NCERT Class 11-Biology Exemplar Chapter –9 Biomolecules Part 4

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Question 2:

Is rubber a primary metabolite or a secondary metabolite? Write four sentences about rubber.


Rubber is a secondary metabolite.

It is considered as a secondary metabolite, due to its unknown function in plants physiology.

Economically rubber is of great importance.

It is sticky, when obtained from the plant as exude.

It is used for synthesis of various products like tyre, eraser etc.

Question 3:

Schematically represent primary, secondary and tertiary structures of a hypothetical polymer say for example a protein.


Following diagrams show primary, secondary and tertiary structures of protein:

Structures of protein

Structures of Protein

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Question 4:

Nucleic acids exhibit secondary structure, justify with example.


DNA and RNA are known to exist in form of helix.

DNA forms double helix and RNA exist in a single stranded helical form.

As helix is considered to be a secondary structure, therefore, nucleic acids exist in secondary structure.

Question 5:

Comment on the statement “living state is a non-equilibrium steady state to be able to perform work”.


Equilibrium is the state of stability, in which work done is assumed to be zero.

As biological system always performs tasks, it is considered to be in in equilibrium.

In biological system, metabolic reactions always remain on and influx and efflux of metabolites takes place constantly, hence it can be said that living state is a non-equilibrium steady state which is able to perform work.

Long Answer Type Questions

Question 1:

Formation of enzyme-substrate complex (ES) is the first step in catalysed reactions. Describe the other steps till the formation of product.


Step 1:

It involves the formation of E-S substrate complex, formed when enzyme binds to substrate at active site.

Step2: Transient phase

The structure of substrate changes, during this very high energy of activation is involved.

Step3: Formation phase

Finally the product gets formed.

Enzyme gets free to bind with new substrate.

Potential energy of the system declines.