2. By the end of this chapter, you should be able
to….
• Explain the concept of nutrition and food nutrients.
• Outline the importance of nutrition in living things.
• Identify different types of food substances and their
functions in human body.
• Explain the concept of balanced diet in terms of food
quantity and quality.
• Explain nutritional requirements for different groups of
people
• Outline different types of nutritional deficiencies and
disorders in human beings.
3. What is nutrition?
• Nutrition is the process by which living things feed on
materials from their environment. The process by which
an organism takes in and uses nutrients.
• It also includes the study of relationship between diet
(nutrients taken), health and diseases.
• Organisms eat food which is then broken down into
smaller molecules that later serves as sources of energy,
building blocks for growth, maintenance and repair.
4. Cont..
• These building blocks are called nutrients.
• Nutrients are substances needed by the body for
growth, repair and maintenance and as sources of
energy.
• Professionals who study nutrition are nutritionists and
dieticians.
5. How much nutrients do we need???
• Some nutrients are needed in a large amount, these
nutrients are called macronutrients.
• Such nutrients include, protein, carbohydrates and
lipids.
• Other nutrients are needed in a small amount, these
nutrients are called micronutrients.
• Such nutrients include, vitamin and mineral salts.
6. There are two main types of nutrition..
i. Autotrophic nutrition.
Type of nutrition whereby organisms manufacture their
own food from simple inorganic substances like carbon
and hydrogen using either light energy (photosynthesis)
or chemical energy (chemosynthesis).
ii. Heterotrophic nutrition.
Type of nutrition whereby organisms get nutrients by
eating other organisms. (organisms that feed on already
made food).
They take in complex food substances and break them
down to provide energy and simple substances that can be
absorbed into the body.
7. There are various types of heterotrophism…
1. Holozoic nutrition:
Involves taking in of complex food substances,
digestion, absorption and assimilation.
The undigested and indigestible food is finally
egested (removed from the body) as faces.
This mode of nutrition is divided into three modes
Carnivorous mode
Herbivorous mode
Omnivorous mode
8. Cont..
2. Saprophytic nutrition
• Organism absorb nutrients from dead organic matter.
• Example, mushroom that grows on logs of trees.
9. Cont.
3. Symbiosis.
• This is a close relationship between two species.
• This can takes several forms:
i. Commensalism
ii. Mutualism
iii. Parasitism
10. Commensalism
• Commensalism is a type of relationship between two living
organisms in which one organism benefits from the other
without harming it.
• Examples, Golden jackals, once they have been expelled
from a pack, will trail a tiger to feed on the remains of its
kills.
• Tree frogs use plants as protection.
• Remora fish have a disk on their heads that makes them
able to attach to larger animals, such as sharks, mantas, and
whales. When the larger animal feeds, the remora detaches
itself to eat the extra food.
11. Mutualism
• Occurs where both species benefits from the
relationship.
• Organisms live in mutualistic relationships for a
number of important reasons, including a need for
shelter, protection, and nutrition, as well as for
reproductive purposes.
• Mutualistic relationships can be categorized as either
obligate or facultative.
12. Cont..
• In obligate mutualism, the survival of one or both
organisms involved is dependent upon the relationship.
• In facultative mutualism, both organisms benefit from
but are not dependent upon their relationship for
survival.
13. Cont..
• Examples, Insects and animals play a vital role in the
pollination of flowering plants. While the plant-
pollinator receives nectar or fruit from the plant, it also
collects and transfers pollen in the process.
• Some ant species herd aphids in order to have a
constant supply of honeydew that the aphids produce.
In exchange, the aphids are protected by the ants from
other insect predators.
14. Cont..
• Oxpeckers are birds that eat ticks, flies, and other
insects from cattle and other grazing mammals. The
oxpecker receives nourishment, and the animal that it
grooms receives pest control.
• Nitrogen-fixing bacteria live in the root hairs of legume
plants where they convert nitrogen to ammonia. The
plant uses the ammonia for growth and development,
while the bacteria receive nutrients and a suitable place
to grow.
15. Parasitism
• Is a type of symbiotic relation where one species (the
parasite)benefits while the other specie (the host) is
harmed.
