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Chapter 10 Food and Diet

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Title: Chapter 10 Food and Diet


1
Chapter 10 Food and Diet
2
Think about it How do humans obtain food? What
are primary food substances? What are protective
food substances? How can we test for the
presence of some food substances? Why is a
balanced diet important to us?
3
Joe is answering a questionnaire about diet and
fitness.
Do you think that Joe is fit?
4
Joe is answering a questionnaire about diet and
fitness.
What makes him become fat?
5
Joe is answering a questionnaire about diet and
fitness.
What health problems may he have?
6
Joe is answering a questionnaire about diet and
fitness.
We need to eat to obtain energy for our body
activities. However, if we take in energy more
than we need, like Joe, we will become overweight
and may have health problems.
What health problems may he have?
7
How do humans obtain food?
Humans have to obtain food from other organisms
? this mode of nutrition is called heterotrophic
nutrition (????)
we are called heterotrophs (????)
8
How do humans obtain food?
Food has 3 main uses for us
  • provides energy and keeps us warm
  • provides raw materials for growth and repair
  • maintains health and regulates metabolism

9
The food requirements of humans
We require 7 types of food substances to stay
healthy.
Food substances
protective food substances (???????) (to stay
healthy)
primary food substances (??????) (essential to
life)
dietary fibre (????)
vitamins (???)
minerals (???)
carbohydrates (?????)
fats (??)
proteins (???)
water
10
What are primary food substances?
Carbohydrates
  • made up of carbon (C), hydrogen (H) oxygen (O)
    atoms
  • HO ratio is 21

? e.g. glucose C6H12O6
2 1
  • can be classified into 3 types

11
What are primary food substances?
Carbohydrates
polysaccharides
disaccharides
monosaccharides
  • simplest type of carbohydrates
  • examples glucose, fructose (??) galactose
    (???)

12
What are primary food substances?
Carbohydrates
disaccharides
polysaccharides
monosaccharides
  • formed by joining 2 monosaccharide molecules
    through condensation, in the presence of enzyme
  • during condensation, 1 water molecule is released

condensation (??)
monosaccharide
H2O

disaccharides
monosaccharide
13
What are primary food substances?
Carbohydrates
disaccharides
polysaccharides
monosaccharides
  • disaccharides can be broken down into single
    monosaccharide molecules through hydrolysis

condensation (??)
monosaccharide
H2O

disaccharides
hydrolysis (??)
monosaccharide
14
What are primary food substances?
Carbohydrates
disaccharides
polysaccharides
monosaccharides
  • examples sucrose (??)

, lactose (??) and
maltose (???)
glucose fructose ? sucrose H2O
glucose galactose ? lactose H2O
glucose glucose ? maltose H2O
15
What are primary food substances?
Carbohydrates
polysaccharides
disaccharides
monosaccharides
  • long chains of monosaccharides joined together
  • examples starch, glycogen (??) and cellulose
    (???)

glucose
16
What are primary food substances?
Carbohydrates
Sugars
  • All water-soluble carbohydrates are called sugars.
  • Some sugars can react with oxygen-containing
    substances and remove oxygen from them.

? reducing sugars
  • examples glucose, fructose, galactose,
    maltose and lactose

17
What are primary food substances?
Carbohydrates
Sugars
  • reducing sugars can form a brick-red precipitate
    in Benedicts test (?????)

Sucrose does not have this property!!
? non-reducing sugars
18
What are primary food substances?
Carbohydrates
Functions
  • as a main source of energy

1 g of carbohydrates ? 17.1 kJ of energy
  • If in excess ? converted to glycogen or fat
    for storage

19
What are the sources of carbohydrates?
Carbohydrates
Sources
  • cereals (e.g. rice, wheat and oat)
  • root crops (e.g. potatoes and taros)
  • cereals food products (e.g. noodles, bread,
    biscuits cakes and oatmeal)

