Chap 6 : Life Processes (NCERT 10th class short Notes)

CHAPTER6: Life Processes

Autotrophic Nutrition

·         Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis.

·      Material is taken in the form of carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll.

·         The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve.

·         similar situation is seen in us where some of the energy derived from the food we eat is stored in our body in the form of glycogen.

·         The following events occur during Photosynthesis process:

1)      Absorption of light energy by chlorophyll.

2)      Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

3)      Reduction of carbon dioxide to carbohydrates.

·         Desert plants take up carbon dioxide at night.

·         Massive amounts of gaseous exchange takes place in the leaves through stomata (पर्णरंध्रे) for the purpose of photosynthesis. Since large amounts of water can also be lost through these stomata. The opening and closing of the pore is a function of the guard cells.

·         Note that exchange of gases occurs across the surface of stems, roots and leaves as well.

·         Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites.

Heterotrophic Nutrition

·         Some organisms break-down the food material outside the body and then absorb it. Examples are fungi like bread moulds, yeast and mushrooms.

·         Some organisms derive nutrition from plants or animals without killing them. This parasitic nutritive strategy is used by a wide variety of organisms like cuscuta (amar-bel), ticks, lice, leeches and tape-worms.

Nutrition in Human Beings

·         The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar.

·         The gastric glands present in the wall of the stomach. These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus.

·         The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin.

·         The mucus protects the inner lining of the stomach from the action of the acid under normal conditions.

·         Small intestine is the longest part of the alimentary canal.

·         Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

·         The small intestine is the site of the complete digestion of carbohydrates, proteins and fats.

·         The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

·         The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

·         Villi: The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption.

·         The unabsorbed food is sent into the large intestine where more villi absorb water from this material.

RESPIRATION

·         Some organisms use oxygen to break-down glucose completely into carbon dioxide and water, some organisms use other pathways that do not involve oxygen.

·         In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm.

·         Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. (anaerobic respiration)

·         Breakdown of pyruvate using oxygen takes place in the mitochondria.

·         anaerobic respiration: absence of air (oxygen)

·         aerobic respiration:  presence of air (oxygen)

·         The release of energy in this aerobic process is a lot greater than in the anaerobic process.

·         Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken. (Here the pyruvate is converted into lactic acid). This build-up of lactic acid in our muscles during sudden activity causes cramps.

·         ATP is the energy currency for most cellular processes. The energy released during the process of respiration is used to make an ATP molecule from ADP and inorganic phosphate.

·         ATP can be used in the cells for the contraction of muscles, protein synthesis, conduction of nervous impulses and many other activities.

·         The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

·         The alveoli in the lungs provide a surface where the exchange of gases can take place.

·         If the alveolar surface were spread out, it would cover about 80 m².

·         If diffusion were to move oxygen in our body, it is estimated that it would take 3 years for a molecule of oxygen to get to our toes from our lungs.

TRANSPORTATION

·         Blood transports food, oxygen and waste materials in our bodies.

·         Plasma (present in blood) transports food, carbon dioxide and nitrogenous wastes in dissolved form.

·         Oxygen is carried by the red blood cells.

·         Fishes have only two chambers to their hearts.

·         Blood pressure:

-          much greater in arteries than in veins.

-          Systolic pressure: The pressure of blood inside the
artery during ventricular systole (contraction).

-          Diastolic pressure: Pressure in artery during ventricular diastole (relaxation).

-          The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

-          Blood pressure is measured with an instrument called sphygmomanometer.

-          High blood pressure (hypertension) is caused by the constriction of arterioles, which results in increased resistance to blood flow.

·         The blood has platelet cells which circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

·         Lymph or tissue fluid:

-          Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues to form the tissue fluid or lymph.

-          similar to the plasma of blood

-          colourless and contains less protein

-          Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.