In glycolysis, ________ is oxidized and ________ is reduced.
a. NAD⁺ ... glucose
b. Glucose ... oxygen
c. ATP ... ADP
d. Glucose ... NAD⁺

Verified step by step guidance

1. Understand the process of glycolysis: Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, producing ATP and NADH in the process. It involves oxidation-reduction reactions.
2. Identify the molecule being oxidized: In glycolysis, glucose (a six-carbon sugar) is broken down and oxidized to form two molecules of pyruvate. Oxidation involves the loss of electrons or hydrogen atoms.
3. Identify the molecule being reduced: During glycolysis, NAD+ (nicotinamide adenine dinucleotide) acts as an electron carrier. It is reduced to NADH by gaining electrons (or hydrogen atoms) from glucose.
4. Eliminate incorrect options: a) NAD+ is not oxidized, it is reduced. b) Oxygen is not directly involved in glycolysis. c) ATP and ADP are involved in energy transfer, not oxidation-reduction. d) Glucose is oxidized, and NAD+ is reduced, which matches the correct description.
5. Conclude the correct answer: Based on the oxidation of glucose and the reduction of NAD+, the correct answer is 'd. glucose ... NAD+'.

Key Concepts

Glycolysis

Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP and NADH in the process. It occurs in the cytoplasm of cells and is the first step in cellular respiration. Understanding glycolysis is essential for identifying which molecules are oxidized and reduced during this process.

Oxidation and Reduction

Oxidation refers to the loss of electrons or an increase in oxidation state by a molecule, while reduction is the gain of electrons or a decrease in oxidation state. In glycolysis, glucose is oxidized, meaning it loses electrons, while NAD+ is reduced, gaining those electrons to form NADH. This electron transfer is crucial for energy production.

NAD+ and NADH

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme that acts as an electron carrier in various metabolic reactions, including glycolysis. When NAD+ accepts electrons during the oxidation of glucose, it is reduced to NADH. This conversion is vital for cellular respiration, as NADH carries electrons to the electron transport chain for further ATP production.