Revolutionize Your Biology | Long/Comprehensive answers on Chapter 8 "Nutrition"

Get Straight A's in Biology Class 9 | Mastering "Nutrition and Digestion" with Our Comprehensive Notes for BISE and Federal Board Exams and Tests

    Are you a Grade IX level student preparing for the BISE or Federal Board Examination, or an aspiring candidate for entrance tests like ETEA, MDCAT, NEET, NTS, or others? If so, you know how crucial it is to have comprehensive and well-organized notes for your biology exams. Biology is a vast subject that covers a wide range of topics, from the smallest organisms to the largest ecosystems. In this article, we will provide you with detailed and extensive notes on some of the most critical topics in the Nutrition Chapter, including mineral nutrition in plants, organic and inorganic fertilizers and their advantages and disadvantages, carbohydrates, proteins, fats, their sources and functions, malnutrition and its various forms, and the human digestive system and its components. With these notes, you can prepare thoroughly for your exams and increase your chances of success. So, let's dive into the world of biology and take your first step towards acing your exams and entrance tests.

Biology Notes on Introduction to Nutrition and Digestive System
From the Notes Library of H.E.S (Health, Education, and Skills) 

Describe mineral nutrition in plants in detail.

Mineral nutrition in plants

An inorganic substance that is required by organisms in their food is called a mineral.                 

    All plants are autotrophs, which means that they can manufacture their own food. Along with the basic factors necessary for photosynthesis, plants need much nutrition. Plants are anchored in soil and soil is the storehouse of minerals. Plants take these nutrients from the soil. On the basis of the requirements of plants, minerals are classified into micronutrients and macronutrients as given in the table

Macronutrients
Carbon	CO2	Component of organic compounds
Oxygen	Co2 or O2	Component of organic compounds
Hydrogen	H2O	Component of organic compounds
Nitrogen	NO3 or NH4	·       Amino acid ·       Proteins ·       Nucleotides ·       Nucleic acids ·       Chlorophyll ·       Coenzymes
Potassium	K+	·       Enzymes ·       Amino acids ·       Protein synthesis ·       Activator of enzymes ·       Opening and closing of stomata
Calcium	Ca+2	·       Cofactor ·       Cell permeability
Phosphorous	H2PO4	·       Formation of ATP and ADP ·       Nucleic acid ·       Phosphorylation of sugars ·       Several essential enzymes ·       Phospholipids
Magnesium	Mg+2	·       Part of chlorophyll ·       Coenzyme A
Sulfur	SO4-2	·       Some amino acids and proteins ·       Coenzyme A
Micronutrients
Iron	Fe+2 or Fe+3	·       Chlorophyll synthesis ·       Cytochrome ·       Nitrogenase
Copper	Cu-3	Activator of certain enzymes
Manganese	Mn-2	Activator of certain enzymes
Sodium	Na+1	For osmotic and ionic balance
Molybdenum	Mo-2	Nitrogen fixation
Boron	B-3	Influence Ca+2 utilization
Minerals essential for some plants or Organisms
Cobalt	Co+2	Trace is required by nitrogen-fixing organisms.
Zinc	Zn+2	Activator of certain enzymes

Discuss the organic and inorganic fertilizers. Also, describe the advantages and disadvantages of each.

i. Organic fertilizers

Those fertilizers which are obtained from plant and animal sources are called organic fertilizers. 

    Organic fertilizers may be obtained either through naturally occurring fertilizers (such as manure, seaweed, sewage, etc.) or from naturally occurring minerals (such as sulfate of potash, limestone, and rock phosphate).

Advantages of organic fertilizers

• They improve the structure of the soil.
• They help to retain soil moisture.
• They release nitrogen slowly.
• They are less subjected to leaching i.e. washout.   

Disadvantages of organic fertilizers     

• They are not easily available.
• They take more time for breaking down.
• They are expensive and not affordable.
• They require a greater amount of labor.

ii. Inorganic fertilizers/ Nitrogen fertilizers

    Those fertilizers which are derived from inorganic compounds, such as ammonium nitrate, ammonium phosphate, potassium chloride, etc. are called inorganic fertilizers or nitrogen fertilizers. 

Advantages/ importance of inorganic fertilizers 

• They provide larger fruits, healthier roots, and more flowers.
• They encourage the growth of stems and leaves (because nitrogen facilitates protein and chlorophyll synthesis).
• They are not too much expensive.
• They are easy to use.

