Amino Acid Metabolism Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of amino acids during periods of starvation?

They are converted to lipids for energy storage.

They are used to replenish TCA cycle intermediates and gluconeogenesis. (correct)

They are primarily stored for future use.

They are solely excreted as waste without being utilized.

Which of the following describes the significance of amino acid oxidation?

It leads to the formation of stored fat.

It increases the rate of protein synthesis.

It is the primary source of energy during high-carbohydrate intake.

It allows excess amino acids to be catabolized for fuel. (correct)

What is the main function of transamination in amino acid catabolism?

To remove ammonia from amino acids.

To transfer amino groups to keto acids. (correct)

To synthesize non-essential amino acids from essential ones.

To oxidize the carbon skeleton of amino acids.

Which enzyme is responsible for the oxidative deamination of glutamate?

Glutamate dehydrogenase Signup and view all the answers

What distinguishes amino acids from carbohydrates and fatty acids in terms of storage?

Excess amino acids are not stored and are catabolized. Signup and view all the answers

Which process is NOT associated with the removal of ammonia from amino acids?

Glycolysis Signup and view all the answers

What is the function of pyridoxal phosphate (PLP) in amino acid metabolism?

It acts as a coenzyme in transamination reactions. Signup and view all the answers

Which statement about non-essential amino acids is correct?

Their biosynthesis involves the flow of C, N, and S. Signup and view all the answers

What is the primary product of oxidative deamination of glutamine in the liver?

Ammonia Signup and view all the answers

Which enzyme is responsible for the conversion of ammonia and bicarbonate to carbamoyl phosphate in the liver?

Carbamoyl phosphate synthetase I Signup and view all the answers

In which compartment of the cell does the urea cycle primarily occur?

Mitochondrial matrix Signup and view all the answers

Which of the following amino acids can be categorized as both glucogenic and ketogenic?

Isoleucine Signup and view all the answers

Phenylketonuria is caused by a deficiency in which enzyme?

Phenylalanine hydrolase Signup and view all the answers

Methionine is primarily involved in the biosynthesis of which compound?

Cysteine Signup and view all the answers

Which amino acid is primarily degraded to oxaloacetate in the metabolic pathway?

Asparagine Signup and view all the answers

What role does tetrahydrofolate (THF) play in amino acid metabolism?

One-carbon group transfer Signup and view all the answers

Glucogenic amino acids are primarily degraded to which of the following?

Pyruvate Signup and view all the answers

Which branched-chain amino acid is degraded to succinyl-CoA?

Valine Signup and view all the answers

What is an essential amino acid that cannot be synthesized by mammals?

Histidine Signup and view all the answers

Which of the following amino acids is not classified as glucogenic?

Leucine Signup and view all the answers

What is the primary function of the nitrogen-fixing bacteria in legumes?

Fixation of atmospheric nitrogen Signup and view all the answers

Which compound is formed from the combination of ammonium and carbon dioxide in the liver?

Carbamoyl phosphate Signup and view all the answers

Study Notes

Amino Acid Metabolism Learning Objectives

Explain the significance of amino acid oxidation.
Recognize the reaction steps for ammonia removal and the urea cycle (enzymes, metabolites, chemical changes, flow of carbon and nitrogen).
Briefly understand the oxidation of carbon skeletons in various amino acids, noting the flow of carbon, nitrogen, and sulfur.
Explain the significance of amino acid biosynthesis.
Recognize the reaction steps for ammonia assimilation.
Briefly understand the biosynthesis of non-essential amino acids, noting the flow of carbon, nitrogen, and sulfur.

Amino Acid Catabolism

During starvation, amino acids replenish TCA cycle intermediates and serve as gluconeogenesis precursors.
Organisms with high protein diets can oxidize excess amino acids as fuel.
Excess amino acids are not stored; they are catabolized (oxidized).
In animals, amino acids released from proteins are the major nitrogen sources.
Amino acids differ from carbohydrates and fatty acids in their ability to be oxidized.

Removal of Amino Group from Amino Acids

Amino acids are broken down to release ammonia (NH3)
The carbon skeletons are converted into various metabolites, including glucose, acetyl-CoA, and ketone bodies.
Urea is formed from ammonia to be excreted.