20
  • Carbohydrates also present in the form of sugars
  • Fructose
  • - a simple sugar
  • - found in most fruits
  • Sucrose
  • - a double sugar
  • - present in large quantities in sugar cane and
    beet root
  • - often sold as table sugar and rock sugar
  • Lactose
  • - a double sugar
  • - present in milk

21
Fate of carbohydrates?
Carbohydrates
Fate
  • Simple sugars (e.g. glucose)
  • absorbed by body as the size are relatively small
  • broken down release energy
  • an immediate energy source
  • Double sugars
  • broken into simple sugars as the size is too
    large

Some tonic drinks, such as Lucozade, are
claimed to supply energy quickly. Why do the
manufacturers make such a claim?
22
  • In the human body, carbohydrates may not be used
    immediately in respiration. They can be
  • stored as glycogen in the liver and skeletal
    muscles
  • converted into fat and stored inside the body

23
What are primary food substances?
Fats
  • made up of carbon, hydrogen and oxygen atoms
  • HO ratio ? much greater than 21
  • insoluble in water but soluble in organic
    solvents, e.g. ether (??) and ethanol (??)
  • at room temperature

semi-solid form ? fats
liquid form ? oils
24
What are primary food substances?
Fats
  • a fat molecule is usually formed from the
    condensation of 1 glycerol (??) molecule 3
    fatty acid (???) molecules

condensation
H2O

hydrolysis
3 fatty acid molecules
1 glycerol molecule
1 fat molecule
25
What are primary food substances?
Fats
Functions
a) as a food reserve and stored in adipose
tissues (????)
b) subcutaneous fat (????) reduces heat loss
c) as a shock-absorber for protection
d) help transport fat-soluble vitamins
e) important in forming cell membranes
26
What are primary food substances?
Fats
Sources
  • Dietary fats can be divided into two main groups
  • Saturated fats and Unsaturated fats
  • Saturated fats found in
  • meats, cheese, butter, egg yolk, palm oil, etc.
  • Unsaturated fats found in
  • corn oil, olive oil, vegetable oil, fishes,
    margarine, etc.

27
What are primary food substances?
Proteins
  • made up of carbon, hydrogen, oxygen and nitrogen
    atoms

? some also contain sulphur (?)
28
What are primary food substances?
Proteins
  • basic units ? amino acids (???)

side chain (R group)
central carbon atom
amino group (??)
carboxyl group (??)
29
What are primary food substances?
Proteins
amino acid

amino acid
dipeptide
polypeptide

amino acid

amino acid
. . .
30
What are primary food substances?
Proteins
protein
31
What are primary food substances?
Proteins
There are 20 types of amino acids.
  • we can make 12 of them

? non-essential amino acids (??????)
  • the other 8 must be obtained from food

? essential amino acids (?????)
32
What are primary food substances?
Proteins
  • Many proteins are soluble in water.
  • denatured at

? high temperatures
? high/low pH values
33
What are primary food substances?
Proteins
Functions
  • for growth and repair
  • provide energy if carbohydrates and fats stored
    are used up
  • excess amino acids cannot be stored and will be
    broken down through deamination (????)

? the remaining parts will be converted into
carbohydrates or fats
34
Fate of Protein?
Proteins
Fate
  • broken down by the gut into amino acids before
    absorption
  • carried by blood to the cells to form different
    types of proteins

35
  • Excess amino acids in the body are broken down in
    the liver by a process called deamination
  • The carbon and hydrogen form carbohydrate (or
    sometimes fat), which may be stored up in the
    body or broken down to release energy
  • The nitrogen-containing part of the amino acid
    forms ammonia, and quickly converted to urea
    which leaves the body through the urine

36
What are primary food substances?
Protein
Sources
  • present in meat, fish, egg white, milk and beans

37
What are primary food substances?
Water
  • inorganic food substance
  • no energy value

Functions
a) acts as a solvent
b) acts as a medium for chemical reactions
c) helps transport substances in the body
38
What are primary food substances?
Water
  • inorganic food substance
  • no energy value

