Metabolism — Flashcards

Flashcard 1021: The Ubiquitin-Proteasome system is recruited in response to _____ proteins as a result of cellular stress

Answer: damaged

Flashcard 1022: Prolactin is structurally homologous to _____

Answer: growth hormone

Flashcard 1023: What is the most common porphyria?_____

Answer: Porphyria cutanea tarda

Flashcard 1024: O2- is converted to _____ by the enzyme superoxide dismutase (oxidative burst)

Answer: H2O2

Flashcard 1025: What mitochondrial enzyme reduces superoxide (O2-) to H2O2? _____

Answer: Superoxide dismutase

Flashcard 1026: Pyruvate dehydrogenase deficiency is characterized by _____ serum alanine starting at infancy

Answer: increased

Flashcard 1027: What is the rate-limiting enzyme of the HMP shunt? _____

Answer: Glucose-6-phosphate dehydrogenase (G6PD)

Flashcard 1028: _____ deficiency results in buildup of adenosine, which is toxic to lymphocytes; causes SCID

Answer: Adenosine deaminase

Flashcard 1029: When insulin binds its receptor, the receptor _____ and is activated via tyrosine kinase activity

Answer: autophosphorylates (or undergoes autophosphorylation)

Extra: The insulin receptor (and IGF-1 receptor) is unique among receptor tyrosine kinases because it exists as a **pre-formed tetramer** ($\alpha_2\beta_2$ structure) linked by disulfide bonds. Unlike other RTKs (e.g., EGF, PDGF receptors) which must **dimerize** upon ligand binding, the insulin receptor simply undergoes a conformational change that triggers **autophosphorylation** of its internal tyrosine kinase domains.

Flashcard 1030: Atrophy via decrease in cell size may occur via _____ degradation of cytoskeleton

Answer: ubiquitin-proteasome