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[[Category:Biology]]
== Explanation ==
The cell is the most basic and fundamental building block of [[life]] on [[Earth]] that undergoes cell growth and [[cell division]] to replicate itself. The cell consists of a [[cell wall]] and a protective [[semipermeable membrane]], protecting the [[cytoplasm]] of the cell along with the [[cell nucleus]]. They are classified as [[prokaryote]] that has no cell nucleus and [[Eukaryote]] that have one.
== Frequently Asked Questions ==
=== Where did the first cell come from? ===
As of today, there are no answers for the actual mechanism of [[abiogenesis]]. There are several hypotheses that advocate that the first cell or protocell could have been formed out of a primordial [[RNA world]].<ref>Schrum, J. P., Zhu, T. F., & Szostak, J. W. (2010). The Origins of Cellular Life. Cold Spring Harbor Perspectives in Biology, 2(9), a002212. http://doi.org/10.1101/cshperspect.a002212</ref><ref>Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. The RNA World and the Origins of Life. Available from: https://www.ncbi.nlm.nih.gov/books/NBK26876/</ref>
=== What is the source of energy for a cell? ===
The [[energy]] of the cell comes from an [[organelle]] called [[mitochondrion]], which produces [[adenosine triphosphate|ATP]] by [[glycolysis]]. ATP breaks down to [[adenosine diphosphate|ADP]] by [[hydrolysis]], losing a phosphate group and thus releasing and energy.

ATP+H<sub>2</sub>O→ADP+P<sub>i</sub>+Energy
=== How cells interact with the surroundings and receive chemical signals? ===
The outer plasma membrane of a cell is a semipermeable membrane that has many [[protein]] [[receptor]]s embedded in it. When a signaling protein binds to these receptors, they change shape and initiate a particular chemical reaction that is attributed to it. There are also receptors found inside the cytoplasm that works the same way.
== References ==
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