BCH3004- Protein and Amino Acid Metabolism

Pyridoxal phosphate (PLP) is a coenzyme for aminotransferases, the enzymes responsible for transamination. It acts as a carrier for the amino group during the transfer process. Lack of vitamin B6 would lead to a deficiency in PLP, impairing the activity of aminotransferases and disrupting amino acid catabolism. This could hinder the removal of amino groups from amino acids, affecting their subsequent metabolism.

Amino acids are the building blocks for proteins, which are essential for various bodily functions. The absorbed amino acids are transported to peripheral tissues for protein synthesis or to the liver for catabolism.

The general hydrolysis reaction is: Protein or Peptide + H2O → Products. Water is essential for the breakdown of peptide bonds, as the addition of water molecule breaks the bond and releases the amino acids.

<p>Most amino acids undergo transamination, a process where the amino group is transferred from the amino acid to a molecule of α-ketoglutarate, forming glutamate. This allows for the collection of amino groups from various amino acids into a single molecule.</p> Signup and view all the answers

<p>Glutamate acts as a central hub for amino group metabolism. It collects amino groups from various amino acids via transamination and serves as a single source of amino groups for further processes, either for biosynthesis or excretion.</p> Signup and view all the answers

<p>Ammonium (NH4+) is toxic and can accumulate in the body if not removed. It can lower the concentration of α-ketoglutarate, a substrate for the citric acid cycle, hindering cellular energy production. This is particularly detrimental to brain cells, which highly depend on glucose metabolism.</p> Signup and view all the answers

<p>Glucogenic amino acids can be converted into glucose through gluconeogenesis, whereas ketogenic amino acids can be converted into ketone bodies. Examples of glucogenic amino acids include alanine and aspartate, while examples of ketogenic amino acids include leucine and lysine.</p> Signup and view all the answers

<p>Amino acids categorized as both glucogenic and ketogenic can be converted into both glucose and ketone bodies, depending on the metabolic needs of the body. This duality provides flexibility by allowing the body to utilize these amino acids for different metabolic pathways.</p> Signup and view all the answers

<p>Aminotransferases are found mainly in mitochondria, where they participate in important metabolic processes like the TCA cycle, urea cycle, and specific amino acid metabolism. However, some are also located in the cytoplasm depending on the specific metabolic needs of the cell.</p> Signup and view all the answers

<p>The small intestine is the primary site for protein digestion and amino acid absorption. Enzymatic digestion breaks down proteins into smaller peptides and amino acids, which are then absorbed across the intestinal lining. These absorbed amino acids are then transported to different parts of the body for various metabolic processes.</p> Signup and view all the answers

<p>Urea is the primary waste product, formed from the hydrolysis of arginine by the enzyme arginase during the urea cycle.</p> Signup and view all the answers

<p>Arginase catalyzes the hydrolysis of arginine to produce urea and ornithine, a crucial step in the urea cycle for detoxifying ammonia.</p> Signup and view all the answers

<p>The nitrogen atoms in urea come from ammonium (NH4+) and the amino acid aspartate, both of which originate from glutamate.</p> Signup and view all the answers

<p>A complete block in the urea cycle can lead to hyperammonemia, nausea after protein ingestion, and gradual mental retardation.</p> Signup and view all the answers

<p>α-keto acids help pick up excess NH4+ and can be converted into essential amino acids missing in a low-protein diet.</p> Signup and view all the answers

<p>Nitrogen is recycled through the excretion of urea or uric acid, and the hydrolysis of proteins from dead organisms into amino acids, releasing ammonia.</p> Signup and view all the answers

<p>Ammonia serves as a central metabolite that acts as a substrate for enzymes that convert it into various organic nitrogen compounds.</p> Signup and view all the answers

<p>Inorganic forms include nitrate ion (NO3-), nitrite ion (NO2-), hyponitrite ion (N2O2), nitrogen gas (N2), hydroxylamine (NH2OH), and ammonia (NH3).</p> Signup and view all the answers

<p>Microbial degradation hydrolyzes proteins from dead organisms into amino acids, leading to the release of ammonia, which is vital for nitrogen recycling.</p> Signup and view all the answers

