Protein Degradation and Use of Amino Acids for Energy
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Questions and Answers

What is the main reason excess amino acids can be challenging for mammalian metabolism?

  • Ammonia production (correct)
  • Insufficient protein synthesis
  • Excessive energy production
  • Accumulation of carbohydrates

Which part of the body is responsible for converting amino acid carbon skeletons into intermediates of the Krebs cycle for energy production?

  • Kidneys
  • Pancreas
  • Lungs
  • Liver (correct)

Which enzyme in the small intestine is responsible for breaking down proteins into smaller peptides?

  • Isomerase
  • Lipase
  • Amylase
  • Trypsin (correct)

During which conditions are amino acids primarily used for energy production?

<p>During fasting (D)</p> Signup and view all the answers

Where are peptidases found in the body?

<p>Small intestine brush border (D)</p> Signup and view all the answers

What is the fate of ammonia produced from amino acid degradation in mammalian metabolism?

<p>Converted to urea or other less toxic forms (D)</p> Signup and view all the answers

Which biological role do amino acids play in immune function?

<p>As building blocks of proteins (C)</p> Signup and view all the answers

What happens to amino acids during dietary protein excess?

<p>Used for energy production (B)</p> Signup and view all the answers

Which enzymes are responsible for the breakdown of proteins into smaller peptides by cleaving peptide bonds?

<p>Trypsin and chymotrypsin (D)</p> Signup and view all the answers

What is the primary fate of amino acids under conditions of fasting or starvation when carbohydrates are not available?

<p>Deaminated and used for energy production (A)</p> Signup and view all the answers

What role do amino acids play as precursors in biological processes?

<p>Precursors for synthesis of hormones and neurotransmitters (A)</p> Signup and view all the answers

What is the purpose of a zymogen in enzyme regulation?

<p>To prevent damage to cells and tissues (D)</p> Signup and view all the answers

In the context of amino groups, what is the role of α-ketoglutarate?

<p>Accepts an amino group to form glutamate (D)</p> Signup and view all the answers

What distinguishes transamination from oxidative deamination in amino acid metabolism?

<p>Formation of new amino acids vs. removal of ammonia (D)</p> Signup and view all the answers

How is ammonia primarily transported to the liver for detoxification?

<p>As glutamine or part of alanine in the glucose-alanine cycle (D)</p> Signup and view all the answers

Which best describes the physiological function of the Glucose-Alanine Cycle?

<p>Facilitating nitrogen removal from muscle to the liver (A)</p> Signup and view all the answers

What is a characteristic excretory form of nitrogen in birds and reptiles?

<p>Uric acid (D)</p> Signup and view all the answers

What reaction is catalyzed by alanine transaminase?

<p>Conversion of alanine and α-ketoglutarate to pyruvate and glutamate (D)</p> Signup and view all the answers

How is the urea cycle related to the citric acid cycle?

<p>Metabolically linked, forming the 'Krebs bicycle' (A)</p> Signup and view all the answers

What activates carbamoyl phosphate synthase I, a key enzyme in the urea cycle?

<p>N-acetylglutamate (A)</p> Signup and view all the answers

Which category of amino acids can lead to ketone body formation during degradation?

<p>Ketogenic amino acids (A)</p> Signup and view all the answers

What can a carbon skeleton with 3 carbons from an amino acid be converted into?

<p>Pyruvate for gluconeogenesis or energy production (D)</p> Signup and view all the answers

What metabolite can glycine contribute to during its degradation through the glycine cleavage system?

<p>Urea formation (D)</p> Signup and view all the answers

Which enzyme is responsible for converting acyl-CoA to trans-enoyl-CoA during β-oxidation of fatty acids?

<p>Enoyl-CoA hydratase (C)</p> Signup and view all the answers

What is the role of carnitine in the β-oxidation of fatty acids?

<p>Transferring the acyl group across the mitochondrial membrane (C)</p> Signup and view all the answers

What is produced at the end of the β-oxidation cycle of fatty acids?

<p>Propionyl-CoA (A)</p> Signup and view all the answers

Which enzyme is involved in converting L-β-hydroxyacyl-CoA to β-ketoacyl-CoA?

<p>β-hydroxyacyl-CoA dehydrogenase (C)</p> Signup and view all the answers

During β-oxidation of fatty acids, what does β-ketothiolase do?

<p>Converts β-ketoacyl-CoA to acetyl-CoA (A)</p> Signup and view all the answers

What is the function of carnitine-palmitoyl transferase II during β-oxidation?

<p>Converting acyl group back to CoA inside the mitochondrion (D)</p> Signup and view all the answers

Which molecule is NOT a product of the β-oxidation cycle of fatty acids?

