NCERT Class 11-Biology: Chapter –8 the Unit of Life Part 6

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Question 9:

Write the functions of the following

a. Centromere

b. Cell wall

c. Smooth ER

d. Golgi Apparatus

e. Centrioles


a. Centromere - Centromere holds two chromatids or sister chromatids of a chromosome.

b. Cell wall – It is present only in plant cells. It gives the cell a shape and protects it from mechanical damage and from undesirable macromolecules.

c. Smooth ER – It is a major site for lipid synthesis. In animal cells, lipid-like steroidal hormones are synthesised at Smooth ER.

d. Golgi apparatus – It is an important site of formation of glycolipids and glycoproteins.

e. Centrioles - They form the base body of cilia and flagella and spindle fibres that give rise to spindle apparatus during cell division in animal cells.

Question 10:

Are the different types of plastids interchangable? If yes, give examples where they are getting converted from one type to another.


Yes, plastids are interchangeable in their form.

There are three types of plastids - Chloroplasts (green colour), Chromoplasts (red, yellow, orange colour), and Leucoplasts (Colourless). Depending upon different circumstances, these plastids interchange.

For example -

The colour of green tomatoes changes to red due to replacement of chloroplasts with chromoplasts.

The stem tuber of potato has leucoplasts but when exposed to sunlight, the leucoplasts are replaced by the chromoplasts.