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1.
(b)
Green plants, with the help of sunlight and
in the presence of enzymes, synthesize organic
compounds like starch from inorganic compounds
like CO2 and H2O. This is known as photosynthesis.
Chloroplast is the organelle to perform photosynthesis.
Plants that are devoid of chloroplast cannot
synthesize starch.
2.
(c)
Mitochondria is known as the “power house
of the cell.” It is involved in the continuous
production of energy. It releases necessary
energy for different functions of the cell through
processes like respiration, electron transport
and oxidative phosphorylation.
3.
(a)
Each cell has two main components - Cytoplasm
and the nucleus. Usually there is a nucleus
in the cell. Organisms without any cytoplasmic
organizations and devoid of definite nuclear
material are grouped as Akaryota. (e.g. Virus)
Organisms having a primitive type of nucleus
in cell, are classified Prokaryota. (e.g. Bacteria
and Blue green algae.) Organisms having a cell
with a well developed nucleus are grouped as
Eukaryota. (e.g. Fungi-yeast, mushroom).
4.
(a)
Cell division is a very complex process. There
are two main types of cell division:
1.
Mitosis
2. Meiosis
1
Mitosis: In this type of cell division, chromosomes
are equally distributed in each daughter cell.
As a result, the number of chromosomes in the
daughter cells is the same as that in the mother
cell. It is also known as equational division.
(e.g. Somatic cells division)
2. Meiosis: In this type of cell division, chromosomes
are divided in half of the original mother cells,
therefore the daughter cells consist of half
the number of chromosomes that are in the mother
cell. (e.g. reproductive or sex cells division)
5.
(c)
Nitrogen fixing bacteria on root nodules of Leguminous
plants are known as Rhizobium. They fix the atmospheric
nitrogen and convert it into ammonia. The nitrogen
fixing bacteria are also known as nitrifying bacteria.
Azobacteria are present in the soil. They convert
atmospheric nitrogen into nitrates and nitrites.
In this way, they increase the fertility of the
soil. These ammonium nitrates and nitrites are
then absorbed by plants to obtain nitrogen.
6.
(b)
RNA consists of ribose pentose sugar. Unlike DNA,
it consists of only one polynucleotide chain.
It also contains two purine and pyrimidine bases.
Uracil (U) is the nitrogen base which is present
in RNA but absent in DNA. Thus RNA contains Adenine
(A) and Guanine (G) as purine bases, and Cytosine
(C) and Uracil (U) as pyrimidine bases.
7.
(c)
Glycogen is considered the principal storage form
of glucose and is found mainly in the liver and
muscle, with kidney and intestines adding minor
storage sites. Glycogen is formed by the liver
from glucose in the bloodstream and is stored
in the liver. Glycogen is also produced by and
stored in muscle cells; during short periods of
strenuous activity, energy is released in the
muscles by direct conversion of glycogen to lactic
acid. During normal activity, energy is released
by metabolic oxidation of glucose to lactic acid.
Glycogenesis (formation of glycogen from glucose)
and glycogenolysis (break down of glycogen into
glucose) are two principal mechanisms by which
blood glucose level has been maintained.
8.
(b)
Ligaments are strong flexible white fibrous bands.
They bind the articular surfaces of bones together.
They provide necessary freedom for the bones as
well as protect joints from external injury and
bones from dislocation. Tendons are white bands
which join muscles with bones while ligaments
hold bones together at joints and are inelastic.
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