• Parasitism is also defined as a relationship between two
species in which one organism (parasite) lives on or
within the other organism (host), causing the host some
degree of harm.
16. Grouping of parasites
• There are multiple ways to classify types of parasitism.
• Parasites may be grouped according to where they live.
• Ectoparasites, such as fleas and ticks, live on the
surface of a host.
• Endoparasites, such as intestinal worms and protozoa
in blood, live inside a host's body.
17. Cont..
• The life cycle can be a basis for classifying parasites.
• An obligate parasite requires a host in order to
complete its life cycle.
• A facultative parasite can complete its life cycle
without a host.
18. Examples of parasitism..
• Over 100 different types of organisms can parasitize
humans including fungi, leeches, lice, ticks, mites,
tapeworms, protozoa, viruses, and helminths.
• Aphids are small green insects that parasitize plants by
eating their sap. Many types of fungi can also attack
plants and can spoil wheat, fruit, and vegetables.
21. Types of food substances..
• Human being needs several types of food substances in their bodies .
• The basic ones are
i. Protein
ii. Carbohydrates
iii. Lipids
iv. Vitamins
v. Minerals
vi. Roughages
vii. Water.
• Every Individual needs to take in a certain amount of each nutrient daily,
depending on their age, size, sex and activity.
22. • Carbohydrates, proteins, fats and vitamins are all organic substances.
• This means that they are made by living organisms (plants) and contain carbon
atoms in their structures.
• Plants make organic substances from inorganic materials like carbon dioxide,
water and inorganic minerals. Animals are unable to do this.
24. Proteins:
• These are also organic compounds, they contain the elements Carbon, Hydrogen,
Oxygen, Nitrogen and sometimes Phosphorus or Sulfur.
• A molecule of protein is a long chain of simpler units called amino acids.
• These amino acids are linked together by what’s called “peptide bond” by a
reaction called condensation reaction..
25. • There are about 20 amino acid that are known to have significance in
human nutrition.
• Some of these can be made by the animal’s body themselves while
others have to be ingested by the organism from outside sources.
• This gives the basis of classification of the amino acids into two:
a. ESSENTIAL AMINO ACIDS
b. NON ESSENTIAL AMINO ACIDS
26. ESSENTIAL AMINO ACID.
• These are the amino acids that cannot be synthesised by the
organism fast enough to supply its demand, and must therefore come
from the diet.
• Of the 20 known amino acids only nine are essential.
• These are: Phenylalanine, valine, threonine, tryptophan, methionine,
leucine, isoleucine, lysine, and histidine.
27. NON ESSENTIAL AMINO ACIDS
• These are the amino acids that can be synthesised by the cells of an
organism itself.
• Being called non essential doesn’t mean they are not important, it
only means that we do not need it in our diets at high amounts
because our bodies can manufacture it.
28. Types of protein in human body
• Protein can be found in both animal sources such as beef, chicken,
fish and also in their products such as milk, cheese, eggs etc and in
plant sources such as beans, peas, cereals etc.
• The protein from animals and animal products offers us with the
essential amino acids and therefore they are known as proteins of
high biological value.
• The proteins from plants on the other hand, offers us with most of
the non essential amino acids and they are therefore referred as
proteins of low biological value.
29. Why do we need protein in our body?
• Making new body cells.
• Growth and repair.
• Making enzymes (they are proteins in nature).
• Build up hormones.
• Making antibodies.
30. Digestion of protein in human.
• The digestion of protein begins in the stomach.
• The stomach releases gastric juice which contains two enzymes;
a. Pepsin and
b. Renin
31. Renin.
• Renin is produced in the stomach in an inactive form called prorenin.
• The prorenin is activated by hydrochloric acid and converted to renin.
• Renin has a function of catalysing the conversion of soluble milk
protein into insoluble milk protein.
• In other words, renin performs coagulation or curdling of milk in the
stomach.
• The coagulated milk is semi solid and can be retained in the stomach
for relatively long time for proper digestion.
• This is very important for lactating young mammals.
32. Pepsin
• Pepsin is produced in the stomach in an inactive form called
pepsinogen.
• The pepsinogen is converted into pepsin by the hydrochloric acid
present in the stomach.
• This enzyme converts protein into peptides.
