Biochemistry MCQ Quiz in मल्याळम - Objective Question with Answer for Biochemistry - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is It declines the enzyme action

Concept:

• Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy.
• Enzyme inhibitors are molecules that decrease the activity of enzymes.
• Competitive inhibitors specifically bind to the active site of an enzyme, competing with the substrate.
• Enzymes are sensitive to the presence of inhibitors. The presence of an inhibitor will prevent the binding of substrate.
• Competitive inhibitors are those that, in terms of molecular structure, closely match the substrate and stop the enzyme from working.
• The inhibitor and substrate compete for the enzyme's substrate-binding site because of their similar structural makeup. As a result, the substrate cannot bind, which reduces the activity of the enzyme.

Explanation:

• Competitive inhibitors: They compete with the substrate for the enzyme's active site. When a competitive inhibitor binds to the active site, it prevents the substrate from binding, thus reducing the rate of the enzyme-catalyzed reaction.
• Active site alteration: While competitive inhibitors bind to the active site, they do not alter its shape; rather, they block the substrate from binding.
• Enhancing enzyme action: Competitive inhibitors do not enhance enzyme action; they reduce it by preventing substrate binding.
• Inhibition of bond breaking: Competitive inhibitors do not interfere directly with the chemical bond breaking process but prevent the substrate from accessing the enzyme's active site.

The correct answer is It serves as a part of the enzyme's active site

Concept:

Cofactors are non-protein chemical compounds or metallic ions that are required for an enzyme's biological activity to occur. Cofactors can be broadly categorized into three main types:-

• Prosthetic Groups: Tightly bound, integral to the enzyme (Haem, FAD, Biotin).
• Coenzymes: Loosely bound, temporary carriers (NAD+, Coenzyme A, TPP).
• Metal Ions: Can be loosely or tightly bound, involved in structural and catalytic roles (Zinc, Magnesium, Iron).

Explanation:

• Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme.
• For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.

The correct answer is Statement 1 is true, but Statement 2 is false.

Concept:

• Ligases: These are enzymes that catalyze the joining of two molecules by forming new chemical bonds, such as C-O, C-S, or C-N, often requiring energy in the form of ATP.
• Hydrolases: These are enzymes that catalyze the hydrolysis of various bonds, involving the addition of water (H₂O) to break the bond. These are the enzymes that catalyze the hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds.
• Lyases: These are enzymes that catalyze the removal of groups from substrates by mechanisms other than hydrolysis, typically forming double bonds.

Explanation:

• Statement 1: Ligases catalyze the joining of two compounds by forming bonds such as C-O, C-S, or C-N, which is true.
• Statement 2: Hydrolases do not catalyze the removal of groups by mechanisms other than hydrolysis. Instead, they catalyze the hydrolysis of various bonds. The enzymes that remove groups leaving double bonds are lyases. Therefore, Statement 2 is false.

The correct answer is 35° - 40°C

Explanation:-

• Enzymes are biological catalysts that speed up chemical reactions within living organisms. They are highly sensitive to temperature changes, and their activity is influenced by temperature.
• Enzymes have an optimal temperature range within which they function most efficiently.
• Enzymes are most functional within a moderate temperature range around the normal physiological temperature of the organism. For many enzymes found in human cells and most mesophilic organisms, the optimal temperature range is approximately 35°C to 40°C.
• At temperatures below this range, enzyme activity decreases as the rate of chemical reactions slows down.
• Conversely, at temperatures above this range, enzyme activity also decreases due to denaturation, where the enzyme's structure is disrupted, rendering it non-functional.

Conclusion:- 35° - 40°C is the most suitable temperature range for enzymes to be most functional.

The correct answer is Beta - galactosidase 

Explanation-

• Lactose is a disaccharide sugar composed of one molecule of glucose and one molecule of galactose.
• Beta-galactosidase is the enzyme responsible for breaking down lactose into its constituent monosaccharides, glucose, and galactose.
• This enzyme catalyzes the hydrolysis of the glycosidic bond linking the glucose and galactose molecules in lactose.
• Beta-galactosidase is particularly important in organisms such as humans for the digestion of lactose present in milk and dairy products.

Conclusion- Therefore, the correct answer is Beta-galactosidase

Key Points

• Deoxyribonucleic acid or DNA is a polynucleotide of deoxyribonucleotides.
• Thus nucleotides are the basic units of these molecules.
• A nucleotide has 3 components -

1. Pentose sugar - It is ribose in RNA and deoxyribose in DNA.
2. Nitrogenous base - It is a nitrogen-containing molecule with the properties of a base. It is of 2 types: 
   1. Purine - It includes Adenine (A) and Guanine (G).
   2. Pyrimidine - It includes Cytosine (C), Thymine (T) and Uracil (U).
3. Phosphate group

​Explanation:

• Thymine is present only in DNA and gets replaced by Uracil in RNA.
• Therefore, a DNA strand will contain A, T, G and C bases, while RNA will contain A, U, G and C.
• Nucleoside -
  • It is formed when a nitrogenous base is linked to the pentose sugar by N-glycosidic linkage.
  • The nucleosides are named as deoxyadenosine, deoxyguanosine, deoxycytidine or deoxythymidine, depending on the nitrogenous base.
• ​Nucleotide -
  • ​It is formed when a phosphate group is linked to the 5'-OH of a nucleoside.
  • The linkage present is phosphoester linkage.

