Topic
X
3
Nutrition
and Classes
of Food
LEARNING OUTCOMES
By the end of this topic, you should be able to:
1.
Describe the different types of nutrition;
2.
List the characteristics of the different classes of food;
3.
Explain the concept of a balanced diet;
4.
Define food chains, food webs and energy pyramids;
5.
List the various nutrients needed by plants;
6.
Explain the process of photosynthesis;
7.
Describe food technology, including genetically modified food; and
8.
Explain how to practise a healthy lifestyle.
X INTRODUCTION
All living things need food to survive. Food provides us with energy for all living
processes such as growth and development and also to maintain optimal health.
In this topic, you will learn about the different types of nutrition, the classes of
food, the concept of a balanced diet, food technology and how to practise a
healthy life style. You will also explore nutrition in plants, the process of
photosynthesis and the concepts of food chains, food webs and energy pyramids.
TOPIC 3
3.1
NUTRITION AND CLASSES OF FOOD
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TYPES OF NUTRITION
What exactly is nutrition? Nutrition is the process by which organisms obtain
energy from food for growth, maintenance and repair of damaged tissues.
Nutrients are the useful substances that are present in food.
We shall first look at the different types of nutrition. There are two main types of
nutrition as can be seen in Table 3.1.
Table 3.1: Types of Nutrition
Autotrophic Nutrition
x
x
Heterotrophic Nutrition
It is a process in which organisms make x
their own food from simple inorganic
raw materials such as carbon dioxide,
and water by using light or chemical
x
energy.
In photosynthesis, organisms make
complex organic compounds from
carbon dioxide and water using light
x
energy in the presence of chlorophyll.
Example: all green plants.
x In chemosynthesis, organisms make
It is a process in which organisms feed
on complex, ready-made organic foods
to obtain the nutrients they require.
The three main types of heterotrophic
nutrition
are
holozoic
nutrition,
saprophytic nutrition and parasitic
nutrition.
In holozoic nutrition, organisms feed on
solid organic material derived from the
bodies of other organisms. Examples:
humans and cows.
complex organic materials from carbon x
dioxide and water using chemical
certain types of
energy. Example:
bacteria.
In saprophytic nutrition, organisms
feed on the dead and decaying matter
on which they live and grow. Examples:
fungi and certain bacteria.
x
In parasitic nutrition, organisms feed on
other living organisms known as hosts.
Examples: tapeworms and ticks.
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NUTRITION AND CLASSES OF FOOD
Now, let us take a look at Figure 3.1 which summarises the various types of
nutrition.
Figure 3.1: Types of nutrition
3.1.1
Holozoic Nutrition
Let us take a closer look at holozoic nutrition. Can you recall what holozoic
nutrition is? Yes. Holozoic organisms feed on solid organic matter which can be
either plants or animals. Holozoic organisms may be classified according to their
diet; whether their diet is made up of plants, animals or both. Study Figure 3.2
which shows how holozoic animals are classified according to what they eat.
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NUTRITION AND CLASSES OF FOOD
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Figure 3.2: Classification of animals according to what they eat
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NUTRITION AND CLASSES OF FOOD
SELF-CHECK 3.1
1.
In your own words, explain the term „nutrition‰ and „nutrients‰.
2.
Explain each of the following types of nutrition. Give one example
for each type:
(a)
Autotrophic nutrition;
(b)
Heterotropic nutrition; and
(c)
Holozoic nutrition.
3.
Classify the following animals into herbivores, carnivores or
omnivores: eagles, lions, goats, bears, elephants and chickens.
4.
Discuss how the animals named in Question 3 have adaptations to
suit their diet.
3.2
CLASSES OF FOOD
The nutrients in food can be divided into seven classes based on their functions
as shown in Figure 3.3.
Figure 3.3: Classes of food
Let us look at each of them in detail.
