Q Name the cells having branches structure.
Ans Nerve Cell.
Q Why cells could not be observed before seventeenth century?
Ans Cells could not be observed before seventeenth century because till that time microscope was not invented.
Q Why plant cell have cell wall?
Ans Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture, etc.
They are exposed to these variations because they cannot move. That's why they have cell wall.
Q Which organism has the smallest cell?
Ans Mycoplasmas, a bacteria has the smallest cell of the size of 0.1 micron i.e. ten thousandth part of a mill metre. '
Q Which is the largest cell visible by unaided eye?
Ans Ostrich egg has the largest visible cell by unaided eye.
Q Name the four elements, which fonn major part of protoplasm.
Ans These are carbon, hydrogen, oxygen and nitrogen.
Q Give two examples of prokaryotes.
Ans Bacteria and blue green algae.
Q Name the largest organelle present in a cell.
Q Why do we stain the small components of section, before seeing under the microscope? Name a
stain. Marks (2)
Ans) Staining with coloured dyes makes the parts clearly visible. The dyes react with cellular components to give colour to the components. Eosin is a stain which gives a red orange colour.
Q Why is the cell called basic unit of living organism?
Ans Cell is the structural and functional unit of an organism because a cell in itself is the smallest part of an organism which is capable of functioning independently and can carry out the fundamental duties of life like reproduction, metabolism (photosynthesis and/or respiration).
Q What is the function of cell membrane?
Ans The function of the cell membrane is to let particles move in and out, to or from the cell.
Q Why mitochondria is called powerhouse of cell?
Ans Mitochondria provide the energy to the cell for carrying out various activities. So it is called powerhouse of cell.
Q. Write the functions of the following a) Mitochondria b) Chromosomes c) Plastids Marks (3)
Ans Functions are as follows:
( a ) Mitochondria provide the energy to the cell for carrying out various activities. Mitochondria are rod shaped and very minute bodies present in cytoplasm. They are concerned with release of energy from food during respiration. Because of this they are often referred to as the power house of the cell.
(b) Chromosomes transfer the characters from parents to the next generation.
(c) Plastids found in plant only and are the largest cell organelle containing pigments. They give colour to ﬂowers and fruits, which help in pollination.
The green plastids in the plants are celled chloroplasts. They help in the synthesis of food.
The red colour plastid in tomato is due to the plastids with red pigments
Ans Nucleus contains chromosomes, which have genes present on them. These genes carry information about characters of an individual. These genes are transferred from parent to children and hence characters are transmitted from parents to children.
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