BIOL 112 - LECTURE 10: Redox Reactions & Glycolysis

What is end-product inhibition in metabolic pathways?

End-product inhibition is the process where the final product of a metabolic pathway inhibits the pathway’s first enzyme to prevent overproduction.

What is cooperativity in enzyme complexes?

Cooperativity occurs when two or more identical enzyme subunits form a complex, where binding of an inhibitor to one subunit affects the binding of inhibitors to other subunits, leading to sigmoid (S-shaped) inhibition curves.

Why are catabolic pathways long and complex?

Catabolic pathways are long and complex to release energy slowly, allowing the cell to capture some of the energy. This is better than releasing all energy at once, which would be wasteful.

What is the complete oxidation of glucose, and how much energy does it release?

The complete oxidation of glucose releases -686 kcal/mol, with half of the energy captured as ATP and the other half released as heat.

What is the relationship between oxidation and reduction in redox reactions?

Oxidation is the loss of electrons or hydrogen atoms, while reduction is the gain of electrons or hydrogen atoms. These reactions are always coupled (redox pairs).

How is energy stored during the oxidation of glucose?

Energy from oxidation is stored in NADH, which acts as a temporary electron carrier. NADH is later oxidized, releasing energy.

What determines the direction of electron flow in redox reactions?

The direction of electron flow depends on the redox potential of the half-reactions involved. Electrons flow from the more negative to the more positive redox potential.

Why is oxygen an excellent electron acceptor in biological reactions?

Oxygen is an excellent electron acceptor due to its high redox potential, making it efficient at capturing electrons in cellular respiration.

How is glucose oxidized in glycolysis?

In glycolysis, glucose is oxidized in a series of steps, starting with energy-consuming reactions followed by energy-releasing ones, such as the oxidation of glyceraldehyde 3-phosphate coupled with NAD+ reduction.

What is substrate-level phosphorylation in glycolysis?

Substrate-level phosphorylation is the direct transfer of a phosphate group from a "high-energy" substrate molecule to ADP to form ATP, as seen in glycolysis.

How are unfavorable energy-consuming steps in glycolysis driven?

Unfavorable steps in glycolysis are driven by favorable steps that follow them, particularly through sequential coupling, where free energy changes are additive.

Where does glycolysis occur in the cell?

Glycolysis occurs in the cytosol of the cell.

What is the end product of glycolysis?

The end product of glycolysis is pyruvate, which is further oxidized in the mitochondrial matrix to form acetyl-CoA.

What is acetyl-CoA and why is it important?

Acetyl-CoA is a key molecule in metabolism, formed from pyruvate, and serves as an energy carrier. It is used in the citric acid cycle and is essential for breaking down sugars, fats, and amino acids.

How does acetyl-CoA function in metabolism?

Acetyl-CoA transfers a 2-carbon group to other molecules to initiate the citric acid cycle, and it also serves as a building block for making fats and other metabolites.