Biology For Class IX - Chapter No.8 - NUTRITION - Questions and Answers

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CHAPTER 8
NUTRITION

Q.1: Define nutrition and nutrients?
Ans: NUTRITION:
Process by which organisms obtain and use the nutrients required for maintaining life is called nutrition.
Nutrition is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health, and diseases.

NUTRIENTS:
Essential substances that our body needs in order to grow and stay healthy are known as nutrients.

Q.2: Briefly describe the process by which food is obtained or prepared?
Ans: Plants and animals do not obtain food by the same processes. Plants and some bacteria have the green pigment chlorophyll to synthesize food, while animals, fungi and other bacteria depend on other organisms for food. Based on this, there are two main modes of nutrition:

1. Autotrophic and
2. Heterotrophic

1. Autotrophic Nutrition:
The term 'autotroph' is derived from two Greek words-autos (self) and trophe (nutrition). It is the mode of nutrition in which an organism makes its own food from the simple inorganic materials like carbon dioxide, water and minerals present in the surrounding (with the help of energy). The processes are photosynthesis or either chemosynthesis.
Example: Green plants or Living organism containing chloroplast.

2. Heterotrophic Nutrition:
The word 'heterotroph' is derived from two Greek words-heteros (other) and trophe (nutrition). It is the mode of nutrition in which an organism can't make its own organic material but depends on other organisms for its food and use it for growth and energy. As heterotrophs depend on other organisms for their food, they are also called consumers.
After taking complex organic materials as food, heterotrophs break them into simple molecules with the help of biological catalysts, i.e., enzymes and utilize them for their own metabolism.
Example: All animals, non-green plants like bacteria and fungi come under this category.

Q.3: Name and describe the process by which plants prepare their food?
Ans: Green plants, which are autotrophes, synthesize food through the process of photosynthesis.
PHOTOSYNTHESIS:
Photosynthesis is a process by which green plants, algae and some bacteria having chlorophyll, synthesize the simple sugar (glucose) from the simple raw materials i.e. water and carbon dioxide by using the energy of sunlight. Oxygen is released in this process. The overall equation of photosynthesis is:

Q.4: Define heterotrophic nutrition.  Describe types of heterotrophic nutrition in animals and plants?
Ans: HETEROTROPHIC NUTRITION:
The word 'Heterotroph' is derived from two Greek words-heteros (other) and trophe (nutrition). It is the mode of nutrition in which an organism can't make its own organic material but depends on other organisms for its food and use it for growth and energy. As heterotrophs depend on other organisms for their food, they are also called consumers.
After taking complex organic materials as food, heterotrophs break them into simple molecules with the help of biological catalysts, i.e., enzymes and utilize them for their own metabolism.
Example: All animals, non-green plants like bacteria and fungi come under this category.

TYPES OF HETEROTROPHIC NUTRITION IN ANIMALS: They may be:

1. Herbivores: Consumers which consume herbs and other plants are called herbivores.
   e.g. Goat, cow etc.
2. Carnivores: Those which consume animals are called carnivores.
   e.g. Lion, Cat etc.

TYPES OF HETEROTROPHIC NUTRITION IN ANIMALS AND PLANTS:
Depending upon the mode of living and the mode of intake of food, heterotrophs may be parasitic, saprotrophic or holozoic.
(i) Parasitic nutrition:
Parasitic organisms, or parasites, live on or inside other living organisms, called hosts, and obtain their food from them. The host does not get any benefit from the parasite. This mode of nutrition is called parasitic nutrition.
Example: Different parasites, like Cuscuta (akash-bel), hookworms, tapeworms, leeches, etc., have different modes of feeding, depending upon habit, habitat and modifications.

(ii) Saprotrophic nutrition:(Gr: Sapros = rotten, Trophic = nutrition):
Saprotrophic organisms, or saprotrophes, derive their food from dead and decaying organic material. This mode of nutrition is called saprotrophic nutrition. They secrete enzymes that are released on food material outside their body. These enzymes break down complex food into simple forms.
Examples: Common examples of saprotrophes are fungi (moulds, mushrooms, yeasts) and many bacteria.

(iii) Holozoic nutrition: (Gr:Holo=Whole, Zoikos=of animal):
In holozoic nutrition complex organic substances are ingested (taken in) without their being degraded or decomposed. After intake, such food is digested by enzymes produced within the organism. Digested food is absorbed into the body and the undigested product is egested (expelled out) from the body.
Example: This kind of nutrition is found mainly in non-parasitic animals-simple ones like Amoeba and complex ones like human beings.

Q.5: How does Amoeba obtain its nutrition? Or Describe the mode of nutrition in Amoeba?
Ans: Different organisms obtain food in different ways.
Nutrition In Amoeba:
Nutrition in unicellular organisms like Amoeba is known as holozoic nutrition. It involves ingestion by the cell surface, digestion and egestion. Amoeba takes in complex organic matter as food.
Ingestion by the cell surface:
Amoeba first identifies its food then throws out a number of small pseudopodia (projections of cytoplasm, also called false feet). These pseudopodia enclose the food particle and prevent it from escaping. The food enclosed in the cell membrane forms a food vacuole.
Digestion:
The complex food is broken down into simpler molecules with the help of digestive enzymes produced by an organelle called lysosome. The digested food is distributed in the cytoplasm.
Egestion:
The undigested food is egested through the cell membrane.

