Transcript 8A Food and Digestion

8A Food and Digestion
© Tony P. Thould
September 2000
DIGESTION
The breaking down
of complex foods into
simple soluble substances
CARBOHYDRATES
Potatoes
Rice Pasta
Bread
Energy giving
foods full of
Starch
PROTEINS
FATS
Butter
Cream
Fried Food
Peanuts
Meat
Fish
Soya
For growth
Stored energy and repair
and insulation
VITAMINS
FIBRE
MINERALS
Fresh fruit
and
vegetables
Prevent
deficiency
diseases
Fresh fruit
vegetables
milk
Prevent
deficiency
diseases
Cereals
fruit
vegetables
Provides
bulk to
move food
along.
CARBOHYDRATES
PROTEINS
FATS
Potatoes
Rice Pasta
Bread
Amylase breaks
down the
Starch in these
foods to
Glucose sugar
Butter
Cream
Fried Food
Peanuts
Lipase breaks
down fats to
Fatty Acids and
Glycerol
Meat
Fish
Soya
Protease
breaks
down
Protein to
Amino
Acids
CARBOHYDRATES
PROTEINS
FATS
Protease
Amylase
Lipase
breaks down
the Starch in
these foods to
Glucose sugar
breaks down
fats to Fatty
Acids and
Glycerol
breaks
down
Protein to
Amino
Acids
FOOD GROUPS
There are SEVEN main food groups :-
•Carbohydrates
•Fats
•Proteins
•Vitamins
•Minerals
•Water
•Fibre
FOOD GROUPS
There are SEVEN main food groups :-
•1
•2
•3
•4
•5
•6
•7
A BALANCED DIET
You must have the right amounts of
all of the seven food groups in
order to keep healthy
Too much of one group or not enough of
another or missing groups out from your
diet will mean an unbalanced diet and ill
health.
WHAT IS IN FOOD?
There are tests that can be done on foods to find
out which food groups are present in that food.
IODINE is an orange/brown liquid that turns black when it
reacts with Starch
BIURET TEST involves adding the Biuret reagent to the
food and then adding up to the same amount of Sodium
Hydroxide to it. If a purple colour appears this means that
the food contains proteins.
BENEDICTS TEST tests for Reducing Sugar ( Glucose ). It
is a blue liquid that when heated with a food solution turns
green to orange to Brick red depending upon the amount of
sugar present.
ENZYMES
These rare chemicals made in the body whose
job it is to breakdown the complex foods into
simple soluble substances
BD CF SSS
The three different food groups each need
their own special Enzymes to break them
down from a complex food into a simple
soluble substance
A SUMMARY OF DIGESTION
FOOD
GROUP
Carbohydrate
ENZYME
SIMPLE
SOLUBLE
SUBSTANCE
Amylase Glucose Sugar
Proteins
Pepsin
Amino Acids
Fats
Lipase
Fatty Acids &
Glycerol
THE ENZYME AMYLASE
Enzymes are Catalysts made
from Protein
Amylase will only break down
Carbohydrates such as Starch
Carbohydrates must end up
as a simple soluble substance
Iodine is a chemical test for starch
If a drop of Iodine, which is normally
red brown in colour, is placed upon a
substance that contains starch, the
iodine will turn black.
If the substance contains no starch the
iodine stays the same colour I.e. red
/brown.
A CHEMICAL TEST
FOR STARCH
IODINE is a red /
brown liquid
Starch
STARCH + AMYLASE
EXPERIMENT
•Amylase is added to Starch solution, placed
in a water bath at 37ºC
•A drop of this mixture removed every two
minutes for 24 minutes and tested in a dimple
tray with Iodine.
WHAT RESULTS WOULD YOU EXPECT?
Iodine in a dimple tray at the start of the
experiment with Starch + Amylase
How do you explain these results after 24mins.
