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OLEVEL
BIOLOGY - 5090
ANIMAL NUTRITION

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PAPER-2 Animal Nutrition

NOTES

A balanced diet is a diet that provides all the nutrients in the correct amounts needed to carry out life
processes. 
 
Effects of Age, Sex, and Activity
on Human Dietary Needs

Age:
As an infant, a child needs as many nutrients as possible. Breast milk is the best option for kids because it
provides all extra immune building properties, necessary calories, and fats. As a child grows into
toddlerhood, they become active. This will increase their calories, proteins and calcium needs. As for adults,
nutritional requirements do not change greatly, except for pregnancy and breastfeeding. 

Pregnancy:
A pregnant woman with an adequate diet needs no extra food. Her body’s metabolism will adapt to the
demands of the growing baby. If her diet is deficient in some nutrients, she will need to increase the intake
of those substances. The baby needs proteins, calcium and vitamin D, and iron. 

Lactation:
The production of milk makes a large demand on the mother’s resources. Her metabolism will adjust to
these demands if her diet is already adequate. Otherwise, she may need to take in more proteins, vitamins,
and calcium.

Sex/Gender:
In most cases, men and women require similar nutritional proportions, but there are exceptions. Women
tend to have lower calorie needs because they carry less muscle. Women should eat more nutritional-
dense food e.g. complex carbohydrates. Calcium should be consumed in higher amounts by women as
they have higher chances of Osteoporosis i.e. fragile bones. Men should at proper nutritional
carbohydrates. 

Activity:
An athlete has different nutritional requirements compared to that of a worker. Exercise improves metabolic
efficiency in some people and increases nutrient requirements.  

Principal Sources and Dietary Importance

of Food Types

Food Type Principle Importance

Sources

Carbohydrates Crop plants They give the energy for respiration

(rice, wheat,
potatoes), Fruits,
Vegetables, Milk

Fats Dairy products, They provide energy for our bodies and support for cell growth.
Nuts, They protect organs
Avocadoes,
Seeds, Fish

Proteins Seafood, Meat, They help in the growth and repair of cells and tissues
Dairy products,
Beans, Lentils

Vitamin C & Vitamin C: V-C helps in preventing cell damage and reduces some diseases.
Vitamin D Citrus Fruits, They also help in healing cuts. V-D boosts your immune system
Leafy and strengthens bones. They increase the absorption of calcium
Vegetables and phosphates.  

Vitamin D:
Organ meats,
Eggs, Dairy
products,
Sunlight

Iron Red meat, It forms an integral part of hemoglobin.

Beans, Cereals,
Fruits, Dark leafy
vegetables

Calcium Dairy products, It helps in the development of bones, teeth and the body.
Fruits, Leafy
greens, Seafood

Fiber Cereals, Fruits, It helps in the proper functioning of the digestive system and
(Roughage) Vegetables, weight management. It also maintains cholesterol levels.
Lentils
 Water Fruits, It helps to get rid of waste materials.
Vegetables,
Meat, Eggs

Vitamin C: 
Lack of vitamin C causes scurvy. It leads to tiredness, anemia, gum disease, and skin problems.

Vitamin D: 
You can get vitamin D through sunlight and organ meat. Lack of vitamin D causes bowing of legs, known as
rickets. It also causes the softening of bones, known as degeneration. 

Iron: 
Iron, found in red meat, fruits, and vegetables, is a very important component to make hemoglobin. Lack of
iron causes hemoglobin synthesis. This results in nutritional anemia. 

Protein: 
Lack of protein causes a swollen abdomen, known as Kwashiorkor. It is most common in the areas where
there is famine or limited food supply. It also causes loss of weight, known as marasamus.

Malnutrition
Malnutrition can be defined as a lack of proper nutrition that causes health problems. There are several
effects of it, as mentioned below.

i. Starvation: It is a severe lack of nutrition. It causes a lack of concentration, a drop in metabolism, and can
even cause further organ damage.

ii. Constipation: When waste materials move too easily through the digestive tract, causing it to become dry
and hard.

iii. Coronary heart disease: As a result of plaque buildup in the coronary arteries, there will be a blockage.
Arteries will become narrow and rigid, and this restricts blood flow.

iv. Obesity: Lack of energy balance, inactive lifestyle, genes, and lack of sleep lead to obesity.

v. Scurvy: Lack of vitamin C causes scurvy. Vitamin C makes a substance, known as collagen which helps in
the repair of various tissues.