OR

Q.6: Describe nutrition or ingestion of food in Paramecium?
Ans: Nutrition In Paramecium:
In Paramecium, a unicellular organism with a specific shape, food is ingested through a special opening, the cytostome (cell mouth). Food is brought to this opening by the lashing movement of cilia that cover the entire surface of the cell.

Q.7: Define mineral nutrition in plants and its type? Also draw chart of classification of essential plants nutrients.
Ans: Mineral nutrition in plants:
The process involving the absorption, distribution and utilization of mineral substances by the plants for their growth and development is called mineral nutrition.

Types Of Minneral Nutrition:
Plants have the most efficient mechanism for preparing there food by using many elements essential for plant nutrition. The mineral nutrients are:

1. Macronutrient i.e Minerals which require in large quantity by plants. e.g:
   i. Primary nutrients: Nitrogen, Phosphorus
   ii, Secondary nutrients: Calcium, Magnesium
   
   
2. Micronutrient i.e Minerals which require in small quantity by plants. e.g.
   Zinc, Copper, Manganese, Iron, Boron, Molybdenum, Chlorine, Nickel.

Q.8: Why nitrogen is essential for plants? What are the symptoms of nitrogen deficiency?
Ans: Nitrogen"
Nitrogen is essential for plants to synthesize amino acids, which are the building blocks for protein synthesis and also required for the production of chlorophyll, nucleic acids, and enzymes. From all metabolic elements which plants use from soil, nitrogen needs in the largest amounts.

Symptoms of nitrogen deficiency:
Nitrogen-deficient plants exhibit stunted growth, reduced yields and their foliage pale green.

Q.9: Why magnesium is essential for plants? What are the symptoms of magnesium deficiency?
Ans: Magnesium:
Many enzymes in plant cells require magnesium in order to perform properly and is a constituent of the chlorophyll molecule, which is the driving force of photosynthesis.

Symptoms of magnesium deficiency:
Magnesium deficiency is most prevalent on sandy-textured soils, which are subject to leaching, particularly during seasons of excess rainfall. The predominant symptom is interveinal chlorosis (dark green veins with yellow areas between the veins). The bottom leaves are always affected first.

Q.10: What are fertilizers? Define its types and also write down the importance of fertilizers?
Ans: Fertilizers:
are substances containing chemical elements such as manure or mixture of nitrates that improve growth of plants.

Types Of Fertilizers:

1. Inorganic Fertilizer:
   Naturally occurring materials which are not chemically modified called inorganic fertilizer.
   
   
2. Organic Fertilizer:
   Chemical substances which are more complex and takes time to be broken down into useable form called organic fertilizer.

Importance of fertilizers:

• They improve growth of plants.
• They give nutrition to the crops and produce more fruit, faster growth, more attractive flowers.
• When added to soil or water, plants can develop tolerance against pests like weeds, insects and diseases. And the use of manure and composts as fertilizers is probably almost as old as agriculture.
• Modern chemical fertilizers include one or more of the three elements that are most important in plant nutrition: nitrogen, phosphorus, and potassium. Chemicals fertilizers are simply plant nutrients applied to agricultural fields to supplement required elements found naturally in the soil.

Q.11: Describe the environmental hazards related to chemical fertilizers?
Ans: Environmental Hazards Related To Chemical Fertilizers:
An environmental hazard is a condition, which has the potential to threat natural environment or adversely affect people's health, including pollution and natural disasters. The farmers apply fertilizer for better growth of their crops, but on the other side these fertilizers pollute water and soil as well.

1. Soil nutrient holding capacity:
   The massive quantities of inorganic fertilizers affect the soil nutrient holding capacity.
2. Eutrophication:
   The high solubility of fertilizers also degrade ecosystem through eutrophication (means an increase in chemical nutrients typically compounds containing nitrogen or phosphorus in an ecosystem).
3. Emission of greenhouse gas:
   Storage and application of some nitrogen fertilizers may cause emission of greenhouse gas, e.g nitrous oxide.
4. Soil acidity:
   Ammonia gas (NH₃) may be emitted from applied inorganic fertilizers. This extra ammonia can also increase soil acidity.
5. Pest problems:
   Excessive nitrogen fertilizers can lead to pest problem by increasing their reproduction rate.
6. Nutrient balance:
   It is recommended that nutrient content of the soil and nutrient requirement of crop should be carefully balanced with application of inorganic fertilizers. It is critical to apply no more than it is needed; any excess in nutrient will definitely develop pollution of any kind.

Q.12: What are componenets of human food? Name them and write down function of each food type in body.
Ans: Components of Human Food OR Classes OF Nutrients:
Holozoic nutrition is the type of heterotrophic nutrition.Heterotrophic organisms have to acquire and take in all the organic substances they need to survive. There are seven major classes of nutrients:

1.  Carbohydrates
2. Protein
3. Fats
4. Minerals
5. Fiber
6. Vitamins
7. Water.

FUNCTIONS OF FOOD COMPONENTS:

Q.13: Write down role, functions and sources of carbohydrates, proteins and fats.
Ans: CARBOHYDRATES:
Carbohydrates are necessary for our body specially glucose, which is primary source of energy. They are generally divided in two categories:

1. Simple Carbohydrates
2. Complex Carbohydrates

Simple carbohydrates such as sucrose, which digest quickly.
Complex carbohydrates such as starch etc, which digest slowly.

Function:

1. Sugar For energy
2.  Starch For energy
3. Fibre Prevents constipation

Sources of carbohydrates:
Simple carbohydrates include fruits, sugars and processed grains, such as white rice or flour.
Complex carbohydrates are find in green or starchy vegetables, potatoes, whole grains, beans and lentils.
The most common and abundant forms are sugars, fibers, and starches.