TOPIC 3
3.2.1
NUTRITION AND CLASSES OF FOOD
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Carbohydrates
Carbohydrates are the main source of energy and should be the major part of our
daily intake. Carbohydrates consist of three elements:
(a)
Carbon;
(b)
Hydrogen; and
(c)
Oxygen.
There are three main types of carbohydrates based on the number of simple
sugars in the molecules. This is shown in Table 3.2.
Table 3.2: Types of Carbohydrates
Type
Number of Simple Sugar
Example
Monosaccharide
(simple sugars)
One unit
Glucose, fructose, galactose.
Disaccharide
(complex sugars)
Two units
Lactose, maltose, sucrose.
Polysaccharide
Many units
Starch, glycogen, cellulose.
Now, let us learn the terms used in Table 3.1. Sugars are sweet crystalline
compounds, which can dissolve in water and are found in syrup, honey, sugar
cane and fruits. Starch is found in rice, bread and potatoes and is the main energy
storage compound in plants. Glycogen is the main storage compound in animals
and is stored in the liver and muscle cells. Cellulose is the substance that plant
cell walls are made up of. Vegetables and fruits are two examples of food
containing cellulose. All carbohydrates are broken down into simple sugars
(monosaccharide) by enzymes in the digestive tract. However humans cannot
digest cellulose like herbivores because humans do not have the enzyme
cellulose. This means that we cannot get energy from cellulose but it still
performs a useful function: it forms dietary fibre (roughage). We will learn about
the importance of fibre later in this topic.
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NUTRITION AND CLASSES OF FOOD
Before we end the discussion about carbohydrates, let us look at Figure 3.4 which
summarises the main characteristics of carbohydrates.
Figure 3.4: Characteristics of carbohydrates
3.2.2
Proteins
Proteins are complex organic substances which are made up of carbon,
hydrogen, oxygen and nitrogen. Most proteins also contain sulphur and
phosphorus. Foods that are rich in protein include fish, meat, milk, nuts, cheese,
and eggs as shown in Figure 3.5.
Figure 3.5: Sources of protein
Source: http://www.buzzle.com
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The basic unit of protein is amino acid. There are 20 naturally occurring amino
acids. These can be divided into two groups:
(a)
Essential Amino Acids
Essential amino acids are amino acids that cannot be made by the body. We
must get them from our diet. There are altogether nine essential amino
acids. They are vital for good health and the absence of just one can have
severe consequences.
(b)
Non-essential Amino Acids
Non-essential amino acids are amino acids that can be made by the body.
These amino acids are formed from other amino acids. There are eleven
non-essential amino acids.
Animal proteins such as meat contain all the essential amino acids and are
considered as a „complete protein‰. Animal proteins are known as first class
proteins. Plant proteins such as beans are „incomplete proteins‰ in that they do
not contain every essential amino acid. Plant proteins are known as second class
proteins. The common sources of all essential amino acids are food from animal
sources such as eggs and milk while a variety of plant products must be taken
together to provide all the other necessary proteins.
Proteins form the main structure of our body. Therefore, we need protein for
growth of new cells and repairing worn out or damaged body tissues. We also
need proteins to produce enzymes, hormones and some components of
antibodies. In addition, proteins can provide energy when needed. Figure 3.6
summarises the characteristics of proteins.
Figure 3.6: Characteristics of proteins
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3.2.3
TOPIC 3
NUTRITION AND CLASSES OF FOOD
Fats
Fats are a subgroup of the compound known as lipids. Fats are organic
compounds that contain carbon, hydrogen and oxygen, but unlike
carbohydrates, they contain much less oxygen. Fats are insoluble in water.
Fats are also known as triglycerides. A triglyceride is formed from a molecule of
glycerol and three molecules of fatty acids. Figure 3.7 shows the structure of fat.
