NUTRITION -1
Is the process by which an organism
provides itself or is provides itself or is provided with materials
necessary for energy release, growth and repair of body tissues and keeping the
body in a good condition.
FOOD
Is any liquid or solid which
provides the body with materials for growth and repair, energy release or
keeping the body in a good (healthy) condition.
KINDS OR MODES OF NUTRITION
Basically there are two kinds of
nutrition
1. AUTOTROPHIC NUTRITION
2. HETEROTROPHIC NUTRITION
AUTOTROPHIC NUTRITION
This is mode of nutrition where by
organisms can make their own food from simple inorganic substance, such as
carbon dioxide and water using either light energy (photosynthesis) or chemical
energy (chemosynthesis). Organisms which feed by this way are known as AUTOTROPHS
Example
1. Green plants
2. Iron bacteria and sulphur bacteria
HETEROTROPHIC NUTRITION
This is the mode of nutrition where
by organisms use organic materials as the only source of food. Organisms which
feed by this way are known as HETEROTROPHS. They feed on already made
food.
There are three types of
heterotrophic nutrition
- Saprophytic nutrition
- Symbiotic nutrition
- Holozoic nutrition
- Saprophytic nutrition
This is the mode of nutrition where
by organisms feed on dead decaying bodies parts of animals or their excrete;
Organisms feeding by this way are known as SAPROPHYTES
2. Holozoic nutrition
This is mode of nutrition where by
organism take food by mouth. It passes through a digestive system and broken
down, finally absorbed into body tissue.
FORMS OF HOLOZOIC NUTRITION
1. Herbivores – Are animals
which feed on plants only Example cow, goat and
zebra
2. Carnivores – Are
animals which feed on flesh only e.g. lion, tiger.
3. Omnivores – Are animals
which feed on varieties o food (flesh, plants, insect etc) example. Man,
monkey, pig.
4. Insectivores – Are animals
that feed on insects e.g. shrews, ant
3. Symbiotic
nutrition
This mode of nutrition in which an
organism of different species exist in a nutrition relationship with other
organism;
There are three kinds of symbiotic
associations
- Mutualism
- Commensalism
- Parasitism.
- Mutualism
This is a nutritional relationship
in which the two partners benefit each other by living together Example
Nitrogen Fixing Bacteria in the roots of legumes.
2. Commensalism
This is an association of two group
where by the host does not get any partnership. Example Epiphytes (are plants
that grow on other plants) e.g. Moses and algae which grow on upper parts of
big trees to get sunlight easily
3. Parasitism
This is a nutritional relationship
between two organisms in which one organism live inside/on other living
organism and depends on food. The parasite causes harm to the host. The host
provides food and shelter for the parasite.
Endoparasites are living inside the body of the host e.g. tapeworm,
roundworm and plasmodia.
Ectoparasites;Parasite that lives on
host’s surface [outside the body] examples includes some mites, flea and body
lice.
The importance of nutrition
- Nutrition enables an organism to get nutrients and
energy required for various life processes. These processes include growth
and development of cells.
- To protect body against diseases.
- Enable in replacement of worn out tissue and dead cell.
NUTRITION IN MAMMALS
HUMAN NUTRITION
FOOD SUBSTANCES
There are several types of
substances that are needed by the human body for its proper functioning. The
basic food substances include proteins, carbohydrates, lipids, vitamins,
minerals, roughage and water.
- CARBOHYDRATES.
These are compounds which contain
the following elements
- Carbon (C)
- Hydrogen (H)
- Oxygen (O)
Carbohydrates are also known as SACCHARIDES
There are three groups of
saccharides
- Monosaccharides
- Disaccharides
- Polysaccharides
- MONOSACCHARIDES
These are
simplest form (basic unit of carbohydrates) which are absorbed directly
in the blood. These are also known as REDUCING SUGARS
Their general formula is C6 H12 O6
Exampleof Monosaccharide
- Glucose
Occurs
freely in grapes, honey, tomato and germinating maize
- Fructose
Occurs
freely in all ripe sweet fruits E.g. banana, pineapple
3.
Lactose
It is found in mammalian milk
(B) DISACCHARIDES
These are also known as NON – REDUCING SUGARS. They are found when two
molecules of monosaccharides condense and release molecules of water. Their
general formula is C11 H22 O11.Example of
disaccharides.
(1) Maltose is formed when two molecules of glucose condense.
Glucose + glucose = maltose + water
(2) Sucrose is formed by condensation of glucose and that of fructose.