PROTEINS:
Proteins consist of units called amino acids, attach together in complex formations. Proteins are complex molecules, the body takes longer to break them down. As a result, they are much slower and long lasting source of energy than carbohydrates.
Essential Amino Acids
There are 20 amino acids. The body synthesizes some of them from components within the body, but it cannot synthesize 9 of the amino acids called essential amino acids. They must be consumed in the diet.

Funtion Of Protein:
For growth and repair of cells.
The body needs protein to maintain and replace tissues and their function. Protein is not usually used for energy. However, if the body is not getting enough calories from other nutrients or from the fat stored in thebody, protein is used for energy.

Sources Of Proteins:
Meat, poultry, fish, eggs, dairy foods, fruits, vegetables, grains, nuts, and seeds.

FATS:
Fats are complex molecules composed of fatty acids and glycerol.

Function:
For energy and insulation
The body needs fats for growth and energy. It also uses them to synthesize hormones and other substances needed for the body's activities. Fats are the slowest source of energy but the most energy-efficient form of food. The body deposits excess fat in the abdomen (omental fat) and under the skin (sub cutaneous fat) to use when it needs more energy. The body may also deposit excess fat in blood vessels and within organs, where it can block blood flow and damage organs, often causing serious disorders.

Sources:
Some typical sources of saturated fats include:

• Fatty cuts of beef and lamb.
• Poultry skin
• High fat dairy foods (whole milk, butter, cheese, sour cream, ice cream).
• Tropical oils (coconut oil, palm oil, cocoa butter)

Q.14: Define Calories?
Ans: Calories:
The energy obtained from carbohydrates, proteins, and fats is measured in units called calories.

Q.15: Write a note on Vitamins? OR Define vitamins and its types? Also write down effects of vitamins deficiency?
Ans: VITAMINS:
A vitamin is an organic molecule (or related set of molecules), an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. They are for maintaining normal health and development. Lack of vitamins can cause several diseases.
Source Of Vitamins:
Milk, Fruits and Vegetables.

TYPES OF VITAMINS:
They are divided into two types:

1. Fat Soluble Vitamins:
   Vitamin which can soluble in organic solvent are called Fat-soluble vitamins (A, D, E and K) are less excreted from the body as compared to water-soluble vitamins.
2. Water Soluble Vitamins:
   Vitamin which are soluble in H₂O. These are vitamins B and C. Cooking or heating destroys the water soluble vitamins more readily than the fat-soluble vitamins.

Functions, chemical names and deficiencies of important vitamins

Vitamin generic name	Deficiency diseases
Vitamin K	Bleeding disorder
Vitamin D	Rickets and osteomalacia
Vitamin C	Scurvey
Vitamin B	Beriberi
Vitamin A	Night blindness, eye-infection, rough skin, respiratory infections

Q.15: What are minerals?
Ans: MINERALS:
Definition: A class of naturally occurring solid inorganic substances with a characteristic crystalline form are known as minerals.
Essential minerals: include calcium, iron, zinc, iodine and chromium.
Benefits: Minerals are vital for proper human health.
Deficiencies can result in serious health conditions such as brittle bones and poor blood oxygenation.
Source: Minerals are found in a variety of foods including dairy and meat products.

Q.16: Write down metabolic functions, sources and deficiency symptoms of calcium and Iron? OR Write down note on Calcium and Iron
Ans: CALCIUM:
Metabolic function of Calcium:
Calcium metabolism refers to the movements and regulation of calcium ions (Ca⁺²) in and out of various body compartments. Good calcium nutrition, along with low salt and high potassium intake, prevents from hypertension and kidney stones.

Sources of calcium include:

• Milk, cheese and other dairy foods
• Green leafy vegetables
• Soya beans
• Nuts
• Bread
• Fish

Deficiency symptoms of calcium:

• Fainting
• Heart failure
• Numbness and tingling sensations around the mouth or in the fingers and toes.
• Difficulty swallowing
• Voice changes due to spasm of the larynx
• Chest pains
• Wheezing
• Muscle cramps, particularly in the back and legs; may progress to muscle spasm (tetany)

IRON:
Metabolic function of iron:
Iron plays a major role in oxygen transport and storage. It is a component of haemoglobin in red blood cells and myoglobin in muscle cells.

Sources Of Iron:
Some of the best plant and animal sources of iron:

• Beans and lentils
• Tofu
• Dark green leafy vegetables such as spinach

Deficiency symptoms of iron:

• Extreme fatigue
• Pale skin
• Chest pain, fast heart beat or shortness of breath
• Brittle nails
• Weakness
• Headache, dizziness
• Inflammation or soreness of tongue
• Poor appetite in infants

Q.17: Write down metabolic functions of water and dietary fibres?
Ans: WATER:
Metabolic function of Water:

• Water is the medium for various enzymatic and chemical reactions in the body.
• It moves nutrients, hormones, antibodies and oxygen through the blood stream and lymphatic system.
• Water maintains the body temperature through evaporation as in sweating.

Deficiency Of Water:

• Severe dehydration causes cardio-vascular problems.

Metabolic function of Dietary Fibres:

• Dietary fiber is the edible part of plants, or similar carbohydrates, that can't be digested and absorbed in the small intestine.
• Fibre plays very important role to prevent from constipation.
• Soluble fibre helps in lowering the blood cholesterol and blood sugar level.

