Respiration 205 PDF

(J) Mitocho~ {Single = mitoo/H)ndrion) rI J Stru~tore C- adaptation or mitochondria to its functions} It is surrounded by 2 membranes (double membrane/ envelope) : Cal Outer smooth membrane ---> permeable to allow entry of small molecules needea in cellular respiration (e.g. p...

(J) Mitocho~ {Single = mitoo/H)ndrion) rI J Stru~tore C- adaptation or mitochondria to its functions} It is surrounded by 2 membranes (double membrane/ envelope) : Cal Outer smooth membrane ---> permeable to allow entry of small molecules needea in cellular respiration (e.g. pyruvate). Cb} Ipper folded membrane ---> folded to fonn finger-lilce cristae which project into a solution called (matrix). The cri~tae cany stalked particles which contain the respiratory enzymes. (,rrPSY'l\t\-it1'"u.s~ e"'3ytw\t). _So/ I'ww>~YIW'I~ ~Yo.II\~,·~¼.hly Ft.fole4 -,. bs- it1CYe:t.Se s.-,t. of #,e cv-i~+"" Wl?lJ... ulll-f,,Jns~JK~/.-qyfk&-s ,--+ h , c.},, covd-a.in v~,,·ralbvy e1.1zytw1es (c 9. -Ir. p/f"Tf 5'y 111 fA~¼eevr zy,,..,e) bs- fYoclu.ce.-w10.r"e e.,evy~ (c) Thematrix: (1) contains ribosomes and DNA so, they can make their own proteins. (~) Contains many Soh,ble.e.)'jz.y,vnes_... ~eol J;r""cellular respiration.. '~.,J.../~~·· ,. :~ "··.. :t';. )' ~-,, :fp,;..,{-;..;1....,]fri~ I ;,{ ~.·...,... '.... ·.· ' ··....,,,..., , ,, \ J , ff' I. ,. "'., ,_·l."" "' 'I 0 F[/t, 0J] to rvcl.uce [evie2i \ le sj>i'Ya. fo 1/ S°IA~ , ·frJe _ ___..enos1·vie· -tr-; BJ G/11.cose Cff/cho/ce) Phasf JtJ,, \., -ryl- V\ t.l cl e.o t-,· e I Cr H,J. t -t t ".z. ( l"l_ t- 'Hi o+ ft IP (J) ra-+s @ 'Pro te,t1 s J> lveJ So v.ree er{ entV"_J)" I 111J;.,-"J source of ev.ery Y :::=. Cel h me>ney ·:::=: che7ue tt 5 Jt @IlJ teclttcerl Nh D [ Stages of Respiration: I l) Glycolysis-> takes place in the cytoplas~. 2) Kreb's cycle (citric acid cycle.. tricarboxylic acid cycle) ---------> takes place in the·matrix of mitochondria. 3) oxidative phosphorylation: (Talces place in the cristae of the.inner membrane of the mitochondria. rJ ~e\e\1-S. o;..· :.. ~ Products: Net gain of2 ATP by Substrate level phosphorylation (4 produced- 2 used). 2 reduced NAD. N.B.: Conversion oftriose Pinto pyruvate occurs in several steps and includes many intermediates such as Glycerate-3-phosphate (G3P). Link Reaction and Krebs Cycle This phase occurs in the matrix of mitochondria. > Link reaction: Pyruvate diffuses into the matrix of mitochondria. Then it is: Decarboxylated by the removal of CO2. Oxidized by the removal of hydrogen. This forms a 2-carbon fragment = Acetyl group. Acetyl group is then combined with small Coenzyme-A forming acetyl-CoA. The productio11 ofAcetyl-CoA from pyruvate is known as the link reaction because it links glycolysis to the upcoming reactions of the Krebs cycle \ NAO ~ + H.. Pyruvale ':::-, > Acetyl CoA CoA CO2 N.B.: we have 2 pyruvates produced from glyccilysis, so all the products are multiplied by 2. So the link reaction produces 2 reduced NAD and 2 CO2 molecules. 5  > Krebs cycle: In this cycle, Acetyl-CoA reacts with · Oxaloacetic acid (4C acid) to fonn Citric acid (6C acid) with release of Coenzyme A, which is reused again in the link reaction. Then the 6C Citric acid is decarboxylated.fonning a SC acid which is also decarboxylated regenerating the 4C Oxaloacetic acid again. This is why it. is considered a cycle. Each tum of the Krebs cycle gives the following products as shown in c.o, the diagram: NliO" 1. 2 molecules of CO2 given off in two separate decarboxylation Nfl!}/1-, II+ reactions 2. 1 molecule of ATP 3. 3 molecules ofreduced NAD 4. 