Glucose + fructose = sucrose + water
(3) Lactose is found by condensation of galactose molecule and glucose molecule
glucose
+ galactose = lactose + water
(C)
POLYSACCHARDES
These are formed when several units
of monosaccharides linked together.
Example of polysaccharides
1) Starch
Starch is stored in plant cell, in
the muscles and liver of vertebrates as (glycogen) in exoskeleton of arthropods
and fungal cell as chitin
2) Cellulose
It forms the building material of
the plant cell walls.
Source of Carbohydrates
Cereals - e.g. maize, rice, wheat
Sugar – e.g. honey, sugar cane,
glucose, sweet fruits.
Function of Carbohydrates in the
body
1) To provide the body with energy.
2) Carbohydrates combine with
proteins, glucose and lipids which are important components of cell membrane.
Carbohydrate food
2. PROTEINS
Proteins are compounds of carbon,
Hydrogen, Oxygen and Nitrogen. Some protein also contains sulphur and
phosphorus. Proteins are long chains of Amino acid formed through condensation.
Approximately there are twenty Amino
acids that occur naturally. The human body makes ten of this amino acids. These
are called NON – ESSENTIAL AMINO ACIDS. The other ten amino acids must be
obtained from the diet they are called ESSENTIAL AMINO ACIDS. We get essential
amino acids by eating food rich in protein. Food that contains all the
essential amino acid is called first class proteins, animal protein most
fall in these group. Second class protein lack one or one more essential
amino acids, most plant proteins fall in this group.
Functions of protein
- The body use proteins for tissue growth and repair such
as healing of wounds and replacement of skin and mucus membranes.
- Antibodies are made of proteins, Antibodies are
important in offering immunity to the body
- Enzymes which help us to digest food are protein in
nature. In addition hormones, the chemical messengers in our bodies are
also protein.
- They are alternative source of energy in the body
Protein food
3. LIPIDS
Lipids are compounds of carbon,
hydrogen and oxygen. They are insoluble in water the mean form of dietary
lipids is fats and oil. Fats are solid at room temperature while oil is liquid
at room temperature. Lipids are made up fatty acid and glycerol. Fatty acid can
be essential or non – essential. The body can make non essential fatty acids,
it is not able to produce essential fatty acids. We therefore need to eat food
that contain essential fatty acid, Example of such food are oil fish, nuts oil
seed (such as sunflower seeds, maize, avocados and olives.
Functions of lipids
1) Lipids are source of energy; they
produce energy more than all foods substances.
2) They are important component of
cell membrane.
3) Fat deposits protect delicate
organs such as heart and kidney.
4) Stores of fat under the skin help
to insulate the body against loss of heat.
5) Essential fatty acids are
important for the formation of substances that help to control blood pressure.
4. ROUGHAGE
This dietary fiber that is obtained
from indigestive part of plants; Roughage does not have any nutrition at value
as it is not digested and absorbed in the body. However it helps in the passage
of food and faeces through the gut by avoiding contraction of the gut muscle.
Source of roughage : Whole grown cereals, fruits, beans, cabbage, spinach,
cassava and whole baked potatoes.
5. WATER
Water does not provide energy to
body the but there are several ways through which it is important
(i)It used in the digestion and
absorption of food.
(ii) It is a medium of transport for
food and hormonies.
(iii) It acts as lubricants e.g.
eyeball eyelids.
(iv)It helps in excretion of harmful
by product of metabolic process e.g. urine, sweat.
(v)It helps in regulation of heat
loss (evaporation of sweat on body surface causes the body to cool)
(vi)It is used in the manufacture of
different secretions e.g. tears, saliva.
Water can be replaced in the body
through
a) Direct drinking
b) Eating foods and fruits.
6. VITAMINS
Vitamins are complex organic micro
nutrient that is essential for growth and survival. Lack of vitamins in the
body leads to deficiency disease. Vitamins can be grouped into two categories water-
soluble and fat soluble vitamins.
- Fat soluble vitamin can be stored in the body and need
not be consumed daily. Vitamin A, D, E and K are example of fat soluble
vitamins.
- Water – soluble vitamins are not stored in the body.
Therefore they should be consumed. Vitamins B and C are water – soluble.
