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TNPSC BIOLOGY (ENGLISH) 

WHAT IS NUTRITION AND DIETETICS?

Nutrition is a science that interprets the interaction of nutrients and other substance in food in relation to maintenance, growth, reproduction, health and disease of an organism.

There are two types of nutrition,

    ✦ Autotrophic

    ✦ Heterotrophic

Autotrophic nutrition

Mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. E.g.: Green plants, Euglena.

They prepare their own food by photosynthesis.

Heterotrophic nutrition

The mode of nutrition in which an organism depends on other organisms for food as they cannot prepare their own food called for food heterotrophic nutrition. This is done in various ways,

Herbivores such as cattle, tortoises and sparrows eat plants.

Carnivores such as lions, crocodiles, sharks and kestrels eat the flesh of other animals.

Omnivores such as humans can eat both plants and animals.

Saprophytes In saprophytes nutrition, the organism decomposes the dead plant and animal substances and converts them into simple molecules and absorbs them through their body wall.

Parasites

     ✦ The plant Cuscuta depends on other plants for food. This is an example for parasitic mode of nutrition oganisms like head, louse, leech etc., are found attached to the outer surface of the body and get nourishment from the host. So, these are called ectoparasites.

     ✦ Round worm lives inside the body (gut) and derives food from the intestine.So it is an endoparasite.

 

Special type of nutrition

     ✦ Plants like Nepenthes, Drosera and Utricularia are green in colour and are autotrophic. Since they are found in nitrogen deficient soil, they trap insects and kill them to get nitrogen from them.

     ✦ So they are called insectivorous plants.

 

Food - the Source of Energy

            Energy is the basis of life. For example, your ability to maintain a healthy body temperature and support your breathimg is called your basal metabolic rate, and you use more energy for these functions than for any other.

 

Types of Nutrition

Carbohydrates: Provides energy

Proteins             : Help in growth

Fats                      : Provide energy

Vitamins            : Help in physiological activities

Minerals            : Act as regulators in physiological activities

Water                  : Transports food, regulates body temperature

 

Fats:

            The word “fats” may bring up associations with the specialized tissue that stores them, called “adipose” tissue. Fats are a group of substances often used by animals to store energy and for this reason they are dense in energy.

 

Proteins:

            Muscles and flesh are made of protein. In addition to making up structural and functional parts in animals and plants, proteins can also be used as energy. Proteins are made up of “amino acids”, and there are 20 standard amino acids.

            Proteins are polymers of amino acids covalently linked through peptide bonds into a chain. Amino acids are covalently bonded together in chains by peptide bonds. If the chain length is short, it is called a peptide; longer chains are called polypeptides or proteins. Peptide bonds are formed between the carboxyl group of one amino acid and the amino group of the next amino acid.

 

Carbohydrates:

            Carbohydrates in the diet ultimately come from the photosynthesis of plants, which stores energy from the sun in the chemical bonds of sugars.

            The amount of energy in the food is measured with a unit called Calorie. A calorie is defined as the amount of energy needed to raise the temperature of 1 liter of water by 1 degree Celsius.

 

Enzymes:

            Enzymes are biological molecules (proteins) that act as a catalyst and help complex reactions occur everywhere in life. Enzymes are made from amino acids, and they are proteins.

            An enzyme acts as a very efficient catalyst for a specific chemical reaction. For example, the sugar maltose is made from two glucose molecules bonded together. The enzyme maltase is shaped in such a way that it can break the bond and free the two glucose pieces. The only thing maltase can do is break maltose molecules, but it can do that very rapidly and efficiently.

 

Food:

            Food is a basic requirement of all living beings. Food provides energy for different activities in the body. Food also provides organic materials for growth and repair. Carbohydrates, proteins and fats are the major components of food and hence, these are called macronutrients.

 

Digestion:

            The macromolecules in food cannot be utilized by our body in their original form. They need to be broken down and converted into simple substances so that they could be absorbed. The process of converting complex food into absorbable forms is called digestion.

 

Digestive System:

             The human digestive system consists of the alimentary canal and the associated glands.

Alimentary Canal: The alimentary canal begins with the mouth and ends in the anus. The alimentary canal is divided into 5 main parts, viz., mouth, oesophagus, stomach, small intestine and large intestine.

