Tag: enzymes

Quizzes (4) Questions (199)

Questions Related to enzymes

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

Three of the following statements about enzymes are correct and one is wrong. Which one of the following is wrong?

  1. Enzymes require optimum pH for maximal activity.
  2. Enzymes are denatured at high temperature but in certain exceptional organisms they are effective even at temperatures 80-90$^o$C.

  3. Enzymes are highly specific.

  4. Most enzymes are proteins but some are lipids.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Enzymes are the biological catalyst which catalyzes biological reactions within a narrow range of temperature and pH. Certain thermophiles have enzymes which remain functional even at very high temperatures. Most of the enzymes are proteins in nature but a few enzymes are RNA in nature. They are called as catalytic RNAs or ribozymes.

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

Part of enzyme which combines with non-protein part of form functional enzyme is

  1. Apoenzyme

  2. Coenzyme

  3. Prosthetic group

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The conjugate protein consists of two parts protein and non-protein part. Non-protein part is the cofactor and protein part is apoenzymes. Complete conjugate protein is known as Holoenzymes. Apoenzyme is an inactive enzyme. Thus, the correct option is D.

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

Which one value is required for better enzymatic action?

  1. High K$ _i$
  2. Low K$ _i$
  3. Low K$ _m$
  4. High K$ _m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A constant indicating the substrate concentration at which an enzyme catalysed reaction attains half its maximum velocity or 1/2 V$ _{max}$ is known as Michaelis-Menten constant or K$ _m$. Lower K$ _m$ indicates more affinity between the enzyme and substrate and consequently higher reaction rates.

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

Combination of apoenzyme and coenzyme produces

  1. Prosthetic group

  2. Holoenzymes

  3. Enzyme-substrate complex

  4. Enzyme-product complex
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated by the addition of an organic or inorganic cofactor. The holoenzyme is defined as apoenzyme in combination with the cofactor. 
So, the correct answer is option B.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Nobel Prize for discovering enzymes was given to 

  1. Kuhne

  2. Duclaux

  3. Buchner

  4. Dubrunfaut
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Biocatalysts were found accidentally in yeast extract by Buchner in 1897. He prepared a yeast extract and added sugar solution to it. After some time he noticed the alcohol formation in the extract which was a sign of fermentation which took in presence of enzyme. Later on, summer crystallized an enzyme known as urease and reported that all enzymes are protein.
So, the correct answer is option C.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Enzymes are basically made of

  1. Nucleic acids

  2. Proteins

  3. Fats

  4. Vitamins
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated by the addition of an organic or inorganic cofactor. The holoenzyme is defined as apoenzyme in combination with the cofactor. 
So, the correct answer is option B.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Who confirmed protein nature of enzymes?

  1. Monod et al

  2. Arber et al

  3. Berzelius

  4. Northrop
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The proteinous nature of enzyme was proved by Sumner, John Howard Northrop, and Wendell Meredith Stanley. Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated by the addition of an organic or inorganic cofactor. The holoenzyme is defined as apoenzyme in combination with the cofactor. 
So, the correct answer is option D.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

An enzyme acts by

  1. Reducing the energy of activation.

  2. Increasing the energy of activation.

  3. Decreasing the pH.

  4. Increasing the pH.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reactants do not undergo chemical change automatically. They do so in transition state. Transition state has more free energy than reactants or products. The inability of reactants to undergo change due to requirement of extra energy for converting them to transition state is called as 'Energy Barrier'. Energy required to overcome energy barrier is called as 'Activation Energy'.

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

The suffix $-ase$ to enzyme names was proposed by

  1. Duclaux

  2. Buchner

  3. Northrop

  4. Pasteur
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The suffix -ase  is used for the nomenclature of the enzyme. It is used at the end of the substrate. For example, the enzyme that breaks down peroxides are known as peroxidases. Hexokinase are the enzyme which helps in synthesis of hexose sugar. In 1898 Duclaux proposed the suffix -ase.

So, the correct answer is option A.

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

Many enzymes are secreted in inactive form to protect

  1. Cell proteins

  2. Mitochondria

  3. Cell membrane

  4. Cell DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The enzymes are protein in nature and they are generally produced in inactive form so to protect the intracellular damage of protein. For example,  digestive enzymes are secreted in form of zymogens which remains inactive in the cells in which it is produced. The active sites are blocked by the peptide which keeps the enzyme in the inactive stage so the other proteins do not get harmed by the reaction. Cleavage of this peptide cleaves activates the enzyme.

So, the correct answer is option A.