Metabolism — Flashcards

Flashcard 11: Rate-limiting enzyme of the HMP shunt (Pentose Phosphate Pathway)

Answer: Glucose-6-phosphate dehydrogenase (G6PD)

Flashcard 12: What is the rate-limiting enzyme of de novo pyrimidine synthesis?

Answer: Carbamoyl phosphate synthetase II (CPS II) :: rate limiting enzyme

Flashcard 13: What is the rate-limiting enzyme of de novo purine synthesis?

Answer: Glutamine-PRPP amidotransferase (Rate-limiting enzyme)

Inhibited by AMP, IMP, GMP (end products).

Flashcard 14: What enzyme converts pyruvate to acetyl-CoA?

Answer: pyruvate dehydrogenase complex (PDH)

Flashcard 15: What enzyme converts pyruvate to oxaloacetate?

Answer: pyruvate carboxylase (PC)

Flashcard 16: Effect of carbon monoxide (CO) on the electron transport chain (ETC)?

Answer: Inhibits Complex IV (Cytochrome c oxidase) of the Electron Transport Chain

Extra: Carbon monoxide (CO) binds to the heme a3 site of Complex IV, shifting the oxygen dissociation curve to the left and inhibiting oxidative phosphorylation. Common ETC Inhibitors: • Complex I: Rotenone, Amobarbital • Complex III: Antimycin A • Complex IV: CO, Cyanide, Azide, H2S • Complex V: Oligomycin

Flashcard 17: What is the function of thermogenin?

Answer: Uncoupling protein (UCP1) found in brown adipose tissue that generates heat by uncoupling the proton gradient from ATP synthesis.

Extra: Thermogenin increases the permeability of the inner mitochondrial membrane to protons, allowing them to bypass ATP synthase. This 'leaky' membrane dissipates the electrochemical gradient as heat instead of capturing it as ATP. it is essential for non-shivering thermogenesis in newborns.

Flashcard 18: gluconeogenesis

Answer: fructose-1,6-bisphosphatase

Extra: pyruvate carboxylase, PEP carboxylase, F-1,6-BPase, G6Pase mnemonic: Pathway Produces Fresh Glucose

Flashcard 19: oxidative phase of HMP shunt

Answer: G6PD

Flashcard 20: What initial substrate is common to the following four pathways? - to alanine via alanine aminotransferase (ALT) - to oxaloacetate via pyruvate carboxylase (PC) - to acetyl-CoA via pyruvate dehydrogenase complex (PDH) - to lactate via lactate dehydrogenase (LDH)

Answer: pyruvate