Functions
d) helps regulate the body temperature
e) acts as a reactant in hydrolysis
f) dilutes waste and toxins
39
How do we obtain and lose water?
Water
  • Obtain water through intake of foods and drinks.
    Water is also produced during respiration
  • Lose water through breathing, sweating, urination
    and egesting
  • 6-8 glasses of water are needed per day

40
Brief Revision
amino
1 The basic units of proteins are ______ _____ .
acids
2 Under Benedicts test, reducing sugars will
give a _________ precipitate.
brick-red
41
Brief Revision
non-reducing
3 Sucrose is an example of ____________ sugars.
4 Those amino acids that must be obtained from
food are called _________________ .
essential amino acids
5 Excess amino acids can / cannot be stored in
our body.
42
1
What are protective food substances?
Vitamins
  • organic food substances
  • needed in small amounts
  • no energy value
  • help control various metabolic reactions
  • vitamin deficiency diseases will be resulted if
    we do not take in enough

43
What are protective food substances?
Vitamins Vitamins Vitamins
A C D


fat-soluble
water-soluble
fat-soluble
solubility
  • the synthesis and repair of connective tissues
  • the uptake of calcium and phosphate ions from
    blood into the cells
  • forming a visual pigment for vision in dim light
    condition

essential for
  • healing wounds and keeping gums (??), teeth and
    skin healthy
  • the formation of bones and teeth
  • protecting the cornea (??)

44
What are protective food substances?
Vitamins Vitamins Vitamins
A C D


fat-soluble
water-soluble
fat-soluble
solubility
  • building up resistance to infection
  • keeping the linings of the alimentary canal, the
    breathing system and the skin healthy

essential for
  • preventing common cold
  • helping iron absorption by our body

45
What are protective food substances?
Vitamins Vitamins Vitamins
A C D
  • night blindness (??)
  • soft teeth and bones
  • scurvy (???) with the following symptoms
  • rickets (???)
  • drying up and thickening of the cornea

? the connective tissue breaks down slowly
deficiency diseases
  • bone fractures
  • easy infection of the lining of the lungs and
    trachea (??)

? teeth become loose and gums bleed easily
46
What are protective food substances?
Vitamins Vitamins Vitamins
A C D
  • fish-liver oil
  • fish-liver oil
  • green vegetables
  • butter
  • milk, cheese and egg yolk
  • citrus fruits like oranges, lemons and grapefruits
  • eggs yolk and green vegetables

sources
  • certain amount of vitamin D can be produced by
    the skin in sunlight
  • carrots (contain carotene ???? which can be
    converted into vitamin A in the liver)

Excess vitamins A will be stored in the liver
47
2
What are protective food substances?
Minerals
  • inorganic food substances
  • needed in small amounts
  • no energy value
  • important in regulating metabolism and building
    body tissues, e.g. bones

48
2
What are protective food substances?
Minerals
Calcium
  • essential for
  • formation of bones and teeth
  • blood clotting (??)
  • muscle contraction (????) and transmission
    of nerve signal
  • deficiency disease rickets and slow clotting

49
2
What are protective food substances?
Minerals
Calcium
  • Children and pregnant woman requires in large
    amount of it
  • Sources
  • Milk, cheese, yogurt and green leafy vegetable

50
2
What are protective food substances?
Minerals
Iron
  • essential to make haemoglobin (????)
  • deficiency disease anaemia (??)
  • women need more iron than men because of
    mensuration (??)

51
2
What are protective food substances?
Minerals
Iron
Sources
  • Liver, beef, eggs and some vegetables

52
3
What are protective food substances?
Dietary fibre
  • known as roughage (????)
  • an organic substance from the cell walls of
    vegetables and fruits
  • cannot be digested in humans since we have no
    such enzyme

53
3
What are protective food substances?
Dietary fibre
  • it can stimulate peristalsis (??)

