Question

1. Which of the following reaction is directly connected with the urea cycle?

A. From methionine to homocysteine

B. From Citrate to fatty acids

C. From Glycine to Creatine

2. Glucagon is produced by the ____ in the pancreas.

A. Alpha cells

B. Beta cells

C. Delta Cells

3. Which of the following amino acids has a free –OH group in its R chain?

A. methionine

B. Glutamine

C. Serine

D. Glycine

Answer 1

1. Which of the following reaction is directly connected with the urea cycle?

Answer - C. From glycine to creatine.

Explanation - The synthesis of creatine occurs from amino acids glycine, arginine and methionine where the conversion of arginine to ornithine in the presence of glycine results in formantion of guanidinoacetae and then the methyl group from S-adenosyl-L-methonine to S-adenosyl-L-homocysteine results in the generation of creatine

Now, the conversion of arginine to ornithine is directly involve in synthesis of urea. Thus, the conversion of glycine to creatine is directly connected with the urea cycle while the conversion of methionine to homocysteine is indirectly.

Similarly, the conversion of citrate to fatty acids has no direct connection with urea cycle.

Therefore, the correct option is option C. From glycine to creatine.

2. Glucagon is produced by the ____ in the pancreas.

Answer - A. Alpha cells.

Explanation - Alpha cells of pancreas produce glucagon while beta cells produce insulin and delta cells produce somatostatin.

Therefore, glucagon is produced by the alpha cells in the pancreas.

Hence, the correct option is option A.Alpha cells.

3. Which of the following amino acids has a free –OH group in its R chain?

Annswer - C. Serine

Explanation - The side (R) chain of methionine is -CH2-CH2-S-CH3 while side chain of glutamine is -CH2-CH2-CO-NH2, side chain of serine is -CH3-OH and side chain of glycine is -H.

Therfeore, it is only serine from the given options which consist a free -OH group in its R-chain.

Hence, the correct option is option C. Serine.