 

Generally two major types of digestion are encountered

✦ Intra cellular digestion

✦ Extra cellular digestion

 

✦ Intra cellular digestion

Amoeba like unicellular organisms digests its prey inside the food vacuole and expels the undigested food. This type of digestion is called intracellular digestion e.g.Amoeba

 

 

 Extra Cellular digestion

Various glands secrete enzymes into the cavity and digest the food extra cellularly .This kind of digestionoutsidethe cell, but within the cavity is extracellular digestion e.g Human

The alimentary canal

✦ It is a coiled muscular tube extending from the mouth to the anus. It is about 6-9 meters long and consists  of many specialized sections

✦ Arranged sequentially these are mouth, buccal cavity, Pharynx, oesophagus, stomach, small intestine, Large intestine ,rectum and anus

 

Mouth

It is an oval shaped cavity bounded in front by lips and laterally by the jaws. The roof of the cavity is lined by the palate. The floor contains a tongue. The mouth opens into the buccal cavity or oral cavity.

The upper jaw and lower jaw are lined by the tooth. Mouth helps ingestion

 

Teeth

In man teeth are 32 in number. 4 incisors, 2 canines, 4 premolars and 6 molars in each jaw. The last set of molar tooth grow after the age  of 20; Hence they are named as wisdom tooth.

 

Types of Teeth

✦ The first set of teeth grows when a baby is about one year old. This set of teeth is called milk teeth.

✦ They are twenty in number.

✦ When the milk teeth fall off, a new of teeth grow. They are called permanent teeth. They are thirty-two in number

✦ Incisors: These are chisel shaped teeth at the front of the mouth. They are eight in number. Four are present in each jaw .These are used for biting the food.

✦ Canines: These are sharp teeth and pointed teeth. They are four in number and two are present in ea are used for cutting and tearing of food.

✦ Premolars: These are large teeth behind canines on each side. They have large surface. They are eight in number and four are present in each jaw. They help in chewing and grinding the food.

✦ Molars: These are very large teeth present just behind the premolars. They have more4 surface area than premolars. They are used for chewing and grinding of food like premolars. 'They are twelve in number, and six are present in each jaw.

✦ Birds have no teeth.

✦ Rats have continuously growing teeth.

✦ The tusks of elephants are actually incisors that have become very long.

✦ Very few adult humans have all the 32 teeth.

 

Tongue

✦ It is the organ for the sense of taste. It is attached to the floor at the mouth. Its tip is thin and narrow. The upper surface of the tongue contains several papillae or Sensory buds.

✦ The hardest part of the human body is the tooth.

 

Salivary gland

✦ Parotid glands – It is the largest gland of the three pairs.It is found below the air.

✦ Submaxillary gland –it is found below the  jaw and irregular in shape.

✦ Sublingual gland – it is smallest gland. It is found at the base of the tongue.

✦ Parotid gland is the only salivary gland affected by mumps virus.

✦ The three pairs salivary glands secrete approximately 1.5 liters of saliva  every day.

✦ The saliva has the following

1. Ptyalin (Amylase) - enzyme

2.Bicarbonate - salt

3. Mucus - carbohydrate

4. Lysozyme -enzyme

 

Pharynx

Pharynx is found below the nose and mouth. It is about 11 cm in length. This region has 7 openings. They are 2 intemal nostrils, 2 eustachian tubes, mouth, larynx and oesophagus.

 

Oesophagus

 It is a musculo-membranous canal about 22 cm length. It extends from pharynx to the stomach. The inner lining has a mucus coat and it is lined by epithelium.

 

Stomach

✦ Since stomach is the J-shaped bag like structure, main organ of digestion,  it is the most dilated part of the alimentary canal. Stomach is a horizontal chamber containing 3 conspicuous regions. They are cardiac, fundic and pyloric region. The stomach secretes gastric juice.

✦ The gastric juice contains the following:

1. Pepsin

2. Rennin

3. Hydrocloric acid 

 

Small intestine

The stomach opens  into the small intestine through pylorus. The small intestine is divisible into 3 regions duodenum, jejunum and ileum.

 

Duodenum

 Duodenum is around 22 cm in length. In this region where the liver and pancreas are connected to the alimentary canal.

 

Liver

✦ Liver is the largest glandular organ in human. It weighs about 1500 gms. It contains two unequal lobes.

✦ The right lobe is larger.

✦ Liver secretes bile juice which is greenish yellow in colour.

✦ The bile is temporarily stored-in gall bladder.

