Protein- Book Qs

• Trypsin is one of several proteolytic enzymes found in the small intestine that hydrolyze peptide bonds
• Large polypeptides are the product of enzymatic action that occurs in the stomach
• Protein denaturation, effected by HCl (stomach acid), occurs in the stomach
• Active transport processes effect the passage of amino acids through the intestinal lining into the bloodstream
• Which of the following statements about dietary protein digestion is correct?

  1. It begins in the mouth
  2. It occurs to a small extent in the stomach
  3. It occurs only in the small intestine
  4. no correct response

  2
• Dietary protein materials as they leave the stomach are a mixture that contains predominately polypeptides
• The inactive form of pepsin is converted to its active form by hydrochloric acid
• Which of the following is not a proteolytic enzyme?

  1. trypsin
  2. aminopeptidase
  3. secretin
  4. no correct response

  3
• The dominant use for the amino acids of the amino acid pool is the synthesis of proteins
• The most abundant amino acid in the amino acid pool is glutamate
• Which of the following conditions would produce a negative nitrogen balance within the human body?

  1. pregnancy
  2. starvation
  3. growth spurt in a child
  4. no correct response

  2
• Transamination or oxidative deamination?

  The enzyme glutamate dehydrogenase is active

  oxidative deamination
• Transamination or oxidative deamination?

  The coenzyme pyridoxal phosphate is needed

  Transamination
• Transamination or oxidative deamination?

  An amino acid is converted into a keto acid with release of ammonium ion

  Oxidative deamination
• Transamination or oxidative deamination?

  One of the reactants is an amino acid, and one of the products is an amino acid

  Transamination
• The reactants in a transamination reaction are a keto acid and an amino acid
• The products in a transamination reaction are a keto acid and an amino acid
• The net effect of transamination is to collect the amino groups from a variety of amino acids into two compounds, which are both amino acids
• The nitrogen-containing product of an oxidative deamination reaction is ammonium ion
• A derivative pf pyridoxine (vitamin B6) is required as a coenzyme in transamination
• Most aminotransferases are specific for the keto acid a-ketoglutarate
• Which of the following statements concerning the compound urea is incorrect?

  1. Two- NH2 groups are present in its structure
  2. It is a white solid in its pure state
  3. It gives urine its yellow color
  4. no correct response

  3
• Which of the following is not a reactant in the formation of carbomoyl phosphate?

  1. carbon dioxide
  2. water
  3. ammonium ion
  4. no correct response

  4
• The two "fuels" for the urea cycle are carbamoyl phosphate and acetyl CoA
• Which of the following is the correct "nitrogen characterization" for the first step in the urea cycle

  1. N1 + N2 -> N3
  2. N2 + N2 -> N4
  3. N2 + N2 -> N3 + N1
  4. no correct response

  1
• The two nitrogen atoms in a urea molecule have as their biosynthetic source

  1. two ammonium ions
  2. two aspartate ion
  3. an ammonium ion and an aspartate ion
  4. no correct response

  3
• In the urea cycle, the urea producing step involves the reaction of water with arginine
• Which of the following statements concerning the degradation of standard amino acid "carbon skeletons" is correct?

  1. Each type of carbon skeleton is degraded to a different product
  2. All carbon skeletons are degraded to the same product
  3. Each type of carbon skeleton is degraded by a different metabolic pathway
  4. no correct response

  3
• How many standard amino acid carbon skeleton degradation products are citric acid cycle intermediates?

  a.3

  b. 4

  c. 6

  d. no correct response

  b
• Which of the following statements concerning the genicity of standard amino acid degradation products is incorrect?

  1. Some, but not all, standard amino acids are ketogenic
  2. Some, but not all, standard amino acids are glucogenic
  3. All amino acid are both ketogenic and glucogenic
  4. no correct response

  3
• Which of the following pairings of standard amino acid carbon skeleton degradation product and amino acid genicity is correct?

  1. citric acid cycle intermediate and ketogenic
  2. acetyl CoA and glucogenic
  3. pyruvate and both ketogenic and glucogenic
  4. no correct response

  3
• The classification of an amino acid as essential or nonessential for humans can be related to the number of steps in its biosynthetic pathway
• How many of the standard amino acids are biosynthesized in adequate amounts in an adult human body?

  a.5

  b. 9

  c. 10

  d. no correct response

  c
• The simplest pathways for amino acid biosynthesis in the human body involve transamination reactions
• Which of the following statements concerning the first step pf the degradation of the heme portion of hemoglobin is incorrect?

  1. molecular O2 is needed as a reactant
  2. carbon monoxide is a product
  3. ring opening with release of an iron atom occurs
  4. no correct response

  4
• Which of the following statements concerning the bile pigments produced from the degradation of the heme portion of hemoglobin is incorrect?

  1. They are responsible for the yellow color of urine
  2. They are responsible for the brown color of the feces
  3. They are responsible for the yellow jaundiced skin
  4. no correct response

  4
• In the degradation of heme, which of the following substances is produced in the second step of the degradation process?

  1. bilirubin
  2. biliverdin
  3. urobilin
  4. no correct response

  1
• In the degradation of heme, the iron atom present is released and then captured by the iron-storage protein ferritin
• In degradation of the sulfur-containing amino acid cysteine, the sulfur is released in the form of hydrogen sulfide
• The process of sulfate assimulation converts SO4^2- to H2S