Name the three main stages of cellular respiration.
Cellular respiration is a series of metabolic processes by which cells generate
energy in the form of ATP. It involves three main stages: glycolysis, the citric acid
cycle (also called the Krebs cycle) and oxidative phosphorylation. Each of these
stages occurs in different parts of the cell and involves various enzymes and
metabolic pathways.
Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm of
cells. It is an anaerobic process, meaning that it does not require oxygen, and breaks
down glucose into two pyruvate molecules. This process results in the production of
two ATP molecules.
The second stage of cellular respiration is the citric acid cycle. This occurs in the
matrix of the mitochondria and is an aerobic process, requiring the presence of
oxygen. During the citric acid cycle, pyruvate is broken down into carbon dioxide
through a series of metabolic reactions. This process results in the production of two
more ATP molecules, as well as electron carriers that are used in the final stage of
cellular respiration.
The third and final stage of cellular respiration is oxidative phosphorylation, which
occurs in the inner membrane of the mitochondria. This is an aerobic process that
involves electron transport and the production of ATP. During this process, electrons
from the electron carriers produced in the previous stage are transported through a
series of proteins and enzymes. As these electrons move through the system, they
release energy that is used to pump hydrogen ions across the mitochondrial
membrane, creating a gradient. This gradient is then used to produce ATP through a
process called chemiosmosis, resulting in the production of up to 34 ATP molecules.
In summary, cellular respiration involves three main stages: glycolysis, the citric acid
cycle and oxidative phosphorylation. Each stage occurs in different parts of the cell
and involves various enzymes and metabolic pathways, ultimately resulting in the
production of ATP.
References:
- Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., and Walter, P. (2002). Molecular
Biology of the Cell, 4th edition. New York: Garland Science.
- Lodish, H., Berk, A., Zipursky, S.L., Matsudaira, P., Baltimore, D., and Darnell, J. (2000).
Molecular Cell Biology, 4th edition. New York: W.H. Freeman and Company.