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Key words:
nutrients
carbohydrates
molars
canines
stomach
absorption
proteins
vitamins
saliva
pancreas
duodenum
anorexia
minerals
lipids
obesity
enzyme
appendix
bulimia
starch
roughage
gall bladder
ingestion
rectum
glucose
malnutrition
incisors
small intestine
large intestine
villi
bile
anus
liver
ileum
Key definitions to learn:
Balanced diet
Food tests
Energy requirements
Energy intake
Digestion
Peristalsis
Absorption
A diet containing correct balance of different nutrients
Tests carried out on food samples to determine their makeup
Energy needs depending on age, sex, and level of activity
Calculation of energy obtained from eaten food
Breaking food down
Movement of food by muscular contractions down oesophagus
Food molecules taken through the wall of the small intestine
Key Learning Points:
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Food is needed to provide our bodies with nutrients and energy
Energy and nutrients are needed to make new cells and tissue for growth and repair old
and damaged cells and tissue.
Energy and nutrients are also needed to make our muscles work.
A balanced diet must contain sufficient amount of all the food groups as well as the
correct amount of energy. See table of nutrients – later
Malnutrition occurs when a person is not getting all the necessary food groups in their
diet.
Obesity is when a person is 25% over weight.
Anorexia nervosa is loss of appetite because a person thinks they are overweight.
Bulimia usually involves eating food then bringing it up again.
Kilojoule (kJ) is the unit of food energy. Different foods provide different amount of
energy.
Types of Teeth
Incisors
Canines
the sharp, chisel-shaped front teeth used for cutting food.
these teeth are shaped like points (cusps) and are used for tearing
food.
Premolars
these teeth have two pointed cusps on their biting surface and are
sometimes referred to as bicuspids. The premolars are used for both
crushing and tearing.
used for grinding, these teeth have several cusps on the biting surface
Molars
The major nutrient groups are:
Nutrient
Group
Carbohydrates
(Starch and
Glucose)
Found in
Needed
potato, pasta,
cakes, breads
and biscuits
as the main
source of
energy for the
body
Lipids
(fats)
fatty meats,
cream, butter
and cooking
oil,
as a source of
energy, and
insulation for
the body
Proteins
Vitamins and
minerals
Water
Food Test
 test for starch by
 goes black if starch
adding iodine to food
sample
 test for glucose by
adding Benedict’s
solution to food
sample and heat,
 test for lipids (fat)
by adding 1ml of
ethanol to food
sample then 1ml
water
 or rub fat onto
paper
is present
 goes orange, yellow
or green depending
upon the
concentration of
glucose that is present
 cloudy white solid
forms if lipids present.
 test for by adding
meat, fish,
eggs, cheese,
milk and
seeds
for body
growth and
repair
in many
foods,
especially
fruit and
vegetables
found in most
drinks
in small
amounts for
the bodies
chemical
reactions
to live. Without water, we cannot live
for more than 7 days. Water makes up
about 60% of our body cells. Most of
the chemicals in our body are
dissolved in water, or are suspended
in water.
Digestive System
Be able to label the major
organs associated with
digestion.
Result
sodium hydroxide
and copper sulphate
solution to pureed
food (Biuret test)
 fat causes greasy
stain
 goes purple colour if
protein present
 Chewing is the first of digestion, it involves the teeth biting,
chewing and shaping the food, with the help of the tongue.
Saliva, containing the enzyme amylase/ptyalin, is added to
start breaking down starch and to make the food easily
swallowed.
 Muscle contractions called peristalsis moves the food along
down the digestive system.
 The purpose of the stomach is to physically churn and break
down the food using special chemicals and to slowly release
the contents into the small intestine.
 The first part of the small intestine is the duodenum, here the
food is showered with enzymes from the pancreas and bile
from the gall bladder, these break down the food further.
 The ileum is the site of absorption. It is lined with small finger
like extensions called villi. These increase the surface area so
that rapid absorption can occur.
 As food passes along the large intestine excess water is
reabsorbed back into the blood stream.
 Finally the waste food (faeces) passes into the rectum and
remains there until expelled through the anus.