<p>Glycerol (A)</p> Signup and view all the answers

Which molecule inhibits fatty acid entry into mitochondria for beta-oxidation by inhibiting CPT I?

<p>Malonyl-CoA (B)</p> Signup and view all the answers

Where does fatty acid synthesis primarily occur?

<p>Cytosol (A)</p> Signup and view all the answers

Which enzyme catalyzes the synthesis of palmitate from acetyl-CoA and malonyl-CoA?

<p>Fatty Acid Synthase (FAS) (C)</p> Signup and view all the answers

In fatty acid synthesis, what provides the required NADPH?

<p>Pentose Phosphate Pathway (B)</p> Signup and view all the answers

Which molecule regulates Acetyl-CoA Carboxylase (ACC) that converts acetyl-CoA to malonyl-CoA?

<p>Citrate and Palmitoyl-CoA (A)</p> Signup and view all the answers

During periods of low carbohydrate availability, acetyl-CoA is converted to which compound in the liver?

<p>Ketone bodies (D)</p> Signup and view all the answers

'Ketone bodies serve as an alternative energy source for peripheral tissues' is particularly true during which physiological state?

<p>Fasting (A)</p> Signup and view all the answers

'Ketoacidosis' is a serious condition that can occur due to overproduction of which compounds?

<p>'Ketone bodies' (D)</p> Signup and view all the answers

Which enzyme converts arachidonic acid to prostaglandins during eicosanoid synthesis?

<p>Cyclooxygenases (COX I and COX II) (B)</p> Signup and view all the answers

Where are steroids synthesized from cholesterol?

<p>Endoplasmic Reticulum (ER) (A)</p> Signup and view all the answers

What is the key early step in cholesterol synthesis that is a major regulatory point?

<p>HMG-CoA Reductase and Mevalonate (B)</p> Signup and view all the answers

What is the specific role of carnitine in the β-oxidation of fatty acids?

<p>Shuttling the acyl-carnitine across the outer mitochondrial membrane (A)</p> Signup and view all the answers

Which enzyme is responsible for converting L-β-hydroxyacyl-CoA to β-ketoacyl-CoA in the β-oxidation of fatty acids?

<p>Acyl-CoA dehydrogenase (B)</p> Signup and view all the answers

What is produced during thiolysis in the β-oxidation cycle of fatty acids?

<p>Trans-enoyl-CoA (C)</p> Signup and view all the answers

In the final cycle of β-oxidation of fatty acids with an odd number of carbons, how many propionyl-CoA molecules are produced?

<p>One (C)</p> Signup and view all the answers

Which enzyme adds water across the double bond in the β-oxidation of fatty acids?

<p>β-Hydroxyacyl-CoA dehydrogenase (C)</p> Signup and view all the answers

During β-oxidation, what is the role of FAD-dependent acyl-CoA dehydrogenase?

<p>Add water across the double bond (D)</p> Signup and view all the answers

What is the primary fate of ketone bodies in the body during fasting or carbohydrate-restricted diets?

<p>Utilization as an energy source by peripheral tissues (D)</p> Signup and view all the answers

Which enzyme catalyzes the synthesis of prostaglandins from arachidonic acid during eicosanoid synthesis?

<p>Cyclooxygenase (COX) (C)</p> Signup and view all the answers

What is the key early step in cholesterol synthesis that serves as a major regulatory point?

<p>Formation of HMG-CoA from acetyl-CoA (A)</p> Signup and view all the answers

What role does malonyl-CoA play in regulating fatty acid metabolism?

<p>Inhibiting fatty acid synthesis (C)</p> Signup and view all the answers

Where does eicosanoid synthesis primarily occur within the cell?

<p>Cell membrane (D)</p> Signup and view all the answers

During which condition do glucagon and epinephrine decrease the activity of Acetyl-CoA Carboxylase (ACC), reducing fatty acid synthesis?

<p>Low energy availability (D)</p> Signup and view all the answers

What is the primary electron donor required for fatty acid synthesis?

<p>NADPH (B)</p> Signup and view all the answers

Which molecule is released from phospholipids by PLA2 during eicosanoid synthesis?

<p>Arachidonic acid (C)</p> Signup and view all the answers

What is the consequence of overproduction of ketone bodies leading to high blood acidity?

<p>Ketoacidosis (D)</p> Signup and view all the answers

What is the primary energy source for peripheral tissues, including the brain, during fasting or carbohydrate-restricted diets?

<p>Ketone bodies (D)</p> Signup and view all the answers

Which enzyme catalyzes the conversion of acetyl-CoA to acetoacetate and other ketone bodies in the liver?

<p>HMG-CoA synthase (C)</p> Signup and view all the answers

Which compound holds the growing fatty acid chain during fatty acid synthesis?

<p>Acyl carrier protein (ACP) (C)</p> Signup and view all the answers

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