Figure 3.7: Structure of fat
Fatty acids are either saturated or unsaturated. Fats containing saturated fatty
acids are called saturated fats while those containing unsaturated fatty acids are
called unsaturated fats. Saturated fats are solids at room temperature. Examples
of saturated fats are animal fats such as butter. An unsaturated fat is usually
liquid at room temperature and is called oil. Examples of unsaturated fats are
vegetable oils such as corn oil. Cholesterol which is the major component of the
plasma membrane is mostly found in saturated fats.
Fats serve as an efficient source of energy. They also act as a solvent for fatsoluble vitamins and other vital substances such as hormones. Fats keep our
body warm by building a heat insulator under the skin. This may reduce the rate
of heat loss from the skin during the cold season. The oily secretion from certain
glands in the skin can reduce the rate of evaporation of water. Fats are also
important in forming the cell membrane. Figure 3.8 summarises the
characteristics of fats.
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NUTRITION AND CLASSES OF FOOD
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Figure 3.8: Characteristics of fats
3.2.4
Vitamins
Vitamins are organic compounds needed by the body in small quantities to
maintain good health. There are two groups of vitamins:
(a)
Fat Soluble Vitamins
Fat soluble vitamins such as vitamins A, D, E and K can be stored in body
fat.
(b)
Water Soluble Vitamins
Water soluble vitamins cannot be stored in the body and have to be
continuously supplied in the daily diet. Vitamins B and C are water soluble
vitamins.
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NUTRITION AND CLASSES OF FOOD
Figure 3.9 shows the various sources of vitamins.
Figure 3.9: Various sources of vitamins
Source: http://thebest-healthy-foods.com
A varied diet of fresh fruits and vegetables is important to obtain most of
the vitamins that we need. The characteristics of vitamins are summarised in
Figure 3.10.
Figure3.10:Characteristicsofvitamins
3.2.5
Minerals
Minerals are inorganic chemical elements that are usually found in the body.
They are present in the form of ions and are needed in small quantities. They are
required to regulate body processes, build bones, form blood cells, maintain
health and avoid diseases.
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Minerals are divided into two groups:
(a) Major Elements
Some major elements needed in large quantities are potassium, sodium,
calcium, magnesium, iron, iodine and phosphorus.
(b) Trace Elements
Some trace elements needed in small quantities are fluorine and chlorine.
Figure 3.11 summarises the characteristics of minerals.
Figure 3.11: Characteristics of minerals
3.2.6
Fibre
Dietary fibre (roughage) is made up of the indigestible cellulose walls of plant
material. Fibre provides bulk to the contents of the large intestine and stimulates
peristalsis. This leads to defecation and prevents constipation. The presence of
adequate dietary fibre in the diet helps to prevent heart and intestinal disorders.
Fibre also absorbs toxic substances in the large intestine and reduces blood
cholesterol level. Figure 3.12 summarises the characteristics of fibre.
Figure 3.12: Characteristics of fibre
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3.2.7
NUTRITION AND CLASSES OF FOOD
Water
Water makes up 70% of our body weight. The main sources of water are fruits,
vegetables and drinking water. It is a very important compound in our body and
mainly acts as a solvent in the transport of wastes and food substances; a
medium for enzymatic reactions; to regulate body temperature; and to maintain
blood concentration. It is also needed in all metabolic processes. Figure 3.13
summarises the characteristics of water.
Figure 3.13: Characteristics of water
SELF-CHECK 3.2
1.
Name the different classes of food.
2.
Discuss the functions of each of the different classes of foods.
ACTIVITY 3.1
The diseases shown below are due to the lack of a certain vitamin or
mineral. Research these diseases and suggest the vitamin or mineral that
is lacking:
Rickets
Night-blindness
Anaemia
Pellagra
Goitre
Scurvy
Beri beri
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3.3
NUTRITION AND CLASSES OF FOOD
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BALANCED DIET
The food we consume every day makes up our diet. This includes what we drink
as well as what we eat. Our diet must include all the seven classes of food
described in the previous subtopic. A diet which contains all of these substances
in the right quantities is called a balanced diet. The composition of a balanced
diet varies from one individual to another according to age, sex, job, size, age,
climate and state of health. A balanced diet is important mainly to maintain our
body health and growth, to repair or replace old and damaged cells and provide
enough energy.
