Biomolecules Test

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Biomolecules Test - 78

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Question 1
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Compound $$(B)$$ is:

A

B

C

D

Solution
Question 2
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Directions For Questions

$$\text{D-Glyceraldehyde} \xrightarrow[(ii)\, Ba(OH)_2+H_2SO_4]{(i)\, KCN} \text{Product (B)}$$
$$\downarrow \Delta$$ $$\text{(D+E)}\xleftarrow{Na/Hg \ , H_3O^{+}}\text{Product (C)}$$

$$\text{(D)}\xrightarrow[HNO_3]{[O]} \text{Dibasic acid (optically active)(F)}$$

$$\text{(E)}\xrightarrow[HNO_3]{[O]} \text{Dibasic acid (optically inactive)(G)}$$

...view full instructions

The sequence from $$(A)$$ to $$(D+E)$$ is called:

A
Wohl's method

B
Ruff method

C
Kiliani's method

D
Ekenstein method

Solution

The original version of the Kiliani–Fischer synthesis proceeds through cyanohydrin and aldonic acid lactone intermediates.

The first step is to react the starting sugar with aqueous cyanide (typically NaCN); the cyanide undergoes nucleophilic addition to the carbonyl group of the sugar (while sugars tend to exist mainly as cyclic hemiacetal, they are always in chemical equilibrium with their open-chain aldehyde or ketone forms, and in the case of these aldoses it is that aldehyde form that reacts in this synthesis).

The cyanohydrin resulting from this addition is heated in water, which hydrolyzes the cyanide into a carboxylic acid group that quickly reacts with itself to form a more stable lactone.

Hence, the correct option is $$\text{C}$$
Question 3
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Directions For Questions

Amino acids contains as $${NH_2}$$ as well as COOH group. They exist as zwitter ions.Which explain their several characteristic properties, like decomposition on heating, solubility in water,larger dipole moment. Thus in solution, amino acids may exist as dipolar ion (neutral pH), cationic (in strong acidic solution), or anionic (in strongly basic solution).Amino acids undergo usual reaction of the COOH group as well as $${NH_2}$$ group.

...view full instructions

Base treatment of an amino acid usually result in the conversion of the acid to a derivative via the amino carboxylate salt.The above procedure -

A
Decrease the rate of electrophilic reaction of the free amino group.

B
Decrease the rate of nucleophilic reaction of the free amino group.

C
Enhances the rate of nucleophilic reaction of the free amino group.

D
Enhances the rate of electrophilic reaction of the free amino group.

Solution

Base treatment of an amino acid usually result in the conversion of the acid to a derivative via the amino carboxylate salt.The above procedure Enhances the rate of nucleophilic reaction of the free amino group.
Question 4
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The function of an enzyme is to ?

A
Cause chemical reactions that would not otherwise take place

B
Change the rates of chemical reactions

C
Change the directions of reactions

D
Control the equilibrium points of reactions
Question 5
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An enzyme may be rendered inoperative by?

A
Adding apoenzyme

B
Doubling its concentration

C
Blocking its active site

D
Removing byproducts as soon as they are formed
Question 6
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Starch molecules are polymer with repeating glucose units. Select the correct statement.

A
Glucose units are joined through $$\beta$$-glycosidic linkage

B
The branches of amylopectin are linked to the chain with $$\alpha$$-1,4'-glycosidic linkages

C
The linear linkages of amylopectin are formed by $$\alpha$$-1,4'-glycosidic bond

D
Amylose has an unbranched skeleton of glucose molecules with $$\alpha$$-1,6'-glycosidic linkages

Solution

There is only difference. In starch, all the glucose repeat units are oriented in the same direction. The linear linkage of amylopectin are formed by $$1,4-$$glycosidic bond.
Question 7
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The Michaelis constant $${K _m}$$ is equal to

A
$${\frac{K_1}{K_2-K_3}}$$

B
$${\frac{K_2+K_3}{K_1}}$$

C
$${\frac{K_2-K_3}{K_1}}$$

D
$${\frac{K_1\times K_2}{K_3}}$$

Solution

The general equation for Michaelis-Menten equation for an enzymatic reaction is E + S ↔ ES ↔ E + P,
E stands for enzyme, S is the substrate, ES is the enzyme-substrate complex and P is the product.
Thus, the enzyme combines with the substrate in order to form the ES complex, which in turn converts to product while preserving the enzyme. Assuming steady state, the following rate equations may be written as:
Rate of formation of ES = k₁[E][S]
Rate of breakdown of ES = (k_-1 + k₂) [ES]
and set equal to each other (Note that the brackets represent concentrations). Therefore
k₁[E][S] = (k_-1 + k₂) [ES]
Rearranging terms,
[E][S]/[ES] = (k_-1 + k₂)/k₁
The fraction [E][S]/[ES] has been coined K_m, or the Michaelis constant.
So, the correct answer is option B.
Question 8
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Which one of the following is not true for enzymes?

A
They act on a specific substrate.

B
They are made up of fat and sugar.

C
They act at a specific temperature.

D
They act at a specific pH.

Solution

Enzymes are the biocatalyst, which remains active during the specific conditions like optimum temperature, specific pH and substrate. This conditions varies for different enzymes. The enzymes gets denature when, the conditions exceedes an optimum value while, it gets deactivated when the conditions, are below an optimum level. Enzymes are proteinaceous in nature, they are not composed of fat and sugar.
So, the correct answer is option B.
Question 9
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The shape of an enzyme, and consequently its activity, can be reversibly altered from moment to moment by ?

A
Amino acid substitutions

B
Allosteric subunits

C
Sulphur substitutions

D
High pH
Question 10
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Enzymes are?

A
Substances which are broken into simpler substances during digestion.

B
Substances which are made by the combination of carbohydrates.

C
Substances which break complex food molecules into simpler food molecules.

D
Substances which break complex substances and they themselves undergo dissociation reactions.
Solution
A. Correct option - C
B. Explanation for correct option :
Enzymes are proteins that help speed up metabolism/chemical reactions within the body.
Thus enzymes help in the breakdown of complex food molecules into simpler ones that speed up the process of conversion of reactant to products.
Explanation for incorrect option :
Option A: Enzymes themselves are not broken into simpler sentences but they help in digestion by speeding the conversion of larger molecules to smaller ones.
Option B: Enzymes are proteins by nature and not carbohydrates.
Option D: Enzymes themselves do not undergo dissociation reactions.