NCERT Class-9 Science Solutions: Chapter 5-The Fundamental Unit Of Life Part 5

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Question 28:

Living cells were discovered by

  1. Robert Hooke

  2. Purkinje

  3. Leeuwenhoek

  4. Robert Brown

Answer: C

Image of cell discovery History

Image of Cell Discovery History

Image of cell discovery History

Question 29:

Select the odd one out

  1. The movement of water across a semi permeable membrane is affected by the amount of substances dissolved in it.

  2. Membranes are made of organic molecules like proteins and lipids

  3. Molecules soluble in organic solvents can easily pass through the membrane.

  4. Plasma membranes contain chitin sugar in plants

Answer: D

Short Answer Questions

Question 30:

Why are lysosomes known as ‘suicide-bags’ of a cell?

Answer:

Lysosomes are known as ‘suicide-bags’ because when cell gets damaged during the disturbance in cellular metabolism, lysosomes may burst and the digestive enzymes thus released digest their own cell.

Question 31:

Do you agree that “A cell is a building unit of an organism”? If yes, explain why?

Answer:

Cell combine to form tissues, which further combine to form organs, organs combine to form organic systems, which further combine to form organism.

Question 32:

Why does the skin of your finger shrink when you wash clothes for a long time?

Answer:

Soap solution is very concentrated - Hypertonic solution, so water moves out of your finger cells by osmosis

Question 33:

Why is endocytosis found in animals only?

Answer:

Endocytosis generally occurs in animal cells and very rarely in plant cells as the cell membrane in plant cell is surrounded by a rigid cell wall. Cell wall causes hindrance in the invagination of plasma membrane which forms the transport vesicles for the transfer of substances in the cytoplasm of the cell. Cell wall is absent in animals

Question 34:

A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.

Answer:

Exosmosis in intestine causes dehydration

Question 35:

Name any cell organelle which is non membranous.

Answer:

Ribosomes