Food Tests
Food Type
Starch
Description of Test
Add a few drops of iodine solution
Observation of a positive result
Turns from yellow to blue-black
Glucose
Add a few drops of Benedict’s
solution and heat gently
Add 5mLs of sodium hydroxide then a
few drops of copper sulfate
Rub between a piece of filter paper
Turns from blue to green, yellow, orange
or brick red
Turns from blue to mauve (light purple)
Protein
Fats and oils
Leaves a grease stain on the paper
Model Gut
Website URL for revision:
http://www.sciencepages.co.uk/keystage3/year8/module13/m13revision.php
Revision Questions:
1. What are the main food groups?
……………………………………………………………………………………………………
2. Which food provides instant energy?
…………………………………………….……
3. Which food provides slow release energy? ……………………………………………
4. Which mineral is needed for bone growth? …………………………………………….
5. Which food is high in vitamin C?
……….………………………………………….
6. What is digestion?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
7. What is absorption?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
8. What are your incisors used for? …………………………………………………………
9. What are your molars used for? …………………………………………………………
10. What is the function of the stomach?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
11. What purpose does the gall bladder have in digestion?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
12. Model Gut Investigation:
We found that the starch solution turned Iodine from yellow brown to …………………., but
the Benedict’s stayed ……………… . This confirms that the solution contained
……………… but did not contain ……………… . The glucose solution turned
………………….. from blue to brick red when ……………. but did not turn the yellow brown
………………. blue-black. This confirms that the solution contained ……………… but did
not contain ………………… . The water from the beaker …………… the tubing was added
changed the ……………. of neither Iodine nor Benedict’s. ………………… the water
contained neither starch nor glucose.
However, …………… the tubing had soaked in the beaker of …………… for 2O minthe
water did not change the colour of …………………. but changed the colour of
…………………….. solution from blue to orange. This is …………………. that glucose has
moved from …………… the dialysis tubing into the water but the starch ……….. …………. .
Benedict’s starch
inside
blue-black before
glucose
Therefore
evidence
after
starch
colour
water
heated
Benedict’s blue
Iodine
glucose
did not
Iodine
yellow-brown
Draw a mindmap for this unit:
Add to it, as you develop your learning.
Food and
Digestion
Well done you have completed another revision unit.
Now reflect on how you can improve further:
Which aspects of the unit do I need to revise more carefully?
Which aspects of the unit do I need help with?
How will I seek this help?
Answers to Food and Digestion Revision Question
1. Carbohydrates, lipids (fats), proteins. (Food also provides essential vitamins and minerals).
2. Carbohydrate in the form of glucose which is absorbed instantly into the blood stream.
Starch has to be broken down (digested) first.
3. Carbohydrate in the form of starch. It releases energy as it is slowly broken down.
4. Calcium.
5. Citrus fruits e.g. oranges and lemons.
6. The breakdown of large molecules into smaller molecules using enzymes.
7. The passage of small molecules resulting from digestion through the cell membrane of the
villi lining the small intestine
8. Cutting food / Snipping off portions of food
9. Grinding food
10. Store the food, mechanically break it down by churning it up and to add acid and digestive
enzymes to begin digestion (not to digest food).
11. Stores bile which is used to help digest lipids (fats). i.e. it emulsifies the fat droplets,
breaking them down and increasing the surface area for enzymes to act on.
12. We found that the starch solution turned Iodine from yellow brown to blue-black, but the
Benedict’s stayed blue. This confirms that the solution contained starch but did not contain
glucose. The glucose solution turned Benedict’s from blue to brick red when heated but
did not turn the yellow brown Iodine blue-black. This confirms that the solution contained
glucose but did not contain starch. The water from the beaker before the tubing was
added changed the colour of neither Iodine nor Benedict’s. Therefore the water contained
neither starch nor glucose.
However, after the tubing had soaked in the beaker of water for 20 min the water did not
change the colour of Iodine but changed the colour of Benedict’s solution from blue to
orange. This is evidence that glucose has moved from inside the dialysis tubing into the
water but the starch did not.