? prevents constipation (??)
54
Brief Revision
1 Deficiency in vitamin A will result in
_____________ .
night blindness
2 Deficiency in vitamin C will result in ______ .
scurvy
3 Deficiency in vitamin D will result in ______ .
rickets
55
Brief Revision
4 Calcium is good for the growth of bone and
_____ .
teeth
5 Lack of dietary fibre in diets will result in
____________ .
constipation
56
How can we test for the presence of some food
substances?
57
Detection of food substances by food tests
A Test for glucose using Clinistix paper
Procedure
1 Transfer a drop of glucose solution to the
well of a spot plate.
Clinistix paper
glucose solution
58
Detection of food substances by food tests
A Test for glucose using Clinistix paper
Procedure
2 Dip the test end of a Clinistix paper into the
sample and observe any colour change. A purple
colour indicates the presence of glucose.
Clinistix paper
glucose solution
59
Detection of food substances by food tests
B Test for reducing sugars using Benedicts test
Procedure
1 Mix equal volumes (e.g. 1 cm3) of glucose
solution and Benedicts solution in a test tube.
Benedicts solution
glucose solution
60
Detection of food substances by food tests
B Test for reducing sugars using Benedicts test
Procedure
2 Boil the mixture in a water bath for 5 minutes.
water bath
glucose solution Benedicts
solution
boiling water
61
Detection of food substances by food tests
B Test for reducing sugars using Benedicts test
Procedure
3 Stand the test tube in a test tube rack for 15
minutes and observe any change in the mixture
again. A brick-red precipitate indicates the
presence of reducing sugars.
62
Detection of food substances by food tests
C Test for starch using iodine test
Procedure
1 Transfer a drop of starch solution to the well
of a spot plate.
iodine solution
starch solution
63
Detection of food substances by food tests
C Test for starch using iodine test
Procedure
2 Add a drop of iodine solution to the sample
and observe any colour change. A blue-black
colour indicates the presence of starch.
iodine solution
starch solution
64
Detection of food substances by food tests
D Test for fats using grease spot test
Procedure
1 Transfer a drop of cooking oil to a filter
paper and let it dry in the air for 5 minutes.
cooking oil
filter paper
65
Detection of food substances by food tests
D Test for fats using grease spot test
Procedure
2 Hold up the filter paper to the light and
observe any translucent (????) spot.
66
Detection of food substances by food tests
D Test for fats using grease spot test
Procedure
3 Immerse the filter paper into an organic
solvent. Take it out and let it dry.
4 Examine the filter paper against light again.
Note any change in the filter paper. The
disappearance of the spot indicates the presence
of fats.
67
Detection of food substances by food tests
E Test for proteins using Albustix paper
Procedure
1 Transfer a drop of egg white solution to the
well of a spot plate.
Albustix paper
egg white solution
68
Detection of food substances by food tests
E Test for proteins using Albustix paper
Procedure
2 Dip the test end of an Albustix paper into the
sample and observe any colour change. A
blue-green colour indicates the presence of
proteins.
Albustix paper
egg white solution
69
Detection of food substances by food tests
F Test for vitamin C using DCPIP solution
Procedure
1 Put 1 cm3 of DCPIP solution in a test tube.
DCPIP solution
70
Detection of food substances by food tests
F Test for vitamin C using DCPIP solution
Procedure
2 Add in vitamin C solution drop by drop. Stop
when there is any persistent colour change. A
colourless colour indicates the presence of
vitamin C.
vitamin C solution
DCPIP solution
71
Detection of food substances by food tests
F Test for vitamin C using DCPIP solution
Procedure
3 Boil a test tube of 5 cm3 of vitamin C
solution in a boiling water bath for 5 minutes.
Allow the test tube to cool in a beaker of cold
water. Heat destroys the reducing property of
vitamic C and so there is no colour change in the
solution.
72
Investigation of the food substances present in
common foods
A Test for food substances in liquid food sample
Procedure
1 Put about 1cm3 of the liquid food sample into
6 test tubes.
2 Perform the food tests as in previous
Practical. Use distilled water as a control.
73
Investigation of the food substances present in
common foods
B Test for glucose, reducing sugars, starch,
proteins and vitamin C in solid food sample
Procedure
small pieces of food cool distilled water
1 Grind the small pieces of food with a small
quantity of cool distilled water.
74
Investigation of the food substances present in
common foods
B Test for glucose, reducing sugars, starch,
proteins and vitamin C in solid food sample
Procedure
2 Squeeze the ground materials through several
layers of muslin or a filter paper. Put the
extract into 5 test tubes.
pre-moistened fine muslin
75
Investigation of the food substances present in
common foods
B Test for glucose, reducing sugars, starch,
proteins and vitamin C in solid food sample
Procedure
3 Perform the food tests as in previous
Practical. Use distilled water as a control.
76
Investigation of the food substances present in
common foods
C Test for fats in solid food sample
Procedure
1 Grind the small pieces of food with a small
quantity of distilled water.
2 Transfer the ground materials to a boiling tube
containing some distilled water.
3 Boil the suspension in a boiling water bath.
Any fats or oil in the food will escape as oil
droplets.
4 Test for fats as in previous Practical. Use
distilled water as a control.
77
Design an investigation to compare the vitamin C
content in different fruits and vegetables
In the past, scurvy was common among sailors
whose diets were limited to biscuits and salted
meat. It was not known until 1753 that lemons and
oranges, which were rich in vitamin C, could help
prevent the disease.
78
Design an investigation to compare the vitamin C
content in different fruits and vegetables
Are lemons and oranges the best sources of
vitamin C? Design and perform an experiment to
compare the vitamin C content in different fruits
and vegetables.
79
What is a balanced diet?
Diet (??) refers to all the food we eat.
A balanced diet
A balanced diet (????) consists of all of the
seven types of food substances in the right
amounts.
carbohydrates
fats
water
vitamins
proteins
minerals
dietary fibre
In addition, we should take in 6 to 8 glasses of
fluid every day.
80
Why is a balanced diet important to us?
Different people need different balances in their
diets. For example
  • a child needs more proteins than an older person

