Plus One Botany Notes Chapter 10 Respiration in Plants is part of Plus One Botany Notes. Here we have given Kerala Plus One Botany Notes Chapter 10 Respiration in Plants.
|Text Book||NCERT Based|
|Chapter Name||Respiration in Plants|
|Category||Plus One Kerala|
Kerala Plus One Botany Notes Chapter 10 Respiration in Plants
The all living organism are need energy for carrying out daily life activities. It needs absorption, transport, movement, reproduction or even breathing. The process of breathing is very much connected to the process of release of energy from food.
Respiration : The basics
The energy required for all ‘life’ processes is obtained by oxidation of some macromolecules that we call ‘food’. The food are prepare their own by green plants and cyanobacteria it used by the process of photosynthesis they trap light energy and convert it into chemical energy that is stored in the bonds of carbohydrates like glucose, sucrose and starch. The all must remember that in green plants too, only cells containing chloroplasts, that are most often located in the superficial layers, carry out photosynthesis, So even in green plants all other organs, tissues and cells that are non-green, need food for oxidation. Hence, food has to be translocated to all non-green parts. Animals are heterotrophic, i.e., they obtain food from plants.
The mechanism of break down of food materials within the cell to release energy, and the trapping of this energy for synthesis of ATP.
The breaking of the C-C bonds of complex compounds through oxidation within the cells, leading to release of considerable amount of energy is called respiration.
The compounds that are oxidised during this process are known as respiratory substrates. In this process they are released by energy in the form of ATP. ATP acts as the energy currency of the cell. This energy trapped in ATP is utilised in various energy-requiring processes of the organisms.
Energy yield in plants for respiration process. The process of respiration, oxygen is utilised, and carbon dioxide, water and energy are released as products The living organisms, we know of several that are adapted to anaerobic conditions. Some of these organisms are facultative anaerobes, while in others the requirement for anaerobic condition is obligate. But all living organisms retain the enzymatic machinery to partially oxidise glucose without the help of oxygen. This breakdown of glucose to pyruvic acid is called glycolysis
The anaerobic organisms are glycolysis is only process for respiration. It occurs in the cytoplasm of cell and it present in all organisms. So it is occur in cells with the help of enzymes. In first step of glycolysis are involved by respiration to glucose oxidised to pyruvic acid. Then it enter the pyruvic acid to the krebs’ cycle or it undergo the fermentation.
Glycolysis steps for takes place in this pathway :
Step I. Phosphorylation of glucose occur under the action of an enzyme hexokinase and Mg2+ that gives rise to glucose-6-phosphate by the utilisation of ATP.
Step II. Isomerisation of this phosphorylated glucose-6-phosphate takes place to I form fructose-6-phosphate with the help of 5 an enzyme phosphohexose isomerase (reversible reaction).
Step III. This fructose-6-phosphate is again phosphorylated by ATP in order to form fructose 1, 6-bisphosphate in the presence of an enzyme phosphofructokinase and Mg2+. The steps of phosphorylation of glucose to furctose 1, 6-bisphosphate activates the sugar thus preventing it form getting out of the cell.
Step IV. Splitting of furctose 1, 6-bisphosphate takes triose phosphate molecules, i.e., dihydroxyacetone 3-phosphate and 3-phosphoglyceraldehyde(i.e., PGAL). This reaction is catalysed by an enzyme aldolase.
Step V. Each molecule of PGAL removes two redox equivalents in the form of hydrogen atom and and transfer them to a molecule of NAD and accepts inorganic phosphate form phosphoric acid. This reaction in turn leads to the conversion to PGAL to 1, 3-bisphophoglycerate (BPGA).
Step VI. 1, 3-bisphosphoglycerate is converted to 3-phosphoglycerate with the formation of ATP. This reaction is catalysed by an enzyme phosphoglycerate kinase. It is know as energy yielding process. The formation of ATP directly from metabolites constitutes substrate level phosphorylation.
Step VII. In the next step, 3-phosphoglycerate is subsequently isomerised to form 2-phosphoglycerate, catalysed by enzyme phosphoglyceromutase.
Step VIII. In the presence of enzymenolase and Mg2+, with the loss of a water molecules, 2 phosphoglycerate is converted to phosphoenol pyruvate (PEP).
Step IX. High energy phosphate group of phosphoenol pyruvate (PEP) is transfered to a molecules of ADP, by the action of enzyme pyruvate kinase in the presence of Mg2+and K+ this in trun produces two ; molecules of pyruvic acid (pyruvate) and a molecules of ATP by substrate level phosphorylation. The pyruvic acid produced is the final product of glycolysis.
There are three major ways in which different cells handle pyruvic acid produced by glycolysis. These are Tactic acid fermentation, alcoholic fermentation and aerobic respiration. Fermentation takes place under anaerobic conditions in many prokaryotes and unicellular eukaryotes. For the complete oxidation of glucose to CO2 and H2O, however, organisms adopt Krebs’ cycle which is also called as aerobic respiration. This requires O2 supply.
