Question

You are working in a research lab on an oxidation-reduction pathway of a previously unknown organism that involves a number of electron carriers. You have isolated and studied the individual carriers, and named them with letters (P, Q, R, Z, C, A). You have also found a number of inhibitors that prevent them from being oxidized (i.e. the carriers remain in the reduced state with the electron in the presence of the inhibitor). The oxidation-reduction state of a given carrier can be determined rather easily since the absorption of light differs between the oxidized and reduced forms. Given the following experimental evidence, determine the exact sequence of the electron carriers and indicate the point at which each inhibitor blocks electron transport. In the presence of inhibitor 1, R, Q, Z remain reduced. In the presence of inhibitor 2, only Q remains reduced. In the presence of inhibitor 3, R, Q, Z, C, A remain reduced and only P is oxidized. In the presence of inhibitor 4, Z, Q remain reduced. In the presence of inhibitor 5, the addition of reduced will cause the reduction of P; and the addition of reduced A has no effect on the reduction of P, which remains oxidized. Write the order in which electron transfer occurs across the carriers P, Q, R, Z, C, A, and where each inhibitor blocks this electron transport pathway.

Answer 1

The sequence of electron transfer, determined from experimental evidence with inhibitors, is P → A → C → Z → Q → R. Inhibitors provide information on where in the electron transport chain the flow of electrons is blocked, illustrating key points in the oxidation-reduction pathway of the organism.

Step-by-step explanation:

When studying the sequence of electron carriers within the electron transport chain (ETC) of an unknown organism, several inhibitors and their impact on the oxidation-reduction state of the carriers provide insight into the order of electron transfer. Based on the experimental evidence provided, we can deduce the sequence and points of inhibition for each carrier as follows:

Inhibitor 1 leaves R, Q, Z in a reduced state, meaning it blocks the carrier right before R.

Inhibitor 2 keeps only Q reduced, so it must block right before Q.

Inhibitor 3 keeps all carriers except P in the reduced state, indicating it blocks before P but after A.

Inhibitor 4 leaves Z, Q reduced, suggesting it blocks right before Z.

Inhibitor 5 shows that reduced P cannot be achieved by added reduced A, placing A after P and indicating a block before P if P remains oxidized.

Therefore, the electron transfer sequence is P → A → C → Z → Q → R, with inhibitor 3 blocking before P, inhibitor 5 before P or A, inhibitor 4 before Z, inhibitor 2 before Q, and inhibitor 1 before R. Energy production within the cell requires the transfer of electrons from higher to lower reduction potentials, and these inhibitors highlight the critical checkpoints in this oxidation-reduction pathway.

Answer 2

The sequence of electron carriers is P, Q, R, Z, C, A, based on how each inhibitor affects reduction. For instance, inhibitor 3 indicates P is first, while inhibitor 2's effect on Q and inhibitor 1's effect on R, Q, and Z further define the sequence and blocking points.

Step-by-step explanation:

In determining the sequence of electron carriers in a previously unknown organism's oxidation-reduction pathway and identifying the points where inhibitors block electron transport, we can analyze the experimental evidence and use a process of elimination.

Inhibitor 1 causes R, Q, and Z to remain reduced, which suggests that these are upstream of the blockage. Inhibitor 2 only allows Q to remain reduced, which indicates Q is before R and Z in the transfer sequence. With inhibitor 3, all except P stay reduced, meaning P is the first carrier in the sequence. Inhibitor 4 shows that Z and Q are before the inhibition point, putting Z after Q. Finally, the fact that reduced P's addition causes Q reduction and reduced A does not affect P, suggests that P is downstream of A.

Based on this information, the sequence is P, Q, R, Z, C, A. Inhibitor 1 blocks after Z, inhibitor 2 blocks before R, inhibitor 3 blocks before P, inhibitor 4 blocks after Q, and inhibitor 5 blocks after A. This sequence explains all the given observations when placing the inhibitors in the pathway.