because 1) a child is growing actively
2) a child needs more energy per unit of weight
to maintain the body temperature
81
Why is a balanced diet important to us?
  • a person whose workload is heavy needs more
    energy than one whose workload is lighter

because the former needs more energy for
muscular activities
82
Why is a balanced diet important to us?
  • a male usually needs more energy than a female

because 1) he has more muscles to respire 2)
thinner subcutaneous fat
83
Why is a balanced diet important to us?
  • a pregnant woman needs more carbohydrates,
    proteins, minerals and vitamins

because her foetus (??) needs energy and raw
materials
84
Why is a balanced diet important to us?
  • a pregnant woman also needs more calcium, vitamin
    D and iron

because The formation of bones and blood in
the embryo need these food substances
85
Why is a balanced diet important to us?
  • a Breast-feeding woman also needs more
    carbohydrates (e.g. lactose), proteins, vitamins
    (e.g. vitamin A) and minerals (e.g. calcium)

because For the production of milk
86
10.9 Balanced Diet (p. 85)
Critical Thinking 10.1 Average daily energy
requirements of different groups of people
A (kg) B (kJ)
Newborn baby 3 1 800
Age 2 7 5 000
Age 5 20 7 500
Age 10 30 9 500
Age 15 45 12 000
Age 25 (F) - office worker 55 9 000
Age 25 (M) office worker road worker 65 65 12 000 15 000
Pregnant woman 55 10 000
Breast-feeding woman 55 11 500
This table shows the average body weights (A) and
average daily energy requirements (B) of
different groups of people.
Analysis 1. Referring to the data in the table,
construct a bar chart showing the average daily
energy requirements per unit body weight of
different groups of people.
87
10.9 Balanced Diet (p. 86)
88
10.9 Balanced Diet (p. 86)
  • Analysis
  • Make a comparison between different people, as
    listed below. Find out which one shows a higher
    energy requirement per unit body weight, and
    suggest reasons for the difference.
  • (a) a 5-year-old child and an adult