Disadvantages of inorganic fertilizers

• They cause leaching i.e. removal of materials by dissolving them away from solids.
• Due to higher solubility, an increase in chemical nutrients occurs, which is dangerous for the ecosystem.
• They increase soil acidity.
• Too much inorganic fertilizer is dangerous for plant growth as well as for soil fertility.

What are carbohydrates? Also briefly describe types of carbohydrates.  

Carbohydrates (Carbo=Carbon, Hydrate=water)

Hydrates of carbon (CH₂O) are called carbohydrates.                                      (OR)

The organic compounds that are mainly composed of carbon, hydrogen, and oxygen are called carbohydrates.                

    In most carbohydrates, the ratio of hydrogen atoms to oxygen atoms is 2:1. General formula of carbohydrates is C_n(H₂O)_n. where n=1,2,3…. For example, if n=6 then according to the general formula C_n(H₂O)_n, we will have C₆(H₂O)₆, or C₆H₁₂O₆ (which is the formula of Glucose).

Major sources of carbohydrates

i. Starch

    We obtain most of the carbohydrates in the form of starch. Our digestive system then turns this starch into glucose. Glucose is carried to each cell of the body through the circulatory system. Each cell uses it as a main source of energy (ATP). Excess amount of glucose is stored as glycogen in muscles and the liver. Glycogen storing capacity is limited, so unused glucose is converted to fat.

ii. Sucrose

    We also get some of our carbohydrates in the form of sucrose (the chemical name of table sugar). We put it in our tea or coffee.  

Amount of energy production by carbohydrates

    If one gram of carbohydrate is fully oxidized, it produces 17 kilojoules (kj) or 4 kilocalories (kcal) of energy.

Functions of carbohydrates

• They are the major source of energy.
• Starch is the main carbohydrate storage product in plants while glycogen is an animal starch.

Classification of carbohydrates

There are three types of carbohydrates i.e.

i. Monosaccharides (mono=one, saccharide=sugar): Formed from single monosaccharide. Examples: Glycerin (3-C), Glucose (6-C), Ribose (5-C), and Fructose (6-C), etc.

ii. Oligosaccharides (oligo=few, saccharides=sugar): Formed from 2-10 monosaccharides.  Examples: Maltose (Glucose+Glucose), Lactose (Glucose+Galactose), Sucrose (Glucose+Fructose), etc.

iii. Polysaccharides (poly=many, saccharide=sugar): Form from more than ten monosaccharides.     Examples: Cellulose, Starch, Glycogen, Chitin, etc.

Write a detailed note on proteins.         

Proteins (Greek: protos=first/supreme/prime importance)

An organic compound that is mainly composed of carbon, hydrogen, oxygen, nitrogen, and sometimes Sulphur is called protein.               

Amino Acids | the building blocks of proteins

An organic molecule that has one amino group (NH₂), one carboxyl group/ carboxylic acid (COOH), one hydrogen atom, and an alkyl group is called an amino acid.         

    Proteins are large complex molecules that are converted into amino acids by our digestive system. There are 20 different types of amino acids that are converted back into proteins in our body.

Amino acid deamination

    Excess amounts of the amino acid (units of protein) are de-aminated (removal of an amino group), which is excreted with urine.

Sources of Protein

1. Plant sources: Beans, pulses, cereals, and dry fruits.
2. Animal sources: Cheese, milk, poultry, fish, mutton, and beef.

Importance of proteins

• They are important source of energy.
• They are the structural and building material of cellulose membranes.
• Myosin and actin fibers play an important role in the contraction of muscles.
• Hemoglobin, present in red blood cells (RBC), helps in oxygen transport in our body
• Nails, hairs, and skin are also made up of proteins.

Amount of energy obtained per gram of protein

One gram of protein, when fully oxidized, produces 18 kj of energy.

What are fats? What are their sources and importance? 

Fats

    Fats are organic compounds that are made up of C, H and O. Fats belong to a group of substances called lipids. They occur in the form of a liquid or solid state. Fats provide fatty acids, which are not made by our bodies. Fats are stored in our body in fat cells (tissues) called adipose tissues.

Sources of fats:     Butter, ghee, cheese, milk, meat, egg, yolk, nuts, etc. are common sources of fats. 

