All Free Biology MCQs with Answers

• A. Phospho-transferase
• B. Phospho-glyceromutases
• C. Fumarase
• D. Succinic thiokinase

Explanation: Option A is correct.Phospho-transferase enzymes are used to catalyze the addition of ammonia, water, or carbon dioxide to double bonds. Phospho-transferase enzymes are a type of enzyme that transfers a phosphate group from one molecule to another. In the case of phospho-transferase enzymes that catalyze the addition of ammonia, water, or carbon dioxide to double bonds, the phosphate group is transferred from ATP to the substrate molecule. The substrate molecule is then able to react with ammonia, water, or carbon dioxide to form a new product. Phospho-transferase enzymes are involved in a variety of biological processes, including the biosynthesis of amino acids, carbohydrates, and lipids. They are also involved in the degradation of molecules such as fatty acids and nucleotides.

• A. Fe+2
• B. Zn+2
• C. Mg+2
• D. None of these

Explanation: Option A is correct.The activator for cytochrome oxidase is Fe2+. Cytochrome oxidase is an enzyme that is found in the electron transport chain of mitochondria. It is the final enzyme in the electron transport chain, and it catalyzes the reduction of oxygen to water. The cofactor for cytochrome oxidase is heme a3, which is a metal-containing molecule. The iron atom in heme a3 is in the Fe2+ state. This iron atom is the site of oxygen reduction. The Fe2+ state is the most active state of iron for oxygen reduction. When Fe2+ is oxidized to Fe3+, it is less active for oxygen reduction. The Fe2+ cofactor is essential for the activity of cytochrome oxidase. Without the Fe2+ cofactor, cytochrome oxidase would not be able to reduce oxygen to water.

• A. For treatment of cancer
• B. Locally to stop bleeding
• C. To diagnose heart disease
• D. For treatment of rickets

Explanation: Option B is correct.Thrombin is used locally to stop bleeding. It is a protein that is produced by the liver and is involved in the clotting of blood. Thrombin is used in surgery to stop bleeding from small cuts or incisions. It is also used to treat bleeding disorders, such as hemophilia. Thrombin works by converting fibrinogen, a soluble protein in the blood, into fibrin, an insoluble protein. Fibrin forms a mesh that traps red blood cells and platelets, creating a clot that stops the bleeding.

• A. Thrombin
• B. LDH-I
• C. L-asparaginase
• D. Alkaline phosphatase

Explanation: Option C is correct.L-asparaginase is a medication that is used to treat acute lymphoblastic leukemia (ALL), a type of cancer that starts in the blood-forming cells of the bone marrow. L-asparaginase is an enzyme that breaks down asparagine, an amino acid that is essential for the growth of cancer cells.

• A. Apoenzyme
• B. Coenzyme
• C. Cofactors
• D. Holoenzyme

Explanation: Option A is correct.The protein part of an enzyme is called apoenzyme. The apoenzyme is the inactive form of the enzyme. It needs to be activated by a cofactor or coenzyme in order to be functional.

• A. CH3COOH
• B. CICH2COOH
• C. Cl2CHC00H
• D. Cl3CCOOH

Explanation: Option A is correct.The weakest acid among the given options is CH3COOH or acetic acid. Acetic acid has a pKa value of 4.76, which is the lowest among the given acids. The pKa value is a measure of the acidity of a molecule. A lower pKa value means that the molecule is more acidic. The other acids have the following pKa values: CICH2COOH: pKa = 2.86 Cl2CHCOOH: pKa = 2.78 Cl3CCOOH: pKa = 2.67 As you can see, the pKa values of the other acids are lower than the pKa value of acetic acid. This means that the other acids are more acidic than acetic acid. Acetic acid is a weak acid because it does not ionize completely in water. Only about 1% of the acetic acid molecules in a solution will ionize. The rest of the acetic acid molecules will remain in the form of molecules.

• A. Acid halide
• B. Acid amide
• C. Ester
• D. Acid anhydride

Explanation: Acid amide cannot be prepared by the reaction of a carboxylic acid with ammonia. Carboxylic acids react with ammonia to form ammonium salts which on heating produce acid amides. CH3COOH + NH3 --> CH3COONH4 + H2O CH3COONH4 --> CH3CONH2

• A. By the oxidation of alcohol
• B. By acid hydrolysis of alkane nitrite
• C. By the reaction R-Mg-Br with CO2 followed by acid hydrolysis
• D. By the reduction of aldehydes

Explanation: Option D is correct.Aldehydes can be reduced not to carboxylic acids by using a strong reducing agent, such as hydrogen gas and a metal catalyst, such as platinum or palladium. The reduction reaction is shown below:R-CHO + H2 -> R-COOH

• A. Dehydration of carboxylic acid with P2O5
• B. Reaction of carboxylic acid with SOCl2
• C. Reaction of carboxylic acid with NH3
• D. Reaction of carboxylic acid with alcohol in the presence of cone. H2SO4

Explanation: Option A is correct.Acid anhydrides can be prepared by the dehydration of two carboxylic acids in the presence of a dehydrating agent. A common dehydrating agent is phosphorus pentoxide (P2O5). The dehydration reaction is shown below: 2CH3COOH -> (CH3CO)2O + H2O In this reaction, two molecules of acetic acid (CH3COOH) are dehydrated to form acetic anhydride (CH3CO)2O. The water molecule (H2O) is produced as a byproduct.

• A. HCOOH
• B. CH3COOH
• C. CH3CH2COOH
• D. CH3CH2CH2COOH

Explanation: Option A is correct.Formic acid is the simplest carboxylic acid. It has a pKa value of 3.75, which is the lowest among the given acids. The pKa value is a measure of the acidity of a molecule. A lower pKa value means that the molecule is more acidic. The other acids have the following pKa values: CH3COOH: pKa = 4.76 CH3CH2COOH: pKa = 5.07 CH3CH2CH2COOH: pKa = 4.89 As you can see, the pKa value of formic acid is lower than the pKa values of the other acids. This means that formic acid is more acidic than the other acids. Formic acid is more reactive than the other acids because it has a smaller size and a more electronegative carbon atom. The smaller size of formic acid makes it more likely to react with other molecules. The more electronegative carbon atom of formic acid makes it more likely to donate a proton to other molecules.