Vitamins B is named of various forms, namely vitamin B1 B2
B6 and B12
Source,
functions and deficiency of vitamins
|
vitamins |
source |
Function |
Sign of deficiency |
|
Vitamin A (retinol) |
Liver, milk, carrots, orange, and
yellow vegetable |
Essential for the formation of
membrane of the eyes and the respiratory tract |
Night blindness, increased risk of
infection. |
|
Vitamin B1 (thiamine) |
Lean meat, liver, eggs, yeast
extract and brown rice |
Carbohydrate metabolism,
Coordinate of muscle |
Beriberi, a diseases characterized
by loss of appetite, muscle cramps disorder and heart failure. |
|
Vitamin B2 (riboflavin) |
Liver, meat, whole, grain cereals,
yeast extract. |
Needed for metabolism of all food
and release of energy to cell |
Severe and cracking lips corner of
the mouth. |
|
Vitamin B3 (niacin) |
Nuts, fish, meat, yeast, extract
unpolished rice. |
Needed by enzyme to convert food
into energy |
Pellagra a disease characterized
by skin lesions, loss of appetite and muscle weakness |
|
Vitamin B6 (doxine) |
meat, vegetables, yeast, extracts,
whole grown cereals |
Essential in protein metabolism |
Nerve irritability sores in the
mouth, eyes and anemia. |
|
Vitamin B12 (yanocobalamin) |
Fish, meat, eggs, milk, and lever. |
Builds genetic material, helps to
form bloods cells. |
Anemia nerve damage weights loss. |
|
Vitamin C (ascorbic acid) |
Citrus fruits, fresh green
vegetables and tomatoes. |
Antioxidant improves absorption of
iron used in synthesis of collagen in the bones and gums. |
Muscle weakness, easy bruising,
joint pains, scurvy (bleeding gums), poor healing of wounds and
frequent infection. |
|
Vitamin D |
Egg yolk, milk oily, fish and
liver |
Helps to build and maintain teeth
and bones. |
Rickets in children, osteoporosis
(soft bones) in adult |
|
Vitamin E |
Corn of sunflower oil, butter,
brown, rice and peanuts |
Antioxidant prevents damage of all
membranes |
Nerve abnormalities infertility in
rats. |
|
Vitamin K |
Green vegetables and liver |
Needed for normal clothing |
Detective blood coagulation
resulting in excessive bleeding. |
7.Minerals
Certain mineral elements are vital
for the proper functioning of the body. Some are required in relatively large
quantities and are therefore called macro minerals. Others are required
in very small quantity are referred to as micro minerals or trace
element.
The following are example of
minerals, their sources and their functions in the body.
a) Macro minerals
|
Minerals |
Source |
Function |
Deficiency symptoms |
|
Calcium |
Milk, yoghurt, cheese, sardines,
egg, green vegetable |
Helps build strong bones and
teeth, promote muscle and nerve functions, and important in clotting of
blood. |
Weak bones, bleeding easily |
|
phosphorus |
Meat, milk, fish, eggs and nuts |
Builds bones and teeth, help
muscle and nerve activity, aids formation of genetic materials |
Impaired nerve activity bone and
teeth formation |
|
potassium |
Peanut, bananas, orange juice,
green beans and meat. |
Help maintaining regular fluid
balance needed for nerve and muscle |
Poor muscle contraction |
|
Iron |
Liver, meat, beans and green
vegetables |
Essential formulating hemoglobin
[the red pigment in blood) |
anemia |
|
Zinc |
Oysters, shrimp, crab, meat, yeast
extracts |
Activates enzymes, helps to heal
wounds necessary for a healthy immune system |
Impaired teeth, poor immune
response, skin problems |
|
Sodium |
Table salt |
Necessary for nerve and muscle
activity |
Muscle cramps |
|
Chlorine |
Table salt |
Maintenance of water and ionic
balance, formation of hydrochloric acid in the stomach |
Poor digestion of proteins |
|
magnesium |
Spinach, pumpkin seeds, sesame
seeds and black beans |
Relaxation of nerves and muscle
strengthening of bones. |
Muscle weakness, irregular
heartbeat and weaker bones |
b) Micro minerals
|
Iodine |
Iodinated table salt and sea food |
Production of thyroid hormone
which regulate growth, development of bones and teeth, helps prevent tooth
decay |
Goiter (enlarged thyroid gland) |
|
Fluoride |
Fluorinated water and fluoride
tables |
Development of bones and teeth,
helps prevent tooth decay |
Poor development of bones and
teeth , tooth decay |
|
manganese |
Kidneys, liver, tea, coffee nuts
and fruit |
Formation of bones and activation
of enzymes |
Nausea, dizziness, loss of heating
loss of bone mass |
|
Copper |
Meat, fish, and liver |
Synthesis of bones and
haemoglobin, activation of enzymes |
Bleeding under skin, easy
rupturing of blood vessel, bones and joint problems, anemia |
A BALANCE DIET
A balanced diet refers to food
containing all types of food nutrients in the correct proportion. We should eat
a diet low in fats, sugar and salt but high in proteins, carbohydrates,
vitamins, minerals, and roughage, more importantly we should take in large
amounts of water.