✦ The gall bladder in attached to the bile duct. The duct opens into theduodenum. Bile juice helps the digestion of fat.

✦ It does not have any enzyme. It has bile salts and bile pigments,

✦ Excess, of eating fatty foods leads ho the formation of bile stones in the gallbladder.

 

Pancreas

✦ Pancreas is a long, leaf like transparent gland. It is 15 to 20 cms long. Pancreas secretes pancreatic juice and it is connected with duodenum through pancreatic duct. .

✦ Pancreas acts as an exocrine gland and endocrine gland. The gland's upper surface bears the islets of Langerhans.

✦ The pancreatic alpha cells secrete the hormone glucagon, and the pancreatic beta cells secrete the hormone insulin.

 

As an exocrine gland, it secretes the following enzymes:

1. Trypsinogen.

2. Chymotrypsinogen

3. Procarboxy peptidases

4. Amylases

5. Lipases

6. Nucleases

 

Jejunum

 Jejunum constitutes 2/5th  of the small intestine. It starts from the duodenum and ends with ileum.

 The secretion of small intestine is intestinal juice. The intestinal juice contains the enzymes.

1. Sucrase

2, Maltese

3. Lactase

4. Lipase

 

Ileum

✦ It is a coiled tube-like structure which constitutes 3/5th of the small intestine. It contains numerous minute finger-like projections called villi(1 mm) in length

✦ They are approximately 4 million in number .Internally each villus contains fine blood capillaries and lacteal tubes. Food absorption takes place here

 

Large intestine

✦ It extends from the ileum to the anus. It is about 1.5 metres in length. It is divided into caecum, colon and rectum 

 

Caecum

Caecum is a large blind pouch and measures about 5 cm in length. The terminal part of caecum is vermiform appendix. Appendix is a vestigial organ.

 

Colon

It is divided into 3 parts, i.e., an ascending, a transverse and a decending part. The descending colon opens into the rectum, which in turn opens out through the anus.

 

Digestion of food:

Mouth:

✦ Food is broken into small parts with the help of teeth.

✦ The tongue helps in mixing the saliva in the food.

✦ Enzymes in saliva: Salivary Amylase and Lysozyme.

✦ The masticated food particles called bolus passes down through oesophagus due to peristalsis.

 

Gastric Glands:

✦ These are present in the mucosa os stomach.

✦ There are 3 types of gastric glands,

  ⋆Mucus Neck cells: they secrete mucus.

  ⋆Peptic or chief cells: they secrete the proenzyme pepsinogen.

  ⋆Parietal or Oxyntic cells: they secrete HCL and intrinsic factor which is essential for the absorption of vitamin B12.

✦ The proenzyme pepsinogen gets converted into the active enzyme pepsin; on exposure to hydrochloric acid.  Pepsin converts proteins into proteoses and peptones.

✦ HCL provides the acidic pH (1.8) which is optimal for pepsins. Rennin is a proteolytic enzyme , found in gastric juice of infants, which helps in the digeation of milk proteins.

✦ Small amount of lipases are also secreted by gastric glands.

 

Small Intestine:

            The muscularis layer of small intestine generates various types of movements. These movements help in thorough mixing of food with various secretions in the intestine like bile juice, pancreatic juice and intestinal juice.

Absorption: The simple substances formed after digestion are absorbed in the jejunum and ileum regions of the small intestine. The undigested and unabsorbed substances go to the large intestine. No significant digestive activity occurs in the large intestine.

 

Large intestine:

            Absorption of some water, minerals and certain drugs.

            Assimilation: The utilization of nutrients for various activities is called assimilation.

            Egestion: Removal of digestive wastes is called egestion.

The summary of absorption in different parts of Digestive system:

            Mouth: Some Drugs

            Stomach: Water, Simple sugars, alcohol, etc.

            Small Intestine: Final products of digestion like glucose, fructose, fatty acids, glycerol, amino acids, etc.

            Large Intestine: Water, minerals and some drugs.

 

Disorders of Digestive System:

            Bacterial or viral infections lead to the inflammation of the intestinal tract. Infections are caused by tapeworm, roundworm, threadworm, hookworm, pinworm, etc.

Jaundice: Inflammation of liver is called hepatitis. Jaundice is the most common form of hepatitis.

Vomitting: Ejection of stomach content through mouth is called vomittimg. This is a reflex action and is controlled by the vomit center in the medulla.

