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Questions and Answers
Where does protein synthesis occur in cells?
What is the first stage of amino acid catabolism?
What is the primary function of peptide hormones?
How many enzyme-catalyzed reactions occur in the urea cycle?
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What is the primary site of protein degradation?
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What is the final product of the urea cycle?
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What is the function of ubiquitin-proteasome pathway?
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What occurs in the third stage of protein synthesis?
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Study Notes
Protein Synthesis
- Process by which cells create proteins
- Occurs in the ribosomes
- Involves three stages:
- Transcription: mRNA synthesis from DNA template
- Translation: mRNA translation into polypeptide chain
- Post-translational modification: folding, modification, and targeting of nascent protein
Amino Acid Catabolism
- Breakdown of amino acids into simpler molecules
- Occurs in the liver and kidneys
- Involves three stages:
- Transamination: conversion of amino acids to alpha-keto acids
- Deamination: removal of amino group (-NH2) from alpha-keto acids
- Decarboxylation: conversion of alpha-keto acids to acetyl-CoA or other metabolites
Peptide Hormones
- Hormones composed of two or more amino acids
- Examples:
- Insulin
- Glucagon
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Functions:
- Regulate various physiological processes
- Produced by endocrine glands
- Secreted into the bloodstream
Urea Cycle
- Process by which ammonia is converted to urea
- Occurs in the liver
- Involves five enzyme-catalyzed reactions:
- Citrulline synthesis: conversion of ammonia and ornithine to citrulline
- Arginosuccinate synthesis: conversion of citrulline and aspartate to arginosuccinate
- Arginosuccinate lyase: conversion of arginosuccinate to arginine and fumarate
- Arginase: conversion of arginine to ornithine and urea
- Urea excretion: excretion of urea in the urine
Protein Degradation
- Breakdown of proteins into smaller peptides and amino acids
- Occurs in the lysosomes and proteasomes
- Mechanisms:
- Lysosomal proteolysis: breakdown of proteins by lysosomal enzymes
- Ubiquitin-proteasome pathway: breakdown of proteins by proteasomes
- Functions:
- Regulate protein levels
- Remove damaged or misfolded proteins
- Recycle amino acids for new protein synthesis
Protein Synthesis
- Protein synthesis occurs in ribosomes and involves three stages
- Transcription: synthesis of mRNA from DNA template
- Translation: translation of mRNA into polypeptide chain
- Post-translational modification: folding, modification, and targeting of nascent protein
Amino Acid Catabolism
- Breakdown of amino acids into simpler molecules occurs in liver and kidneys
- Involves three stages: transamination, deamination, and decarboxylation
- Amino acids are converted to alpha-keto acids, then to acetyl-CoA or other metabolites
Peptide Hormones
- Hormones composed of two or more amino acids, produced by endocrine glands
- Examples: insulin, glucagon, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH)
- Regulate various physiological processes, secreted into the bloodstream
Urea Cycle
- Process by which ammonia is converted to urea in the liver
- Involves five enzyme-catalyzed reactions: citrulline synthesis, arginosuccinate synthesis, arginosuccinate lyase, arginase, and urea excretion
Protein Degradation
- Breakdown of proteins into smaller peptides and amino acids in lysosomes and proteasomes
- Mechanisms: lysosomal proteolysis and ubiquitin-proteasome pathway
- Functions: regulate protein levels, remove damaged or misfolded proteins, and recycle amino acids for new protein synthesis
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Description
Learn about the process of protein synthesis, including transcription, translation, and post-translational modification, as well as amino acid catabolism and its stages.