However, it is recommended that we
eat more fish, poultry products and legumes (such as pea, beans and peanuts)
Instead of taking red meat as
protein sources. The following should be done in order to maintain a healthy
body.
1. Physical activity can preserve
and improve your health. Therefore, it is important to balance your food intake
and exercise.
2. Minimize your intake of fats and
oils by eating foods low in fats, sugars and salts. This will reduce your risk
of heart attacks, tooth decay and high blood pressure respectively.
3. Include plenty of grains, fruits,
and vegetables in your diet.
4. Eating a variety of food will
provide the body with energy and nutrients that is required in maintaining
proper health.
Nutritional requirements for
different groups of people
Nutritional requirement differ for
different groups of people. The ratio of nutrients varies depending state of
the body. The following are some groups of people and the special nutritional
needs.
1. Expectant and lactating mothers.
Expectant and lactating (breast
feeding) mother need to get enough nutrients.
They should thus eat a
balanced diet because they require nutrients for themselves and the growing
foetus or babies.
Protein is needed for the build – up
of the mother muscles, breast, uterus, blood supply and the baby or foetus
tissue and organs.
Folic acid and vitamin B help to
lower the risk of birth defects such as spina bifida. Spina bifida is a
spinal disorder characterized by a hole in the spine.
It results from incomplete formation
of the spinal cord and the bones of spine. Often the spine protrudes through
the hole and sometimes a fluid filled sac may surround the protruding spinal
cord.
Calcium helps in the development of
the foetus or baby’s bones, if the mothers’ diet does not contain adequate
calcium; it is derived from her bones for the foetus or baby. This weakens the
mother bones.
Zinc is important for the proper
progression of labour and proper growth and development of the baby.
The mother to be requires iron for
her blood supply need, the foetus also needs to store iron for use during the
first few months after birth.
Expectant mother requires adequate amounts of dietary fiber to reduce the
likelihood constipation, which is a common complaints during pregnancy.
2. Children
Children require enough proteins for
the growth and development of body tissues. Inadequate of proteins can lead to
stunted growth.
Minerals like calcium are necessary
for the formation of strong bones and teeth. Zinc is important for body growth.
The zinc resources in the body can be depleted by vigorous physical exercise.
Vitamin B12 is required
for the formation of red blood cells. Because a growing baby needs more oxygen
and more blood) for growth while vitamin C helps children to build their
immunity.
Children also require more energy –
giving foods because they are active than adult.
3. Adolescent
- Need food rich in carbohydrates because of high body
metabolism
- Food rich in protein and mineral salt such as calcium,
iron and phosphorus
- Adolescent girl require additional supply of iron to
compensate for the blood loss during menstruation.
4.The
elderly.
Elderly people require less energy –
giving foods because they are generally less active than young people. This
group should eat food that is rich in fiber in order to reduce constipation and
bowel problems that come with age.
They also need minerals such
as iron, zinc and calcium. Iron is necessary because anemia is a frequent
problem in older age; zinc is required for a healthy immune system and to
increase the rate of healing of wounds.
Old age comes with the loss of
calcium from bones leading to soft and weak bones that can break easily. Old
people therefore require adequate amounts of calcium and vitamin D to counter
the loss.
The elder often have problems of
chewing tough foods because of weakened teeth and swallowing because of
the decreased production of saliva. It is therefore important to ensure they
get food that are nutritious as well as easy to chew and swallow. For example
they can get proteins from eggs or liver instead of meat.
5. Sedentary workers
These are individuals who stay in
one place for a long time while performing their daily occupational activities.
They include workers potter’s weavers, clerk, receptionists and doctors.
Sedentary workers are encouraged to
balance their diets with physical exercise. Due to their lifestyle and
occupation obesity increasingly is common among them. Therefore, it is
recommended that they limit their intake of foods rich in lipids.
6. The sick
Sick people require plenty for
nutrients to help recover their health, those who have incurable disease such
as HIV and AIDS should get food that will help them to manage their conditions.
Proper nutrition helps to keep their
immune system strong and helps the body to fight opportunistic infections and
disease.
Rapid weight loss is a major problem
in the late stage of AIDS. It is therefore important to get enough nutrients so
as that the body can compensate for this.
Proper nutrition helps the body to
withstand heavy medication.
Proper diet and exercise helps to
combat symptoms such as fatigue, nausea, diarrhea and high blood sugar.
Excess caffeine sugar, dried foods,
spicy foods and alcohol should be avoided because they are harmful to a body
whose immune system is already weak.