Structure of fats

    The building blocks of fat molecules are fatty acid and glycerol.

• Fatty acid: It is a long hydrocarbon chain bounded by the carboxyl (COOH) group.
• Glycerol: It is a three-carbon alcohol, with each bearing a hydroxyl (OH) group.

Importance/ functions of fats

• They play a role in controlling inflammation (swelling, redness, pain & warmness).
• They act as heat insulators and lubricants.
• They also serve as the storage substance for the body’s extra calories.
• They also control blood clotting.
• They help in repairing damaged tissues.
• They are required for brain development.
• Fats help in the digestion and transport of vitamins A, D, E, and K (called fat-soluble vitamins) in the body.

Amount of energy obtained from one gram of fats

    One gram of fat, when fully oxidized, produces twice as much energy (36 kj) produced by the same amount of carbohydrates or proteins.

           Define malnutrition. Also, discuss its various forms.

Malnutrition

A term used to describe the intake of food, which is not enough in quantity and quality, is called malnutrition.                                                                                   

Taking a diet in which the required nutrients are either quantitatively too much more or too much less, than the required quantity, is called malnutrition.

Various forms of malnutrition

Various forms of malnutrition are

I. Protein-energy malnutrition (PEM)

Taking too low amount of proteins that affects normal functioning is called protein energy malnutrition

It leads to the following two main disorders i.e.

a. Marasmus

It is a pathologic form (patho = disease/suffering, logy = to study) associated with a nutritional, energy deficit, and infection (gastrointestinal, gastro = stomach, intestinal = intestine). It is common in children in developing countries.

Symptoms of marasmus: Dry skin, loss of skin folds, loss of adipose tissues from the normal areas of fat deposit, abnormal appetite, and 60% less body weight than normal are some of the main symptoms of a marasmus-affected child. 

b. Kwashiorkor 

    This form of malnutrition occurs due to a diet deficient in proteins. Actually, the term kwashiorkor means “the disease of the displaced child”. The deficiency symptoms include weight loss, stunted linear growth, and decreased muscle mass.

II. Mineral deficiency disease (MDD)

Mineral deficiency disease occurs when a person’s nutrient intake falls below recommended requirement. Nutritional deficiency leads to some diseases, such as

a. Anemia

It occurs when the body does not have enough red blood cells to transport oxygen from the lungs to the body cells. Simply by anemia, we mean lack of blood. The most common symptom of anemia is a constant feeling of fatigue.

Treatment of anemia: It can be treated by using a diet containing the proper amount of iron, folate, and vitamin B12.

b. Beri-Beri

In this disease nerves, the heart, as well as other muscles, become damaged. It occurs due to a deficiency of thiamin. It can be prevented by eating a diet rich in thiamin, such as meats, legumes, and wheat bread.

c. Osteoporosis

In this disease, the bones become porous and light. It is due to a deficiency of calcium, Vitamin D, and phosphorous in the diet. It can be treated by eating a diet that contains calcium. Vitamin D can also reduce the risk of developing osteoporosis.

d. Goiter

In this disease, the enlargement of the thyroid gland occurs. It occurs due to iodine deficiency in the diet. Iodine is used by the thyroid gland to produce hormones that control the body’s normal functioning and growth. A large swollen neck is the main symptom of goiter disease. It can be prevented by taking iodine salt.

III. Over-intake of nutrients (OIN)

Taking nutrients much more than the required amount is called over-intake of nutrients (OIN).

OIN can cause the following health problems

• Hypertension (high blood pressure).
• Liver disorders.
• Renal disorders (renal for kidney).
• Heart attack and then heart failure due to excess fat deposition in the coronary artery (arteriosclerosis).
• Cardio-vascular diseases (cardia = heart, vascular = vessels i.e. artery, vein and capillary).
• Diabetes (lack of insulin hormone in the pancreas).
• Dry itchy skin.
• Painful swelling of legs and hands.
• Vomiting.

Discuss the structure of the human digestive system in detail.  (OR)        
Discuss in detail the main components of the human digestive system. 

Structure of components of the digestive system of man

The human digestive system can be broadly divided into the following main parts, which are further subdivided and sub-sub divided i.e.

