10 Sci Chp 6 revsn notes

 10 SCIENCE REVISION NOTES   

     CHAPTER 6 LIFE PROCESSES     

■ The ability to perform the basic life processes distinguishes a living organism from a non-living one.

■ In multicellular organisms, specialized body parts perform various life processes. In unicellular organisms, no such specialized organs are present.

■ Energy required to carry out the different life processes is obtained from carbon-based food sources through nutrition.

■ Depending on the mode of obtaining nutrition, organisms are classified into two major categories heterotrophs. autotrophs and

■ Autotrophs can prepare their own food from simple inorganic substances such as carbon dioxide and water. (Example: green plants, some bacteria)

■ Heterotrophs cannot synthesize their own food and are dependent on the autotrophs for obtaining complex organic substances for nutrition (Example: animals).

■Autotrophic nutrition: The mode of nutrition in which organisms can prepare their own food is called autotrophic nutrition.

■ Green plants prepare their food by the process of photosynthesis, by using carbon dioxide, water and sunlight.

■ The vital processes carried out by living organisms in order to maintain and sustain life are called Life Processes. Molecular movements are essential to carry out the various life processes. with the help of chlorophyll. During photosynthesis, oxygen is liberated as a by-product.

■ During respiration, the digested food materials are broken down to release energy in the form of ATP.

■ Respiration can be classified into two types depending on the requirement of oxygen.

i] Aerobic respiration occurs in the presence of oxygen.

ii] Anaerobic respiration occurs in the absence of oxygen.

■ The end products of aerobic respiration are carbon dioxide and water, whereas the end products of anaerobic respiration are lactic acid or ethanol and carbon dioxide.

■ A large amount of energy is released in aerobic respiration as çompared with anaerobic respiration.

■ Plants release oxygen during the day and carbon dioxide during the night.

■Terrestrial organisms use atmospheric oxygen for respiration whereas aquatic organisms use the oxygen dissolved in water.

10 Sci Chp 4 revsn notes

   10 SCIENCE REVISION NOTES   

            CHAPTER 1 CHEMICAL REACTIONS AND EQUATIONS      

All living structures are carbon based. The earth's crust has only 0.02% of carbon in the form of carbonates, coal and petroleum. The atmosphere has 0.03% of carbon. Carbon compounds are used extensively in manufacturing different useful materials.

Covalent bond in carbon

★  Carbon cannot form C^4- anion, because the nucleus cannot hold on to ten electrons, i.e., extra four electrons.

★  Carbon cannot form C⁴⁺ cation, because it requires a large amount of energy to remove four electrons, leaving behind six protons to hold just two electrons.

★  To overcome both the above problems, carbon forms covalent bonds with other elements by sharing its valance electrons.

Covalent bond in Hydrogen molecule

Covalent bond in Oxygen molecule

Covalent bond in Nitrogen molecule

Formation of Methane molecule

In this process carbon shares its four electrons with four hydrogen atoms to form methane.

Properties of Carbon

Carbon compounds are poor conductors of electricity. They are insoluble in water. They do not give rise to ions. They have low melting and boiling points. Covalent compounds have strong bond within the molecule but the inter-molecular forces are weak.

Versatile nature of carbon

i] Catenation: The ability of carbon to form bonds with other carbon atoms to give long chain molecules is called catenation. There are three types of catenation.

ii] Tetra valency: Carbon shows valency 4. It forms covalent bond with four hydrogen atoms to form methane.

C+2H₂→ CH, (Methane)

iii] Carbon forms single, double and triple bonds with other carbon atoms.

Organic Chemistry

The branch of chemistry which deals with carbon and its compounds is called organic chemistry.

Saturated carbon compounds

Carbon compounds which have only single bond between their carbon atoms are called saturated carbon compounds.