They need to take plenty of fruits
and water. Fruits provide vitamins which are required to fight disease. Water
replaces the amount lost through diarrhea or vomiting.
It is advisable to use food guide
pyramid to know what to eat. The food guide pyramid is a chart showing the
recommended amounts of different food types that dietician considers healthy
eating.
Nutritional deficiencies and disorders
Malnutrition
Malnutrition (limiting the intake of
one or more essential nutrients) results from eating too little from eating the
wrong food. There are different types of nutritional deficiencies and disorders
in human beings, these deficiencies and disorders include obesity, rickets,
kwashiorkor, marasmus, anorexia nervosa and bulimia nervosa.
Nutritional disorders
Nutritional disorders are conditions
of ill health in a person which arise as a result of lifestyle (poor eating
habits) as discussed below.
- Obesity
Obesity is where by a person has
excess body fat. A person sex, age and level of activity among other factor
determine his or her ideal body fat. To maintain fertility, women need more
body fat. Women also store more fat in their breasts, hips and thighs.
Another important influence of body
fat is a person frame size. Individuals with larger bones carry more fat.
Obesity mostly results from eating
too much and not exercising enough. Body weight and health risks associated
with it are correlated by the body mass index (BMI). BMI gives the relationship
between the estimated body fat and the risks of certain disease or conditions.
BMI = Body mass (in kilograms)
persons height (in meters)2
OR
BMI = Body mass (kg).
(Person's height)2 (m2).
For example if your height is 1.65 meters and your body mass is 60 kilograms
your BMI can be calculated as
60/ (1.65)2 = 60/
(2.7225) = 22.04
If an individual’s BMI falls in the
range of 20 – 25, this is considered to be healthy. On the other hand if the
BMI is over 30, one may be at risk of diseases associated with obesity.
The following table shows a general
guide of how different values of BMI are used to define the condition of the
body.
Table BMI
guide
|
BMI |
Body condition |
|
Below 20 |
Underweight |
|
20 – 25 |
Advisable range |
|
25 – 30 |
Overweight |
|
30 – 35 |
Obese |
|
Above 35 |
Very obese |
Obesity increases the like hood of
conditions such as high blood pressure, diabetes and certain types of cancer,
stroke, and respiratory problems.
Obesity can be prevented by eating
properly and engage in regular exercise. The intake of calories should balance
one’s physical activity. It is also important to avoid eating too much fat
foods such as butter, fat meat, chips, margarine, sausage and vitumbua. Avoid
also unhealthy dieting.
Anorexia nervosa and Bulimia nervosa
Anorexia nervosa is also called slimmer’s disease or self starvation
syndrome. It occurs when a person intentionally refuses to eat enough, leading
to a severe loss of body mass.
Sign and symptoms of anorexia
1. Muscle wasting (including
weakening of heart muscle)
2. Excessive loss of body mass
3. Extreme fear of being fat.
4. Disturbed body image or feeling
fat even when one is very thin.
Bulimia nervosa involves excessive eating followed by efforts to remove
food from the body. This effort could involve self- induced vomiting, fasting,
excessive exercising or taking drugs that stimulate, emptying of the bowels or
excessive urination. Bulimics usually have a normal body mass and keeps their
eating behavior secret. Hence it may be difficult to tell that they have a
problem.
Causes of Anorexia and Bulimia
Both Bulimia and Anorexia have
underlined psychological causes, such as depression, low self esteem and
bottled up emotions and the need to fit contemporary standard of beauty Bulimia
and Anorexia mostly affect women.
Effects of Anorexia and Bulimia
- The effects of Anorexia and Bulimia are demonstrated by
heart problems due to weak cardiac muscles or an imbalance of mineral
salts.
- There is an impaired mental function because the brain
lacks adequate amount of glucose. Victims also exhibit dehydration. During
vomiting, the acidic present in the stomach come into contact with the
teeth and gums, the eventually causes, serious damage to the gum and
erosion of the teeth. Other effects include anemia, stomach ulcers,
abdominal cramping and inflammation of the gut, irregular or absent
menstrual periods and dry skin.
Treatment for Anorexia and Bulimia
Anorexia and Bulimia can be treated
by resolving the underlying psychological problems, seeing a medical
practitioner who can prescribe a way of getting back one’s healthy and making
the necessary lifestyle and dietary change.
Nutritional deficiencies.
These deficiencies arise when the
body does not have sufficient supply of a particular food or nutrient. The
following are some of the common nutritional deficiencies.
