Biochemistry week 14 Flashcards
During starvation and fasting what is muscle protein broken down into and their uses
- Amino acids: for essential protein synthesis
-Keto acids: for gluconeogenesis
What are the 2 roles of Dietary protein
- Provides carbon skeletons for metabolism and energy
-Supplies essential amino acids
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What do body protein and dietary protein contribute to
- Amino acid pool
What are body proetin and dietary protein involved in
-Oxidative metaoblism
-Gluconeogenesis
-Energy production
What must proteins be hydrolyzed into for absorption
- Dipeptides
-Tripeptides
-Amino Acids
What type of enzymes are responisble for protein digestion
- Proteolytic enzymes
Name the 3 stages of Digestion of dietary proteins and where they take place
- Gastric Digestion : Stomach
-Pancreatic Digestion: Small intestine
-Small intstin digestion
Explain what happens in the 3 stages of digestion
-Gastric Digestion (Stomach)
(HCl) denatures proteins.
Pepsinogen → Pepsin (activated by HCl) starts breaking down proteins.
-Pancreatic Digestion (Small Intestine)
Pancreatic enzymes further degrade proteins into smaller peptides.
-Small Intestine Digestion
Enzymes break oligopeptides into absorbable amino acids and peptides.
Where can amino acids be obtained from
- Diet,synthesized de novo or from body protein degeneration
What is excess nitrogen removed as
- Ammonia
What is ammonia converted to and why
- A non toxic form as it is toxic
Explain the brief process of how urea is excreted from Ammonia
- Ammonia is transported to the liver in a non toxic form
-Liver converts ammonia to urea - Urea is then excrted in urine
Why is Ammonia converted to urea
- Bcs urea is neutral,less toxic and highly soluble
What is the alternate name for Nitrogen removal process
- Amino acid catabolism
What happens in the first step of Amino acid catabolism(Removal of Amino Acid)
-What is this reaction catalyzed by
- Key enzymes
The transfer of an α-amino group to α-ketoglutarate, forming:
An α-keto acid (from the original amino acid).
Glutamate (which can be further deaminated or used in nonessential amino acid synthesis).
- aminotransferases
-ALT and AST
Explain the clinical revelance of the key enzymes ALT and AST in the amino catabolism reactions
AST and ALT levels are elevated in liver disease
- ALT is more specific for liver disease
What is the name of the second step of Amino acid catabolism
Oxidative Deamination
What happes in the second step of Amino acid catabolism( Oxidative deamination)
- It releases the amino group as free ammnoia and produces:
- α-keto acids, which enter energy metabolism.
Ammonia, used for urea synthesis in the liver.W
Where does Oxidative deamination occur
- Liver and kidneys
What catalyzes the oxidative deamination of glutamate in Oxidative deamination
- Glutatmate dehydrogenase
What is the overall name of the final step of amino acid catabolism
- Dehydration
What happens in the dehydration step (the last step of amino acid catabolism)
- Serine and threonine dehydratases remove a water molecule, forming:
An unstable imine intermediate that spontaneously hydrolyzes.
Results in α-keto acid and ammonia production.
Name the 2 mechanisms for Ammonia transport
- Glutamine synthetase pathway
- Alanine Transamination( Glucose-Alanine cycle)
Explain what happens in the Glutamine Synthetase Pathway (Ammonia transport)
-Ammonia combines with glutamate to form glutamine (non-toxic transport form).
-Glutamine travels to the liver, where glutaminase breaks it into glutamate and ammonia.
-Glutamate Dehydrogenase (GDH) converts glutamate into α-ketoglutarate and ammonia.
-Ammonia is converted to urea in the liver
What happens in the Alanine Transamination(Glucose Alanine cycle)
-Pyruvate is transaminated to alanine.
Alanine travels to the liver and is converted back to pyruvate via ALT (alanine transaminase).
Pyruvate is used to synthesize glucose, which returns to muscles for energy.
What is the purpose of urea
- Primary method of nitrogen disposal
Describe a brief straight line cycle of urea
Liver produces urea → transported in blood → filtered by kidneys → excreted in urine.
Explain the 5 sources of nitrogen in the urea cycle
Nitrogen enters the cycle from amino acids:
-Transamination transfers amino groups to oxaloacetate or α-ketoglutarate, forming aspartate or glutamate.
-Glutamate dehydrogenase (GDH) releases ammonia in the liver.
-Ammonia enters the cycle via carbamoyl phosphate.
-Aspartate provides the second nitrogen for urea formation.
Where do the first 2 and the rest of the Urea cycle reactions take place
-Mitochondria
then the rest cytosol
What is the name of the first step in the Urea cycle and explain what happens
+ What activtaor is required
- Carbamoyl Phosphate formation
-CPS I converts ammonia into carbamoyl phosphate.
Requires N-acetylglutamate (NAG) as an activator.
- NAG
What happens in the second step of urea cycle(Citrulline formation) after (Carbamoyl phosphate formation)
-OTC transfers carbamoyl phosphate to ornithine, forming citrulline.
-Citrulline moves to the cytosol.
What happens in the 3rd step of the urea cycle after Citrulline formation
- Argininosuccinate Synthetase combines citrulline with aspartate, using ATP.
When does some urea enter the intestine
When bacterial urease converts it into carbon dioxide and ammonia
How can Antibotics reduce ammonia production
- By killing urease-producing bacteria
What happens in kidney failure in relation to urea
Excess urea enters the intestines, increasing the ammonia levels
What are the reasons for low Ammonia levels in the blood
- Rapid removal by the liver
-Tissue releasing nitrogen as glutamine and alanine instead of free ammonia
What is the function of Glutamine Synthetase
- Converts glutamate and ammonia into glutamine
Name 3 major sites of glutamine formation
- Skeletal muscle, liver
-CNS
What are the causes of Hyperammonemia
- Genetic defects in the urea cycle
-Liver disease
-
What are symotoms of ammonia intoxication (hyperammonemia)
- Slurred speech
-Vomiting
-Blurred vision
What is the Amino acid classification based on
- Their catabolic products
What can amino acids be classified as
- Glucogenic , ketogenic or both
In glucogenic amino acids what does their catabolism produce
- Pyruvate or TCA cycle intermediates
What does Ketogenic amino acids catabolism produce
acetoacetate, acteyl coA or acetoacetyl CoA
What do the intermediates in ketogenic Amino acid catabolism lead to
- The formation of ketone bodies