I. Alimentary canal

The human digestive system consists of a long tube called the alimentary canal or gastrointestinal tract (GIT) or digestive tract or alimentary tract or nourishment canal.

II.Digestive glands

Some parts of the alimentary canal are associated/ connected with special structures called digestive glands i.e. liver and pancreas.

Parts of the alimentary canal or GIT

The Alimentary canal is further divided into the following parts.

A. Oral cavity/ buccal cavity

This first part of the digestive system is responsible for the intake of food through the mouth. Lubrication and digestion start in the oral cavity. The oral cavity consists of

• Teeth: Teeth help in grinding food. There are four types of permanent teeth that are specialized for particular functions, such as
• Incisor teeth are adapted for cutting and biting.
• Canine teeth are adapted for tearing.
• Premolar and molar teeth are adapted for grinding and mastication of food.
• Tongue: The tongue helps in the selection of food through the sense of smell and taste. The tongue contains taste buds that help to taste food. Besides this, the tongue also helps in chewing and swallowing food.
• Salivary glands: There are three pairs of salivary glands in the mouth cavity. These glands secrete saliva. Saliva contains sodium bicarbonate (NaHCO₃) which stabilizes the pH of the body and it is also antiseptic. Saliva also contains carbohydrate-digesting enzymes (such as amylase or ptyalin and maltase) which digest starch and glycogen to disaccharide maltose. Maltase reduces maltose to glucose. Saliva also helps us to taste food. The food is now changed to form a bolus and is ready to be swallowed.

B. Pharynx and swallowing

    The oral cavity opens into the pharynx. Pharynx is the cavity behind the soft palate. The pharynx plays an important role in swallowing with the help of the tongue, cheeks, palate, etc. The downward movement of food from a buccal cavity is called swallowing. The beginning of swallowing is voluntary (within our control) but when the food reaches the back of the mouth cavity, it becomes automatic (called reflex action). The food is forced into the esophagus by peristalsis.

• Peristalsis

The alternate contraction and relaxation of the muscular wall of the digestive tract by which food is moved along the cavity of the alimentary canal is known as peristalsis. 

• Antiperistalsis

The reverse process of peristalsis is called antiperistalsis.

Antiperistalsis occurs due to irritation in the esophagus or stomach, so the process is reversed and may lead to vomiting.

C. Esophagus/ food pipe

It is a muscular tube that extends from the pharynx through the diaphragm into the stomach. It is about 10 inch or 25-cm long tube. It lies between the trachea and vertebral column. It passes the food into the stomach by peristalsis.

D. Stomach

The stomach is a sac-like, elastic, muscular j-shaped structure that performs physical and chemical digestion. It changes shape and size according to the position of the body and the amount of food inside it. The stomach is about 12 inches (30.5 cm) long and 6 inches (15.2 cm) wide organ. Its capacity is about 1 liter. The first part of the stomach is connected with the esophagus through the cardiac sphincter which prevents the backward movement of food. 

Structure of stomach wall

The stomach is composed of four main layers

• Mucosa: It is the innermost layer of the stomach that contains gastric glands. These glands produce gastric juice. Gastric juice consists of HCl, mucus, and pepsinogen. HCl helps in the sterilization of food (a method used for killing bacteria). Mucus protects the inside of the stomach as it is alkaline. Pepsinogen in the presence of HCl is activated to pepsin, which converts proteins into peptides. A hormone called “gastrin” controls the secretion of gastric juice. Food is now converted into an acidic chyme. The average time occupied in producing this change is two to four hours. The fluids pass on in 20 to 30 minutes.
• Sub-mucosa: It is the layers of loose connective tissue underlying the mucus membrane. 
• Muscularis: Sub-mucosa is surrounded by the muscularis, a layer of muscle that moves and mixes the stomach contents.
• Serosa: It is the outermost layer of the stomach. It is wrapping for the stomach.
• Pyloric Sphincter: The last part of the stomach into the duodenum (first part of the small intestine) is called the pyloric sphincter.

