Tag: enzymes

Questions Related to enzymes

Which of the following is an example of isozyme?
properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. $\alpha$-amylase

  2. Glucokinase

  3. Lactate dehydrogenase

  4. All of the above

Show answer
Correct Option: D
Explanation:
The multiple molecular forms of an enzyme occurring in the same organism and having a similar substrate activity are called isoenzymes or isozymes. They have similar properties but different molecular weights and locations. Over 100 enzymes are known to have isoenzymes. $\alpha$-amylase of wheat endosperm, has 16 isozymes, lactate dehydrogenase has 5 isozymes. Glucokinase is an isozyme of hexokinase.
So, the correct answer is 'All of the above'.

Which one of following vitamin is a precursor of FAD

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Niacin

  2. Riboflavin

  3. Thiamine

  4. Ubiquinor

Show answer
Correct Option: B
Explanation:

FAD also is known as Flavin Adenine Dinucleotide. It is a redox-active co-enzyme associated with various proteins. Riboflavin is the precursor of FAD.

So, the correct option is 'Riboflavin'.

The active site of an enzyme is formed by

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Exposed sulphur bonds

  2. Side chains of the amino acids

  3. Amino groups of the amino acids

  4. Carboxyl group of the amino acids

Show answer
Correct Option: B
Explanation:

The enzyme active site is composed of the amino acid residues. Side chains of the amino acids are seen in the active site region of the enzyme. The difference in the identity, charge, and spatial orientation of the functional groups located there results in the difference in enzyme specificity. 

So, the correct option is ' side chains of amino acids'.

Read the following statement
(i) The enzymes acts on 'N' terminal of a polypeptide chain is present in A
(ii) The enzymes in 'C' terminal of a polypeptide chain is present in BChoose the option which correctly fills up the blanks
A and B

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Gastric juice Pancreatic juice

  2. Pancreatic juice Gastric juice

  3. Pancreatic juice Succus entericus

  4. Intestine juice Pancreatic Juice

Show answer
Correct Option: A
Explanation:
The Pancreatic juice containing carboxypeptidases cleave the amino acid from the peptides from the carboxyl-terminal or C terminal.
The aminopeptidases present in the succus entericus cleave the amino acid from the amino-terminal or the N-terminal.

So, the correct answer is 'Pancreatic juice Succus entericus'

The enzymes are functional at 

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. 0-5$^{\circ}$C

  2. 15-25$^{\circ}$C

  3. 25-40$^{\circ}$C

  4. 70-85$^{\circ}$C

Show answer
Correct Option: C
Explanation:

Enzymes works precisely at certain narrowly optimum conditions, such as appropriate temperature, pH, and ion concentration. Deviation from the optimal conditions adversely affects enzyme activity.  Most enzymes have an optimal temperature, at which the rate of reaction is fastest. For human enzymes, the temperature optima are near the human body temperature (35-40$^o$C). Enzymatic reactions occur slowly or not at all at low temperatures. As the temperature increases, molecular motion increases, resulting in more molecular collisions. The rates of most enzyme-controlled reactions, therefore, increase as the temperature increases, within limits. High temperatures rapidly denature most enzymes. The molecular conformation (3-D shape) of the protein becomes altered as the hydrogen bonds responsible for its secondary, tertiary, and quaternary structures are broken. Because this inactivation is usually not reversible, activity is not regained when the enzyme is cooled.

Identify the incorrect statement about enzymes.

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. They consist of proteins, with or without a non-protein part.

  2. They change the rate of the catalyzed reaction.

  3. They change the value of $\triangle$G of the reaction.

  4. They are not sensitive to heat.

Show answer
Correct Option: D
Explanation:

Enzymes are biological catalyst which catalyze biological reactions. Most of the enzymes are proteins in nature. Some of the enzymes have non protein part which helps them to carry out reaction. Enzymes change the rate of chemical reaction by bringing about a decrease in free energy requirement. Thus, changing the free energy of the reaction. Because enzymes are proteins, they are highly sensitive to heat. Thus, enzymes catalyze reactions only at physiological conditions of temperature and pH.

In a chemical reaction, the

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Rate depends on the value of $\triangle$G.

  2. Rate depends on the activation energy.

  3. Entropy change depends in the activation energy.

  4. Activation energy depends on the value of $\triangle$G.

Show answer
Correct Option: D
Explanation:
$\triangle$G describes change in free energy during occurrence of a chemical reaction. $\triangle$G can be calculated by the difference in free energy content of product and substrate. $\triangle$G value does not describes the rate of a reaction but only decides about the feasibility of a reaction. In case the free energy of product is less than the free energy of substrate the value of $\triangle$G will be negative and the reaction will be feasible but the rate at which it will be converted to product depends on a number of factors. The activation energy required for a reaction depends on the magnitude of $\triangle$G. For a feasible reaction, i.e., a reaction for which the free energy content of product is less than the free energy content of substrate, more the difference between free energy content of product and substrate, more negative will be $\triangle$G and lesser will be the activation energy required for completion of a reaction.

Which of the following is the transition state structure of the substrate formed during an enzymatic reaction?

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Permanent but unstable

  2. Transient and unstable

  3. Permanent and stable

  4. Transient but stable

Show answer
Correct Option: B
Explanation:

Reactions do not undergo chemical changes automatically. They do so in transition states. Transition state has more free energy than reactants or products. Higher free energy helps in collision of transition state reactants. The enzymes binds to substrate molecules and form an unstable transient state called as transition state. The transition state rapidly undergoes degeneration into products and unchanged enzyme molecule.

In presence of an enzyme, the activation energy

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Increases

  2. Decreases

  3. First increases and then decreases

  4. Activation energy in not affected at all

Show answer
Correct Option: B
Explanation:

There is an energy barrier between substrate and products, the energy required for alignment of reacting groups, formation of transient unstable charges, bond rearrangements, and other transformations required for the reaction to proceed. This is illustrated by the energy hill. The difference between the energy levels of the ground state and the transition state is the activation energy. The rate of a reaction reflects this activation energy : a higher activation energy corresponds to a slower reaction. Reaction rates can be increased by raising the temperature, thereby, increasing the number of molecules with sufficient energy to overcome the energy barrier. Alternatively, the activation energy can be lowered by adding a catalyst (enzyme). Catalysts enhance reaction rates by lowering activation energies.

As the water evaporates from the skin of a swimmer who has just left a pool, the swimmer begins to shiver and goose bumps form on his skin. As the blood vessels under his skin move more internally, the goose bumps that form and the shivering are reactions to counteract the lowering of body temperature. After the swimmer has dried off the shivering stops and his body temperature returns to normal. This is an example of

properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

  1. Product inhibition

  2. Disequilibrium

  3. A negative feedback mechanism

  4. A positive feedback mechanism

Show answer
Correct Option: C
Explanation:

When there is a drop in body temperature due to a drop in environmental temperature. The sensory receptors on the skin sends signal to the hypothalamus, which increases the body temperature by causing vasoconstriction and prevents blood from flowing closer to the skin, this also causes piloerection or goosebumps, this is to conserve energy and raise the body temperature. Once the swimmer has dried himself  the thermosensors of the skin send a feed back of temperature returning to normal to the hypothalamus and the shivering is stopped. This is called negative feedback mechanism.

So, the correct answer is 'A negative feedback mechanism'