NAD is known as nicotinamide adenine dinucleotide. It is a dinucleotide which has two dinucleotides joined by the phosphodiester bond. It is a coenzyme found in all living cell. NAD+ acts an electron acceptor in metabolic reaction. During glycolysis, it accepts the electron and changes to NADH which is further changed to ATP. One NADH produces three ATP. 
Nicotinamide adenine dinucleotide phosphate is known as NADP. It acts as an electron acceptor. The reduced form of the NADP is known as NADPH.
Purines are double ring while pyrimidines are single ring structure. Adenine and guanine are purines while thymine and cytosine are pyrimidines. A purine is attached to pyrimidine by hydrogen bond. Adenine is attached to thymine by two hydrogen bonds while three hydrogen bond is present between guanine and cytosine.
So, the correct answer is option A.

Cofactor is a non protein part of the enzyme. It can be metal ions or the organic chemical. The cofactors which are organic chemicals are known as coenzyme. These are loosely attached to the apoenzyme. Vitamins acts as a coenzyme and activates the protein part of enzyme. Vitamin B2 complex like flavin (FMN) acts as a prosthetic group of the protein. FAD gets reduced to FADH2 by addition of hydrogen ion and two electron. The FADH2 helps in redox reaction during metabolic process. In electron transport chain, FADH2 breaks to form FAD+ and releases two electron which passes to electron carriers. FMN also acts as a prosthetic group and a strong oxidizing agent.
So, the correct answer is option A

A lysosome is a membrane-bound organelle found in nearly all animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules.

Restriction endonucleases are enzymes which scan the DNA molecule for a particular nucleotide sequence. These are called recognition sequences. Once the endonuclease finds this sequence it halts and cuts the strand. Thus the correct answer is option C.

Desmolase catalyzes the formation or destruction of carbon-carbon bonds within a molecule. It is involved in the transfer of electrons.

Hydrolase is the enzyme which catalyzes the splitting of compounds by addition of water.

Dehydrogenase is an enzyme which participates in the oxidoreductase reaction by using an electron acceptor.

Transaminase catalyzes aminotransferase reaction between an amino acid and a α-keto acid.

Yes because ex, enzyme hexokinase which catalysis glucose to glucose 6 phosphate is inhibited by glucose 6 phosphate called feedback allosteric inhibitor.

The molecule ATP can function as a coenzyme because when phosphate group is removed from turning ATP to ADP energy is released and since energy is required for doing chemical reactions so ATP can be used as to give energy in the reactions.

Feedback inhibition is the process by where the end product terminates the reaction. The accumulation of the end product interferes with the enzymatic activity by changing the shape of its active site. On changing the shape of the active site, the substrate does not attach to the active site and thus the reaction terminates. During glycolysis, the glucose changes to glucose 6 phosphates in presence of hexokinase. When the amount of glucose 6 phosphate exceeds it deactivate hexokinase.

So, the correct answer is option B.

Proteins that are enzymes form only a subset of the total protein population. Non-enzymatic proteins include structural proteins and receptors, among others.

While most enzymes are indeed proteins, there are some that are not. These are the enzymatic RNAs, also known as ribozymes.

Coenzyme is an organic nonprotein molecule that associates with an enzymes molecule in catalysing biochemical reactions. It usually participates in the substrate-enzyme interaction by donating or accepting certain chemical groups.
Apoenzyme is an inactive enzyme that must associate with a specific cofactor molecule in order to function.
Isoenzyme or isozyme is one of the several forms of an enzyme that catalyse the same reaction but differ from each other in such properties as substrate affinity and maximum rates of enzymes-substrate reaction.

Hydrolases are the enzymes which break large molecules into smaller ones with the help of hydrogen and hydroxyl groups of water molecules, this phenomenon is known as hydrolysis. Amylase is the enzyme produced by the salivary gland and is found in saliva. It breaks starch into glucose. Thus, the correct answer is A.

A competitive inhibitor is one which competes with the substrate molecules for the active site of the enzyme. Competitive inhibitor resembles the natural substrate and combines reversibly to the free enzyme at the active site. This results in the competition between the substrate and inhibitor for the active site of the enzyme. Malonate inhibits succinate dehydrogenase activity. The structure of malonate is similar to succinate. This is an example of competitive inhibition. 
Thus, the correct answer is option C.

Endoenzymes are the enzymes which functions inside the cell. It is secreted inside the cell and catalyzes the reaction inside the cell. Hexokinase and glycogen synthase are two endoenzyme. The optimum pH for the endoenzyme is neutral. Fluctuation in pH from the optimum causes ionization of R-groups of amino acids which decrease the enzyme activity. 

So, the correct answer is option C