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8.2 Cell Respiration
- 1. 8.2 Cell Respiration Essential Idea: Energy is converted to a usable form in cell respiration. Nature of Science: Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. http://www.phschool.com/science/biology_place/bi ocoach/images/cellresp/Overview.gif Compiled By Darren Aherne
- 2. Statement Guidance 8.2 U1 Cell respiration involves the oxidation and reduction of electron carriers. 8.2 U2 Phosphorylation of molecules makes them less stable. 8.2 U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. The names of the intermediate compounds in gylcolysis and the Krebs cycle are not required. 8.2 U4 Glycolysis gives a small net gain of ATP without the use of oxygen. 8.2 U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction. 8.2 U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide. 8.2 U7 Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
- 3. 8.2 U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping. 8.2 U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP. 8.2 U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water. 8.2 U11 The structure of the mitochondrion is adapted to the function it performs. 8.2 A1 Electron tomography used to produce images of active mitochondria. 8.2 S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur. 8.2 S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
- 4. 8.2 U1 Cell respiration involves the oxidation and reduction of electron carriers. Remember Oil Rig: Oxidation Is Loss of electrons Reduction Is Gain of electrons Oxidation & reduction always happen together- they involve the loss and gain of electrons. Example: Benedicts test- a test for monosaccharides & reducing disaccharides. Cu2+ is blue In presence of reducing sugars, Cu2+ is reduced by adding electrons Cu is red or orange & insoluble Image from: http://biology- igcse.weebly.com/uploads/1/5/0/7/15070316/743953.jpg?43 7
- 5. Electron carriers: substances that can accept and give up electrons as needed. • In cell respiration, the electron carrier is NAD. NAD From PubChem NAD + 2 electrons ïƒ reduced NAD In more detail: Remember that hydrogen atoms consist of a proton and an electron NAD+ + 2H ïƒ NADH + H+ This shows that reduction can be a result of gaining hydrogen, because H has an electron. Conversely, oxidation can be a result of losing hydrogen. Gaining oxygen is oxidation, losing oxygen is reduction
- 6. 8.2 U2 Phosphorylation of molecules makes them less stable. Phosphorylation is gaining a phosphate molecule PO4 3- • Phosphorylation makes molecules more unstable. • Unstable molecules react more easily. Phosphorylation of glucose- the 1st step of glycolysis Notice that it is coupled with the hydrolysis of ATP Image from http://www.namrata.co/wp- content/uploads/2012/07/gly1.bmp
- 7. 8.2 U4 Glycolysis gives a small net gain of ATP without the use of oxygen. 8.2 U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. Glycolysis is the splitting of a glucose (6C) molecule in to 2 pyruvate (3C) molecules without the use of oxygen. • Costs 2 ATP in the phosphorylation of the sugar • Creates 4 ATP • Net gain is 2 ATP • 2 NADH are also created. These are used later in the Krebs cycle in the mitochondria. Image from http://preuniversity.grkraj.org/html/8_RESPIRATI ON.htm Guidance: The names of the intermediate compounds in gylcolysis and the Krebs cycle are not required.
- 18. Watch this animation and video!! http://highered.mheducation.com/sites/007250 7470/student_view0/chapter25/animation__ho w_glycolysis_works.html Craig Savage on Cell Respiration
- 19. 8.2 U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction. Decarboxylation is a chemical reaction that removes a carboxyl group (-COOH) and releases CO2 In the presence of oxygen, the pyruvate is moved into the mitochondrion where it is fully oxidized. 2 CH3—CO—COOH + 5 O2ïƒ 6 CO2 + 4 H2O Carboxyl group is removed releases CO2 From pyruvate (Pyruvate) Reaction summary
- 20. Oxydation of pyruvate occurs because it loses two hydrogen atoms. (remember that oxidation can happen as a result of losing hydrogens) • These hydrogen atoms are accepted by NAD+ and another compound called FAD. • NAD+ & FAD deliver these hydrogens to the electron transport chain where oxidative phosphorylation occurs. From Biology Course Companion, Allott & Mindorf,, Oxford University Press, 2014, p. 383
- 23. The Link Reaction- links glycolysis to reactions that follow in the mitochondria In the link reaction pyruvate (3C) is converted into acytyl coenzyme A (2C + CoA) 1. Pyruvate moves from cytoplasm to the matrix of a mitochondria 2. In the matrix, the pyruvate is decarboxylated & oxidized to form an acetyl group 3. 2 high-energy electrons are lost from pyruvate 4. The electrons join NAD+ to make NADH From http://sorokaapbiology1415.blogspot.tw/2014/09/cellular-respiration-all-you- ever.html
- 25. 8.2 U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide. The Krebs cycle involves two more decarboxylations and 4 more oxidations following the link reaction. • Most energy released through oxidations in the link reaction & Krebs cycle is used to reduce hydrogen carriers NAD+ & FAD. From http://drchadedwards.com/244/energy-production- through-the-krebs-cycle/
- 27. 8.2 U7 Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD. The oxidations that occur during glycolysis, the link reaction, & the Krebs cycles is coupled to the reduction of NAD & some FAD. (FADH2 is produced in the Krebs cycle) • Oxydative phosphorylation- ADP is phosphorylated to produce ATP in the final stage of aerobic respiration • Oxydative phosphorylation is the release of energy from oxidation of FADH2 & NAD. • These molecules carry energy from reactions of aerobic respiration to the cristae of mitochondria. • Oxydative phosphorylation is related to the electron transport chain (ETC)
- 29. 8.2 U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping. From i-biology.net
- 34. 8.2 U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP. http://web.biosci.utexas.edu/psaxena/MicrobiologyAnimations/Ani mations/ElectronTransport/PLAY_etc.html
- 36. http://highered.mheducation.com/olc/dl/120071/bio11.swf The electron transport chain animation
- 38. 8.2 U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water. From i-biology.net
- 39. 8.2 U11 The structure of the mitochondrion is adapted to the function it performs. From i-biology.net
- 42. Nature of Science: Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. Peter Mitchell From Nobelprize.org Peter Mitchell, in 1961, proposed a new theory of chemiosmotics, which was very different from previously held beliefs. • Electron transport in the inner mitochondrial membrane is coupled with ATP synthesis. • It took a long time for his theory to be accepted. • He won the Nobel Prize for Chemistry in 1978.
- 43. Thanks to these fine folks, and any others that I may have forgotten!