THE ENZYME AMYLASE
Enzymes are Catalysts made
from Protein
Amylase will only break down
Carbohydrates such as Starch
Carbohydrates must end up
as a simple soluble substance
STARCH IS A COMPLEX FOOD
- it is too big to be absorbed and
must be broken down by amylase
into a simple soluble substanceglucose so that it can pass into the
blood
S
T
A
R
C
H
STARCH IS A COMPLEX FOOD
S
T
A
R
C
H
Enzymes are chemical scissors cutting up the
large complex food molecules ( starch ) into a
simple soluble substances ( Glucose )
G
G
G
G
G
G
STARCH IS A COMPLEX FOOD
S
T
A
R
C
H
AMYLASE is the
Enzyme that breaks down
Starch into Glucose
G
G
G
G
G
G
S
T
X
A
X
R
C
X
H
X
The complex starch molecule is too big to pass into the blood vessel
G
G
G
G
G
Easily absorbed
G
S
A
T
X
R
X
C
X
H
X
No starch gets into the blood and would pass out of the body unused
The soluble glucose is easily absorbed into the
bloodstream and carried around the body.
G
G
G
G
G
BY NOW YOU SHOULD KNOW
•The definition of Digestion
•The main food groups, sources and uses
•What Enzymes are and what they do
•Three named Enzymes, what food group
they act upon and what they break down
the food into
THE DIGESTIVE SYSTEM
Salivary Glands
Oesophagus
( Gullet )
Liver
Stomach
Gall Bladder
Pancreas
Colon
Large
Intestine Appendix
Rectum
Anus
Duodenum
Ileum
Small
Intestine
THE DIGESTIVE SYSTEM
Salivary Glands
These make the
liquid Saliva in the
mouth.
Just the thought of
food can make these
work - they make
your mouth water or drool like a dog
waiting to be fed.
Saliva moistens the
food, lubricating it
so that it is easier to
swallow
Saliva contains an
Enzyme called
Amylase which can
break down the large
molecules of Starch
into soluble Glucose
ready to be absorbed
into the blood
THE DIGESTIVE SYSTEM
Food going down
the Oesophagus
into the stomach
Oesophagus or
Gullet
The food is forced
down the
Oesophagus by
muscular
contractions
squeezing behind
it. This is called
Peristalsis
THE DIGESTIVE SYSTEM
Hydrochloric acid
and the Enzyme
Pepsin ( Protease )
are made by cells in
the Stomach wall.
Together they make
up Gastric Juice.
Stomach
Pepsin starts the break
down of Proteins into
Amino Acids which are
soluble and easily
absorbed into the blood.
This is where
Protein Digestion
begins
THE DIGESTIVE SYSTEM
The Liver makes a liquid
called Bile. This is stored
in the Gall Bladder
before passing down the
tube - Bile Duct - into the
Duodenum.
Liver
Bile emulsifies Fats.
This means that the fat
is turned into small
pieces. This gives the
fat a larger surface area
for the Enzyme Lipase
to chemically attack it
and break it down
Gall Bladder
Duodenum
Bile also neutralises the
acid stomach contents
so that the Pancreatic
enzymes can work in a
neutral pH
THE DIGESTIVE SYSTEM
Lipase breaks down the
emulsified fats into Fatty
Acids and Glycerol.
These are soluble and are
absorbed first into the
Lymph System before
going into the
bloodstream through
veins in the neck.
The Pancreas is an “
Enzyme Factory “ It
makes lots of different
Enzymes including
Lipase, Amylase and
Trypsin.
Pancreas
These Enzymes pass
down the tube Pancreatic Duct - into
the Duodenum
THE DIGESTIVE SYSTEM
The Duodenum
and Ileum together
make up the Small
Intestine
Duodenum
Ileum
In the Duodenum all
of the Enzymes from
the Pancreas
( Pancreatic Juice )
digest the remaining
complex foods into
simple soluble
substances before
passing on into the
Ileum
THE DIGESTIVE SYSTEM
The simple soluble ( liquid )
food is now absorbed into
the bloodstream
For this to happen quickly
the inner wall of the Ileum
is tightly folded each fold
is known as a Villus
Ileum
Villi increase the
surface area of the
inner wall of the Ileum
They have a good
blood supply ready to
carry away the soluble
food.
Any undigested food
carries on into the
Large Intestine
THE DIGESTIVE SYSTEM
The Colon, Appendix,
Rectum and Anus
together make up the
Large Intestine
The Appendix has no
function
Undigested remains
pass out of the Anus Egestion
Excess water is
absorbed back into the
blood through the wall
of the Colon.
Lumps of undigested
remains - Faeces - are
stored in the Rectum
Colon
Appendix
Anus
Rectum
THE DIGESTIVE SYSTEM
BY NOW YOU SHOULD KNOW
•The main parts of the Digestive System
•The location of these parts in the body
•The main functions of these parts