Q.18: Define and describe the balance diet related to age, sex and activity? Also draw the healthy eating pyramid.
Ans: BALANCE DIET:
A diet which contains all of the nutrients like carbohydrates, fats, proteins, vitamins and minerals in proper proportion according to the requirement of the body is called balanced diet.

A BALANCED DIET IS RELATED TO AGE, SEX AND ACTIVITY:
Different factors affect the nutritional requirement during the periods of body growth &anm; development. Energy requirements change through life and depend on many factors, such as: Age; Sex and Level of activity.
Related To Age
The key stages in life include:
Childhood:

• The energy requirements of children increase rapidly because they grow quickly and become more active
• Young children do not have large stomachs to cope with big meals. Therefore, to achieve the relatively high energy intake for their age, foods should be eaten as part of small and frequent meals.

Adolescence:

• It is a period of rapid growth and development and is when puberty occurs.
• The demand for energy and most nutrients are relatively high. Boys need more protein and energy than girls for growth.
• Children should be encouraged to remain a healthy weight with respect to their height.

Adulthood:

1. A good supply of protein, calcium, iron, vitamin A and D, as part of a healthy, balanced diet, are important.
2. Calcium is needed for healthy tooth development, and together with vitamin D, can help develop strong bones.

Related To Sex And Level Of Activity:

• Men are more active than women so they need more energy than women of same age group.
• Muscular tissues are more in men, their body size is larger, and therefore, boys of growing age need more body building nutrients (Proteins, Calcium) as compared to girls of same age.

Q.19: Define malnutrition and its type?
Ans: MALNUTRITION:
Problems related to nutrition are grouped as malnutrition. The malnutrition is a condition that occurs when a body does not get enough nutrients. Malnutrition results from a poor diet or a lack of food. It happens when the intake of nutrients or energy is too high, too low, or poorly balanced. Consuming less than 2100 calories a day, one is considered to be under-nourished and suffering from hunger.

TYPES OF MALNUTRITION:
There are two types of malnutrition:

1. Chronic malnutrition
2. Acute malnutrition

1. Chronic Malnutrition:
Characterized by delayed growth in the children.

2. Acute Malnutrition:
Characterized by insufficient weight in relation to the child's height (emaciation). Acute malnutrition can be moderate or severe according to the child's weight.
Under-nourishment and malnutrition have serious consequences for the health of the younger children. Worldwide,

Characteristics / Cause Of  Malnutrition
Three nutrient deficiencies are of particular concern:

• Vitamin A deficiency is the world's most common cause of preventable child blindness and vision impairment.
• Iron deficiency is associated with decreased cognitive abilities and resistance to disease.
• Iodine deficiency is the major preventable cause of mental retardation worldwide.

Q.20: What do you know about malnutrition problems in Pakistan?
Ans: Malnutrition Problems In Pakistan:
Malnutrition is one of the most prevalent public health problems in Pakistan. It is one of the major underlying factors for high infant and under 5 mortality rate in Pakistan. Poverty, lack of education, poor environmental hygiene and food fads are some of the reasons for its high prevalence in Pakistan.

Q.21: What do you mean by protein energy malnutrition (PEM)? Describe diseases caused due to protein energy malnutrition?
Ans: Protein Energy Malnutrition (PEM):
Protein deficiency disorders: is also called Protein energy malnutrition (PEM). It refers to inadequate availability or absorption of energy and proteins in the body. It is the leading cause of death in children in developing countries.

Protein Deficiency Diseases:
PEM may lead to diseases such as;
(a) Kwashiorkor:
 Kwashiorkor is a severe form of malnutrition, caused by a deficiency in dietary protein. The extreme lack of protein causes an osmotic imbalance in the gastro-intestinal system causing swelling of the gut diagnosed as an edema or retention of water.

(b) Marasmus:
Marasmus is a form of severe malnutrition characterized by energy deficiency. It can occur in anyone with severe malnutrition but usually occurs in children. A child with marasmus looks emaciated. Body weight is reduced to less than 62% of the normal (expected) body weight for the age.

Q.22: Describe Mineral deficiency diseases?
Ans: Mineral Deficiency Disease:
Diseases resulting from deficiency of a mineral are relatively rare among humans some are given below:
1. Goiter:
Symptoms: Goiter is a condition in which thyroid gland becomes enlarged and it results in swelling in neck.
Cause: Goiter is caused by an insufficient amount of “Iodine” in diet. Iodine is used by thyroid gland to produce hormones that control the body's normal functioning and growth.

2. Anemia (most common of all mineral deficiency diseases):
The term anemia literally means “a lack of blood”.
Cause: The condition is caused when number of red blood cells reduced to a level lower than normal. Haemoglobin molecule contains four atom of iron. If body fails to receive sufficient amount of iron, an adequate number of haemoglobin will not be formed. So, there are not enough functioning red blood cells.
Symptoms: A person becomes weak and there is shortage of oxygen supply to body's cells.

Q.23: What do you know about over intake of nutrients:
Ans: Over Intake Of Nutrients:
It is a form of malnutrition in which more nutrients are taken than the amount required for normal growth, development and metabolism.
Cause: The effects of over-intake of nutrients are usually intensified when there is reduction in daily physical activity (decline in energy expenditure).
Symptoms: High intake of carbohydrates and fats leads to obesity, diabetes and cardiovascular problems. Similarly, high dose of vitamin A causes loss of appetite and liver problems. Excess dose of vitamin D can lead to deposition of calcium in various tissues.