A balanced diet will be able to meet the daily energy requirements of the body.
Energy in food is measured in joules (J) or calories (Cal). One calorie equals to 4.2
joules. The amount of heat energy released when one gram of food is completely
burnt in the air is known as its calorific value. Each type of food has a different
calorific value. Therefore, we should choose the correct types of food to ensure
our bodies get sufficient energy. We can use the food pyramid as a guide for a
balanced diet as shown in Figure 3.14.
Let us take a look at the food pyramid based on the Malaysian Dietary
Guidelines (MDG) 2010 as shown in Figure 3.14.
Figure 3.14: The food pyramid
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NUTRITION AND CLASSES OF FOOD
The food pyramid is one way for people to understand how to eat healthily.
When choosing a healthy diet, simply follow the food pyramid guidelines. Select
the suggested number of servings from the five basic food groups as shown in
the previous Figure 3.14. The food pyramid shows you what and how much food
you should eat to remain healthy. These are the recommendations according to
the food pyramid:
(a)
Eat adequately: Rice, noodles, breads, cereals, cereal products and tubers
(48 servings/day);
(b)
Eat plenty: Vegetables (3 servings/day);
(c)
Eat plenty: Fruits (2 servings/day);
(d)
Eat in moderation: Milk and milk products (13 servings/day); and
(e)
Eat in moderation: Fish, poultry, meat and legumes (2 servings of
poultry/meat/day, 1 serving of fish/day, 1 serving of legumes/day).
The sixth group (fats, oil, sugar and salt) consists mostly of items that are
pleasing to the palate, but high in fat and calories. These should be eaten in
moderation or the intake should be limited.
ACTIVITY 3.2
Your friend is a champion in bodybuilding sports. Explain to him the
reasons bodybuilders need more proteins such as eggs and meat in
their diet.
3.4
FOOD CHAINS, FOOD WEBS AND ENERGY
PYRAMIDS
The main energy source on earth is the Sun. Solar energy is used by plants to
make food. Green plants which are autotrophs store solar energy in
carbohydrates during photosynthesis. Green plants are also known as producers
as they are capable of producing their own food. Heterotrophs are known as
consumers as they feed on producers. Herbivores are known as primary
consumers as they feed on the producer organisms. Carnivores are secondary
consumers as they eat the primary consumers. What do you think tertiary
consumers are?
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3.4.1
NUTRITION AND CLASSES OF FOOD
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Food Chain
Producers and consumers play different roles in a community. The linear feeding
relationship which indicates the transfer of energy from producers to consumers
is known as a food chain. Study Figure 3.15 which shows a food chain.
Figure 3.15: A food chain
Source: http://www.kidsgeo.com
As can be seen in Figure 3.15, notice how all organisms are linked in the food
chain. Each stage of a food chain is called a trophic level. The arrows in the food
chain represent the flow of energy through the ecosystem. Can you identify the
herbivore and carnivores in this food chain? Additionally, try to determine the
primary, secondary and tertiary consumers as well.
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3.4.2
TOPIC 3
NUTRITION AND CLASSES OF FOOD
Food Web
In reality, an organism usually feeds on several different types of food. Instead of
one simple food chain, there are many food chains which share the same
organism. Many food chains interconnect to form a food web. A food web helps
to maintain a balanced environment by controlling the number of organisms at
each level of the food chain. Study Figure 3.16. How many food chains can you
detect from this food web?
Figure 3.16: A food web
Source: http://ed101.bu.edu
3.4.3
Energy Pyramids
Do you know why there are more herbivores than carnivores in any ecosystem?