Ans The energy required by a child is higher
than that of an adult, because (1) he needs
energy for growth, (2) he tends to be more active
physically, (3) a relatively greater surface area
of the body means that more energy is required to
maintain body temperature
(b) an office worker and a road worker
Ans A road worker needs more energy for
maintaining greater muscular activity than an
office worker
89
10.9 Balanced Diet (p. 86)
  • Analysis
  • Make a comparison between different people, as
    listed below. Find out which one shows a higher
    energy requirement per unit body weight, and
    suggest reasons for the difference.

(c) A pregnant woman and a woman who is not
pregnant and not breast-feeding.
Ans A pregnant woman requires more energy
because extra energy is used in maintaining the
growth of the developing embryo
90
What happens to the body of a starving person?
  • When the daily energy requirement of a person is
    not being met,
  • glycogen stored in the liver and skeletal
    muscles,
  • fat stored under the skin or around internal
    organs,
  • will be used to release energy, leading to
    weight loss
  • If the fat stored in the body becomes depleted,
    some body proteins (e.g. skeletal muscles) will
    be used. This will adversely affect the persons
    health

91
Diets of people in different countries
? People in different countries have different
diets. Try to find out the differences in diets,
and how these are related to the peoples social,
cultural and economic backgrounds.
92
Health problems resulting from an improper diet
1) Obesity (??)
if we take in more energy than our body needs and
the body weight exceeds normal
? overweight
? in serious cases obesity
93
Health problems resulting from an improper diet
2) Anorexia nervosa (?????)
when the energy intake lt normal requirement
? the person may become thin and unhealthy
? serious cases anorexia nervosa
94
Health problems resulting from an improper diet
? Discuss with your classmates how eating
disorders such as anorexia nervosa can affect
health.
95
Summary concept diagram
Food
consists of
food substances
if not in the right types and amounts
when in the right types and amounts
balanced diet
improper diet
leads to
detected by
health problems
examples are
food tests
anorexia nervosa
obesity
96
Summary concept diagram
food substances
can be
primary food substances
protective food substances
include
vitamins
minerals
dietary fibre
Back to summary concept diagram
97
Summary concept diagram
primary food substances
include
fats
proteins
carbohydrates
water
made up of
made up of
polypeptides
made up of
amino acids
fatty acids
glycerol
Back to summary concept diagram
98
Summary concept diagram
carbohydrates
classified into
monosaccharides
disaccharides
polysaccharides
some are
reducing sugars
Back to summary concept diagram
99
Chapter 10 (p. 91)
Check Your Concepts
The following statements contain some wrong
concepts commonly held by students. Point them
out and give correct statements.
1. Animals cannot use cellulose for food.
Ans Other than human, cellulose contributes to
the diet of many animals, especially herbivores,
such as sheep, cattle and rabbit
2. Excess amino acids are useless and they are
removed from the body as urea.
Ans Excess amino acids are broken down by the
liver, the resulted carbon and hydrogen form
carbohydrates that may be stored up in the body
or broken down to release energy through
respiration. The remaining nitrogen-containing
part forms ammonia and quickly converted to urea
for excretion
100
Chapter 10 (p. 91)
Check Your Concepts
The following statements contain some wrong
concepts commonly held by students. Point them
out and give correct statements.
3. Essential amino acids are more important than
the non-essential amino acids.
Ans Both essential and non-essential amino acids
are important to the body. Where non-essential
amino acids are the ones the body is able to
synthesize, while essential amino acids are the
ones must be obtained from food
4. The human body cannot synthesize vitamins.
Ans Vitamins are mostly come from food, but
vitamin D can also be produced in human skin when
exposed to sunlight
101
Chapter 10 (p. 91)
5. A vegetarian diet would not make a person
become overweight.
Ans Although a vegetarian diet includes mainly
plant products, the consumption of large amount
of carbohydrates-rich plant products, such as
rice and potato, can still make a person become
overweight
6. To avoid being overweight, we can take in more
carbohydrates but less fats.
Ans Since carbohydrates are important food
substances to provide energy, the intake of large
amount of carbohydrates can make a person
overweight
102
Chapter 10 (p. 91)
103
10.9 Balanced Diet (p. 89)
Activity 10.1
A study of anorexia nervosa
  • Based on the information given, discuss the
    following with your classmates
  • your idea about body build
  • the proper ways to reduce body weight if
    necessary