Q.24: Describe the effects of malnutrition in human?
Ans: The Effects Of Malnutrition:
Malnutrition hurts people both mentally and physically. The more malnourished a person is; the more nutrients the person is missing, the more likely person will experience health issues. Some of them are given below:
1. Starvation:
It is a severe deficiency in caloric energy intake. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, death.

2. Heart Diseases:
The term "heart disease" is often used interchangeably with the term "cardiovascular disease." Cardiovascular disease generally refers to conditions that involve narrowed or blocked blood vessels that can lead to a heart attack, chest pain (angina) or stroke. Heart problems occur in those people who take unbalanced diet. Fatty foods increase blood cholesterol level. It obstructs the blood vessels leading to heart diseases.

3. Constipation:
People do not schedule their meals. This irregularity cause many health problems like constipation. It can be well defined, a condition in which there is difficulty in emptying the bowels, usually associated with hardened faeces.

4. Obesity:
It is a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health. Obesity is most commonly caused by a combination of excessive food intake, lack of physical activity, and genetic susceptibility. Obesity is known as mother disease and may lead to heart problems, hypertension, diabetes etc.

Q.25: Describe the social problems related to malnutritions?
Ans: Social Problems Related To Malnutrition:
Chronic malnutrition disables and even kills its victims. The World Health Organization (WHO) believed that malnutrition is a causative factor in nearly half of the 10.4 million deaths among children under age five in developing countries. An adequate amount of food or dietary energy supply is necessary to enjoy a healthful and productive life. Malnutrition is not a simple problem with a simple solution. It results from the complex interplay of social and biomedical factors.
1. Food Insecurity:
Food insufficiency refers to insufficient food supplies to meet minimum daily diet requirement.
Several countries in Africa and parts of other developing countries do not produce enough food to keep up with the food needs and increased population. Not only they do not produce sufficient food supplies to meet their own needs, but they are economically unable to purchase available food from the exporting countries, which has led to food insecurity in poor countries; as a result, millions are hungry and malnourished.
Besides these problems drought (lack of water) and flood (over flow of water) play terrible role in decreasing crop yields.

2. Poverty:
For various reasons people in developing countries are increasingly unable to produce enough food to meet their own needs.
To meet the on going demand for food, food-deficit countries (those unable to produce sufficient food to meet their needs) must import additional food and make it available to people. Even if there is an abundance of food, some people may not have access to it, because more and more, access to food in developing countries is determined by household income.

3. Inequality:
Because of a cultural preference for men over women in many developing countries, many women risk malnutrition throughout their lives.
The risk for malnutrition in girls begins at an early age. Although nutritional needs are the same for boys and girls in the first 10 years of life, boys often get more food than girls do.

4. Risk Of Infection:
The normal human body has the capacity to resist foreign organisms or toxins through the immune system, but the immune system ceases to function properly when the body is malnourished. When the immune system (the general process of body) is compromised by malnutrition, the skin's ability to resist the invasion of organisms, the acid secretion produced by the stomach to resist foreign agents, or the production of chemical compounds in the blood that destroy toxins can be affected adversely.

Q.26: Draw graphic representation to show the:

1. Role of society regarding malnutrition
2. To overcome social and economic problems related to malnutrition

Ans (i) Role of society regarding malnutrition

ii) To overcome social and economic problems related to malnutrition

Q.27: Define the terms digestion and egestion? Why digestion process is important?
Ans: Digestions:
Digestion is the process in which large and non-diffusible molecules of food are converted into smaller and diffusible molecules that can cross the membranes by the action of enzymes.

Egestion:
After absorption of the digestible material, indigestible material expelled out of the body through the process of egestion.

Importance Of Digestion Process:
Digestion is important for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. Food and drinks must be changed into smaller molecules of nutrients before the blood absorbs them and carries them to cells throughout the body.

Q.28: Name and define the steps involved in digestion?
Ans: STEPS INVOLVED IN DIGESTION:
The digestion consists of following steps:

• Ingestion: Intake of food.
• Propulsion: Peristalsis-alternate waves of muscular contraction and relaxation in the primary digestive organs. The end result is to squeeze food from one part of the system to the next.
• Mechanical Digestion: Physical preparation of food for digestion.
• Segmentation: Mixing of food in the intestines with digestive juices.
• Chemical Digestion: Carbohydrates, Fat, and Proteins are broken down by enzymes.
• Absorption: Transfer of the digested portion of food into the blood from the digestive canal.
• Egestion (Defecation): Removal/elimination of the waste products from the body.

Q.29: Give short account of digestive system of human and draw labelled diagram also.
Ans: HUMAN DIGESTIVE SYSTEM:
The digestive system is made up of the:

• Alimentary canal and
• Digestive Glands

Alimentary Canal Of Human:

• The alimentary canal (also called the digestive tract) is the long tube of organs. It including the oral cavity,  esophagus, stomach, and intestines.
• It runs from the mouth to the anus.
• An adult's digestive tract is about 30 feet (about 9 meters) long.

Digestive Glands:

• The other abdominal organs  that play a part in digestion, such as the liver and pancreas.

Q.30: Describe human digestive system?
Ans: HUMAN DIGESTIVE SYSTEM:
The digestive system is made up of the:

• Alimentary canal and
• Digestive Glands

Alimentary Canal Of Human:

• The alimentary canal (also called the digestive tract) is the long tube of organs. It including the esophagus, stomach, and intestines.
• It runs from the mouth to the anus.
• An adult's digestive tract is about 30 feet (about 9 meters) long.

