Biochemistry : Protein Catabolism
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Example Question #2 : Other Protein Catabolism Concepts
During the urea cycle, which enzyme catalyzes the rate-limiting step in the mitochondria?
Phosphofructokinase (PFK)
Triose phosphate isomerase
Citrate synthase
Glucose-6-phosphate dehydrogenase
Carbamoyl phosphate synthase
Carbamoyl phosphate synthase
Triose phosphate isomerase catalyzes the isomerization between dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. Glucose-6-phosphate dehydrogenase is a regulatory enzyme for the pentose phosphate pathway. Citrate synthase is a regulatory enzyme for the Krebs cycle, catalyzing the synthesis of citrate from acetyl-CoA and oxaloacetate. PFK catalyzes the rate-limiting step in glycolysis.
Example Question #3 : Other Protein Catabolism Concepts
What is the difference between ketogenic and glucogenic amino acids?
I. Ketogenic amino acids are degraded to acetyl-CoA and ketones; glucogenic amino acids can be converted to glucose
II. Ketogenic amino acids are alanine and glutamine
III. The ketogenic amino acids are leucine and lysine
IV. Amino acids that are glucogenic and ketogenic are: phenylalanine, tyrosine, tryptophan, isoleucine and threonine
I and IV
II and III
III and IV
I, III, and IV
I, II, III, and IV
I, III, and IV
Ketogenic amino acids are degraded to Acetyl Coenzyme A (CoA) and ketones; glucogenic amino acids can be converted to glucose. Amino acids that are both ketogenic and glucogenic can be metabolized to both glucose and ketone bodies. Purely ketogenic aminoacids are leucine and lysine. Amino acids that are glucogenic and ketogenic are: phenylalanine, tyrosine, tryptophan, isoleucine and threonine. All the other amino acids are glucogenic.
Example Question #4 : Other Protein Catabolism Concepts
All of the following are intermediate molecules in the urea cycle except __________.
ornithine
citrulline
arginosuccinate
citrate
arginine
citrate
In the urea cycle, carbomyl phosphate first combines with the molecule ornithine. This forms citrulline. Citrulline then reacts with aspartate to form arginosuccinate. Fumarate dissociates from arginosuccinate forming arginine, and then the addition of water forms urea and ornithine once again to complete the cycle. Citrate is not involved in this cycle, it is however in the Krebs cycle.
Example Question #749 : Biochemistry
Carbomyl phosphate is a molecule that can enter into the urea cycle. It is formed from the coupling of what two molecules?
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