<p>Ammonia serves as a substrate for enzymes that facilitate the conversion of ammonia into organic nitrogen compounds necessary for amino acid metabolism.</p> Signup and view all the answers

<p>Krebs cycle intermediates are essential for energy production and serve as precursors in various biosynthetic pathways, including amino acid synthesis.</p> Signup and view all the answers

<p>Excess ammonia can lead to soil toxicity, affect plant growth, and contribute to water pollution through runoff.</p> Signup and view all the answers

<p>Key organic nitrogen compounds include amino acids, proteins, purines, pyrimidines, and porphyrins.</p> Signup and view all the answers

<p>It catalyzes the oxidative deamination of glutamate, facilitating the release of ammonia for nitrogen metabolism.</p> Signup and view all the answers

<p>Ammonia directly provides nitrogen for reactions, while glutamine serves as a safe and stable nitrogen source in nitrogen metabolism.</p> Signup and view all the answers

<p>Tyrosine is synthesized from phenylalanine, which means it does not need to be obtained directly through the diet.</p> Signup and view all the answers

<p>Protein turnover is vital for maintaining cellular homeostasis by balancing the synthesis of new proteins with the degradation of old or damaged ones.</p> Signup and view all the answers

<p>They are primarily derived from intermediates of glycolysis, citric acid cycle, and pentose phosphate pathway.</p> Signup and view all the answers

<p>Amino acids are likely to be used for energy during excess dietary intake, protein turnover, starvation, or untreated diabetes.</p> Signup and view all the answers

<p>The two key aspects are protein synthesis and protein degradation.</p> Signup and view all the answers

<p>Glutamine serves as a nitrogen donor in the synthesis of other amino acids, playing a crucial role in nitrogen metabolism.</p> Signup and view all the answers

<p>Three essential amino acids are lysine, methionine, and threonine; they must be supplied through the diet as they cannot be synthesized by the body.</p> Signup and view all the answers

<p>The degradation provides free amino acids that can be catabolized for energy, helping to sustain bodily functions during nutrient scarcity.</p> Signup and view all the answers

<p>Ubiquitin marks specific proteins for degradation.</p> Signup and view all the answers

<p>Autophagosomes engulf cellular components and merge with lysosomes for degradation.</p> Signup and view all the answers

<p>E3 ubiquitin ligase facilitates the transfer of ubiquitin to target proteins.</p> Signup and view all the answers

<p>Peptidases, including pepsin, trypsin, and chymotrypsin, are involved in protein degradation.</p> Signup and view all the answers

<p>Carboxypeptidase removes amino acids from the C-terminus, while aminopeptidase removes from the N-terminus.</p> Signup and view all the answers

<p>The ultimate product is free amino acids, which are used for various cellular functions.</p> Signup and view all the answers

<p>Lysosomal enzymes degrade the contents of autophagosomes into basic cellular components.</p> Signup and view all the answers

<p>The proteasome is the structure responsible for proteolytic activity.</p> Signup and view all the answers

<p>It ensures only damaged or unneeded proteins are degraded, maintaining cellular homeostasis.</p> Signup and view all the answers

<p>Elastase specifically cleaves peptide bonds in elastin.</p> Signup and view all the answers

Nitrogen gas that makes up about 80% of the Earth's atmosphere.

Ammonium is converted from urea or uric acid by microorganisms in the soil.

Nitrogen is recycled back to the soil through excretion of urea or uric acid and the breakdown of dead organisms by microorganisms.

Ammonia can be toxic in high concentrations, but is essential for the synthesis of various organic nitrogen compounds when at lower levels.

The conversion of ammonia into various organic nitrogen compounds by four enzymes allows organisms to utilize it for growth and development.

Inorganic nitrogen compounds like nitrates and nitrites are converted into organic nitrogen compounds like amino acids, proteins, purines, pyrimidines, and porphyrins by living organisms.

The process of utilizing ammonia to synthesize various organic nitrogen compounds such as amino acids, proteins, purines, and pyrimidines.

Nitrogen is found in essential organic compounds such as amino acids, proteins, purines, pyrimidines, and porphyrins, which are crucial for various biological processes.

