In: Chemistry

# In glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role in the overall conversion of the energy in foods to energy in ATP.

Part A - Redox (oxidation-reduction) reactions in glycolysis

In glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role in the overall conversion of the energy in foods to energy in ATP. These reactions involving electron transfers are known as oxidation-reduction, or redox, reactions.

Drag the words on the left to the appropriate blanks on the right to complete the sentences.

• 1. When a compound donates (loses) electrons, that compound becomes . Such a compound is often referred to as an electron donor.
• 2. When a compound accepts (gains) electrons, that compound becomes ___________ . Such a compound is often referred to as an electron acceptor.
• 3. In glycolysis, the carbon-containing compound that functions as the electron donor is
• 4. Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called
• 5. ____________ is the compound that functions as the electron acceptor in glycolysis.
• 6. The reduced form of the electron acceptor in glycolysis is.

## Solutions

##### Expert Solution

Concepts and reason

The concept used to solve the given problem is the knowledge of glycolysis reaction with the knowledge of redox reaction.

Fundamentals

Glycolysis is the metabolic pathway involves the conversion of hexose sugar glucose into smaller triose fragment pyruvic acid by several steps in which reduction and oxidation reaction occurs. Oxidation of any species involves the loss of electrons while reduction involves the gain of electrons. In glycolysis, the substrate glucose is converted into pyruvic acid by the action of several enzymes and oxidizing power $$\mathrm{NAD}^{+}$$ which get reduced into the reducing power NADH.

Part 1 When any species is in its lower oxidation state, and have the greater tendency to increase its oxidation state or number. Then the oxidation reaction may occur.

When any species such as $$\mathrm{Fe}^{2+}$$ in its $$\mathrm{II}^{\text {nd }}$$ oxidation state try to gain its higher oxidation state as $$\mathrm{Fe}^{3+}$$ in its $$\mathrm{III}^{\mathrm{rd}}$$ oxidation state. This process of increase in its oxidation state is known as oxidation.

To increase the oxidation number from the lower oxidation state to higher oxidation state, there is a loss/ donation of electrons. The process of gaining high oxidation state by the loss of electrons is known as oxidation. The product obtained after oxidation is oxidized product.

When a compound loses electrons, it gains the higher oxidation state and thus product species is said to be oxidized species or the compound become oxidized.

Part 2 When any species is in its higher oxidation state, and have the greater tendency to decrease its oxidation state or number. Then the reduction reaction may occur.

When any species such as $$\mathrm{Pb}^{4+}$$ in its $$\mathrm{IV}^{\text {th }}$$ oxidation state try to gain its more stable lower oxidation state as $$\mathrm{Pb}^{2+}$$ in its II $$^{\text {nd }}$$ oxidation state. This process of decrease in its oxidation state is known as reduction.

To decrease the oxidation number from the higher oxidation state to lower oxidation state, there is a gain/acceptance of electrons. The process of gaining lower oxidation state by the gain of electrons is known as reduction. The product obtained after reduction is reduced product.

When a compound gains or accepts electrons, it gains the lower oxidation state and thus product species is said to be reduced species or the compound become reduced.

Part 3 During the glycolysis glucose acts as the substrate and undergo several reactions to convert finally into pyruvate. This conversion involves several enzymes and oxidizing power to accomplish the glycolysis reaction. The nutshell reaction of glycolysis is as follows:

Glucose $$\longrightarrow$$ oxidationPyruvate

Glucose acts as the substrate for the oxidation reaction involve in the glycolysis. The oxidation of glucose starts with the formation glucose-6-phosphate and further which ends with product pyruvate.

As in the glycolytic pathway, glucose undergo oxidation reaction hence the glucose here acts as the electron donor.

The oxidation of glucose is carried out with the release or loss of an electrons which is further accepted by any oxidizing power species.

Part 4 During the glycolysis glucose acts as the substrate and undergo several reactions to convert finally into pyruvate. This conversion involves several enzymes and oxidizing power to accomplish the glycolysis reaction. The nutshell reaction of glycolysis is as follows:

Glucose $$\longrightarrow$$ oxidationPyruvate

Glucose acts as the substrate for the oxidation reaction involve in the glycolysis. The oxidation of glucose starts with the formation glucose-6-phosphate and further which ends with oxidized product pyruvate.

As in the glycolytic pathway, glucose undergo oxidation reaction hence the glucose here acts as the electron donor and result into the oxidized product pyruvate.

The oxidation of glucose is carried out with the release or loss of an electrons which is further accepted by any oxidizing power species. Thus, the oxidized product formed is pyruvate.

Part 5 During the glycolysis glucose acts as the electron donor and get converted into pyruvate by losing its electron. The nutshell reaction of glycolysis is as follows:

Glucose $$\longrightarrow$$ oxidationPyruvate $$+\mathrm{e}^{-}$$

Glucose acts as the substrate for the oxidation reaction involve in the glycolysis. And as each redox reaction which involves oxidation always encounters the reduction of another species.

As in the glycolytic pathway, glucose undergo oxidation reaction. There is the presence of oxidizing power which itself undergo reduction by accepting electrons released from glucose oxidation and promotes the oxidation of glucose. The oxidizing power here in this glycolytic pathway is $$\mathrm{NAD}^{+}$$ which functions as the electron acceptor and reduces itself. The reaction involves in the reduction $$\mathrm{NAD}^{+}$$ is as follows:

$$\mathrm{NAD}^{+}+\mathrm{H}_{2} \rightarrow \mathrm{NADH}+\mathrm{H}^{+}$$

The $$\mathrm{NAD}^{+}$$ acts as oxidizing power in the glycolysis receives an electron from the phosphate group released from the glucose and reduces itself to NADH (reductant).

Part 6 During the glycolysis glucose acts as the electron donor and get converted into pyruvate by losing its electron. The $$\mathrm{NAD}^{+}$$ acts as oxidizing power accepts the electron get reduced itself and oxidizes other.

Here $$\mathrm{NAD}^{+}$$ acts as the hydrogen carrier and accepts electron to get reduced. $$\mathrm{NAD}^{+}$$ has great tendency to get reduced by the gain of electron and hydrogen.

The oxidizing power here in this glycolytic pathway is $$\mathrm{NAD}^{+}$$ which functions as the electron acceptor and reduces itself. The reaction involves in the reduction $$\mathrm{NAD}^{+}$$ is as follows:

$$\mathrm{NAD}^{+}+\mathrm{Pi} \rightarrow \mathrm{NADH}+\mathrm{H}^{+}$$

The reduced form of electron acceptor in glycolysis is NADH .

The $$\mathrm{NAD}^{+}$$ acts as oxidizing power in the glycolysis receives an electron from the phosphate group released from the glucose and reduces itself to NADH (reductant), the reduced form of an electron acceptor.

When a compound donates (loses) electrons, that compound becomes oxidized. Such a compound is often referred to as an electron donor.

When a compound accepts (gains) electrons, that compound becomes reduced. Such a compound is often referred to as an electron acceptor.

In glycolysis, the carbon-containing compound that functions as the electron donor is Glucose.

The $$\mathrm{NAD}^{+}$$ is the compound that acts as an electron acceptor in glycolysis