33. • The remaining protein that might not have been digested in the
stomach will be digested in the first part of the small intestine called
duodenum.
• In there duodenum, there is an accessory organ called pancreas
which releases its secretions (pancreatic juices).
• Among the contents for the pancreatic juices is an enzyme called
trypsin.
• This converts the remaining protein to peptides.
34. • The completion of digestion of protein takes place in the second part
of the small intestine called ileum.
• The walls of the ileum produces an enzyme called erepsin which
converts the peptides to amino acid.
• Amino acid is the end product of digestion of protein.
• The amino acid will be absorbed into the blood and taken to the cells
for assimilation process.
35. Fate of excess proteins in our body.
• Although proteins are needed in high amounts, the body will only
absorb as much as needed.
• The remaining amino acids will not be allowed to stay in the body
because of presence of amino group which is toxic.
• So excess protein (amino acids) is removed from our bodies in form of
urea after it undergoes a process called deamination in the liver.
36. Deamination process.
• The blood containing excess amino acid is taken to the liver where the
deamination process takes place.
• There the amino acid will be broken down into two components:
a. Keto acid
b. Ammonia
• The keto acid will be converted into glucose and used by the body to
get energy.
37. Cont..
• Since ammonia is extremely toxic it will not be allowed into our blood
since its accumulation may lead to death.
• There for the ammonia formed will immediately combine with carbon
dioxide from the deoxygenated blood to form UREA.
• Urea is a metabolic waste product that is less toxic than ammonia so
it will be allowed to travel in the blood streams to the kidney where it
will be excreted out of our bodies.
38. Food test for protein (Biuret test)
Procedure
Add 2 cm3 of protein solution to a test
tube.
Add an equal volume of sodium
hydroxide solution and mix.
Add 2 drops of 1% copper sulphate
solution and mix.
39. Observation
Violet/purple colouration is develop
slowly in the presence of protein.
Biuret reagent can be used directly
for detecting the presence of protein
without heating.
40.
41. The basis for the positive results
When mixed with dilute alkaline
copper sulphate solutions, nitrogen
atoms in the peptide bonds form a
purple complex with copper (II) ions.
42. LIPIDS
• These are composed of carbon, hydrogen and oxygen. But their ratios
are different than that of carbohydrates.
• Then contents of oxygen is usually smaller than that of hydrogen and
carbon in lipids.
• One fat molecule is made of a glycerol unit and three molecules of
fatty acids.
43. TYPES OF LIPIDS
• There are two types of lipids:
a. Saturated Lipids (fats)
b. Unsaturated Lipids (oil)
44. Saturated Lipids
• They are lipids that are found as solid at room temperature
• They are known as FATS
• Usually found in animals
• Example; butter
45. Unsaturated Lipids
• These are lipids that are liquid at room temperature.
• They are called OIL.
• Usually found in plants
46. DIGESTION OF LIPIDS
• Digestion of lipids begins in the duodenum
• Lipids are usually insoluble in water, so for it to digested it has to be
broken down into small droplets.
• This processes is known as emulsification
• It is done in the duodenum by the help pf bile juice, which contains
bile salts that performs the emulsification.
• After the lipids are emulsified, their surface area is increased in order
to be well digested.
47. • The enzyme that digests the lipids is produced by the pancreas and it
is called lipase.
• it converts lipids into fatty acid and glycerol.
• This enzyme is also found in the ileum to complete the digestion of
lipids that was not done in the duodenum
48. Sudan III test for lipids
Lipids include oils, fats, and waxes.
Procedure
Add 2 cm3 of solution to a test tube.
Add a few drops of Sudan III and
shake.
Observation
A red stained oil layer of droplets
separate out on the water surface
49.
50. The basis for a positive
results of Sudan III test
Sudan III is a red fat-soluble and it
therefore react with the lipids to
stain red in colour
The lipids are less denser than water
51. However, since the oil is less dense
than water and insoluble in water, the
oil will form a layer or globules above
the water and appear as a red layer
above the water in the test tube.
53. Importance of lipids in our bodies
• Release high amounts of energy
• Make cell membranes
• Store them under the skin to insulate heat
• Forming a layer of fats around organs to protect them from damage
• Storing energy (better than glycogen)
54. Carbohydrates:
• Carbohydrates are among the fundamental classes of
macromolecules found in living organisms.
