?
Small intestine
secretes lactase.
Hydrolyses lactose
into glucose and
galactose.

7. Lactose intolerance
1.Explain why babies produce larger
amounts of lactase compared to
adults.
2.Explain how some adults become
lactose intolerant.
3.List some symptoms of this
disorder and explain how they
occur.
4.Lactose intolerance is not life
threatening however describe other
problems sufferers may have.
Read through the
information on pg 25 and
answer the following qu’s.

8. Better milk for cats?!
Cats are unable to digest large
amounts of lactose. Milk can
be treated with the enzyme to
make a lactose- reduced milk
suitable for cats or humans
who are lactose intolerant.
The milk is treated by injecting
enzyme into the carton by
using an immobilised
enzyme.

9. What’s wrong with this?
Monosaccharides are sweet tasting, insoluble
substances, e.g. glucose. To test for this non-reducing
sugar you carry out the Benedict’s test
where a red precipitate of copper sulphate is
produced if the sugar is present.
Disaccharides are when two monosaccharides are
linked by a glucose bond, this happens due to a
condensation reaction where a molecule of water is
added. E.g. glucose linked with fructose forms
maltose.
Polysaccharides are when many monosaccharides
are linked, e.g. glucose. To test for this add iodine
and a blue-black colour indicates a polysaccharide.
What’s wrong with this?
Monosaccharides are sweet tasting, insoluble
substances, e.g. glucose. To test for this non-reducing
sugar you carry out the Benedict’s test
where a red precipitate of copper sulphate is
produced if the sugar is present.
Disaccharides are when two monosaccharides are
linked by a glucose bond, this happens due to a
condensation reaction where a molecule of water is
added. E.g. glucose linked with fructose forms
maltose.
Polysaccharides are when many monosaccharides
are linked, e.g. glucose. To test for this add iodine
and a blue-black colour indicates a polysaccharide.

10. Carbohydrate digestion
Complete the boxes to describe how
carbohydrates are hydrolysed by enzymes in
the digestive system.
Then summarise these notes by completing
the table below.
Produced where? Enzyme? Poly/disaccharide Monosaccharide
Salivary amylase
Pancreas
Small intestine
(Ileum)
Sucrose
Glucose
Glucose +
galactose

11. Produced where? Enzyme? Poly/disaccharide Monosaccharide
Salivary glands Salivary amylase Starch Maltose
Pancreas Pancreatic amylase Starch Maltose
Small intestine (Ileum) Maltase
Sucrase
Lactase
Maltose
Sucrose
Lactose
Glucose
Glucose + fructose
Glucose + galactose

12. Produced where? Enzyme? Poly/disaccharide Monosaccharide
Salivary amylase
Pancreas
Small intestine (Ileum)
Sucrose
Glucose
Glucose + galactose
Produced where? Enzyme? Poly/disaccharide Monosaccharide
Salivary amylase
Pancreas
Small intestine (Ileum)
Sucrose
Glucose
Glucose + galactose