They can compare their results against the provided results and evaluate any possible sources of error. This investigation provides two different protocols, one of which students could alter to investigate a range of variables. In the first protocol the respiratory activity in tissue slices of fruit are investigated by using tetrazolium chloride TTC , which produces a red colour in respiring tissues.
This is a straightforward observation activity however students could be asked to alter the protocol to consider one or more of the following:. The second protocol in this investigation entitled Measuring carbon dioxide from respiration using baryta water involves using a titration, following the absorption of carbon dioxide by barium hydroxide solution. This investigation using a respirometer provides a quantitative method of exploring metabolism.
There are alternative investigations available, which will give a rate of respiration, but this investigation provides a suitable level of challenge for A level. In this investigation students will be able to calculate the respiratory quotient.
There is a downloadable student sheet for this investigation scroll to the bottom of the page which does include some useful post experimental questions remember to remove the last page which gives the answers.
Respirometer questions are popular in exams at A level as well as GCSE , so this would be a very useful investigation for students to have completed. As with any respirometer investigation if the respiring material used are invertebrates, it is very important to handle these organisms carefully.
Students conduct Thin Layer Chromatography TLC individually or in pairs to separate and identify the photosynthetic pigments from plant material within half an hour. This simple method has been designed to produce good separation of photosynthetic pigments using solvents that are suitable for use in a school biology laboratory. By using grass from a school lawn or playing field, students can see the variety of different molecules that can be separated from a plant that they are all very familiar with.
These resources and this practical allow students to develop their understanding of photosynthetic pigments and how chromatography separates molecules. By taking simple distance measurements from the chromatogram for calculating Rf values, this practical provides a good opportunity to introduce the concept of percentage error.
It provides students with the opportunity to develop and demonstrate their skills of taking quantitative measurements as well as their ability to consider variables that need to be controlled. Electrons provide the energy to pump protons from the mitochondrial matrix to the intermembrane space.
This creates a steep proton gradient across the inner mitochondrial membrane. Most of the ATP generated by cellular respiration is made by the electron transport chain. Cellular Respiration Tutorial by Dr.
Funded by the U. Description of Cellular Respiration Life is possible only if molecules and cells remain organized. Glycolysis Glycolysis is the first of the three steps used to breakdown glucose to produce ATP.
Krebs Cycle The end product of Glycolysis, pyruvate, is transported into the mitochondrion and converted to a compound called acetyl coenzyme A or acetyl CoA. The Krebs Cycle consists of nine enzyme-catalyzed reactions that can be divided into 3 stages: 1. Two carbons are removed as carbon dioxide. The process of respiration occurs in 3 steps when oxygen is present :. The following tutorial looks at the chemistry involved in respiration and the creation of ATP, and why oxygen is essential for respiration in the long term.
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See Figure 2 for the structure of ATP. Oxygen is used in cellular respiration. It is a diatomic molecule i. As it pulls electrons towards it, it releases energy from the chemical bonds. Potential energy from our food is combined with oxygen and creates products of carbon dioxide CO 2 and water H 2 O which releases energy to form the molecule ATP.
For example, the monosaccharide glucose , the most basic form of carbohydrate can be combined with oxygen. The high-energy electrons that are found in the glucose are transferred to the oxygen and potential energy is released.
The energy is stored in the form of ATP. This final process of cellular respiration takes place on the inner membrane of the mitochondria. Instead of all the energy being released at once, the electrons go down the electron transport chain. The energy is released in small pieces and that energy is used to form ATP.
See below to understand more about the stages of cellular respiration including the electron transport chain. Forum Question: How many water molecules are produced by cellular respiration? Featured Answer! Cellular respiration can be written as chemical equations. An example of the aerobic respiration equation is in Figure 3.
Below are examples of aerobic respiration and anaerobic cellular respiration : lactic acid fermentation and alcoholic fermentation. Most prokaryotes and eukaryotes use the process of aerobic respiration. As mentioned above, it is the process of cellular respiration in the presence of oxygen.
