During which stage of cellular respiration is glucose broken down into two molecules of pyruvic acid?
a electron transport chain
b glycolysis
c krebs cycle
d acetyl coa formation

D

Explanation:

Step 1. A carboxyl group is snipped off of pyruvate and released as a molecule of carbon dioxide, leaving behind a two-carbon molecule.

Step 2. The two-carbon molecule from step 1 is oxidized, and the electrons lost in the oxidation are picked up by \text{NAD}^+NAD

N, A, D, start superscript, plus, end superscript to form \text{NADH}NADHN, A, D, H.

Step 3. The oxidized two-carbon molecule—an acetyl group, highlighted in green—is attached to Coenzyme A (\text{CoA}CoAC, o, A), an organic molecule derived from vitamin B5, to form acetyl \text{CoA}CoAC, o, A. Acetyl \text{CoA}CoAC, o, A is sometimes called a carrier molecule, and its job here is to carry the acetyl group to the citric acid cycle.

B glycolysis

Explanation:

To see how a glucose molecule is converted into carbon dioxide and how its energy is collected in the form of ATP and NADH / FADH2 in one of the cells of your body, let's see step by step the four stages of cellular respiration.

Glycolysis In glycolysis, glucose - a six-carbon sugar - undergoes a series of chemical transformations. In the end, it becomes two molecules of pyruvate, an organic three-carbon molecule. In these reactions ATP is generated and NAD+ becomes NADH

Oxidation of pyruvate (Opens in a new window) Each glycolysis pyruvate travels to the mitochondrial matrix, which is the innermost compartment of the mitochondria. There, pyruvate is converted into a two-carbon molecule bound to coenzyme A, known as acetyl-CoA. In this process carbon dioxide is released and NADH is obtained.

Citric acid cycle The acetyl-CoA obtained in the previous step is combined with a four-carbon molecule and goes through a cycle of reactions to finally regenerate the initial four-carbon molecule. In the process ATP, NADH, FADH2 is generated and CO2 is released.

Oxidative phosphorylation.   The NADH and FADH2 produced in previous steps deposit their electrons in the electron transport chain and return to their "empty" forms.

The movement of electrons through the chain releases energy that is used to pump protons out of the matrix and form a gradient. Protons flow back to the matrix, through an enzyme called ATP synthase, to generate ATP. At the end of the electron transport chain, oxygen receives the electrons and collects protons from the medium to form water.