Amino Acids Metabolism

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Which disease is characterized by protein deficiency with adequate energy intake in children?

Marasmus

Fatty liver

Kwashiorkor (correct)

Oedema

At what age does Marasmus commonly occur?

Between 3 and 6 months

Under 1 year

Above 3 years (correct)

Between 6 months and 3 years

Which disease is associated with the preservation of subcutaneous fat?

Fatty liver

Marasmus

Kwashiorkor (correct)

Oedema

In which disease is fatty liver enlarged?

Kwashiorkor Signup and view all the answers

Which classification of amino acids is based on the polarity of side chains?

Chemical Classification Signup and view all the answers

What is a common feature of both Kwashiorkor and Marasmus diseases?

Presence of oedema Signup and view all the answers

What is the primary pathway where extracellular, membrane-associated, and long-lived intracellular proteins are degraded?

Lysosomes Signup and view all the answers

What percentage of total body protein do humans turn over daily?

1% to 2% Signup and view all the answers

Which organelle contains proteases for proteins, lipases for lipids, and many other hydrolases involved in non-specific protein degradation?

Lysosomes Signup and view all the answers

What is the term used to express the relative susceptibility of a protein to degradation?

Half-life (t1/2) Signup and view all the answers

In which processes do increased lysosomal activity play a significant role?

Disuse atrophy of muscles and regression of the uterus after childbirth Signup and view all the answers

What percentage of amino acids liberated by protein degradation are reutilized?

75% Signup and view all the answers

What is the primary enzyme involved in proteolytic digestion in the stomach?

Pepsin Signup and view all the answers

During which situations must protein synthesis exceed protein degradation?

Growth, pregnancy, and illness recovery Signup and view all the answers

Which enzyme cleaves peptide chains mainly at the carboxyl side of lysine or arginine?

Trypsin Signup and view all the answers

What is the function of elastase in protein digestion?

Hydrolysis of large hydrophobic residues Signup and view all the answers

What is the optimal pH for pepsin, the primary enzyme in stomach digestion?

2 (highly acidic) Signup and view all the answers

Which type of bonds does chymotrypsin preferentially hydrolyze in protein digestion?

Involving tyrosine, phenylalanine, and tryptophan Signup and view all the answers

What is the main cellular mechanism responsible for the degradation of regulatory proteins with short half-lives and abnormal proteins?

Ubiquitin-Proteasome System Signup and view all the answers

Which molecule is required for the attachment of Ub molecules to the target protein during ubiquitination?

ATP Signup and view all the answers

How does the number of Ub molecules attached to a protein affect its degradation rate?

Increases degradation rate Signup and view all the answers

What type of bond is formed between the carboxyl terminal of Ub and lysyl residues in the target protein during ubiquitination?

Isopeptide bond Signup and view all the answers

Which amino acid residues at the amino terminus of a protein affect its rate of ubiquitination?

Methionine (Met) or Serine (Ser) Signup and view all the answers

Where does the subsequent degradation of Ub-tagged proteins take place?

Proteasome Signup and view all the answers

Which amino acid is primarily extracted by the liver in the postabsorptive state?

Alanine Signup and view all the answers

Which amino acid serves as a source of ammonia for excretion by the kidney?

Glutamine Signup and view all the answers

Which amino acid is predominantly taken up by the brain from muscle in the postabsorptive state?

Valine Signup and view all the answers

In the fed state after a protein-rich meal, which tissues release amino acids?

Splanchnic tissues Signup and view all the answers

Which organ provides a major source of serine for uptake by peripheral tissues in humans?

Kidney Signup and view all the answers

What is the function of ubiquitin in eukaryotic cells?

It differentiates between functional and intracellular proteins for degradation Signup and view all the answers

Which amino acid residues at the amino terminus accelerate the ubiquitination of a protein?

Aspartate Signup and view all the answers

What macromolecule is responsible for the degradation of Ub-tagged proteins in eukaryotic cells?

Proteasomes Signup and view all the answers

What is the energy requirement for the addition of Ub molecules to proteins during ubiquitination?

ATP hydrolysis Signup and view all the answers

Which type of residues at the amino terminus of a protein retard its ubiquitination?

Methionine Signup and view all the answers

Which cellular organelle is responsible for the degradation of regulatory proteins with short half-lives?

Proteasomes Signup and view all the answers

What determines the rate of degradation of a protein with Ub molecules attached to it?

Number of Ub molecules attached Signup and view all the answers

In which cellular compartment does the degradation of Ub-tagged proteins mainly occur?

Cytosol Signup and view all the answers

Which enzyme is responsible for adding Ub molecules to proteins during ubiquitination?

Ubiquitin ligase Signup and view all the answers

What is the role of lysosomal enzymes in chronic inflammatory diseases such as rheumatoid arthritis?

Attack surrounding tissues Signup and view all the answers

What determines the rate of degradation of normal proteins with comparable functions?

N-terminal residue Signup and view all the answers

Which amino acid residues at the amino terminus of a protein accelerate its ubiquitination?

Arginine (Arg) and Aspartate (Asp) Signup and view all the answers

What is the function of PEST sequences in proteins?

Accelerate ubiquitination Signup and view all the answers

Where does the degradation of polyubiquitinated proteins occur?