1 molecule ofreduced FAD N.B.: As glucose is broken down into 2 pyruvates in glycolysis, for each glucose molecule · we have 2 turns of the Krebs cycle, they both produce: 4 CO2 molecules 2 ATP (substrate level phosphorylation). 6 reduced NAD 2 reduced FAD A summary for the products of glucose breakdown in glycolysis and Krebs cycle: Step Product... CO2 ATP Reduced NAO Reduced FAD Glycolysis 0 2 2 0 Link reaction 2 0 2 0 Krebs Cycle 4 2 6 2 Totals 6 4 10 2 6  ATP synthesis by Chemiosmosis: 0-.tor M1tochand11~ , -.0 ~J t nni, t M t cd'o ri d n i11- tn on, br ;an ,:, M -1: t n ;\c f. NAIJtol H , DHz - FAD +20 ,::--., ' C , ; ' - NAO + 2 1(!/ 0 2© +mo 2 - H2o ""if: "l [ ATP 0- 1\ f l> w nth ~, h (-Ollpktl with M (1uolo n) llow d own Uw conurntr In the absence of oxygen, many organisms and sometimes tissues of organisms continue to respire anaerobically. Anaerobic respiration has two types: "* Alcoholic fermentation: occurs in as in yeast and roots of plants in water logged soil. It produces Ethanol, Carbon dioxide & energy. Glucose -. Ethanol + Carbon dioxide + Energy.,._ Lactic acid fermentation: occurs in mammalian muscle ti~sue. It produces lactic acid & energy. Glucose -. Lactic acid + Energy Reaction Pathways of anaerobic respiration: ·l Glurosr glrcn(,n Z P~·run1tr~ - - - --- 2NADH "-,. co, }---211,__ 2 Ethmrnl :! '.'\.\l) I_ -~ 2NADII 2 Lactic acid f ·· ·-m - { 2 Ethanol - 2 :'\.\ O ~-= In Anaerobic respiration, oxygen is not available to act as a final electron and hydrogen acceptor. So the reaction is limited to glycolysis occurring in the cytoplasm and the energy produced in both pathways is limited to the 2 ATPs generated from Glycolysis. In lactic acid fermentation, Pyruvate acts as the final hydrogen acceptor to restore oxidized NAO. This coverts Pyruvate into lactic acid. In alcoholic fermentation, Pyruvate is decarboxylated forming Ethanal then Ethanal acts as hydrogen acceptor to restore oxidized NAD for glycolysis to continue. This converts Ethanal into Ethanol. 9 Importance of Anaerobic respiration In muscles > When oxygen supply fails to meet the oxygen demand of muscles, they respire anaerobically. Although it is inefficient compared to aerobic respiration, but it is rapid and can supply muscles with ATP. > However, lactic acid produced lowers the PH and this can inhibit muscle enzymes causing muscle fatigue & cramps. ) Fate of Lactate: Once oxygen supply is resumed, lactate is converted back into pyruvate that either enters the Krebs cycle to produce energy, C(h & water OR is transported in blood to the liver where it is broken down or stored as Glycogen. > The extra oxygen needed to breakdown lactate is known as Oxygen Debt that is why we continue to breathe fast and deep after strenuous exercise in order to repay the oxygen debt. [Excess Post-Exercise Oxygen Consumption (EPOC)]. ~ N..B. Most of the cellular respiration reactions occur through metabolic pathways. In a metabolic pathway, each step is catalyzed by a different enzyme due to enzyme specificity. The product of each step is the substrate of the next step. Without all enzymes present, the final product is never reached. Enzymes are responsible for lowering the activation energy needed for the reactions to take place. For example: _____o_H_AP_ ____.H.___2-P_G_ ____,~._I__PE_P_ __.~I Pyruvate Cellular respiration flowchart (Overview) Glucose ' Glycolyat1... In eytopl0$111 An«aeroblc R-,lnatlon In eytop/asm ¢:::J ' Pyruvate (2ATP) Mrob1c.~uplratfon in mi tochondria ij Muscles Lcictlc Acid J Yeast/ Plants Ethanol + CO 2 ! CO 2 + H20 (36-38 ATP) 10