Parts Of Alimentary Canal:
(i) Oral Cavity:
It is the first part of alimentary canal. It is equipped with four kinds of teeth. The teeth grind the food. Oral cavity or mouth also has three pairs of salivary glands which produced saliva.
Functions:
Saliva contains an enzymes Ptyalin which converts starch into maltose (sugar).

(ii) Pharynx:
The pharynx, a passageway for food and air, is about 5 inches (12.7 centimeters) long. A flexible flap of tissue called the epiglottis reflexively closes over the windpipe when we swallow to prevent choking.
Functions:
From the throat, bolus travels down a muscular tube in the chest called the esophagus.

(iii) Oesophagus:
It is a long muscular tube which opens into stomach. At the end of the oesophagus, a muscular ring called a sphincter allow food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the oesophagus.
Functions:
This tube brings food into the stomach.

(iv) Stomach:
It is a large bag like, thick walled organ which stores food. Its walls contain gastric glands which secrete gastric juice. Gastric juice contains HCI and enzymes called pepsin and renin.
Functions:
Pepsin breaks down proteins into peptones, renin curdles milk in infant and HCI kills germs.

(v) Small Intestine:
The small intestine is made up of three parts:

• duodenum
• jejunum
• ileum

(a) The Duodenum:
It is the first part of small intestine which is about 25 cm (10 inches) long. It is C-shaped part of small intestine.
Functions:
The duodenum receives chyme from the stomach and it is a part of alimentary canal where most of the digestive process occurs. It receives pancreatic juice and bile from the pancreas and liver respectively.

(b) The Jejunum:
It is the coiled shaped mid-section of small intestine.

(c) The Ileum: It is the final section of small intestine which leads into the large intestine. Its inner surface bears numerous finger-like projections called villi, which has numerous blood capillaries and a lymph vessel.
Functions:
Ileum absorbs completely digested food.

(vi) Large Intestine:
It consists of three parts:

• Colon,
• Caecum and
• Rectum.

(a) Colon:
It consists of three portions, an ascending, a transverse and a descending portion.
Function:
It reabsorbs water and salts from the undigested food.

(b) Caecum:
At the junction of the small and large intestine is a sac like structure the caecum and has a small finger like projection called appendix.
Function:
It has no specific function is food digestion; but in human the appendix may get infected with germs -and foreign bodies. This causes severe inflammation and pain in the appendix and leads to appendicitis.

(c) Rectum:
It is the last part of large intestine. It opens to the outside by anus.
Function:
It stores undigested food.

DIGESTIVE GLANDS:
Digestive Glands:
The other abdominal organs  that play a part in digestion, such as the liver and pancreas.

Liver and its Functions:
It is the largest gland of human digestive system.

• The liver produces bile, which helps the body to digest and absorb fat. Bile is stored in the gallbladder until is needed. Bile travels through special channel (bile duct) directly into the small intestine.
• It also makes a substance that neutralizes stomach acid.
• The liver also plays a major role in the handling and processing of duct nutrients, which are carried to the liver in the blood from the small intestine. 
• The Liver is a metabolically active organ responsible for many vital life functions.

Pancreas and its function:
Pancreas is second digestive gland. Pancreatic juice is a liquid secreted by the pancreas, which contains a variety of enzymes, including:

• Protease like Trypsinogen: converts protein (polypeptides) into amino acid.
• Pancreatic Lipase: converts lipids (fats) into fatty acids and glycerol.
• Amylase: convert carbohydrates into glucose (simple sugar).

Q.31: What is oral cavity? Describe its function.
Ans: Oral Cavity:
Oral cavity is the space behind mouth in-between upper and lower jaw. Digestion begins in the oral cavity, before food reaches the stomach.
When we see, smell, taste, or even imagine a tasty snack, our three pairs of salivary glands, which are located under the tongue and near the lower jaw, begin producing saliva. This flow of saliva is coordinated with a brain reflex that triggered when we sense food or think about eating. In response to this sensory stimulation, the brain sends impulses through the nerves that control the salivary glands, telling them to prepare for a meal.

Function Of Oral Cavity:
Oral cavity has many important functions:

• Food Selection:
  When food enters the oral cavity it is tasted and felt. Here food is selected or rejected due to the taste, hard object or dirt. Smell and vision also help in selection.
  
  
• Grinding of food:
  The second function of oral cavity is the grinding of food by teeth. It is known as chewing or mastication. It is useful because oesophagus can pass only small pieces through it as well as enzymes cannot act on large pieces of food.
  
  
• Lubrication of food:
  The third function of the oral cavity is lubrication of food by mixing saliva secreted by saliva. It has two main functions.
  (i) Adds water and mucus to the food.
  (ii) Partial digestion of starch by saliva which contains an enzyme salivary amylase.
  
  
• Chemical digestion:
  Saliva contains an enzyme salivary amylase which helps in the digestion of starch partially. Than the pieces of food are rolled up by the tongue into small, slippery, spherical mass called bolus.
  
  
• Swallowing of the bolus:
  Swallowing is accomplished by muscle movements by the tongue and mouth, food moves into the throat, or pharynx.