- Marasmus
Marasmus is a form of malnutrition
in children caused by lack of adequate amount of food
Sign and symptoms of Marasmus
A child suffering from marasmus
shows weight loss, slowed growth, decreased activity and lack of energy. They
also have wrinkled skin, are irritable and have extreme hunger
Treatment of Marasmus
Getting adequate amount of food that
contains all the nutrients in the right proportions.
2. Kwashiorkor
Kwashiorkor is caused by a
deficiency of proteins. It affects children, mostly after stopping to breast
feed.
Signs and symptoms of kwashiorkor
The signs and symptoms of
kwashiorkor include extremely thin arms and legs, poor growth, swollen thin arms
and legs, swollen abdomen due to enlargement of the liver and reddish or
yellowish thin and weak hair. Other symptoms are weakened immunity, diarrhea,
anemia, and dry skin that cracks easily
Treatment for kwashiorkor
Kwashiorkor is treated by providing a
child with a diet that has adequate amounts of proteins.
3. Rickets
Rickets is a condition where by the
bones of a child soften, leading to fractures and deformities. The cause of
rickets is lack of vitamin D, phosphorous and calcium.
Sign and symptoms of Rickets
A child suffering from rickets can
be identified by observable skeletal deformities such as bow legs, knock knees,
an odd – shaped skull and a deformed spine. A child feels bone pain,
experiences dental problems such as weak teeth or delayed formation of teeth
and develops weak muscles. The child’s bones are easily fractured, shows slow
growth and gets muscle spasms and muscle cramps.
Prevention of Rickets
Rickets is prevented by increasing
the amount of vitamin D, phosphates and calcium in the diet and by ensuring
exposure to sufficient amount of sunlight.
FOOD TEST
Food test is used to determine which
nutrients are present in a food specimen. At this level we will learn how to
test for carbohydrates, proteins and lipids.
- Test for carbohydrates
|
|
Procedure |
Observation |
Conclusion |
|
|
Test for reducing sugar |
|
|
|
|
Dissolve specimen in water |
colour changes from blues to green
to yellow then orange |
Reducing sugar is present |
|
|
Add an equal amount of Benedict’s
solution to the solution |
||
|
|
Boil the mixture |
||
|
|
Test for non reducing sugar |
|
|
|
1. |
Dissolved the specimen in water Put 2cm3 of the
solution in a test tube. Add 1cm3 of(dilute hydrochloric acid
neutralizes disaccharides to monosaccharide’s) Boil the mixture Allow the mixture to cool Add small amounts of sodium
hydroxide at a time (sodium addition) Continue until fizzing stops. Add 2cm3 of Benedict’s
solution, then boil the mixture |
Colour changes from blue, green to
yellow to orange. |
Non – reducing sugar is present |
|
|
|||
|
3. |
|||
|
|
|||
|
5. |
|||
|
|
|||
|
|
Test for starch |
|
|
|
|
Add a few drops of iodine solution
to the specimen |
Colour changes to blue - black |
Starch is present |
Test for Protein
|
Procedure |
observation |
Conclusion |
|
Biuret test |
|
|
|
The specimen should be in solution
form |
Color changes to purple |
Proteins are present |
|
Pour 2cm3 of specimen
in a test tube |
||
|
Add 1cm3 of sodium
hydroxide solution then a drop of copper sulphate solution shaking the
mixture after each addition |
Test for lipids
|
|
Procedure |
observation |
Conclusion |
|
|
Grease spottiest |
|
|
|
|
Rub the specimen on a piece of dry
filter paper |
a translucent mark is formed |
Specimen contain lipids |
|
|
Hold the paper against the light |
||
|
|
Sudan III test |
|
|
|
|
The specimen should be in solution
form |
Droplets of oil turn red |
Specimen contains lipids |
|
|
Add some drops of Sudan III test |
||
|
|
Emulsion test |
|
|
|
|
Ensure the specimen is in solution
form |
The clear mixture turns cloudy
forming a milky suspension |
Specimen contains lipids are
present. |
|
|
Put the specimen in a test tube
along with an equal amount of acetone, benzene or ethyl alcohol. |
||
|
|
Shake the mixture |
||
|
|
Add an equal volume of water |
DIGESTIVE SYSTEM IN HUMAN
Some common terms concerned with the
movement of food along the alimentary canal.
INGESTION – This is taking in a food
to the mouth.
DIGESTION – This is the process by
which food is broken down to small particles which are absorbed and assimilated
in the body.
ABSORPTION – This is the process by
which soluble end products of digestion diffuse into the blood stream.
ASSIMILATION – This is the
incorporation of products of digestion into the cell metabolism.