E. Small intestine

The stomach opens into the small intestine. The small intestine has a small diameter as compared to the large intestine. It is an elongated narrow and coiled tube. It is divided into the following three parts.

i. Duodenum: It is the first part of the small intestine, which is very important for the chemical breakdown of food. It is about 12 inches long and curved like “C”. it receives chyme from the stomach. The chyme in the duodenum meets the bile from the liver and pancreatic juice from the pancreas. Thus two important, which are associated with the duodenum, are

1. Liver as digestive gland

The liver is a large reddish-brown gland that acts as a metabolic factory, detoxification, and storage organ. The liver consists of many small lobes. The liver secretes bile which is a green alkaline liquid without any enzyme. It contains water, sodium-bi-carbonate, excess calcium, and breakdown products of hemoglobin.

Functions of bile

• Bile acts as an antiseptic that kills the germs and bacteria present in food.
• Bile neutralizes the acidity of chyme.
• It also helps in the emulsification of fats

The process whereby large globules of fats are broken down into smaller globules and made water soluble is called the emulsification of fats. 

2. Pancreas as digestive gland   

Pancreas is a long, narrow, leafy, and lobed gland lying below the stomach. It is about 7 inches long and 1.5 inches wide.

Pancreatic juice: Pancreas secretes pancreatic juice, which is slightly alkaline (pH = 8). It neutralizes the chyme and helps in the breakdown of protein, fats, and starch. It consists of the following three types of enzymes

• Trypsinogen: The inactive trypsinogen is converted into active trypsin by the duodenal enzyme, trypsin. Trypsin converts proteins into peptides and amino acids.
• Amylase/ amylopsin: The pancreatic amylase act on starch and converts it into a simple form (maltose).
• Lipase: Lipase act on emulsified fats and converts them into fatty acids and glycerol (building blocks of fats).

ii. Jejunum

It is the second part of the small intestine, which secretes intestine juice to perform the breaking of proteins, carbohydrates, and lipids. It is about 2.4 meters long. 

iii. Ileum

It is the third part of the small intestine in which chemical digestion is almost completed. It is about 2.6 meters long. It also secretes intestinal juice which acts on leftover undigested materials.

Absorption of digested food 

The passage of simple sugars, amino acids, fatty acids, glycerol, vitamins, minerals, and water into the circulatory system is called the absorption of food.  

• The internal surface of the small intestine has numerous finger-like projections called villi. Each villus has an outer layer of epithelium cells and contains blood vessels and small lymphatic vessels called lacteals.
• The villi contain thousands of microscopic projections called microvilli. Microvilli increase the surface area of the villus.
• Simple sugars, amino acids, vitamins, and minerals enter the blood capillaries in the villi. These capillaries join up to form the hepatic portal vein which carries the nutrients to the liver. Some to fatty acids and glycerol are absorbed along with simple sugar and amino acid.
• A major portion of fatty acid and glycerol are absorbed into lymph vessels or lacteals, which pour them into the bloodstream.

F. Large intestine 

It is part of the digestive system where the waste products from the food, that we eat, are collected and processed into feces. It is about 1.5 meters long and is composed of the following parts

i. Caecum: Caecum is the first part of the large intestine. It connects the small intestine with the colon. It is located on the right side of the lower abdomen. The material it obtains consists of undigested food fiber, water, some vitamins, minerals, and salts.     

ii. Appendix: It is a small, blind, and finger-like projection. It is a vestigial organ (functionless organ) in man, but sometimes it gets infected due to the trapping of food, causing a disease called appendicitis. Appendicitis needs surgical removal of the appendix, called an appendectomy.      

iii. Colon: It is the largest part of the large intestine, which contains mostly bacteria. It is an inverted U-shaped structure.

• Ascending colon: It starts from the right side of the caecum and goes upward towards the liver.
• Transverse colon: Transverse means across. This part of the colon extends across the abdomen from right to left. 
• Descending colon: This part of the colon goes down on the left side of the abdomen. 
• Sigmoid colon: It is the last part of the colon of the large intestine and is located on the bottom left side of the abdomen. It is an S-shaped connection between the descending colon and rectum. 

Functions

• Within the colon, the mixture of fiber, a small amount of water, and vitamins mix with mucus and bacteria, that live in the small intestine, and start to form feces.
• Bacteria help in the breakdown of materials and the formation of vitamins like B6, B12, and K.
• Inorganic salts, vitamins, and water are absorbed into the colon.
• The muscular movement of the colon pushes the feces to move into the rectum.   

iv. Rectum  

It is the last part of the large intestine which stores undigested food (waste products) for some time. Anus and egestion: It is the muscular part of the digestive system through which the egestion of undigested food takes place.