Transamination

The initial step in the catabolism of most amino acids is transamination.
A universal amino group acceptor is a-ketoglutarate.
The reaction results in the formation of glutamate and an a-keto acid.
The reaction is catalyzed by aminotransferases, often requiring pyridoxal phosphate (PLP).

Oxidative Deamination of Glutamate

Glutamate dehydrogenase catalyzes the oxidative deamination of glutamate in the mitochondrial matrix.
Oxidation results in the formation of a-ketoglutarate and ammonia (NH3).
NAD(P)+ is reduced to NAD(P)H in the process.

Non-liver Tissues

Glutamine synthetase converts glutamate to glutamine, which is transported in the bloodstream.

Glutamine Transport to Liver

Glutaminase in the liver mitochondria converts glutamine back to glutamate.
Oxidative deamination of glutamate releases ammonia (NH3).

Urea in Liver

Ammonia is converted to urea via the urea cycle.
This process takes place within the mitochondrial matrix.

The Urea Cycle

The urea cycle involves several enzymatic steps, converting ammonia and carbon dioxide into urea.
The urea cycle intermediates are crucial for the cycle to function.
The cycle involves both mitochondrial and cytosolic processes.

Linkage between Urea Cycle and TCA Cycle

There are connections between the urea cycle and the citric acid cycle.
Fumarate, the intermediator, links the two cycles and is used in both (and in the production of amino acids, such as aspartate).

Metabolism of Carbon Skeleton

The carbon skeleton from amino acids can be converted into various intermediary metabolites.
These include glucose, acetyl-CoA, and ketone bodies.
Ammonia is a byproduct.

Oxidation of Carbon Skeletons in Amino Acids

Glucogenic amino acids are degraded to intermediates in the citric acid cycle (or their precursors).
Ketogenic amino acids are degraded to acetyl-CoA or acetoacetate .

Specific Amino Acid Oxidation

Alanine, cysteine, glycine, serine, and threonine are all oxidized to pyruvate.
Isoleucine, leucine, and valine are transformed into acetyl-CoA or propionyl-CoA.
Lysine degrades into acetoacetate.

Methionine Metabolism

Methionine degradation leads to succinyl-CoA via propionyl-CoA.
The cycle involves the recycling of a methyl group.

Leucine, Valine, Isoleucine

Branched-chain amino acids are broken down to various intermediates that enter either the citric acid cycle or form acetyl-CoA, acetoacetate, or succinyl-CoA.

Lysine Degradation

Lysine is degraded to acetoacetate.
This involves transamination, decarboxylation steps, and the formation of intermediates like α-aminoadipate.

Tryptophan Degradation

Tryptophan is degraded to acetoacetate and pyruvate,

Phenylalanine and Tyrosine Degradation

Phenylalanine and tyrosine are degraded into acetoacetate and fumarate.

Phenylketonuria

Phenylketonuria is a genetic disorder due to a defective phenylalanine hydroxylase.
Phenylalanine accumulates and leads to the production of harmful metabolites.

Aspartame

Aspartame is an artificial sweetener.
It is a dipeptide containing phenylalanine.

Amino Acid Biosynthesis

The nitrogen cycle involves nitrogen fixation (converting atmospheric N2 to NH3).
Various bacteria, fungi, and plants use nitrogenase to perform this process
Plants use the ammonia to make amino acids

Synthesis of Essential and Non-Essential Amino Acids

List of essential and non-essential amino acids, including their related precursors.

Biosynthesis of Specific Amino Acids

Describe the pathways for the creation of various amino acids from precursor molecules.
Specific pathways for proline, arginine, serine, and glycine are described.

Tyrosine Biosynthesis

Tyrosine synthesis starts from the essential amino acid phenylalanine.

Cysteine Biosynthesis

Cysteine is synthesized starting from methionine and serine.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the essential concepts of amino acid metabolism, focusing on oxidation, biosynthesis, and catabolism. You'll explore the importance of amino acid processes such as the urea cycle, ammonia removal, and the role of amino acids during starvation. Test your understanding of these key biochemical pathways and their significance.