What is respiration in cells

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While many different organic molecules, sugars, amino acids, and lipids, can be used in cellular respiration, glucose is used as the prototype. Thus the equation for cellular respiration is C6 H12 O6 plus six O2, leads to six CO2 plus six H20 plus energy, the reverse of photosynthesis.

This reaction actually occurs in multiple steps. Glycolysis is in the cytoplasm, pyruvate oxidation and the citric acid cycle occur in the mitochondria, and oxidative phosphorylation takes place over the inner mitochondrial membrane.

Together these processes power cellular activities from flagellar movement, muscle contraction, through the breakdown of organic molecules to produce ATP. Organisms harvest energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored in nutrients into a more usable form: adenosine triphosphate ATP. ATP stores energy in chemical bonds that can be quickly released when needed.

Cells produce energy in the form of ATP through the process of cellular respiration. Although much of the energy from cellular respiration is released as heat, some of it is used to make ATP. During cellular respiration, several oxidation-reduction redox reactions transfer electrons from organic molecules to other molecules. Here, oxidation refers to electron loss and reduction to electron gain.

Some prokaryotes use anaerobic respiration, which does not require oxygen. Most organisms use aerobic oxygen-requiring respiration, which produces much more ATP. Aerobic respiration generates ATP by breaking down glucose and oxygen into carbon dioxide and water.

Both aerobic and anaerobic respiration begin with glycolysis, which does not require oxygen. Glycolysis breaks down glucose into pyruvate, yielding ATP.

Importantly, several types of yeast use alcoholic fermentation. Human muscle cells can use lactic acid fermentation when oxygen is depleted. Anaerobic respiration ends with fermentation. Aerobic respiration, however, continues with pyruvate oxidation.

Pyruvate oxidation generates acetyl-CoA, which enters the citric acid cycle. The final stage of cellular respiration, oxidative phosphorylation, generates most of the ATP. The electron transport chain releases energy that is used to expel protons, creating a proton gradient that enables ATP synthesis. Lane, N. Martin, W. The Origin of Mitochondria. Plant cells also include chloroplasts, which are responsible for photosynthesis. Use these classroom resources to examine how cells function with your students.

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Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Twitter Facebook Pinterest Google Classroom. Overview Vocabulary. Krebs cycle. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. The mitochondria , found in the cell cytoplasm, are where most respiration happens.

Jon Chase explains aerobic respiration. During hard exercise, not enough oxygen can reach your muscle cells. So, aerobic respiration is replaced with anaerobic respiration. This does not need oxygen for it to happen. Here is the word equation for anaerobic respiration in humans:. Anaerobic respiration produces much less energy than aerobic respiration. The waste product, lactic acid , builds up in the muscles causing pain and tiredness. This leads to cramp. Lactic acid is only broken down when you start aerobic respiration again.