TLS Online TPP Program

#Question id: 10308


Oxidative decarboxylation of pyruvate to acetyl-CoA by the PDH complex, how the pyruvate dehydrogenase complex carries out the five consecutive reactions in the decarboxylation and dehydrogenation of pyruvate?

 A) Pyruvate reacts with the bound thiamine pyrophosphate (TPP) of pyruvate dehydrogenase, undergoing decarboxylation to the hydroxyethyl derivative

 B) A transesterification in which the —SH group of CoA replaces the —SH group of E2 to yield acetyl-CoA and the fully reduced (dithiol) form of the lipoyl group

 C) The reduced FADH2 of E3 transfers a hydride ion to NAD1 , forming NADH, the enzyme complex is now ready for another catalytic cycle

 D) The transfer of two electrons and the acetyl group from TPP to the oxidized form of the lipoyllysyl group of the core enzyme, dihydrolipoyl transacetylase, to form the acetyl thioester of the reduced lipoyl group

 E) Dihydrolipoyl dehydrogenase promotes transfer of two hydrogen atoms from the reduced lipoyl groups of E2 to the FAD prosthetic group of E3 , restoring the oxidized form of the lipoyllysyl group of E2

 Find out the correct sequence of action of this complex enzyme?

#Unit 1. Molecules and their Interaction Relevant to Biology
  1. E→C→B→E→D
  2. A→D→B→E→C
  3. E→B→D→A→C
  4. D→A→E→B→C
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TLS Online TPP Program

#Question id: 11223

#Unit 7. System Physiology – Animal

Of those listed, which event occurs first following a depolarizing stimulus applied to the presynaptic membrane of an axon terminal?

TLS Online TPP Program

#Question id: 11224

#Unit 7. System Physiology – Animal

How could you increase the magnitude of excitatory postsynaptic potentials (EPSPs) generated at a synapse?

TLS Online TPP Program

#Question id: 11225

#Unit 7. System Physiology – Animal

What happens if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive in close proximity at a postsynaptic neuron?

TLS Online TPP Program

#Question id: 11226

#Unit 7. System Physiology – Animal

At the neuromuscular junction, the neurotransmitter acetylcholine (ACh) is degraded by acetylcholinesterase. If a neurophysiologist applies the naturally occurring acetylcholinesterase inhibitor, onchidal (produced by the mollusc Onchidella binneyi), to a synapse, what would you expect to happen?

TLS Online TPP Program

#Question id: 11495

#Unit 7. System Physiology – Animal

In a neuron with a resting membrane potential of −65mV, the distribution of which ion across the neuronal membrane represents the greatest potential electromotive force (EMF)?

TLS Online TPP Program

#Question id: 11496

#Unit 7. System Physiology – Animal

Forced rapid breathing results in alkalization of the blood which would lead to which of the following changes in neuronal activity?