• They are primary products of photosynthesis and energy providing
substrates for various organisms including mammals.
• carbohydrates comprises of starches and sugars.
55. Structure and composition.
• Carbohydrates contains three elements, namely:
a. Carbon
b. Hydrogen
c. Oxygen
• In this composition, hydrogen and oxygen are in the ratio of 2:1 (two
hydrogen atoms and one oxygen atom)
• This proportion of hydrogen to oxygen is the same as that of water
hence the name hydrates of carbon (carbohydrates).
56. Properties of carbohydrates.
• They are either simple sugars or compound sugars. The compound
sugars are made by combination of simple sugars via a reaction called
condensation reaction (reaction in which combination of one
substance to the other results to a release of water molecule).
Example, starch is formed by condensation of several glucose units.
• They have one hydrated carbon (CH2O) hence the name
carbohydrates.
• The ratio of hydrogen to oxygen in carbohydrates is always 2:1.
• Carbohydrates can be oxidized (burnt in presence of oxygen) to yieled
energy. Example is burning of glucose during respiration.
𝐶6𝐻12𝑂6 + 6𝑂2 → 6𝐶𝑂2 + 6𝐻2𝑂 + 𝐸𝑁𝐸𝑅𝐺𝑌
57. • Carbohydrates can be classified based on the number of sugar
(saccharide) units present in a molecule.
• These classes include the following:
a) Monosaccharides
b) Disaccharides
c) Polysaccharides
Classes of carbohydrates.
58. Monosaccharide.
• These are simplest carbohydrates, having only one sugar or
saccharide, which cannot be hydrolyzed (broken down) smaller
molecules.
• The monosaccharides are also classified further according to the
number of carbon present. Example:
a. Triose (3 carbon)
b. Tetrose (4 carbon)
c. Pentose (5 carbon)
d. Hexose (6 carbon)
e. Heptose (7 carbon)
59. Examples of monosaccharides.
• Good examples of monosaccharides are:
a. Glucose (coming from digestion of starch).
b. Fructose (sugars found in fruits).
c. Galactose (sugars found in milk).
All these are reducing sugars.
60. Properties of monosaccharides.
• Most of them have a sweet taste.
• They exist in crystallin solid form at room temperature.
• The are very soluble in water.
• They are reducing sugars, in that they have the ability to reduce mild
oxidizing agents such as Benedict’s reagents.
61. Disaccharides
• The word disaccharide literally means double sugars or two sugars.
• This is a type of carbohydrates that is formed from combination of two
monosaccharides by a reaction called condensation reaction (dehydration
reaction).
• In this reaction one hydrogen from one monosaccharide and one hydroxyl
group from the other monosaccharide are released during the combining
of the two monosaccharide.
• But we know that one hydrogen and one hydroxide when combined form
water. So during this reaction water is released hence the name
condensation or dehydration.
• The bond formed between the two monosaccharides is called glycosidic
bond.
62. Examples of disaccharides.
• Good examples of disaccharides are such as:
a. Maltose (malt sugar)
Maltose is a double sugar which occurs naturally in roots & radicles of
germinating cereals such as, maize, sorghum and finger millet. This is a source
of reducing sugar.
b. Sucrose (cane sugar)
This is a double sugar that naturally occurs in stems of sugar cane plant. This is a
source of non-reducing sugar.
c. Lactose (milk sugar)
This is found exclusively in the milk of mammals and milk products. This is a
reducing sugar.
63. Properties of disaccharides.
• They are composed of two monosaccharides bonded by a glycosidic
bond.
• Like monosaccharides, disaccharides are sweet in taste and are
crystallin water soluble compounds.
• Among the disaccharides, maltose and lactose are reducing sugars
while sucrose is a non-reducing sugar.
64. Polysaccharides
• These are multi-sugars.
• They are polymer (large molecule) carbohydrates composed of long
chain of monosaccharide units bonded together by glycosidic bonds.
• On their hydrolysis (digestion), they give their constituent
monosaccharide.
• They rage in structure, from linear to highly branched.