Energy flows in one direction along a food chain. Energy is transferred along the
food chain from the photosynthetic producers through several levels of
consumers. The more levels in the food chain, the lesser the energy at the end of
the chain. For example, when a herbivore eats, only a fraction of the energy (that
it gets from the plant food) becomes new body mass; the rest of the energy is lost
as waste or used up by the herbivore to carry out its life processes (e.g.,
movement, digestion, reproduction). Therefore, when the herbivore is eaten by a
carnivore, it passes only a small amount of total energy (that it has received) to
the carnivore. Of the energy transferred from the herbivore to the carnivore,
some energy will be „wasted‰ or „used up‰ by the carnivore.
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An energy pyramid is a graphical representation of the energy at each level in a
food chain. They are called pyramids because of the shape of these graphs. An
energy pyramid shows maximum energy at the base and steadily diminishing
amounts at higher levels. This is shown in Figure 3.17.
Figure 3.17: An energy pyramid
Source: http://www.vtaide.com
The energy pyramid shown in Figure 3.17 shows many trees and shrubs
providing food and energy to giraffes. Note that as we go up, there are fewer
giraffes than trees and shrubs and even fewer lions than giraffes. In other words,
a large mass of living things at the base is required to support a few at the top.
Many herbivores are needed to support a few carnivores. This is why there are
more herbivores than carnivores.
SELF-CHECK 3.3
Define food chains, food webs and energy pyramids. Give examples for
each.
ACTIVITY 3.3
Using producers and consumers from a community near where you
live, draw several interconnecting food chains that form a simple food
web.
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3.5
TOPIC 3
NUTRITION AND CLASSES OF FOOD
NUTRIENTS IN PLANTS
Plants also need nutrients for healthy growth and development. Plants need
carbon, hydrogen, oxygen, phosphorus, sulphur, magnesium, potassium and
iron elements in large quantities. For this reason these elements are called major
elements or macronutrients. In addition to the major elements, certain other
elements are required as well. These are required in small amounts and known as
trace elements or micronutrients. Examples of micronutrients are iron, copper,
manganese, molybdenum and boron. Carbon, hydrogen and oxygen are
macronutrients that can be easily absorbed from carbon dioxide in the
atmosphere and water from the soil. Therefore, deficiency in these nutrients
rarely occurs. The remaining mineral elements are obtained in the form of
inorganic ions from the soil. Table 3.3 shows some essential nutrients in plants.
Table 3.3: Essential Nutrients in Plants
Nutrients Needed by Plants
Major nutrients from water and CO2
Primary Macronutrients
Secondary Macronutrients
Micronutrients
C
Carbon
H
Hydrogen
O
Oxygen
N
Nitrogen
P
Phosphorus
K
Potassium
Ca
Calcium
Mg
Magnesium
S
Sulphur
Fe
Iron
Cu
Copper
Mn
Manganese
Mo
Molybdenum
B
Boron
Macronutrients and micronutrients are involved in the synthesis of chemical
substances essential for the healthy growth of plants. They are also required for
the various metabolic processes which take place in plants. The absence of one or
more of these nutrients can lead to mineral deficiencies in plants. Table 3.4 shows
the effects of nutrient deficiencies in plants.
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Table 3.4: Effects of Nutrient Deficiencies in Plants
Type of
Nutrients
Macronutrients
Micronutrients
Elements
Symptoms
Oxygen
Growth retardation
Nitrogen
Chlorosis; leaves turn yellow
Potassium
Occur in mature tissues, growth retardation,
leaves turn to yellowish brown
Calcium
Occur in young tissues, drying of the tips of root
and leaf, twisted leaf morphology, retardation of
root growth and decrease in plant growth rate
Magnesium
Chlorosis in veins mainly in young leaves,
necrotic at the tip of the leaves, severe deficiency,
necrosis occurs in the entire leaves
Phosphorus
Old leaves turn to dark green, appearance of dark
purple pigment (anthocyanin), delayed maturity
Iron
Occur in young tissues
Manganese
Appear in young leaves in the form of white spots
and interveinal chlorosis
Zinc
Spots of necrosis
Copper
Necrosis of the leaf margin and reduction in the
concentration of plastocynin pigment
Molybdenum
Chlorosis and retardation of plant growth
Figure 3.18 shows phosphorus and calcium deficiency in bean plants.