Q.32: Describe the functions of salivary glands?
Ans: SALIVARY GLANDS:
When we see, smell, taste, or even imagine a tasty snack, our three pairs of salivary glands, which are located under the tongue and near the lower jaw, begin producing saliva. This flow of saliva is coordinated with a brain reflex that triggered when we sense food or think about eating. In response to this sensory stimulation, the brain sends impulses through the nerves that control the salivary glands, telling them to prepare for a meal.
Function Of Salivary Gland:
The main function of the salivary gland is lubrication of food by mixing saliva secreted by saliva. It has two main functions.

• Adds water and mucus to the food.
• Partial digestion of starch by saliva which contains an enzyme salivary amylase.

Q.33: Describe the function of pharynx and oesophagus?
Ans: Functions of Pharynx:
The pharynx, a passageway for food and air, is about 5 inches (12.7 centimeters) long. A flexible flap of tissue called the epiglottis reflexively closes over the windpipe when we swallow to prevent choking.

Functions of Oesophagus:
From the throat, bolus travels down a muscular tube in the chest called the esophagus. Waves of rhythmic movements of muscle contractions and relaxation called peristalsis force down food through the oesophagus to the stomach. At the end of the oesophagus, a muscular ring called a sphincter allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the oesophagus.

Q.34: What is peristalsis?
Ans: PERISTALSIS:
Waves of rhythmic movements of muscle contractions and relaxation called peristalsis force down food through the oesophagus to the stomach. A person normally isn't aware of the movements of the esophagus, stomach, and intestine that take place as food passes through the digestive tract.

Q.35: Briefly describe the structure and function of stomach? And draw labelled diagram also.
Ans: Structure Of Stomach:
Stomach is j-shaped thick walled, expandable bag, located in the left of abdomen just beneath the diaphragm. The stomach has three regions:

• Cardiac, just after the oesophagus,
• Fundus, the largest part of stomach and
• Pyloric, part located at the other end of stomach and opens into small intestine.

Stomach has two sphincters (opening which are guarded by muscles).

• The cardiac sphincter is between stomach and oesophagus.
• Pyloric sphincter is between stomach and small intestine.

Function Of Stomach:

• Break Food into small pieces: The stomach muscles churn and mix the food with acids and enzymes, breaking it into much smaller, digestible pieces. An acidic environment is needed for the digestion that takes place in the stomach.
• Gastric Juice: Glands in the stomach lining produce about 3 quarts (2.8 liters) of these digestive juices each day. When food enters into the stomach the gastric juice is secreted by gastric glands found in the stomach wall. It is composed of:
  * Mucous,
  * Hydrochloric acid and
  * Protein digesting enzyme pepsinogen.
  Hydrochloric acid converts the inactive enzyme pepsinogen into active form called pepsin. HCl also kills micro-organisms present in food.
• Mucous Protection: Stomach is protected against the action of acid by mucus.
• Enzyme Pepsinogen (Pepsin): Pepsin partially digests the protein portion of the food into polypeptides and shorter peptide chains.
• Churning Of Food: In stomach food is further broken apart through a process called churning. The walls of stomach contract and relax and these movements help in mixing of the gastric juice and food. The churning action also produces heat which helps to melt the lipid contents of the food.
• Chyme: By the time food is ready to leave the stomach, it has been processed into a thick paste like liquid called chyme. The pylorus keeps chyme in the stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted down into the small intestine, where digestion of food continues.

Q.35: Describe the structure and function of small intestine?
Ans: STRUCTURE OF SMALL INTESTINE:
The small intestine is made up of three parts:

1. The duodenum, about 25 cm (10 inches) long, C-shaped first part.
2. The jejunum, the coiled mid section.
3. The ileum, the final section that leads into the large intestine.

Function Of Duodenum:
The duodenum receives chyme from the stomach and it is a part of alimentary canal where most of the digestive process occurs. Ducts that enter into the duodenum deliver pancreatic juice and bile from the pancreas and liver, respectively.

• Bile salts have detergent action on particles of dietary fat which causes fat globules to break down or be emulsified into minute, microscopic droplets.
• Pancreatic juice is a liquid secreted by the pancreas, which contains a variety of enzymes, including:
  * Protease like trypsinogen: Coverts proteins (polypeptides) into amino acid.
  * Pancreatic lipase: Converts fats into fatty acid and glycerol.
  * Amylase: Converts carbohydrates into glucose (simple sugar).
• Intestinal juices produced from the small intestine contain enzymes and pancreatic juice break down all four groups of molecules found in food (polysaccharides, proteins, fats, and nucleic acids) into their component molecules.

Function Of Ileum (Absorption):
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi (singular, villus). Each villus is connected and richly supplied with blood capillaries and lymphatic vessels, i.e lacteal. The walls of villus are made up of only one layer of cells, in thickness. The villi are the vehicles through which nutrients can be absorbed into the body. They increase the surface area over which absorption and digestion occur. These specialized cells help absorbed materials (simple sugars, amino acids and nucleosides) cross the intestinal lining into the bloodstream.
From the small intestine,the undigested food travels to the large intestine through a muscular ring, that prevents food from returning to the small intestine.

Role Of Macromolecues

Polymers	Monomers	Roles
Complex Carbohydrates (i.e. starch)	Glucose and other simple sugars	Broken apart to get energy to make ATP.
Proteins	Amino acids	Used to make our own enzymes and other body proteins.
Lipids (Fats, waxes, oils, and steroids)	Fatty acid chains, glycerine (except steroids)	Used for cellular energy and energy storage; used to make cell membranes, steroid hormones.

Q.36: Describe the action of bile salt, pancreatic juice and intestinal juice.
Ans: Bile salts:
have detergent action on particles of dietary fat which causes fat globules to break down or be emulsified into minute, microscopic droplets.

