Answer:
The purine ring is built onto ribose-5-phosphate of PRPP for its de-novo nucleotide biosynthesis, while the ring structure of the pyrimidine bases are synthesized separately and then coupled to ribose-5-phosphate via the C-N glycosidic bond.
Explanation:
In the de novo synthesis of nucleotides, their metabolic precursors such as aminoacids, ribose-5-phosphate, CO₂ and NH₃ are used as starting materials.
In purine nucleotide synthesis, the ring structure is built up on ribose-5-phosphate of PRPP by addition of one or a few atoms one at a time starting with the amino group donated by glutamine until the first intermediate inosinate is synthesized.
In pyrimidine ring synthesis, orotate is first synthesized from carbamoyl phosphate and aspartate, and then is attached to ribose-5-phosphate of PRPP, before it is then converted to the common pyrimidine nucleotides starting from uridylate.
B, false. Vegetarians do not consume the food that is known to cause cancer, meat.
Answer:
Citrate Synthase facilitates the formation of citrate by deprotonating Acetyl CoA and by protonating the carbonyl oxygen of oxaloacetate
Explanation:
Citrate synthase is a key enzyme in the citric acid cycle that functions to catalyze the formation of citrate from oxaloacetate and acetyl-CoA: acetyl-CoA + oxaloacetate + H2O >> citrate + CoA-SH (Coenzyme A ). This enzyme contains three amino acids at its active site that work together to catalyze the conversion of acetyl-CoA and oxaloacetate into citrate. This active site acts by abstracting (deprotonating) a proton from the alpha carbon of Acetyl CoA which serves as the nucleophile. Subsequently, the active site of the enzyme also protonates the carbonyl oxygen of oxaloacetate, which then suffers nucleophilic attack and thereby facilitating nucleophilic substitution reaction.
<span>The correct answer is B. Lack of water. When there's no water and you start to dehydrate, your salivary glands start working extra hard because your mouth can't be dry and the salivary glands produce saliva to keep the mouth and the throat dry. If your throat and mouth are dry you can't even swallow.</span>