Figure 3.18: Phosphorus and calcium deficiency in bean plants
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SELF-CHECK 3.4
1.
List all the elements that are needed in large amounts by
plants.
2.
Name three elements that will result in the yellowing of leaves
(chlorosis) in plants if a deficiency of these elements occurs.
3.6
PHOTOSYNTHESIS
Photosynthesis is derived from two words: ÂphotoÊ which means light, and
ÂsynthesisÊ which means making. Therefore, photosynthesis means the making of
food with the help of light. Photosynthesis can be defined as a process carried out
by green plants to make glucose from carbon dioxide and water in the presence
of sunlight and chlorophyll. Oxygen is a by-product of photosynthesis. Here is
the equation for photosynthesis.
Sunlight
Carbon dioxide + Water
Glucose + Oxygen
Chlorophyll
3.6.1
Requirements of Photosynthesis
Photosynthesis requires carbon dioxide, chlorophyll, sunlight and water. Carbon
dioxide is absorbed from the air through stomata into the chloroplast.
Chlorophyll is the pigment in chloroplasts which captures sunlight. Sunlight
provides the energy needed for photosynthesis. Water is absorbed through the
roots.
3.6.2
Importance of Photosynthesis
Photosynthesis is important because it:
(a) Provides the Basic Food Source
Plants use light energy to make their own food. Most organisms depend
directly or indirectly on plants for food. Plants are producers and are very
important in providing the basic food source for other life forms on earth.
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(b)
NUTRITION AND CLASSES OF FOOD
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Maintains the Oxygen Balance
Animals and plants continuously use up oxygen. Combustion (burning of
fuels) and daily human activities (e.g. cooking) also uses up oxygen
through respiration. Through photosynthesis, plants release oxygen into
the environment and replace the oxygen that has been consumed. 3.6.3 Experiment to Show that Photosynthesis has
Taken Place
How can you determine if photosynthesis has taken place in plants? When the
process of photosynthesis takes place, glucose is formed as a product. The
glucose produced during photosynthesis is stored in the plant in the form of
starch. Iodine reacts with starch to produce a deep dark blue (almost black)
colour. The presence of starch in leaves shows that photosynthesis has taken
place.
Carry out the following experiment to determine whether photosynthesis has
taken place in a plant.
Title:
Experiment to determine if photosynthesis has taken place.
Procedure:
1.
Pluck a leaf from a plant, which has been exposed to sunlight for a few
hours.
2.
Immerse the leaf in a beaker of boiling water to kill it.
3.
Place the softened leaf inside a boiling tube containing ethanol.
4.
Place the boiling tube inside a beaker of hot water to remove
chlorophyll.
5.
Return the leaf to a beaker of hot water to soften leaf and allow
penetration of iodine.
6.
Place the leaf on a white tile.
7.
Drop iodine solution onto the leaf surface.
8.
Record your observation.
Observation:
1.
The leaf turns the iodine to dark blue.
2.
This shows the presence of starch in the green leaf.
3.
This proves that photosynthesis has taken place in the green leaf.
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SELF-CHECK 3.5
1.
Define photosynthesis.
2.
Explain the significance of photosynthesis.
ACTIVITY 3.4
Draw a flow chart to show the relationship between the following:
water
carbohydrates
oxygen
chlorophyll
carbon
dioxide
chloroplast
light
3.7
FOOD TECHNOLOGY
The increase of the world population means there is a need for greater food
supply. The quality and quantity of food production should also be improved to
meet the demands of this increasing population. Food technology is a branch
of food science that deals with the production processes to make foods.
