College of Massage Therapists of British Columbia (CMTBC) Practice Exam

In which part of the cell do the Kreb cycle and electron transport chain take place?

1. Nucleus

2. Cytoplasm

3. Mitochondria

4. Endoplasmic reticulum

The correct answer is: Mitochondria

The Krebs cycle, also known as the citric acid cycle, and the electron transport chain are both integral components of cellular respiration, which occurs in the mitochondria. The mitochondria are often referred to as the "powerhouses" of the cell because they are responsible for producing ATP, the energy currency of the cell. The Krebs cycle takes place in the mitochondrial matrix, where acetyl-CoA is processed to produce energy carriers like NADH and FADH2. These energy carriers are then used in the electron transport chain, which is located in the inner mitochondrial membrane. The electron transport chain utilizes the electrons from NADH and FADH2 to create a proton gradient that drives the production of ATP through oxidative phosphorylation. Other parts of the cell do not conduct the Krebs cycle or electron transport. The nucleus is primarily involved in storing genetic information, the cytoplasm plays a role in various metabolic processes but is not the site for these specific pathways, and the endoplasmic reticulum is mainly involved in protein and lipid synthesis. Therefore, the mitochondria are uniquely equipped for these critical energy-producing processes.