The alcoholic fermentation are occur in fungi and other higher plants under a anaerobic conditions by the reaction of pyruvic acid that converts to CO2 and ethanol. When oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase. In the case of lactic acid fermentation the organism like some bacteria are produces lactic acid as the end product from pyruvic acid.
The process aerobic respiration that leads to a complete oxidation of organic substances in the presence of oxygen, and releases CO2, water and a large amount of energy present in the substrate. This type of respiration is most common in higher organisms.
glycolysis and fermentation:
|It is the step of respiration which occurs without requirement of O2 and is common to both aerobic and anaerobic mode of respiration.||It is anaerobic respiration which does not require oxygen.|
|It produces pyruvic acid.||Fermentation produces different products. The common ones are ethanol and lactic acid|
|It porduces two molecules of NADH per glucose molecule.||It generally utilises NADH produced during glycolysis.|
|Glycolysis forms 2ATP moleclu per glucose
|It does not produce ATP.|
For aerobic respiration to take place within the mitochondria, the final product of glycolysis, pyruvate is transported from the cytoplasm into the mitochondria. The crucial events in aerobic respiration are
- The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, leaving three molecules of CO .
- The passing on of the electrons removed as part of the hydrogen atoms to molecular O2 with simultaneous synthesis of ATP.
- The reactions catalysed by pyruvic dehydrogenase require the participation of several coenzymes, including NAD+ and Coenzyme A.
- In this process the two molecules of NADH are produced from metabolism of two molecules in pyruvic acid. The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle, more commonly called as Krebs’ cycle after the scientist Hans Krebs who first elucidated it.
Tricarboxylic acid cycle
It is the acetyl co-Athat enter a cyclic pathway in mitochondria matrix is krebs’ cycle. There are mainly these steps are takes place in it.
- Condensation is the krebs’cycle with the acetyl group with the oxaloacetic acid and water to yield the citric acid.
- The citric acid undergoes reorganisation ofto step to form order in the presence of an enzyme acinotase.
- In next steps there is two succesive isocitrate are oxidative decarboxylation that leads to
α -ketoglutaric acid and succinyl Co -A, catalysed by α complex.
- The summary equation for this phase of respiration is
- The final steps of krebs’ cycle having such that converts to form fumaric acid and malic acid by using catalyst enzymes.
Final it synthesised 2 ATP molecules in this reaction.
|It takes place in the cytoplasm.||It takes place in the matrix of mitochondria.|
|It is a linear paihway.||it is a cyclic pathway.|
|It occurs in aerobic as well as anerobic respiration.||It occurs in aerobic respiration only.|
|It consumes 2 ATP molecules.||It does not consume ATP.|
|it does not produces O2.||It produces O2.|
Electron transport system (ETS) and oxidative phosphorylation
It is a metabolic pathway through which the electron passes from one carrier to another. It occur in the inner mitochondrial membrane.
Electrons are then transferred to ubiquinone located Ubiquinone also receives reducing equivalents via FADH2 (complex II) that is generated during oxidation of succinate in the citric acid cycle. The reduced ubiquinone (ubiquinol) is then oxidised with the transfer of electrons to cytochrome c via cytochrome be, complex (complex III). Cytochrome c is a small protein attached to the outer surface of the inner membrane and acts as a mobile carrier for transfer of electrons between complex III and IV. Complex IV refers to cytochrome c oxidase complex containing cytochromes a and a3, and two copper centres.
When the electrons pass from one carrier to another via complex I to IV in the electron transport chain, they are coupled to ATP synthase (complex V) for the production of ATP from ADP and inorganic phosphate. The number of ATP molecules synthesised depends on the nature of the electron donor. Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH2 produces 2 molecules of ATP. Although the aerobic process of respiration takes place only in the presence of oxygen, the role of oxygen is limited to the terminal stage of the process.
The respiratory balance sheet.
This is possible to make calculations of the net gain of ATP for every glucose molecule oxidised. They can assumption that:
- There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle and ETS pathway following one after another.
- The NADH synthesised in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation. None of the intermediates in the pathway are utilised to synthesise any other compound.
- Only glucose is being respired no other alternative substrates are entering in the pathway at any of the intermediary stages.
|It accounts for only partial breakdown of glucose.||It have completely degradation of glucose to CO2 and H2O.|
|There is net gain, of only 2 molecules of ATP in glucose to pyruvic acid.||It generated more number of ATP molecules.|
|ETS is absent.||ETS is present.|
The amphibolic is defined as a biochemical pathway involving both catabolism and anabolism.
The respiratory ratio term defined as the ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration. It represent by
Respiratory quotient of carbohydrates.
carbohydrates are used as substrate and are completely oxidised, the RQ will be 1, because equal amounts of CO2 and O2 are evolved and consumed.
When fats are used in respiration, the RQ is less than 1
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