Tests
• protein (Biuret test)
• Starch (Iodine in potassium iodide solution)
• fats (Ethanol emulsion test)
• reducing sugars (Benedict’s solution)

Human Alimentary Canal

Ingestion: 
Taking in substances into the body through the mouth.

Mechanical Digestion: 
Breakdown of food into small particles without any chemical change to the food molecules.

Chemical Digestion: 
The disintegration of large, insoluble molecules into smaller, soluble molecules.

Absorption: 
Movement of small food molecules and ions through the wall of the intestine into the blood.

Assimilation: 
It is the movement of absorbed food molecules into the cells of the body.

Egestion: 
Passing out of food that has not been digested or absorbed (feces) through the anus.

Regions of the Alimentary Canal

Region of the Function
Alimentary Canal

Mouth Ingestion of food; Mechanical digestion through teeth; Chemical digestion of

starch by amylase; Secretes enzyme

Salivary glands Produce saliva containing amylase, which is required for chemical digestion of
starch

Oesophagus It moves the ingested food to the stomach by peristalsis. No digestion takes place
here

Stomach Produces gastric juice which has pepsin, which is used for chemical digestion of
protein; Produces hydrochloric acid to kill bacteria

Duodenum  It carries out chemical digestion of proteins, fats, and starch; It also gets bile for the
emulsification of fats

Ileum  The digested food is absorbed into the blood and lymph

Pancreas Secrete pancreatic juice into the duodenum

Liver Produces bile; Deamination of amino acid takes place in the liver

Gall bladder Stores bile

Colon It absorbs water and bile salts

Rectum  It stores feces

Anus It is responsible for the Egestion of feces

Mechanical Digestion

It is the breakdown of food into smaller molecules without any chemical change to the food particles. This is
done by teeth, through a process known as Mastication.

Incisors are chisel-shaped. 8 of them are present in our mouth. They have 1 root and no ridges. They are
used for biting and cutting off pieces of food.
Canines are sharper than the incisors. They have 1 ridge and are used for holding and tearing the food
apart. There are 4 of them in our mouth. The molars and premolars have similar functions. They are used for
crushing and grinding the food particles. Premolars have 1-2 roots and 2-4 ridges, while the molars have 3-
4 roots and ridges.

Figure (i) Human teeth, Credit: Weebly.com

Structure of the Human Tooth

The top, visible part of the tooth is called the crown, while the bottom part is known as root. The gums
overlay the jaw. Enamel is the shiny, hard outer shell that covers the crown. Beneath the enamel is the
dentine. The dentine is the substance that makes up the tooth. It contains a pulp cavity, which has blood,
lymph vessels, and nerve fibres. It supplies nutrients to the dentine. Cement is the tissue covering the
surface of the root. It fixes the teeth. 

Figure (ii) Teeth, Credit: wikipedia

Dental decay
There are bacteria present on the surface of our teeth. Food deposits and bacteria form a large layer of
plaque. Bacteria in the plaque may affect the gums. They feed on sugars present in the food, producing
acid. The acid will dissolve the enamel, forming a hole. The dentine underneath the enamel is softer, thus
dissolves more rapidly. If the hole reaches the pulp cavity, bacterial infection can get to the nerve, resulting
in tooth decay.

Dental care
• Avoid foods with high sugar content.
• Make sure to brush your teeth twice a day, and also make use of dental floss.
• Regular checkups at the dentist.

Chemical Digestion
Enzyme Site of Action Conditions Substra Products
te

Amylase Mouth, Slightly alkaline Starch Maltose, Glucose

Duodenum

Protease Stomach, Acidic in the stomach, Alkaline in the Protein Amino acids
Duodenum duodenum

Lipase Duodenum Alkaline Fat Fatty acids,

Glycerol

The Mouth
Saliva is a digestive juice that lubricates the food. The salivary gland produces a special enzyme, known as
salivary amylase. This works on pH 8. It digests starch into maltose. Maltose breaks down into its monomers
in the other part of the body. This semi-digested food is known as a bolus. The bolus is passed to the
oesophagus through the food pipe.