Water and carbon dioxide are the end products of this reaction along with energy. See Figure 3. In lactic acid fermentation, 6 carbon sugars, such as glucose are converted into energy in the form of ATP. However, during this process lactate is also released, which in solution becomes lactic acid. See figure 4 for an example of a lactic acid fermentation equation.
It can occur in animal cells such as muscle cells as well as some prokaryotes. In humans, the lactic acid build-up in muscles can occur during vigorous exercise when oxygen is not available. The aerobic respiration pathway is switched to the lactic acid fermentation pathway in the mitochondria which although produces ATP; it is not as efficient as aerobic respiration.
The lactic acid build-up in muscles can also be painful. Alcoholic fermentation also known as ethanol fermentation is a process that converts sugars into ethyl alcohol and carbon dioxide. It is carried out by yeast and some bacteria. Alcoholic fermentation is used by humans in the process of making alcoholic drinks such as wine and beer. During alcoholic fermentation, sugars are broken down to form pyruvate molecules in a process known as glycolysis.
Two molecules of pyruvic acid are generated during the glycolysis of a single glucose molecule. These pyruvic acid molecules are then reduced to two molecules of ethanol and two molecules of carbon dioxide. The pyruvate can be transformed into ethanol under anaerobic conditions where it begins by converting into acetaldehyde, which releases carbon dioxide and acetaldehyde is converted into ethanol.
Figure 5 shows an alcoholic fermentation equation. Methanogenesis is a process only carried out by anaerobic bacteria. These bacteria belong to the phylum Euryarchaeota and they include Methanobacteriales, Methanococcales, Methanomicrobiales, Methanopyrales, and Methanosarcinales. Methanogens only occur in oxygen-depleted environments, such as sediments, aquatic environments, and in the intestinal tracts of mammals.
There are 3 pathways for methanogenesis:. This process involves activating acetate into acetyl-coenzyme A acetyl-CoA , from which a methyl group is then transferred into the central methanogenic pathway. Acetoclastic methanogens split acetate in the following way:. Acetoclastic methanogenesis is performed by Methanosarcina and Methanosarcinales and is most often found in freshwater sediments. Here, it is thought that acetate contributes to around two-thirds of the total methane formation on earth on an annual basis.
In methylotrophic methanogenesis, methanol or methylamines serve as the substrate instead of acetate. This process can be observed in marine sediments where methylated substrates can be found. Some acetoclastic methanosarcinales and at least one member of the Methanomicrobiales can also use this second pathway. Finally, hydrogenotrophic methanogenesis is a process that is used by Methanobacteriales, Methanococcales, Methanomicrobiales, Methanopyrales, and Methanosarcinales i.
In this reaction, hydrogenotrophic methanogens use hydrogen for the reduction of carbon dioxide, carbon monoxide, or formate according to the following:. Although methanogenesis is a type of respiration, an ordinary electron transport chain is not used. Methanogens instead rely on several coenzymes, including coenzyme F, which is involved in the activation of hydrogen, and coenzyme M, which is involved in the terminal reduction of CH3 groups to methane Figure 6.
What are the 4 stages of cellular respiration? There are 4 stages of the cellular respiration process. These are Glycolysis, the transition reaction, the Krebs cycle also known as the citric acid cycle , and the electron transport chain with chemiosmosis. Glycolysis is a series of reactions that extract energy from glucose by splitting it into 2 molecules of pyruvate.
Glycolysis is a biochemical pathway that evolved long ago and is found in the majority of organisms. In organisms that perform cellular respiration, glycolysis is the first stage of the process. Before glycolysis begins, glucose must be transported into the cell and phosphorylated. In most organisms, this occurs in the cytosol. Glycolysis does refer to other pathways, one such pathway described is the Entner—Doudoroff pathway.
This article concentrates on the EMP pathway. Glycolysis takes place in 10 steps.
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