Diarrhoea: Abnormal frequency of bowel movement and increased liquidity of faecal discharge is called diarrhea.

Constipation: Irregular bowel movements may lead to retention of faeces in the rectum. This condition is called constipation.

Indigestion: A condition in which food is not properly digested and a feeling of fullness prevails is called indigestion.

 

Nutritional Requirements:

The indicators include energy ad 13 nutrients: 2 macro nutrients: Fat and Protein; and 11 micronutrients: Iodine, Iron, Vitamin A, Vitamin C, Niacin, Thiamine, Riboflavine, Vitamin B6, Vitamin B9 (Folic Acid), Vitamin B12 and Zinc.

Human and other animals need a minimum intake of food energy to sustain their metabolism and to drive their muscles. Foods are composed chiefly of carbohydrates, fats, proteins, water, vitamins, and minerals.

            Carbohydrates, proteins, and fats supply 90% of the dry weight of the diet and 100 percent of its energy. All three provide energy (measured in calories), but the amount of energy in 1 gram (1/28 ounce) differs:

1. 4 calories in a gram of carbohydrate or protein

2. 9 calories in a gram of fat

 

Vitamin Requirements of Humans:

Water – Soluble Vitamins are B and C

Fat Soluble vitamins are A,D,E,K

 

Water – Soluble Vitamins

Vitamin

Major Dietary Sources

Some Major Functions in the Body

Possible Symptoms of Deficiency of Extreme Excess

                              Water – Soluble Vitamins

Vitamin B1 (thiamine)

Pork, legumes, peanuts, whole grains

Coenzyme used in removing CO2 from organic compounds

Beriberi (nerve disorders, emaciation, anemia)

Vitamin B2(riboflavin)

Dairy products, meats, enriched grains, vegetables

Components of coenzymes FAD and FMN

Skin lesions such as cracks at corners of mouth

Niacin

Nuts, meats, grains

Component of coenzymes NAD+ and NADP+

Skin and gastrointestinal lesions, nervous disorders Flushing of face and hands, liver damage

Vitamin B6 (pyridoxine)

Meats, vegetables, whole grains

Coenzyme used in amino and metabolism

Irritability, convulsions, muscular twitching, anemia Unstable gait num feet, poor coordination

Panthothenic acid

Most foods: meats, dairy products, whole grains (also made by colon bacteria)

Component of coenzyme A

Fatigue, numbness, tingling of hands and feet

Folic acid (folacin)

Green vegetables, oranges, nuts, legumes, whole grains (also made by colon bacteria)

Coenzyme in nucleic acid and amino acid metabolism

Anemia, gastrointestinal problems may mask deficiency of Vitamin B12

Vitamin B12

Meats, eggs, dairy products

 Coenzyme in nucleic acid metabolism; needed for maturation of red blood cells

Anemia, nervous system disorders

Biotin

Legumes, other vegetables, meats

Coenzyme in synthesis of fat, glycogen and amino acids

Scaly skin inflammation, neuro – muscular disorders

Vitamin C (ascorbic acid)

Fruits and vegetables, especially citrus fruits, broccoli, cabbage, tomatoes, green peppers

Used in collagen synthesis (e.g., for bone, cartilage, gums); antioxidant; aids in detoxification; improves iron absorption

Scurvy (degeneration of skin, teeth, blood vessels), weakness, delayed wound healing, impaired immunity Gastrointestinal upset.

 

Plant Nutrition

            Plant nutrition refers to the need for basic chemical elements for plant growth. The term fertilization refers to the application of plant nutrients to supplement the nutrients naturally occurring in the soil.

            At least 17 elements are known to be essential nutrients for plants. In relatively large amounts, the soil supplies nitrogen, phosphorous, potassium, calcium, magnesium and sulphur; these are often called the macro nutrients. In relatively small amounts, the soil supplies iron, manganese, so – called micronutrients. Nutrients must be available not only in sufficient amounts but also in appropriate ratios.

 

Non – Mineral Nutrients

The Non – Mineral Nutrients are hydrogen (H), oxygen (O) and carbon (C). These nutrients are found in the air and water.

            In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 –Carbon and oxygen) and water (H2O – hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant’s food.

 

Mineral Nutrients

            The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through the roots of a plant.

 

 

Macronutrients

            Macronutrients can be broken into two more groups; primary and secondary nutrients. The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.