Development of food technology occurs in two ways:
(a)
Technological Development to Improve Quality and Quantity of Food
Production
Various methods are employed to improve the quality and quantity of food
production such as direct seeding for rice, hydroponics and aeroponics,
breeding of plants and animals, tissue culture, genetic engineering, soil
management, and biological control.
(b)
Technological Development in Food Processing
Technology development in food processing includes the activities
involved in the preparation and preservation of food. This is to ensure that
the food remains safe for consumption whether eaten immediately or later.
The main purpose of food processing is to preserve food by overcoming the
factors that can cause food spoilage. Examples of food processing and
preservation methods are freezing, pickling, fermentation, dehydration,
canning, pasteurisation, radiation and sterilisation.
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What is genetic engineering? Genetic engineering is a technique that can increase
the quality and quantity of food production. It is a technique that enables the
characteristics of an organism to be altered by changing the genetic composition
of the organism. For example, genes from plants can be inserted into the DNA of
animal cells and vice versa. The genetically modified organism (GMO) is called a
transgenic organism. Developments in genetic engineering have enabled
transgenic crop plants such as wheat, paddy, tomatoes, legumes, soya beans and
potatoes to be cultivated commercially. These crop plants contain genes from
other organisms to enhance their growth or nutritional properties. Figure 3.19
shows an example of how genetically modified plants are created.
Figure 3.19: Creation of a genetically modified pest resistant plant
Source: http://www.gmac.gov.sg
ACTIVITY 3.5
Currently there is a controversy over the use of genetically modified
(GM) foods. Research this issue and discuss the pros and cons of GM
foods.
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3.8
NUTRITION AND CLASSES OF FOOD
DEVELOPING GOOD EATING HABITS
It is important to practise good eating habits. Figure 3.20 shows some guidelines
on how to develop good eating habits.
Figure 3.20: Guidelines on how to develop good eating habits
Do you realise that there are many types of diseases related to imbalanced diets?
Table 3.5 shows the different types of nutrient deficiency diseases in humans.
Table 3.5: Nutrient Deficiency Diseases in Humans
Name of
Diseases
Nutrient
Deficiency
Symptoms
Kwashiorkor
Protein
x
x
x
x
x
x
Dry and scaly skin.
Hair loss.
Wasting muscles.
Loss of appetite and diarrhoea.
Easily tired
Distended abdomen.
Oedema
Protein
x
x
Loose muscles and skin.
Some parts of body become swollen.
Marasmus
Energyproducing food
x
x
x
Very thin.
Very weak.
Starvation.
Anaemia
Iron
x
x
x
x
Shortness of breath and headache.
Some parts of body lack oxygen.
Chest pain.
Lips are pale and cracked.
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Goitre
Iodine
x
x
NUTRITION AND CLASSES OF FOOD
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x
Thyroid gland becomes swollen.
Swelling will press the surface of trachea and
oesophagus.
Breathing difficulties.
Cretinism
Iodine
x
x
x
Mental retardation and stunted growth.
Rough skin.
Tongue becomes swollen.
Scurvy
Vitamin C
x
x
x
x
Walls of blood vessels break easily.
Bruises appear under skin surface.
Bleeding and swollen gums.
Joints become swollen and painful.
Beri beri
Vitamin B
x
x
x
x
x
x
Diarrhoea.
Swelling at ankles and legs.
Numbness of legs and hands.
Stiffness of muscle.
Mental deterioration.
Heartbeats become faster.
Pellagra
Vitamin B
x
x
x
x
Pain in the mouth and tongue.
Dry and reddish skin.
Diarrhoea.
Slow thinking and memory loss.
Rickets
Vitamin D
x
x
x
Incomplete development of teeth and bones.
Soft and pliable bones.
Head becomes big.
Figure 3.21 shows a photo of a child suffering from kwashiorkor.