Oesophagus
The Oesophagus connects your mouth to your stomach. Food moves through a wave-like contraction into
the stomach, known as peristalsis. Circular and longitudinal muscles work together but opposite to each
other. These are antagonistic pairs. In front of the bolus, circular muscles relax and longitudinal muscles
contract. Behind the bolus, longitudinal muscles relax and circular muscles contract.

Stomach
Pepsin is a protease enzyme produces in the stomach. It requires a low pH to function, which is why the
stomach produces hydrochloric acid. The bolus reaches the stomach and lets the walls secrete gastric
juices. The hydrochloric acid lowers the pH (2-3). It also denatures enzym3w in harmful microorganisms in
food and gives the optimum pH for pepsin activity. It stimulates the digestion of protein through the
protease enzyme. It will be partially digested, and this partially digested food is known as a chime. 

Small Intestine
The sphincter is a circular muscle. When it is released, it allows materials to pass through the opening. When
contracted, it closes the opening. The food passes from the stomach to the small intestine when sphincter
opens. The small intestine is 6 meters long and highly coiled up in the abdominal cavity. In the duodenum,
major digestion takes place. It has glands (lining), and it produces three different types of juices (Intestinal
juice from itself, bile from the liver, and pancreatic juice from the pancreas). The chime enters the
duodenum, which is the first part of the small intestine.

• Bile: The liver, situated above the small intestine, secretes bile. Bile is stored in the gall bladder and is
poured into the intestine through the bile duct. It is an alkaline juice that neutralizes the acidic mixture of
food and gastric juices entering the duodenum from the stomach to provide a suitable pH for enzyme
action. Bile also emulsifies fats to increase the surface area for the chemical digestion of fats to fatty acids
and glycerol through the enzyme, lipase.

• Pancreatic juice: Pancreas secretes the pancreatic juice which pours into the gall bladder. Emulsified lipids
in the pancreatic juice into pancreatic lipase to fatty acids and glycerol. Semi-digested starch is digested
by pancreatic amylase. As a result, it produces maltose.
• Intestinal Juice: This is secreted by the small intestine. It contains an enzyme, known as intestinal lipase,
which changes into fatty acids and glycerol.

Absorption
The small intestine is the region where this process occurs. The adaptations of the small intestine are as
following:

• Small intestine cells are changed into villi and microvilli, which are finger-like projections.

• Villi increase the surface area required for absorption. 

• 6 meters long

• It contains blood capillaries to carry away the absorbed food molecules.

• They have a thin foiled lining for easy movement of food molecules.

Structure of Villus
In each villus, there are two types of capillaries present: Lacteal and blood. The lacteal capillary is a
lymphatic capillary which absorbs fatty acids. Blood capillaries absorb all amino acids, glucose, mineral
salts and water.

Large Intestine
Water and mineral salts mostly dissolve in the large intestine. Undigested food (fibre/cellulose) is stored in
the rectum for a certain period and comes out as faeces. The fibre helps in peristalsis. Faeces moves from
rectum Anus is the opening of the rectum. The act of removing the faeces from the body is known as
Egestion.

Diarrhea
It is the loss of watery feces. When you contaminated food, water does not dissolve in blood, causing a
problem in the intestine. Therefore, faeces become thin and watery. It can be treated by Oral Rehydration
Therapy (ORS), which is a fluid replacement strategy used to treat dehydration caused by diarrhea.

Cholera
Cholera is a disease caused by a bacterium, Vibrio Cholerae. Intake of contaminated food or drink can
cause this disease. The bacterium produces a toxin that causes the secretion of chloride ions into the small
intestine. Thus, water goes into the large intestine with feces. This causes the osmotic movement of water
into the alimentary canal. This leads to diarrhea, dehydration, and loss of mineral salts from the blood.
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