Nutrition Notes For Class 10
Nutrition:- Nutrition is a process of providing nutrients to the body cell. In this the food is ingested, digested and assimilated by the organisms. The assimilated food is utilized by the cell to produce energy, synthesis of protein, etc.
Autotrophic nutrition:- The term “autotroph” is derived from two Greek words- autos (self) and trophe (nutrition). In autotrophic nutrition, an organism makes its own food with the help of simple raw materials. They are also called producers.
Heterotrophic nutrition:- The word “heterotroph” is derived from two Greek words- heteros (other) and trophe (nutrition). They depend on other organism for their food, so they are called consumers. All animals and non-green plants fall under this category. The consumers which consume plants and herbs are called herbivores and those consume animals are called carnivores. After taking complex organic material in food heterotrophs break them into small molecules with the help of biological catalysts or enzymes.
Photosynthesis:- All green plants, which are autotrophic, synthesize their food with the process of photosynthesis. In this process plants have chlorophyll synthesize the simple sugar from the raw materials water and carbon-dioxide using the energy of sunlight. Oxygen is released in this reaction. The overall equation of photosynthesis is:-
6CO2 + 12H2O C6H12O6 + 6H2O + 6O2
The food produced in plant is stored in the form of starch.
Q.1. Why leaves are more suitable for photosynthesis?
=> All green parts of plant are capable of performing photosynthesis; the leaves are suitable organ for this process. The cells of the leaves have special organelles called chloroplast, which are the main site of photosynthesis. These are plastids, which contain light-absorbing green pigment chlorophyll.
Requirement for photosynthesis:- The photosynthesis requires chlorophyll, carbon-dioxide, water and sunlight. Let’s know more about these:-
1. Chlorophyll:- Chlorophyll is green pigment found in photosynthetic organism and is responsible for their green colour. In plants chlorophyll is mainly found in leaves. Young stem and leaves may also have chlorophyll. In lower plants like algae, the whole body is green and takes part in photosynthesis.
2. Carbon-dioxide:- Air contains 0.03% of carbon-dioxide. Terrestrial plants use atmospheric carbon-dioxide in photosynthesis. Aquatic plants use carbon-dioxide dissolved in water. Plants obtain carbon-dioxide through the pores called stomata present on the surfaces of leaves. The opening and closing of stomata is regulated by the guard cells, which surrounds the stomata.
3. Water:- Water is important raw material for photosynthesis. Water is absorbed by root hairs through the soil. Water is then transported to leaves through stem.
4. Sunlight:- Light energy is used in splitting of water molecules into hydrogen and oxygen. The splitting of water in the presence of sunlight is called photolysis.
Q.2. What are the two main stages in the entire process of photosynthesis?
=>The first stage is dependent on light (light reaction). The second stage does not require light (dark reaction).
Q.3. During these two stages, what events occur?
=>The following events occur are:- 1. Light energy is first absorbed by chlorophyll molecules found inside the chloroplasts. 2. The absorbed energy causes splitting of water molecules into hydrogen and oxygen. During this process the light energy gets converted into chemical energy. 3. Finally, carbon-dioxide is reduced to carbohydrate (the end product of photosynthesis).
Parasitic:- Parasitic organism or parasites, live on or inside other living organism, called hosts, and obtain their food from them. The host does not get any benefit from the parasite. Different parasites like hookworms, tapeworms, leeches, etc., have different modes of feeding, depending upon habit, habitat and modification.
Saprophytic:- Saprophytic organisms or saprophytes derive their food from dead organism. They secrete enzymes that are released on food. These enzymes break down complex food into simpler form. Common examples are fungi and many bacteria.
Holozoic:- In holozoic nutrition, complex organic substances are ingested without degraded or decomposed. After intake such food is digested by enzymes produced inside the body. The digested food is absorbed into the body and undigested food is egested from the body. For ex: - amoeba and human beings.
Q.4.How organisms like amoeba obtain nutrition?
Amoeba takes in complex organic matter as food. Amoeba first identifies it food and then throws a number of pseudopodia. These pseudopodia enclose the food particles and prevent it from escaping. The food enclosed in cell membrane forms a food vacuole. The complex food is broken down into simpler molecules with the help of digestive enzymes of the organelle called lysosomes. The digested food is distributed in the cytoplasm and the undigested food is egested through the cell membrane.
Q.5. How paramoecium obtain nutrition? In paramoecium, food is ingested through a special opening called cytostome. Food is brought to this opening by the lashing movement of cilia that cover the entire surface of the cell.