65. Examples of polysaccharides.
• Good examples of polysaccharides include:
a. Starch
A polymer of hexose sugar (glucose) that can be extracted as a white powder. It is the
storage form of carbohydrates in plants.
b. Glycogen
Is the form in which carbohydrates are stored in animals and fungi. It is often called
animal starch and is mainly stored in the liver and skeletal muscles. Like starch, it is also
made of glucose.
c. Cellulose.
Is an important structural polysaccharide of plants, which largely constitutes the
chemistry of the cell wall of a plant cell.
d. Chitin.
Is an extracellular structural polysaccharide found in large quantity in the body
covering cuticles of insects and exoskeletons of crustaceans. It is also found in the cell
wall of fungi cells.
66. Digestion of carbohydrates.
• The chemical digestion of carbohydrates begins at the mouth where
starch is broken down into maltose by the help of an enzyme called
salivary amylase present in the saliva.
• Remember, starch is a polysaccharide, it is broken down into maltose
which is a disaccharide.
• Some of the starch might have not been digested at the mouth, these
will be digested at the duodenum, where pancreas releases an
enzyme called pancreatic amylase which will convert starch into
maltose.
67. • You can notice that maltose is not the end product of digestion of
carbohydrates.
• The rest of the digestion of carbohydrates is done at the ileum where
the intestinal juice is released and mixed with the food.
• The intestinal juice contains several enzymes which act on
carbohydrates. These enzymes are:
70. Iodine test for starch
Starch is only slightly soluble in water
and it forms a colloidal solution in
water.
Starch is a mixture of two
polysaccharides, amylose, and
amylopectin.
The relative amounts of the two
polysaccharides vary widely in
different types of starch. Amylose
molecules consist of long straight
chain of glucose units.
71. Amylopectin has a complicated
branched structure.
The two polysaccharides combine
with iodine to give the characteristic
blue-black colour of the standard
iodine test.
72. Procedure
Add 2 cm3 of starch solution to a test
tube.
Add a few drops of iodine solution
while shaking after each addition.
75. The basis for a positive
results of iodine test
When starch is treated with iodine
solution, a plyiodide complex is
formed with starch
76. Benedict’s test for reducing sugars
Reducing sugars include all
monosaccharides (e.g. glucose and
fructose) and some disaccharides
(e.g. maltose).
Composition Benedict’s solution
Benedict's reagent (or Benedict's
solution) is a
chemical reagent named after
American chemist Stanley Rossiter
77. It is a complex mixture of sodium
carbonate, sodium citrate, and copper
(II) sulphate pentahydrate.
A positive test with Benedict's
reagent is shown by a colour change
from blue to a brick-red precipitate.
78. Procedure
Add 2 cm3 of a solution of the
reducing sugar to a test tube.
Add an equal volume of Benedict’s
solution.
Shake and boil the mixture.
79. Observation
The blue colouration of the mixture
changes to green, then yellow,
orange and may finally form a brick-
red precipitate.
The amount of precipitate gives a
rough indication of the amount of
reducing sugars present.
80.
81. Benedict’s test for non-
reducing sugars
• Procedure
Add 2 cm3 of a solution of the non- reducing
sugar to a test tube.
Add 1 cm3 of hydrochloric acid and boil for one
minute and allow it to cool
Then add 1 cm3 of sodium hydroxide
Add an equal volume of Benedict’s solution.
Shake and boil the mixture.
82. Observation
The blue colouration of the mixture
changes to green, then yellow,
orange and may finally form a brick-
red precipitate.
The amount of precipitate gives a
rough indication of the amount of
non-reducing sugars present.
83. The basis/principle for the
positive of Benedict's test
Benedict's solution contains copper
sulphate
When reducing sugars are boiled with
Benedict's solution they reduce the
copper (II) ions (Cu2+) present in
Benedict's reagent to copper (I) ions
(Cu+) which are precipitated as
insoluble red copper(I) oxide (Cu2O).
84. Sudan III test for lipids
Lipids include oils, fats, and waxes.
Procedure
Add 2 cm3 of solution to a test tube.
Add a few drops of Sudan III and
shake.
Observation
A red stained oil layer of droplets
separate out on the water surface