An enzyme that catalyzes the reversible oxidative deamination of glutamate to α-ketoglutarate, using NAD+ or NADP+ as an electron acceptor.

An enzyme that catalyzes the synthesis of glutamine from glutamate and ammonia, using ATP as an energy source.

An enzyme that catalyzes the synthesis of carbamoyl phosphate from carbon dioxide, ammonia, and ATP.

In some metabolic pathways, either ammonia or glutamine can be used as the nitrogen source that is required for incorporating the nitrogen atom into a molecule.

The processes involved in the creation of amino acids within the body.

Amino acids that the human body cannot synthesize and must be obtained from the diet.

Amino acids that the human body can synthesize from other molecules.

The breakdown of amino acids into smaller components, often for energy production.

The process of producing new proteins and breaking down old proteins within a cell.

The process of synthesizing new proteins from amino acids, forming functional molecules.

Protein degradation is the process of breaking down existing proteins into smaller components.

The ubiquitin-proteasome system is one of the two main pathways for protein degradation. It targets specific proteins for destruction by attaching a small protein called ubiquitin.

The proteasome is a cellular structure responsible for degrading proteins marked with ubiquitin. It acts like a protein shredder, breaking them down into smaller peptides.

Autophagy is the second main pathway for protein degradation. In this process, worn-out cellular components, including proteins, are enclosed in vesicles called autophagosomes.

Autophagosomes are vesicles that engulf cellular components, including proteins, during autophagy. They act like small garbage bags, transporting the waste material.

Lysosomes are cellular organelles that fuse with autophagosomes, breaking down the enclosed material using enzymes. They act like recycling centers for the cell.

Pepsin is a digestive enzyme that breaks down proteins in the stomach, specifically breaking peptide bonds near the amino acids phenylalanine, tyrosine, and tryptophan.

Trypsin is a digestive enzyme that breaks down proteins in the small intestine, specifically breaking peptide bonds on the carboxyl side of lysine and arginine.

Chymotrypsin is a digestive enzyme that breaks down proteins in the small intestine, specifically breaking peptide bonds on the carboxyl side of phenylalanine, tyrosine, and tryptophan.

Carboxypeptidase is a digestive enzyme that removes amino acids from the carboxyl end of a protein chain (C-terminus).

Ammonia (NH4+) is a waste product excreted in different forms depending on the species. Terrestrial vertebrates, including mammals, excrete it as urea via the Urea Cycle. Birds, primates, insects, and reptiles excrete it as uric acid.

The Urea Cycle is a metabolic pathway responsible for the conversion of ammonia (NH4+) to urea in vertebrates. The enzyme arginase, present only in vertebrates, catalyzes the final step, hydrolyzing arginine into urea and ornithine.

The Urea Cycle is a crucial pathway in the removal of excess ammonia (NH4+) from the body. It's a multi-step process involving several enzymes, and its disruption can lead to harmful effects.

The net reaction of the Urea Cycle involves the consumption of CO2, NH4+, ATP, aspartate, and water, producing urea, ADP, Pi, AMP, PPi, and fumarate. This process requires the energy from the cleavage of 4 phosphoanhydrous bonds.

A complete block of any reaction within the Urea Cycle can result in negative effects on humans. Partial deficiency of these enzymes can lead to hyperammonemia, nausea, illness after protein ingestion, and mental retardation.

The breakdown of proteins and peptides into amino acids.

The process of absorbing amino acids, dipeptides, and tripeptides from the small intestine into the bloodstream.

The removal of an amino group from an amino acid. It often involves transferring the amino group to α-ketoglutarate, forming glutamate.

An enzyme that catalyzes the transfer of an amino group from an amino acid to an α-keto acid.

A key molecule in nitrogen metabolism that acts as a central source of amino groups for biosynthesis or excretion.

The process of removing ammonia (NH4+) from the body, primarily occurring in the liver.

Amino acids that can be used to produce glucose through gluconeogenesis.

Amino acids that can be used to produce ketone bodies.

Amino acids that can be used to produce both glucose and ketone bodies.

A condition where high levels of ammonia in the blood can lead to toxicity and potentially damage the brain.