Class 11 Biology - Chapter Cell: The Unit of Life NCERT Solutions | Describe the structure of the following
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome
(i) Nucleus
Nucleus controls all the cellular activities of the cell. It is spherical in shape. It is composed of the following structures:
Nuclear membrane: It is a double membrane separating the contents of the nucleus from the cytoplasm. The narrow space between the two membranes is called the perinuclear space. Nuclear membrane has tiny holes called nuclear pores. These holes allow specific substances to be transferred into a nucleus and out from it.
Nucleoplasm/Nuclear matrix: It is a homogenous granular fluid present inside the nucleus. It contains the nucleolus and chromatin. Nucleolus is a spherical structure that is not bound by any membrane. It is rich in protein and RNA molecules, and is the site for ribosome formation. Chromatin is an entangled mass of thread-like structures. It contains DNA and some basic proteins called histones.
(ii) Centrosome
Centrosome consists of two cylindrical structures called centrioles. Centrioles lie perpendicular to each other. Each has a cartwheel-like organisation.
A centriole is made up of microtubule triplets that are evenly spaced in a ring. The adjacent triplets are linked together. There is a proteinaceous hub in the central part of a centriole. The hub is connected to the triplets via radial spokes. These centrioles help in organising the spindle fibres and astral rays during cell division. They form the basal body of cilia and flagella as well.
More Questions From Class 11 Biology - Chapter Cell: The Unit of Life
- Q:-
Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
- Q:-
Multicellular organisms have division of labour. Explain.
- Q:-
What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
- Q:-
Cell is the basic unit of life. Discuss in brief.
- Q:-
What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
- Q:-
Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials. - Q:-
Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
- Q:-
What are nuclear pores? State their function.
- Q:-
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
- Q:-
What are the characteristics of prokaryotic cells?
Popular Questions of Class 11 Biology
- Q:- Why are living organisms classified?
- Q:- Discuss how classification systems have undergone several changes over a period of time?
- Q:- What is the basis of classification of algae?
- Q:- What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
- Q:- What is meant by modification of root? What type of modification of root is found in the (a) Banyan tree (b) Turnip (c) Mangrove trees
- Q:- State the location and function of different types of meristem.
- Q:- Answer in one word or one line. (i) Give the common name of Periplaneta americana. (ii) How many spermathecae are found in earthworm? (iii) What is the position of ovaries in the cockroach? (iv) How many segments are present in the abdomen of cockroach? (v) Where do you find malphigian tubules?
- Q:- What are macromolecules? Give examples.
- Q:- What is the average cell cycle span for a mammalian cell?
- Q:- What are the factors affecting the rate of diffusion?
Recently Viewed Questions of Class 11 Biology
- Q:- How are the minerals absorbed by the plants?
- Q:- What are the different types of movements exhibited by the cells of human body?
- Q:- Differentiate between
(a) Racemose and cymose inflorescence
(b) Fibrous roots and adventitious roots
(c) Apocarpous and syncarpous ovary - Q:-
Define a taxon. Give some examples of taxa at different hierarchical levels.
- Q:- List five main groups of natural plant growth regulators. Write a note on discovery, physiological functions and agricultural/horticultural applications of any one of them.
- Q:-
Bile juice contains no digestive enzymes, yet it is important for digestion. Why?
- Q:- Discuss how classification systems have undergone several changes over a period of time?
- Q:- Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
- Q:- Describe transpiration pull model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?
- Q:- Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size.
6 Comment(s) on this Question
Awesome,keep it up
Thank you
Nice
ð¹ ð ð¦ ð³ ð° ð¸ ð§ ð· ð´
Tnank you very very very much
Thank you very muchððð......
- All Chapters Of Class 11 Biology
- All Subjects Of Class 11