HUMAN DIGESTIVE SYSTEM
Alimentary canal:- The alimentary canal in human beings measures about 8 to 10 metres in length. It extends from the mouth to the anus. It has the following parts:-
Mouth:- The mouth consists of the oral cavity, through which food is ingested. It is bounded by lips and cheeks. It contains gums, teeth, a tongue and muscles. The tongue tastes the food and moves it into the pharynx. Teeth help in biting, cutting and chewing food. Teeth masticate the food. This makes it easier to swallow food and increase its surface area for various digestive secretions to act on. The four types of teeth are incisors, canines, premolars and molars. Our teeth are covered with a hard protective layer of enamel. The enamel covers dentine, a yellowish substance which forms the bulk of tooth. When we eat sweets, chocolates and ice creams, bacteria acts on sugar and produce acids which soften outer covering. This causes dental carries. Bacterial cells and food particles stick to the teeth and form dental plaque. If the teeth are not brushed properly after meals, bacteria may invade deeper into the teeth. This leads to infection and toothache. The presence of food in the mouth stimulates the three pairs of salivary gland to secrete saliva. Saliva has mucin, which lubricates the mouth and food. Saliva also has salivary amylase, a digestive enzyme that breaks down starch and glycogen to maltose (a simpler sugar).
Pharynx:- The oral cavity opens in pharynx. The swallowing mechanism guides the masticate food through the pharynx into a tube called Oesophagus.
Oesophagus:- Oesophagus is tubular, muscular part of the alimentary canal. The muscular walls of the Oesophagus moves in a rhythmic wavelike manner, which carries food down to the stomach. This muscular movement is called peristalsis.
Stomach:- It is located below the diaphragm (muscular partition between chest cavity and abdominal cavity). It serves as storehouse of food where partial digestion takes place. It is saclike muscular structure. Columnar cells line the inner wall of stomach. The inner lining has sunken pits. Each pit constitutes a gastric gland. The cells lining a gastric gland or pit are of three types:- 1. Mucous cells: - secrete mucus; protect the inner lining and glands from being digested by gastric juice. 2. Parietal or oxyntic cells: - secreting hydrochloric acid, when hydrochloric acid is in gastric juice converts propepsin into active pepsin and also kills bacteria ingested with food. 3. Chief or zymogen cells: - secreting inactive propepsin, when it is converted into active pepsin. Pepsin breaks down protein into peptones. About 3 L of gastric juice is produced per day. Excess secretion of gastric juice, particularly in an empty stomach, erodes the lining of the stomach. This erosion causes lesion and round depression called peptic ulcer in the stomach walls. Gastric lipase partially breaks down lipids.
Small intestine:- The small intestine is about 6 metre long and 2.5 cm in thickness. There are 3 divisions of small intestine. 1. duodenum 2. jejunum 3. ileum Duodenum is first part. It begins from pyloric stomach, and is C-shaped. In the middle of the duodenum two different ducts open through a common aperture. One of the ducts is common bile duct and another is the pancreatic duct. Bile is a yellowish green alkaline juice, is poured into the duodenum through common bile duct.
Liver:- It is largest gland of the body. It performs many functions. It secretes bile, which helps in digestion. Bile juice is produced by the liver is stored in the gall bladder. There are two main function of bile are:-
1. It emulsifies fats, by rendering them soluble and breaking them into small globules. In this form, fats are better exposed to the action of fat-hydrolyzing enzymes.
2. The acidic food coming from stomach becomes alkaline when it is mixed with bile. This is important as the intestinal enzymes catalyze the breakdown of food only in an alkaline medium.
Pancreas:- It secretes pancreatic juice, which is carried by the pancreatic duct into duodenum. Pancreatic juice contains a number of digestive enzymes such as amylase for the splitting of polysaccharides, lipase for the breakdown of fats and trypsin and chymotrypsin for breakdown of proteins. These enzymes catalyze the breakdown of their substrates in an alkaline medium. But the catalysis does not completely break all the substrates into their simplest units. Jejunum is the middle part of small intestine and found only in man. Ileum is the last and main part of small intestine. The major part of digestion and absorption takes place here.
Intestinal glands:- The complete digestion of food takes place in ileum. There are numerous small glands in the walls of intestine, which secrete intestinal juice. These enzymes break down small peptides into amino acid, disaccharides into monosaccharides, lipids into fatty acids and glycerol and nucleic acid to nucleotides.
Large intestine:- Ileum passes into large intestine. Large into is divided into anterior (colon) and posterior (rectum). At the junction of colon and ileum, there is a blind, one end closed outgrowth called caecum. The caecum ends in vermiform appendix. In man the vermiform appendix has outlived its usefulness, it is a vestigial organ. It is 8 cm long tube and sometimes become a source of trouble. The colon has an ascending part, a transverse part and a descending part. The descending part opened into the rectum. The terminal part of rectum is called anal canal. It opens through anus and guarded by sphincter muscles. the large intestine allows the passage of residual food mass ( faecal matter), which is egested through anus.as the residue passes through large intestine a considerable amount of water in residual food is absorbed into blood through the wall of intestine.
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