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1. What are macromolecules? Give examples.

The large sized complex molecules that get separated in acid-insoluble fraction using trichloroacetic acid are called macromolecules. These are polymers having a molecular mass of 10,000 daltons or more. Examples of macromolecules include proteins, carbohydrates, nucleic acids etc. Lipids are found to be present in the acid-insoluble fraction, however, they are not of high molecular weight. 

14. 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.

A centromere refers to a non- stainable area that attaches two chromatids of a chromosome. On the basis of position of centromerechromosomes can be of following types.  1. Acrocentric chromosomes- Centromere is present sub-terminal regions, chromatids are arranged in J-shaped 2. Metacentric chromosome- Centromere is present in the centre and the chromosome appears V-shaped.  3. Sub-metacentric...

13. Describe the structure of the following with the help of labelled diagrams.  

           (ii) Centrosome

Centrosome The structure of centrosome is made up of two cylindrical structures called centrioles. These centrioles show a cartwheel like organisation and both lie perpendicular to each other. A centriole is made up of microtubule triplets that are evenly spaced in a ring The adjacent triplets are linked together. A proteinaceous hub is present in the central part of a centriole. The hub is...

13. Describe the structure of the following with the help of labelled diagrams.

        (i) Nucleus

The nucleus is the centrally placed, spherical structure found in the cell. It is the primary organelle that controls all the activities of a cell. The structure of the nucleus comprises of nuclear membrane enclosing nucleoplasm or nuclear matrix.  1. Nuclear membrane- The membrane of the nucleus is a double-layered structure consisting of an outer and an inner layer. Both these layers are...

12. Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.

Both lysosome and vacuole are endomembranous structures with only a single membrane, IN case of vacuoles, the membrane is called tonoplast. Despite being endomembranous structures, the function of lysosome and vacuole differs considerably. The lysosome consists of hydrolytic enzymes that hydrolyze various substances except for cellulose. These can even digest worn contents of their own cell if...

10. Cell is the basic unit of life. Discuss in brief.

A living organism is composed of various organ and organs systems. These organ systems are made up of tissues that in turn are composed of cells. A cell is the smallest unit of life which can survive on its own and perform all the essential functions necessary for its survival. It not only supports the structure of an organism but its functions also. Due to this reason cell is the basic...

9. Multicellular organisms have division of labour. Explain.

Division of labour refers to the differentiation of certain components or parts to perform specific functions to cause an increase in the efficiency and survival rate of that organism.  Multicellular organisms are composed of millions of cells. All these cells are different from each other with respect to their structure and function. These cells together are responsible for the survival of the...

8. What are the characteristics of prokaryotic cells?

Characteristics of prokaryotic cells Prokaryotic cells are those cells which do not have a well-defined nucleus. The most important characteristics of prokaryotic cells are as follows: 1. The nucleus of prokaryotic cells is not well defined i.e. it does not possess a nuclear envelope. The DNA of these cells lies freely in the cytoplasm. The DNA is naked and variously coiled. Extrachromosomal...

7. 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.

The two double membrane-bound organelles are mitochondria and chloroplast.  Characteristics of Mitochondria-  1. Mitochondria are cylindrical shaped cell organelles which can be stained by Janus green and observed in the microscope. MItochondria consists of 60-70% proteins, 25-35 % lipids, 5-7% RNA, DNA etc.  2. Mitochondria are encircled by two membranes i.e. an outer membrane and inner...

6. 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?

Neutral solutes are lipid soluble. These move across the plasma membrane by directly crossing through the lipid bilayer. Their rate of movement across the plasma membrane depends on concentration gradient and lipid solubility of neutral solutes. No polar molecules can not move across the membrane in the same manner as neutral solutes. The polar molecules require carrier proteins in order to...

5. What is a mesosome in a prokaryotic cell? Mention the functions that it performs.

Mesosome is a complex membranous structure formed by the infoldings of the plasma membrane in prokaryotic cells. The functions performed by mesosome are as follows: 1. Mesosomes play important roles in cell wall formation, DNA replication etc. 2. Mesosomes are folded structures, this quality helps to increase the surface area of the plasma membrane to carry out enzymatic activities.  3....

4. 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.

The correct statement is  (c) In prokaryotes, there are no membrane bound organelles. All other statements are incorrect as cells of some organism can lack a nucleus (e.g. RBC ), animal cells do not possess a cell wall and cells are formed from pre-existing cells.       

3. Match the following
 Column I                             Column II
(a) Cristae                           (i) Flat membranous sacs in stroma
(b) Cisternae                       (ii) Infoldings in mitochondria
(c) Thylakoids                     (iii) Disc-shaped sacs in Golgi apparatus

The correct matching is (a)- (ii), (b)- (iii), (c)- (i)  Column I                             Column II (a) Cristae                           (ii) Infoldings in mitochondria  (b) Cisternae                       (iii) Disc-shaped sacs in Golgi apparatus (c) Thylakoids                      (i) Flat membranous sacs in stroma 

2. New cells generate from

       (a) bacterial fermentation

       (b) regeneration of old cells

       (c) pre-existing cells

        (d) abiotic materials

(c) . New cells generate from pre-existing cells. According to Rudolf Virchow, the new cells arise from pre-existing cells by their division.

1. Which of the following is not correct?  

      (a). Robert Brown discovered the cell.

      (b). Schleiden and Schwann formulated the cell theory

      (c). Virchow explained that the cells are formed from pre-existing cells.

      (d). A unicellular organism carries out its activities within a single cell



(a) is not correct. All the others are correct. Robert Brown discovered the nucleus and not the cell. Cells were first observed by Robert Hooke when he was studying the cork cells of plants. Metthias Schleiden and Theodore Schwann( 1938) proposed the cell theory which was later modified by Rudolf Virchow(1855). The cell theory states that 1. All living organisms are composed of cells and...