Correct Answer: Option 3

Concept:

• Enzymes are biological catalyst that increases the rate of a chemical reaction. Enzymes lower the activation energy and thus increase the rate of the reaction.
• The substance on which an enzyme acts is called a substrate.
• Examples of enzymes: Lipase acts on lipid molecules, Maltase acts on maltose, Invertase acts on sucrose (breaks down sucrose into glucose and fructose), etc.

Explanation:

• Apoenzyme: It is the protein part of an active enzyme. It is in an inactive state. The binding of another group of non-protein compounds activates the apoenzyme.
• Cofactor: Some enzymes require the binding of a non-protein compound for its activation. These compounds are called cofactors. In the absence of a cofactor, the enzyme remains in the inactive state - apoenzyme.
  • Vitamins, zinc ions, iron ions, etc. are some examples of cofactors
  • There are two basic groups of cofactors - the prosthetic group and the coenzymes.
• Prosthetic group: The cofactors that bind firmly to the apoenzyme are called prosthetic groups. These groups do not get modified during an enzymatic reaction. Eg: Heme in hemoglobin is an example of a prosthetic group.
• Coenzyme: The cofactor that is loosely bound to an apoenzyme are called coenzymes. These groups get modified during an enzymatic reaction.                             Eg: ATP is an important coenzyme in the human body.
• Holoenzyme: Holoenzyme is an active enzyme that is formed of an apoenzyme and a cofactor (coenzyme).

• Option 1: Holoenzyme = Coenzyme + Cofactor - INCORRECT
  • Holoenzyme is made up of a protein molecule (apoenzyme) and a non-protein moelcule (cofactor/coenzyme).
• Option 2: Apoenzyme = Holoenzyme + Coenzyme - INCORRECT
  • ​Apoenzyme is the inactive part of a holoenzyme (active state) which when bound with coenzyme gets activated.
• Option 3: Holoenzyme = Apoenzyme + Coenzyme - CORRECT
  • ​Holoenzymes are active enzymes that are formed by the binding of an apoenzyme with a coenzyme.
• Option 4: Coenzyme = Apoenzyme + Holoenzyme - INCORRECT
  • ​Coenzymes are non-protein molecule that when bound with an apoenzyme activates it forming a holoenzyme.

So the correct answer is option 3.

The correct answer is A- iv, B-iii, C- ii, D-i

Explanation:

• A. Arachidonic acid -iv. Unsaturated fatty acid:-  Arachidonic acid is a long-chain polyunsaturated fatty acid with 20 carbons and 4 cis double bonds. It is a precursor in the biosynthesis of various eicosanoids, which are signaling molecules involved in inflammation and other physiological functions.
• B. Cellulose -iii. Negative iodine test): Cellulose is an unbranched polymer of glucose linked by β(1→4) glycosidic bonds. It does not form a colored complex with iodine, thus showing a negative iodine test. This property distinguishes it from starch and glycogen.Cellulose does not contain complex helices and hence cannot hold I₂.
• C. Palmitic acid -ii. Saturated fatty acid: Palmitic acid is a saturated fatty acid (C16:0), found in both animals and plants. 
• D. Starch- i. Positive iodine test): Starch is a polysaccharide formed by glucose units, primarily consisting of amylose and amylopectin. Amylose, due to its helical structure, reacts with iodine to produce a characteristic blue-black color, indicating a positive iodine test. 

The correct answer is A-II, B-IV, C-I, D-III

Explanation:

A. Lipase - II. Ester bond

• Lipase is an enzyme that catalyzes the breakdown of fats (lipids) into glycerol and fatty acids. This process involves the hydrolysis of ester bonds within the lipid molecules.

B. Nuclease - IV. Phosphodiester bond

• Nucleases are enzymes that cleave the phosphodiester bonds between nucleotides in nucleic acids (DNA and RNA). This results in the breakdown of the nucleic acid polymers into shorter fragments or individual nucleotides.

C. Protease - I. Peptide bond

• Proteases are enzymes that catalyze the hydrolysis of peptide bonds in proteins. This leads to the degradation of proteins into smaller peptides or amino acids.

D. Amylase - III. Glycosidic bond

• Amylase is an enzyme that catalyzes the hydrolysis of glycosidic bonds in starches (polysaccharides), breaking them down into simpler sugars like maltose or glucose.

The correct answer is Competitive inhibition

Explanation:

• Enzymes are proteinaceous in nature. Ribozymes are an exception as they are structurally nucleic acids but function like an enzyme.
• Enzymes are sensitive to the presence of inhibitors. The presence of an inhibitor will prevent the binding of substrate.
• Competitive inhibitors are those that, in terms of molecular structure, closely match the substrate and stop the enzyme from working.
• The inhibitor and substrate compete for the enzyme's substrate-binding site because of their similar structural makeup. As a result, the substrate cannot bind, which reduces the activity of the enzyme.
• Inhibition of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure. Such competitive inhibitors are often used in the control of bacterial pathogens.