EGESTION –This is the process by
which indigested food particles are removed from the body through the anus.
The digestive system is made up of alimentary
canal (gut) and associated organs such as the pancreas and liver
PARTS OF ALIMENTARY CANAL
The alimentary canal is a long
hollow tube that runs from the mouth to the anus. It is also known as digestive
tract.
- It consists of the mouth, pharynx, gullet, stomach,
duodenum, ileum, caecum, colon and rectum
DIGESTION
Digestion is a process by which food
is broken down into form that can be absorbed and used by the body. It involves
both mechanical and chemical breakdown of food. Mechanical take place in the
mouth; the teeth chew the food to reduce it to small piece that can be
swallowed easily
The small pieces have a large
surface area to facilitate the action of digestive juice called enzymes
Chemical breakdown is achieved by
digestive enzymes. The digested food is absorbed and assimilated in the body.
The undigested and indigestible materials are egested as faeces.
THE DIGESTIVE SYSTEM AND DIGESTION
PROCESS
The major regions where digestion
occur in the alimentary canal are mouth, stomach, duodenum and ileum
DIGESTION IN THE MOUTH
In the mouth, food is chewed by
teeth and mixed with saliva to form a ball like to break down food into small
particles thus increase the surface area for enzymatic activities.
-Saliva is alkaline in nature, so it makes the food alkaline when in the mouth.
- Secretion of saliva is controlled by the nervous system. These smell, taste,
sight or thoughts of food cause saliva to flow from the gland.
-Saliva is a mixture of mucus water, a variety of salts and the enzymes known
as salivary amylase.
FUNCTION OF SALIVA
1. Water acts as solvent for
dissolving food substance
2. Mucus lubricates thus food for
easy swallowing.
3. Salivary amylase turns starch to
maltose.
- The tongue rolls the food in the
round mass known as bolus(plural is boli)
- The boli are pushed down the
oesophagus by the tongue
THE PHARYNX
- The region which crosses the air passage is known as
glottis
- There is a structure known as epiglottis which prevent
food from entering the wind pipe or trachea.
- There is no digestive enzymes
THE OESOPHAGUS (GULLET)
- This is the tube which connects the pharynx and the
stomach.
- The food passes the gullet rapidly by contraction and
relaxation of the gullet mode this is known as PERISTALSIS
- Peristalsis is the process by which food substances
move down the alimentary canal in the form of bolus through muscle valve
known as sphincter
- There is no digestive enzymes.
DIGESTION
IN THE STOMACH
- The food is mixed with hydrochloric acid and gastric
juice to produce a semi – solid mass known as chyme.
- The wall of the stomach contains gastric glands which
secrete gastric juices.
- The gastric juices contain water, hydrochloric acid,
mucus and enzymes(pepsin and rennin).
FUNCTION
OF THE HYDROCHLORIC ACID
1)
Provides suitable acidic medium for enzymes to work best
2)
Hydrolyses or breaks down food to simple particles
3) Kills
bacteria present in food
- The
function of pepsin is to breakdown proteins into peptides.
- The
function of rennin is to coagulate (solidifies) soluble milk protein (casein)
into an insoluble form which is then acted on by the enzymes pepsin. This
enzyme is mostly found in young mammals during sucking period.
The
function of mucus is to protect the stomach against corrosion by the
hydrochloric acid.
GENERAL
FUNCTIONS OF THE STOMACH
- It is a temporary storage of food
- Digestion of proteins starts in the stomach
- Helps in mixing food during churning, also absorb water
alcohol and some vitamins.
There is a muscle valve between the
stomach and the duodenum known as pyloric sphincter
The chyme (liquid food) passes
periodically from the stomach through the pyloric sphincter to the duodenum.
DIGESTION IN THE DUODENUM
- Duodenum is the first part of the small intestine
- It is associated with the liver and pancreas.
THE
LIVER
- The liver has cells which secrete bile.
- Bile is stored in the gall bladder and is released
through the bile duct. It is greenish yellow in colour and contains bile
salts.
FUNCTION
OF THE BILE
i) It
emulsifies fats (lipids) i.e. break down fats into tiny fat droplets to
increase the surface area for enzymatic activities.
ii)
Provides an alkaline medium for enzymes to work best.
iii) It
neutralizes the acidic food from the stomach.
THE PANCREASE
The pancreas secretes digestive
juices known as pancreatic juice. The juice contains the following.
1. Pancreatic amylase – it breaks
down the starch into maltose.
2. Pancreatic lipase – digest the
fat droplets into fatty acids and glycerol.