Figure 3.21: A child suffering from Kwashiorkor
Source: http://www.asnom.org
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SELF-CHECK 3.6
1.
Define the term balanced diet.
2.
Explain the special food requirements of:
3.
(a)
A child;
(b)
A pregnant woman; and
(c)
A man who does hard physical work.
Give examples of nutrient deficiency diseases in plants and
humans.
x
Nutrition is the process by which organisms obtain energy from food for growth,
maintenance and repair of damaged tissues.
x
There are two main types of nutrition: autotrophic nutrition and heterotrophic
nutrition.
x
Autotrophic nutrition is the process by which organisms make their own
food from simple inorganic raw materials such as carbon dioxide and water
by using light or chemical energy.
x
Heterotrophic nutrition is the process by which organisms feed on complex,
ready-made organic foods to obtain the nutrients they require.
x
Heterotrophic nutrition consists of holozoic nutrition, saprophytic nutrition
and parasitic nutrition.
x
Holozoic organisms may be classified according to their diets. Herbivores eat
only plants, carnivores eat only animals and omnivores eat both animals and
plants.
x
Food can be divided into seven classes carbohydrates, proteins, fats,
vitamins, minerals, fibre and water.
TOPIC 3
NUTRITION AND CLASSES OF FOOD
W
81
x
Carbohydrates provide energy; proteins provide materials for growth and
repair and fats are a source and storage of energy.
x
Vitamins and minerals are needed in small quantities for optimal health.
x
Fibre is required for the proper functioning of the digestive system.
x
A balanced diet contains all the classes of food in the right quantity and ratio
according to our bodily needs.
x
A food chain shows the feeding relationships among organisms.
x
The interconnections of many food chains form a food web.
x
An energy pyramid is a graphical representation of the energy at each level in
a food chain.
x
Plants need both macronutrients and micronutrients for healthy growth and
development.
x
Photosynthesis is a process carried out by green plants to make glucose from
carbon dioxide and water in the presence of sunlight and chlorophyll.
x
Photosynthesis requires carbon dioxide, chlorophyll, sunlight and water.
x
Photosynthesis provides the basic source of food and also maintains the
oxygen balance in the atmosphere.
x
Food technology is a branch of food science that deals with the production
processes to make foods.
x
Development of food technology occurs in two ways: development in food
production and development in food processing.
x
Genetically modified foods are foods that are derived from genetically
modified organisms. Genetically modified organisms have had specific
changes introduced into their DNA by genetic engineering techniques.
x
An imbalanced diet can lead to health problems, mainly deficiency diseases.
82 X
TOPIC 3
NUTRITION AND CLASSES OF FOOD
Autotrophic nutrition
Macronutrients
Carbohydrates
Micronutrients
Carnivore
Minerals
Chemosynthesis
Nutrition
Deficiency diseases
Omnivore
Energy pyramid
Parasitic nutrition
Fats
Photosynthesis
Fibre
Primary consumer
Food chain
Producer
Food technology
Proteins
Food web
Saprophytic nutrition
Genetically modified foods
Secondary consumer
Herbivore
Trophic level
Heterotrophic nutrition
Vitamins
Holozoic nutrition
Water
MDG. (2010). Executive summary. Retrieved March 20, 2012 from
http://www.nutriweb.org.my/downloads/Executive%20summary.pdf
nutriWEB. (2011). Latest news.
http://www.nutriweb.org.my/
Retrieved
March
20,
2012
from
Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., &
Jackson, R. B. (2010).Campbell biology (9th ed.). San Francisco: Pearson Benjamin Cummings Pub.
Slim With Yoga. (2011). Nutritious food. Retrieved March 20, 2012 from
http://slimwithyoga.com/nutritious/index.html
Taylor, D. J., Green, N. P. O., & Stout, G. W. (2004). Biological science 1:
Organisms, energy and environment (3rd ed.). R. Soper Editor, New York:
Cambridge University Press.