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

Where do the krebs cycle and electron transport chain occur?

1. SER

2. RER

3. Mitochondria

4. Golgi apparatus

The correct answer is: Mitochondria

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, takes place in the mitochondria of eukaryotic cells. This is where acetyl-CoA enters and undergoes a series of enzymatic reactions that lead to the production of energy-rich molecules such as ATP, NADH, and FADH2, which are crucial for cellular metabolism. The electron transport chain, which is responsible for the majority of ATP production in aerobic respiration, also occurs within the mitochondria. Specifically, it is located on the inner mitochondrial membrane. Here, the high-energy electrons carried by NADH and FADH2 are transferred through a series of protein complexes, ultimately leading to the phosphorylation of ADP to form ATP and the reduction of oxygen to water. The other cellular structures mentioned do not perform these functions. The smooth endoplasmic reticulum (SER) is primarily involved in lipid synthesis and detoxification, while the rough endoplasmic reticulum (RER) is involved in protein synthesis and processing due to the presence of ribosomes. The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. Therefore, only the mitochondria provide