3. Sodium hydrogen carbonates (NaHCO3)
provides basic medium for pancreatic enzymes to work best i.e. neutralize the
acidic chyme from the stomach. The resulting food mixture in the duodenum is
known as chyme.
4. Trypsin – break down proteins
into peptide.
DIGESTION IN THE ILEUM (SMALL
INTESTINE)
- The ileum is the largest section in the alimentary
canal.
- The intestine contains secretory cells which secrete
mucus and digestive juice known as intestinal juice or succus entericus.
- The juice has 4 enzymes
1. Erepsin
or peptidase digests peptides to amino acids.
2. Maltose
– breaks down maltose to glucose.
3. Lipase
– breaks down fat droplets to fatty acids and glycerol.
4. Sucrose
– breaks down sucrose (cane sugar) to glucose.
- The ileum has two main functions
a) Digests
all types of food.
b)
Absorption of end products of digestion into the blood stream
NOTES: The
walls of the alimentary canal secrete mucus which performs two major functions.
a) Allows
smooth movement of food materials along the alimentary, absorption of the end
product of digestion into the blood of stream
b) Protect
the wall of the alimentary canal against corrosion (digestion) by digestive
enzymes.
-End
products are:
- Amino acids – simple form of proteins.
- Glucose – simple form of carbohydrates.
- Fatty acids and glycogen – simplest forms of lipids.
ABSORPTION
Absorption is the process by which
the soluble end products e.g. glucose diffuses into the blood stream.
- Absorption takes place mainly in the small intestine
however; absorption of some water, soluble vitamins B and C, and soluble
salts take place into the stomach.
PROCESS OF ABSORPTION
1. Amino acids and glucose. These
materials are absorbed into the blood stream through the process of active
transport
- These materials diffuse into the
blood with the dissolved materials to the HEPATIC PORTAL VEIN
- The hepatic portal vein takes the
blood with the dissolved materials to the river and then joins the general body
circulation.
2. Fatty acids and glycerol.
- They are absorbed into the
location of the villi
- They can drain into lymphatic
vessel and finally join the body circulation at the vena cava.
NOTE: The wall of the small intestine has numerous fingers –
like structure called villi: (singular villus) which increase the surface area
for digestion and absorption of food to take place.
Diagram of villi
Adaption of ileum to its functions
1) It is long to provide large
surface area for digestion and absorption.
2) It is highly coiled to increase
the surface area for digestion and absorption.
3) It has villi and micro – villi
which increase the surface area for absorption.
4) It has dense network of blood
capillaries which facilitate easy diffusion of digested materials.
ASSIMILATION
- This is the process by which the end products of
digestion are incorporated in the cell metabolism. Assimilation occurs as
follows:
Glucose:
some is oxidized during respiration to produce energy (ATP) some is stored as
glycogen in muscle some is converted to fats and stored as tissue beneath the
skin.
AMINO
ACIDS
Some are
used in the synthesis (formation) of proteins, some are used in growth and
repair of worn out cells. In absence of glucose and fats they may be oxidized
to release energy during respiration.
FATTY
ACID AND GRYCELOR
- Are oxidized to release energy during respiration.
- Stored as a dispose tissue beneath the skin. This helps
in insulating the body.
THE
CAECUM AND THE APPENDIX
- These have no function in man.
- In herbivores the caecum and appendix contain bacteria
that secrete an enzyme known as cellulose.
THE LARGE INTESTINE (COLON)
- The large intestine has four functions.
- Absorb water from the undigested materials
- Absorb small amount of digested food.
- Glandular lining of the colon produces mucus which
lubricate the passage of faeces
- It is a temporary storage of faeces up to the time of
defecation (egestion).
EGESTION: The undigested and indigested
materials are known as faeces. The faeces are removed from the body through
anus by the process of egestion.
SUMMARY OF DIGESTION
|
Part of alimentary
canal |
Enzymes secreted |
Substance digested |
Product of digestion |
|
Mouth |
Salivary amylase |
Carbohydrates |
Maltose |
|
Stomach |
Pepsin |
Protein |
Peptides |
|
|
Rennin |
Soluble milk protein (caseinogens) |
Insoluble milk protein e |
|
|
Trypsin |
Protein |
Peptides |
|
Duodenum |
Pancreatic amylase |
Starch |
Maltose |
|
Ileum |
Pancreatic juice |
lipase |
Fattys acids and glycerol |
|
|
|
Maltase |
Glucose |
|
|
|
Sucrase |
Glucose and fructose |
|
|
|
Lactose |
Glucose and galactose |
This is so helpful, well arranged and easy to read,thanks mkamba education
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