59 Questions
What is the main reason excess amino acids can be challenging for mammalian metabolism?
Ammonia production
Which part of the body is responsible for converting amino acid carbon skeletons into intermediates of the Krebs cycle for energy production?
Liver
Which enzyme in the small intestine is responsible for breaking down proteins into smaller peptides?
Trypsin
During which conditions are amino acids primarily used for energy production?
During fasting
Where are peptidases found in the body?
Small intestine brush border
What is the fate of ammonia produced from amino acid degradation in mammalian metabolism?
Converted to urea or other less toxic forms
Which biological role do amino acids play in immune function?
As building blocks of proteins
What happens to amino acids during dietary protein excess?
Used for energy production
Which enzymes are responsible for the breakdown of proteins into smaller peptides by cleaving peptide bonds?
Trypsin and chymotrypsin
What is the primary fate of amino acids under conditions of fasting or starvation when carbohydrates are not available?
Deaminated and used for energy production
What role do amino acids play as precursors in biological processes?
Precursors for synthesis of hormones and neurotransmitters
What is the purpose of a zymogen in enzyme regulation?
To prevent damage to cells and tissues
In the context of amino groups, what is the role of α-ketoglutarate?
Accepts an amino group to form glutamate
What distinguishes transamination from oxidative deamination in amino acid metabolism?
Formation of new amino acids vs. removal of ammonia
How is ammonia primarily transported to the liver for detoxification?
As glutamine or part of alanine in the glucose-alanine cycle
Which best describes the physiological function of the Glucose-Alanine Cycle?
Facilitating nitrogen removal from muscle to the liver
What is a characteristic excretory form of nitrogen in birds and reptiles?
Uric acid
What reaction is catalyzed by alanine transaminase?
Conversion of alanine and α-ketoglutarate to pyruvate and glutamate
How is the urea cycle related to the citric acid cycle?
Metabolically linked, forming the 'Krebs bicycle'
What activates carbamoyl phosphate synthase I, a key enzyme in the urea cycle?
N-acetylglutamate
Which category of amino acids can lead to ketone body formation during degradation?
Ketogenic amino acids
What can a carbon skeleton with 3 carbons from an amino acid be converted into?
Pyruvate for gluconeogenesis or energy production
What metabolite can glycine contribute to during its degradation through the glycine cleavage system?
Urea formation
Which enzyme is responsible for converting acyl-CoA to trans-enoyl-CoA during β-oxidation of fatty acids?
Enoyl-CoA hydratase
What is the role of carnitine in the β-oxidation of fatty acids?
Transferring the acyl group across the mitochondrial membrane
What is produced at the end of the β-oxidation cycle of fatty acids?
Propionyl-CoA
Which enzyme is involved in converting L-β-hydroxyacyl-CoA to β-ketoacyl-CoA?
β-hydroxyacyl-CoA dehydrogenase
During β-oxidation of fatty acids, what does β-ketothiolase do?
Converts β-ketoacyl-CoA to acetyl-CoA
What is the function of carnitine-palmitoyl transferase II during β-oxidation?
Converting acyl group back to CoA inside the mitochondrion
Which molecule is NOT a product of the β-oxidation cycle of fatty acids?
Glycerol
Which molecule inhibits fatty acid entry into mitochondria for beta-oxidation by inhibiting CPT I?
Malonyl-CoA
Where does fatty acid synthesis primarily occur?
Cytosol
Which enzyme catalyzes the synthesis of palmitate from acetyl-CoA and malonyl-CoA?
Fatty Acid Synthase (FAS)
In fatty acid synthesis, what provides the required NADPH?
Pentose Phosphate Pathway
Which molecule regulates Acetyl-CoA Carboxylase (ACC) that converts acetyl-CoA to malonyl-CoA?
Citrate and Palmitoyl-CoA
During periods of low carbohydrate availability, acetyl-CoA is converted to which compound in the liver?
Ketone bodies
'Ketone bodies serve as an alternative energy source for peripheral tissues' is particularly true during which physiological state?
Fasting
'Ketoacidosis' is a serious condition that can occur due to overproduction of which compounds?
'Ketone bodies'
Which enzyme converts arachidonic acid to prostaglandins during eicosanoid synthesis?
Cyclooxygenases (COX I and COX II)
Where are steroids synthesized from cholesterol?
Endoplasmic Reticulum (ER)
What is the key early step in cholesterol synthesis that is a major regulatory point?
HMG-CoA Reductase and Mevalonate
What is the specific role of carnitine in the β-oxidation of fatty acids?
Shuttling the acyl-carnitine across the outer mitochondrial membrane
Which enzyme is responsible for converting L-β-hydroxyacyl-CoA to β-ketoacyl-CoA in the β-oxidation of fatty acids?
Acyl-CoA dehydrogenase
What is produced during thiolysis in the β-oxidation cycle of fatty acids?
Trans-enoyl-CoA
In the final cycle of β-oxidation of fatty acids with an odd number of carbons, how many propionyl-CoA molecules are produced?
One
Which enzyme adds water across the double bond in the β-oxidation of fatty acids?
β-Hydroxyacyl-CoA dehydrogenase
During β-oxidation, what is the role of FAD-dependent acyl-CoA dehydrogenase?
Add water across the double bond
What is the primary fate of ketone bodies in the body during fasting or carbohydrate-restricted diets?
Utilization as an energy source by peripheral tissues
Which enzyme catalyzes the synthesis of prostaglandins from arachidonic acid during eicosanoid synthesis?
Cyclooxygenase (COX)
What is the key early step in cholesterol synthesis that serves as a major regulatory point?
Formation of HMG-CoA from acetyl-CoA
What role does malonyl-CoA play in regulating fatty acid metabolism?
Inhibiting fatty acid synthesis
Where does eicosanoid synthesis primarily occur within the cell?
Cell membrane
During which condition do glucagon and epinephrine decrease the activity of Acetyl-CoA Carboxylase (ACC), reducing fatty acid synthesis?
Low energy availability
What is the primary electron donor required for fatty acid synthesis?
NADPH
Which molecule is released from phospholipids by PLA2 during eicosanoid synthesis?
Arachidonic acid
What is the consequence of overproduction of ketone bodies leading to high blood acidity?
Ketoacidosis
What is the primary energy source for peripheral tissues, including the brain, during fasting or carbohydrate-restricted diets?
Ketone bodies
Which enzyme catalyzes the conversion of acetyl-CoA to acetoacetate and other ketone bodies in the liver?
HMG-CoA synthase
Which compound holds the growing fatty acid chain during fatty acid synthesis?
Acyl carrier protein (ACP)
Explore the biological roles of amino acids as building blocks for proteins, precursors for hormones and neurotransmitters, and contributors to immune function. Understand how amino acids can be utilized as an energy source during dietary protein excess, fasting, or starvation.
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