End of Activity 10.1
Back to main text
104
10.9 Balanced Diet (p. 90)
Enrichment Reading 10.2
Vegetarian diet
  • Questions for Discussion
  • Why can a vegetarian diet reduce the risk of
    having heart diseases?

Ans Vegetarians are people who eat only plant
products. Their diets contain low levels of
saturated fats. Thus, the vegetarian diets tend
to reduce the risk of having heart diseases
2. Why is it possible to obtain maltose from
starch?
Ans Apart from low level of fat, the plant foods
in the vegetarian diet are rich in dietary fibre,
which tends to make a person feels full. This can
help to prevent a person from over-eating
Back to main text
105
10.9 Balanced Diet (p. 90)
3. How can a vegetarian ensure that the diet
provides sufficient proteins?
Ans Vegetarians should consume more beans and
nuts to obtain sufficient proteins
4. Why farmlands can support a larger human
population with a vegetarian diet?
Ans A piece of farmland can only support a small
amount of livestock and produce a limited amount
of animal products. Therefore, the same piece of
farmland can support a larger human population
with a vegetarian diet
5. What kinds of nutrients are usually deficient
in a vegetarian diet? How can this problem be
overcome?
Ans A vegetarian diet is usually deficient in
certain vitamins and minerals. These can be
overcome by taking yeast extract or other food
supplements with the diet
106
End of Chapter 10
107
While Stephanie is eating, she wonders what will
happen to the food in her body.
Dear food, can you tell me what happens to you
after I have eaten you?
What happens to the food in our body so that we
can obtain nutrients?
108
While Stephanie is eating, she wonders what will
happen to the food in her body.
Dear food, can you tell me what happens to you
after I have eaten you?
What are the structures inside our body for this
process?
109
While Stephanie is eating, she wonders what will
happen to the food in her body.
Food is processed by the digestive system (????)
in our body before the nutrients are ready for
use. This system consists of many structures
specially adapted for human nutrition.
Dear food, can you tell me what happens to you
after I have eaten you?
What are the structures inside our body for this
process?
110
How is food ingested?
solid food is broken down into small pieces in
the mouth cavity
? by the actions of the teeth and tongue
111
The structure of a tooth
crown (??)
neck (??)
root (??)
112
The structure of a tooth
1) Enamel (???)
  • the outermost, non-living, hard layer
  • mainly made of calcium phosphate and a small
    amount of organic matter
  • protects the tooth

113
The structure of a tooth
2) Dentine (???)
  • the middle layer
  • hard and bone-like, but softer than enamel
  • has strands (?) of living cytoplasm running
    through it

114
The structure of a tooth
3) Pulp cavity (??)
  • the innermost part
  • contains living cells, blood vessels and nerves

115
The structure of a tooth
4) Cement (???)
5) Periodontal membrane (???)
6) Jawbone
116
The structure of a tooth
1) Incisors (??)
  • chisel-shaped (???)
  • sharp
  • has 1 root
  • for biting and cutting off food

117
The structure of a tooth
2) Canine (??)
  • pointed and curved
  • well-developed in carnivores, e.g. lion
  • has 1 root
  • For piercing and tearing flesh

118
The structure of a tooth
3) Premolars (???)
  • broad top with cusps (??) in humans, or ridges in
    sheep, with sharp edges in dogs for cutting
  • has 2 roots
  • for chewing, crushing and grinding food

