2 – Life Processes in Living Organisms – Part I | Science II | Class 10

The blog presents the Questions and Answers of the Chapter 2, Life Processes in Living OrganismsPart 1, from Science Part II of Class 10 from Maharashtra State Board.

Q1. Fill in the blanks and explain the statements.

a. After complete oxidation of a glucose molecules, 38 number of ATP molecules
are formed.

b. At the end of glycolysis, pyruvic acid, ATP, NADH2 and water molecules
are obtained.

c. Genetic recombination occurs in pachytene phase of prophase of meiosis-I.

d. All chromosomes are arranged parallel to equatorial plane of cell in metaphase
phase of mitosis.

e. For formation of plasma membrane, phospholipid molecules are necessary.

f. Our muscle cells perform anerobic type of respiration during exercise.

Q2: Write definitions.

a. Nutrition:
The mode of taking food by an organism and its utilisation by the body, called nutrition.

b. Nutrients:
The components of food that are necessary for our body, are called nutrients.
Examples: carbohydrates, proteins, fats, vitamins and minerals.

c. Proteins:
Proteins are a type of biomolecules that are made up of amino acids and are very important for the growth and repair of our body, also called as body building foods.
Examples: Soyabeans, beans, meat, fish are examples of sources of proteins.

d. Cellular respiration:
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products.

e. Aerobic respiration:
The process by which the breakdown of glucose occurs in the presence of oxygen
resulting in the release of energy in the form of ATP and also carbon dioxise and water, is called aerobic respiration.

f. Glycolysis
Glycolysis is the first step in respiration, taking place in cytoplasm of a cell. In this step, six-carbon glucose is broken down into a three-carbon molecules of pyruvate.

Q3: Distinguish between:

a. Glycolysis and TCA cycle

b. Mitosis and meiosis.

c. Aerobic and anaerobic respiration.

Q4: Give scientific reasons.

a. Oxygen is necessary for complete oxidation of glucose.

Ans. a. i) Cellular respiration occurs in living organisms in two ways, aerobic respiration and anaerobic respiration.
i) In aerobic respiration a molecule of glucose is completely oxidized in three steps i.e. glycolysis, tricarboxylic acid cycle and electron transfer chain reaction and produces 38 molecules of ATP.
iii) The absence of oxygen, respiration takes place in two steps i.e. glycolysis and fermentation. Also without oxygen glucose is incompletely oxidised with release of only 2 molecules of ATP. This results in less supply of energy to the body.
Therefore oxygen is necessary for complete oxidation of glucose.

b. Fibers are one of the important nutrients.

Ans. i) Along with nutrients like carbohydrates and lipids, fibers are also essential nutrients.
ii) Though we cannot digest the fibers, they help in the digestion of other substances and egestion of undigested substances.
Therefore fibres are one of the important nutrients.

c. Cell division is one of the important properties of cells and organisms.

Ans. Cell division is one of the very important properties of cells and living organisms because :
i) Due to the property of cell division only, a new organism is formed from existing
one, a multicellular organism grows up and emaciated body can be restored.
ii) It results in repair of old and worn out tissues and regeneration of organisms.
iii) It also forms the basis of evolution of various life forms.

d. Sometimes, higher plants and animals too perform anaerobic respiration.

Ans. i) When there is depletion in oxygen level in the surrounding some higher plants, animals some aerobic microorganisms also perform anaerobic respiration instead of aerobic respiration.
ii) Our muscle cells also perform anaerobic respiration while performing the exercise, which results in production of less amount of energy and accumulation of lactic acid, due to which we feel tired.
iii) Seeds perform anaerobic respiration if the soil is submerged under water during germination with production of ethyl alcohol, carbon dioxide and energy.

e. Kreb’s cycle is also known as citric acid cycle.

Ans. i) In glycolysis, a long series of reactions occur where 1 molecule of glucose is converted to 2 molecules of pyruvic acid.
ii) Further there is an intermediate reaction called the Link reaction where pyruvic acid gets converted to Acetyl-CoA.
ii) This Acetyl-CoA which enters the Kreb’s cycle is then further converted to the first stable product of the Kreb’s cycle which is called citric acid (citrate) in the presence of an enzyme called citrate synthase.
Hence the Kreb’s cycle is called the citric acid cycle or tri-carboxylic acid cycle.



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