Test: Structural Organization Of Cell - Class 9 MCQ

Cells are made of a variety of chemical substances - proteins, carbohydrates, fats or lipids and so on. Soil is not a component of  cell. 

Prokaryotic cells are more primitive kind of cells. so 1. they lack nuclear membrane . so they do not have well defined nucleus. 2.they do not have membrane bound cell organelles. 3.they have single chromosome. 4.in photosynthetic bacteria is associated with membranous vesicles.

5-100 micrometre

The term used to describe the entire content of a living cell, including the cytoplasm and the nucleus, is "protoplasm." Protoplasm is often referred to as the living substance of the cell.

Animal cells do not have cell Wall because they do not need them. Cell walls , which are found in plant cells , maintain cell shape, almost as if each cell has its own exoskeleton.

Unicellular organisms are made up of only one cell that carries out all the functions needed by the organism, while multicellular organisms use many different cells to function. Multicellular organisms are composed of more than one cell, with groups of cells differentiating to take on specialized functions

Concept:

• Chromosomes are a highly condensed form of chromatin threads. Chromosomes were first observed by Hofmeister (1818) and Karl Nageli in pollen mother cells of Tradescantia.
• Strasburger described chromosome structure first appeared in the nucleus during cell division.

Explanation:

• Chromosomes are grouped into 4 categories based on the position of the centromere.
• Metacentric: When the centromere is located at mid of the chromosome. These are V-shaped.
• Sub metacentric: When the centromere is located near the centre or midpoint of the chromosome. These are L-shaped.
• Acrocentric: when the centromere is sub-terminal or located near the tip. These are J-shaped.
• Telocentric: When the centromere is terminal or located at the tip of the chromosome. These are I - shaped.

Most prokaryotes contain one circular chromosome. DNA communicateswith the cytoplasm- so it allows direct connection to the transcription and translation. Contain only one copy of the gene. Non essential genes are stored outside of chromosome - in Plasmids.

In order for cells to function and survive, their organelles work together to carry out specific tasks and perform specific roles. Each organelle has its own role that contributes to the survival of the cell. This is called thr Division of labour.