119
The structure of a tooth
4) Molars (??)
  • similar to premolars but larger
  • has 3 roots
  • for chewing, crushing and grinding food

120
Milk teeth and permanent teeth of humans
2 sets
permanent teeth (??)
milk teeth (??)
  • replace milk teeth
  • smaller and whiter than permanent teeth
  • will not be replaced by new teeth if lost
  • delicate (????) and will gradually fall out

121
Dentition (??)
? a term used to describe the types and
arrangement of teeth in a mammal
? represented by a dental formula (??)
122
Dentition (??)
Front
Rear

upper jaw
lower jaw
premolars
molars
incisors
canines
2
3
1
2
2
1
2
3
123
Dentition (??)
The dental formula is
Front
Rear
124
1
Dental diseases
Tooth decay (??)
  • known as dental caries
  • oral bacteria, food debris and saliva (??) form a
    plaque (???) on tooth surface
  • oral bacteria break down the sugar in food debris
    to form acid

125
1
Dental diseases
Tooth decay (??)
  • acid dissolve the enamel and makes small holes

126
1
Dental diseases
Tooth decay (??)
  • bacteria reach the holes and digest the dentine

127
1
Dental diseases
Tooth decay (??)
  • bacteria reach the holes and digest the dentine

and infect the tissue in pulp cavity
128
1
Dental diseases
Tooth decay (??)
  • the acid will irritate the nerves and cause
    toothache

129
1
Dental diseases
Tooth decay (??)
  • for serious cases, abscess (??) is formed and the
    tooth will lose

130
1
Dental diseases
Tooth decay (??)
  • if not too serious, the decayed area can be
    drilled out and replaced with a filling

131
1
Dental diseases
  • sugary food

? enhance acid production
? pH of plaque
132
1
Dental diseases
  • if pH of plaque lt critical pH (??pH?)

? decay can occur
critical pH
133
1
Dental diseases
  • pH will return to normal after about 30 minutes

critical pH
134
11.2 Teeth (p. 107)
Critical Thinking 11.1 The changes in pH in the
mouth of a person before and after eating candy
This graph shows the changes in pH in the mouth
of a person before and after eating a candy.
135
11.2 Teeth (p. 107)
  • Questions
  • Describe the changes in pH inside the mouth after
    eating a candy.

Ans The pH is maintained at about 6.6 before
eating the candy, and continues to drop below 5.2
after eating it. The level gradually returns to
normal after about 10 minutes
136
11.2 Teeth (p. 107)
Questions
2. From the results, what can you tell about the
relation between eating candies and tooth decay?
Ans The pH is dropped below the level that is
reported to cause tooth decay after eating the
candy. In other words, eating candies is more
likely to cause tooth decay
137
2
Dental diseases
Periodontal disease (gum disease)
  • bacteria trap plaque under the gum and release
    toxins (??)

? destroy the periodontal membrane
? periodontal pockets (???) formed around the
tooth
138
2
Dental diseases
Periodontal disease
  • calculus (??) formed from

calcium secretions in the saliva
plaque
  • difficult to remove
  • its rough surface lets plaque accumulate further

The processes of tooth decay and the formation of
periodontal disease
139
Dental diseases
140
Dental diseases
  • The symptoms of periodontal disease are
  • bleeding gum after brushing the teeth
  • red or swollen gums
  • the teeth looking longer than before
  • bad breath
  • aching or itching gums
  • loosening teeth

141
Dental diseases
Prevention of dental diseases
1
Brush your teeth regularly.
2
Brush your teeth properly.
3
Use toothpaste that contains fluoride (???).
142
Dental diseases
Prevention of dental diseases
4
Use dental floss (??) to remove plaque.
Improve your brushing style with the help of
dental disclosing agents (??????).
5
6
Do not eat too much sugary food.
143
Dental diseases
Prevention of dental diseases
7
Have a balanced diet with adequate nutrients.
8
Do not bite very hard materials.
9
Have a dental check-up at least twice a year.
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