            The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of calcium and magnesium are added when lime is applied to acidic soils. Sulfur is usually of soil organic matter, and important reason for not throwing out grass clippings and leaves.

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Micronutrients

            The micronutrients are boron (B), copper (Cu), Iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.

            The kind of deficiency symptoms shown in plants include chlorosis, necrosis, stunted plant gwouth, premature fall of leaves and buds, and inhibition of cell division. Chlorosis is symptom is caused by the deficiency of elements N, K, Mg, S, Fe, Mn, Zn and Mo. Likewise, necrosis, or death of tissue, Cu, K. Lack or low level of N, K, S, Mo causes an inhibition of cell division. Some elements like N, S, Mo delay flowering if their concentration in plants is low.

 

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Photosynthesis

            Photosyntheiss is a process in which the plants use light energy to make   carbohydrate from carbon from carbon dioxide and water. The overall reaction of photosynthesis can be given in a simple form as follows:

6CO2 + 6 H2O + C6H12O6 + 6O2

(Sunlight + Chlorophyll)

Photosynthesis occurs in two stages, viz, light reaction and dark reaction. The light reaction is light dependent. Light energy is captured in this stage and is utilized to make the energy – storage molecules ATP and NADPH. Dark reaction captures and reduces carbon dioxide. Dark reaction does not mean that it happens in the absence of light. 

 

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Chloroplast

Chloroplast is the cell organelle where photosynthesis takes place in plants and algae. A typical plant cell may contain about 10 to 100 chloroplasts. In the light dependent stage or light reactions, light from the sun is absorbed by the chlorophyll of the plant. The light energy is used to split the water molecule (H2O) into hydrogen and oxygen (photolysis).

(Remember that carbon dioxide and water are used to make the sugars produced by photosynthesis).

The equation used to depict photolysis is:

6H2O(I) + 12 H+ (aq) + 3O2(g) + energy

(Oxygen is given off as a by - product)

            The energy produced in the light stage is used to produce ATP (adenosine tri – phosphate). ATP is a high – energy molecule that stores energy for later use. The oxygen that is given off is released from the plants. This is why it is said that plants use CO2 and release O2 during the process of photosynthesis.

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Dark Reaction

These reactions occur without light but can occur with light as well. This stage of photosynthesis is also known as the Calvin Cycle or the dark reactions. The products of the light reaction, ATP and NADPH2, are used during the dark reactions for the reduction of CO2 into sugars. Depending on the first product of the dark reactions, the plants classified into two types:

 

C3 Cycle

1. The CO2 acceptor is ribulose 1,5 diphosphate (RUDP).

2. The first stable product is phophoglyceric acid (PGA).

3. Enzyme catalyzing carboxylation is rubisco or carboxy dismutase.

4. Photo – respiration occurs.

5. Optimum temperature is 100 250C

 

C4 Cycle

1. The CO2 acceptor is phoshenol pyruvic acid (PEPA).

2. The first stable procduct is wxalo acetic acid (OAA).

3. Enzyme catalyzing carboxylation is phospheoenol pyruvate carboxylase.

4. Optimum temperature is 300 – 400C.

 

Special Modes of Plant Nutrition

Symbiosis

Obligate symbiosis is when two organisms are in a symbiotic relationship because they can’t survive without each other. Facultative symbiosis is when the species live together by choice. There are four main types of symbiotic relationships; mutualism, commensalism, parasitism and competition.

            A lichen is not a single organism. Rather, it is a symbiosis between different organisms – a fungus and an alga or cyanobacterium. Cyanobacteria are sometimes still referred to as blue – green algae through they are quite distinct from is called the photobiont.

 

Mycorrhizae:

            When mycorrhizal fungi colonise the plant’s root system, they create a network that increases the plant’s capacity to absorb more water and nutrients such as phosphorus, copper and zinc. This process in turn enhances growth and favours rapid development of roots and plants.

Nitrogen Fixing symbionts Biological nitrogen fixation (BNF) is the term used for a process in which nitrogen as (N­2) from the atmosphere is incorporated into the tissue of certain plants. Only a select group of plants is able to obtain N this way, with the help of soil microorganisms.

 

Insectivorous (carnivorous) Plants

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Carnivorous Plants:

1. Capture and kill prey

2. Have a mechanism to facilitate digestion of the prey

3. Derive a significant benefit from nutrients assimilated from the prey

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