Pancreatic juice:
is a liquid secreted by the pancreas, which contains a variety of enzymes, including:

• Protease like trypsinogen: Coverts proteins (polypeptides) into amino acid.
• Pancreatic lipase: Converts fats into fatty acid and glycerol.
• Amylase: Converts carbohydrates into glucose (simple sugar).

Intestinal juices:
produced from the small intestine contain enzymes and pancreatic juice break down all four groups of molecules found in food (polysaccharides, proteins, fats, and nucleic acids) into their component molecules.

Q.37: What are villi? Explain the role of villi in increasing the absorptive surface of intestine. Also draw labelled diagram of L.S of Villi?
Ans: Villi (Sinular: Villus):
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi (singular, villus). Each villus is connected and richly supplied with blood capillaries and lymphatic vessels, i.e lacteal. The walls of villus are made up of only one layer of cells, in thickness. The villi are the vehicles through which nutrients can be absorbed into the body.
They increase the surface area over which absorption and digestion occur. These specialized cells help absorbed materials cross the intestinal lining into the bloodstream.
The bloodstream carries simple sugars, amino acids and nucleosides to the liver via hepatic portal vein for storage or further chemical changes. From liver, the required food molecules go towards the heart via the hepatic vein. The lymphatic system, a network of vessels that carry white blood cells and a fluid called lymph throughout the body, absorbs glycerol, fatty acids and vitamins.

Q.38: Describe yhe structure and function of large intestine?
Ans: Structure Of Large Intestine:
From the small intestine, food that has not been digested (and some water) travels to the large intestine through a muscular ring, that prevents food from returning to the small intestine. By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine is made up of three parts:

1. Caecum
2. Colon
3. Rectum

1. The Caecum:
is a pouch at the beginning of the large intestine that joins the small intestine to the large intestine. This transition area expands in diameter, allowing food to travel from the small intestine to the large. The appendix, a small, hollow, finger-like pouch, hangs at the end of the caecum. It is no longer appears to be useful to the digestive process.

2. The Colon:
extends from the caecum up the right side of the abdomen, across the upper abdomen, and then down the left side of the abdomen, finally connecting to the rectum. The colon has three parts, the ascending colon, transverse colon and descending colon.

3. Rectum:
is the last part of large intestine. It opens to the outside by anus.

Function Of Large Intestine:

• The large intestine's main function is to remove water from the undigested matter and form solid waste that can be egested.
• The ascending colon and transverse colon absorb fluids and salts, and the descending colon holds the resulting waste (faeces). Faeces mainly consist of undigested material, large number of bacteria, sloughed off gastrointestinal cells, bile pigments and water. Bacteria in the colon help to digest the remaining food products.
• The rectum is where faeces are stored until they leave the digestive system through the anus as a bowel movement.

Q.39:Write a short account on liver and its function?
Ans: Liver:
It is the largest digestive gland in human body. Liver lies beneath the diaphragm, on the right side of abdomen. It is multi lobed and reddish brown in color.
Function Of Liver:

• Produce Bile: Which helps the body to digest and absorb fat.
  Bile is stored in the gallbladder until it is needed. Bile travels through special channel (bile duct) directly into the small intestine.
• Neutralize Stomach Acid: It also makes a substance that neutralizes stomach acid.
• Store And Convert Nutrients: The liver also plays a major role in the handling and processing of nutrients, which are carried to the liver in the blood from the small intestine.
• Metabolic Functions: The liver is a metabolically active organ responsible for many vital life functions.

Q.40: Explain the disorder of gut?
Ans: DISORDERS OF GUT
1. Diarrhea:
Symptoms:

• It is a condition in which the sufferer has frequent watery, loose bowel movements due to fast peristaltic movement.
• This condition may be accompanied by painful abdominal cramps, nausea, fever and generalized weakness.

Cause:

• It occurs when required water is not absorbed in blood from colon.
• The main cause of diarrhea includes lack of adequate safe water, virus and bacteria.
• In malnourished individuals, diarrhoea leads to severe dehydration and can be life threatening.

Treatment:

• To control diarrhea consume adequate amounts of water to replace loss, preferably mixed with essential salts and some amount of nutrients.

2. Constipation:
Symptoms:

• Constipation is a condition, where a person experiences hard faeces that are difficult to eliminate.

Cause:

• The main causes of constipation are hardening of faeces due to excessive absorption of water through colon, insufficient intake of dietary fibre, dehydration, use of medicine (e.g. those containing iron, calcium and aluminum) and tumors in rectum or anus.

Treatment:

• The treatment of constipation are change in diet and exercise habits, use of laxative (e.g. paraffin) may be in some cases. To prevent constipation is easier than treatment.

3. Ulcer (peptic ulcer):
Symptoms:

• It is a sore in gut lining and can be different organs such as; ulcer of stomach is called “gastric ulcer”, Ulcer of duodenum is called “duodenal ulcer”, ulcer of oesophagus is called “esophageal ulcer” and breakdown of tissues by acidic gastric juice.
• Few of the signs are as under; abdominal burning after meals, abdominal pain, rush of saliva after an episode of regurgitation, nausea and loss of appetite and weight.

Cause:
It can be due to the long term use of antiinflammatory medicine (e.g. aspirin), smoking, drinking coffee, colas and eating spicy food.
Treatment:

• Ulcer can be treated with medicine, containing (alkaline composition) and avoiding spicy food.