WHAT DO YOU REMEMBER
ABOUT ENZYMES AND
DIGESTION?
Learning objectives (WALT):
The action of enzymes as
biological catalysts.
How temperature and pH extremes
affect the rate of enzymecontrolled reactions
The role of enzymes in digestion
of food
Learning outcomes (WILF):
That you can state the functions
and mode of action of a simple
digestive enzyme like amylase.
That you can interpret a graph of
reaction rate for enzyme-controlled
reactions at different temperatures
and pH.
That you know some of the
applications of enzymes in industrial
settings
Enjoy the lesson
Main functions of the digestive system
teeth - mechanical digestion
Break food down into smaller
parts. Small chunks are easier
to swallow and have a greater
surface area for digestion
enzymes to act on
Saliva contains the enzyme salivary
amylase (pH optimum 7), which breaks
down starch to maltose.
mouth
Saliva also contains mucus which binds
chewed food together and also lubricates
MORE DETAIL
swallowing
salivary glands
oesophagus
liver
gall bladder
small intestine
(duodenum)
stomach
pancreas
small intestine
(ileum)
large intestine
The liver produces bile which
emulsifies fats and neutralises
stomach acids
appendix
rectum
MORE DETAIL
anus
The role of enzymes in digestion
Enzymes are biological catalysts. They speed up most of the
reactions in the body which would otherwise be far too slow.
Enzymes are made of protein, a sensitive substance whose structure
is altered easily by temperature or pH
Digestive enzymes all break down large molecules into ones small
enough to pass through the intestine wall
The shape of enzymes
is vital to their role as
catalysts and
determines which
reaction they catalyse
amylase
pepsin
The shape of enzymes is
easily changed by heat or
pH. The enzymes stop
working and are said to be
denatured.
The role of enzymes in digestion
part of a starch
molecule
AMYLASE
Amylase is produced by:
The salivary glands (pH 7 neutral)
AMYLASE
The pancreas
The small intestine (pH 8)
sugar molecules
(maltose)
The role of enzymes in digestion
ENZYME-CATALYSED REACTION
Optimum
temperature
HUMAN ENZYME
Rate of
reaction
ENZYMES CATALYSE
EFFECTIVELY ONLY IF THEIR
SHAPE IS CORRECT
Reaction rate
increases due
to kinetic effect
temperature
Enzyme shape
changing denaturation
36.7 deg C
The role of enzymes in digestion
ENZYME-CATALYSED REACTION
Two forms of
trypsin.
Rate of
reaction
Where do
they come
from?
Pancreas /
small
intestine
Stomach
1
2
3
4
5
6
pH
7
8
9
10
11
NOW SEE HOW MUCH OF THIS
YOU CAN REMEMBER
» With thanks to LRGS BIOLAB PRESENTATIONS