ch.9 - cellular respiration.docx

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Biological Sciences
BIOSC 0150
Christine Dahlin- Universityof Pittsburgh Johnstown

1 General Biology 1 Chapter 9 – Cellular Respiration Cellular respiration – extraction of energy from food (at a cellular level) - And converting that energy to ATP (which used to do cellular work) - A process of breakdown molecules for fuel through: Respiration or Fermentation: 1. Aerobic respiration - Oxygen is consumed as a reactant along with organic fuel - Sometimes cell respiration refers exclusively to aerobic respiration 2. Anaerobic respiration - Other types of molecules are being consumed, oxygen is NOT included 3. Fermentation - Partial degradation of sugars with oxygen (anaerobic) Catabolic reactions – metabolic pathway that released stored energy - Organic chemicals possess energy due to arrangement of electrons - Fuel – compounds that can participate in exergonic reactions - Ex/ proteins, fats, phospholipids - Complex molecules are being broken down into simple molecules i.e. – glucose o Make energy that uses for work and heat - C 6 O12 66  6CO2+ 6 H O +2E (ener2y in form of ATP and heat) - G = -686 kcal/mol glucose How do catabolic reactions make E? - Help make ATP - During the break down of molecules, electron gets transfer from organic molecules  this release E which then can use to make ATP - Redox reactions – oxidation-reduction reactions  transfer energy - Electron transfers to electron carriers and pass through the final electron acceptor - As the energy released and move toward oxygen, potential energy decreases and energy released to make ATP. Redox reactions - Oxidation reduction reactions - Oxidation (electron donor) – loss of electron - Reduction (electron acceptor) – gain of electron (also hydrogen) Oxidized Na: electron donor, reducing agent Na + Cl  Na + Cl - Cl: electron acceptor, oxidizing agent Reduced Aerobic respiration - Series of electron (and E) being transfer to oxygen – an ultimate acceptor - Energy captured a lot and lots of ATP 2 General Biology 1 Chapter 9 – Cellular Respiration o Some heat is lost - Human, plants, and many bacteria do aerobic respiration Redox of glucose in cellular respiration + - Electron is transferred with a proton (H )  molecules with lots of hydrogen is good fuel - Oxygen gains electron  reduced - Energy released becomes available for ATP synthesis BUT - Energy can’t be extract all at once and need to sustain - Glucose and organic molecules broken down into step o Each step is catalyzed by enzyme + o At the key steps – electron stripped away from glucose and travels with H + o Passed its first electron to electron carriers before going to oxygen NAD /NADH - NAD is electron carrier - When NAD accepts electrons, they become NADH - Electrons fall down energy gradient, energy is released until electron finally reaches oxygen As an electron carrier: - Organic molecule provides electron (reducing agent) and NAD accept electron through enzym+ dehydrogenase - NAD then become NADH o H-C- OH + NAD  NADH + C=O + H + - NADH then transfers electron to oxygen, which is an ultimate acceptor Oxidized + NADH + O 2 NAD + H O 2 G = -53 kcal/mol Reduced (gain H and electron) Electron Transport Chain (ETC) - Shuttling electron from organic molecules from NADH through many other molecules until they reach O2 o ETC molecules are typically proteins - Located in mitochondria and plasma membrane - Breaks fall of electron and stores more heat to make ATP Noted: Instead of pass energy all at once (cause explosion), energy release a little at once - Oxidation of a donor (glucose for example) + o Electrons get transfer to NAD and electron carrier o Electrons get transfer stepwise until they reach acceptor (oxygen for aerobic respiration) and energy captured and converted as ATP. 4 stages of cellular respiration 1. Glycolysis – in cytosol; only make a little of ATP 2. Pyruvate oxidation 3 General Biology 1 Chapter 9 – Cellular Respiration 3. Citric acid cycle – in the matrix of the mitochondrion 4. Oxidative Phosphorylation – consist of ETC and chemiosmosis  when ATP has finally made (in chemiosmosis) Overview: 1. Glycolysis – an oxidation of glucose convert into pyruvate with a little of ATP made; it’s reduced electron carriers 2. Pyruvate oxidation – pyruvate converts to Acetyl CoA  no ATP made 3. Citric Acid Cycle – Acetyl CoA to CO and a 2ittle of ATP made; it’s reduced electron carriers Glycolysis - Begin degradation of molecules - A glucose molecule converts to two pyruvate molecules o C H 6 12 6 O (py3uv4te3 - Electrons get send to be reduced in electron carriers + - NAD becomes NADH - Not too much of ATP is made ETC – electron carriers are NADH and FADH , they a2cept molecules in stepwise - Energy creates as proton gradient across membrane - Proton flow by enzyme ATP synthase that direct ATP synthesis Oxidative phosphorylation – ATP synthesis via the electron transport chain Food donor electron to NADH/FADH (electron carriers) which transport electron to ETC and to 2 final acceptor Glucose  CO 2 During this process, the donor (glucose) becomes fully oxidized 2 ways ATP can be made 1. 90% made by oxidative phosphorylation: ADP + P  iTP occurs via ETC 2. 10% made by substrate level phosphorylation - Direct transfer of phosphate from organic molecule by enzyme - Glycolysis and citric acid cycle 1. Glycolysis - Sugar split into pyruvate  sugar splitting process - Happens in cytoplasm - Oxygen DOESN’T requires - Spend some ATP “upfront” (investment phase) and gain some net gain of ATP (E payoff phase) - Reduced NADH - Net: glucose  2 pyruvate + 2 waters - Made 4 ATP, 2A+P used  2 ATP made o+erall + - Invest 2NAD + 4 electrons + 4H  2NADH + 2H 4 General Biology 1 Chapter 9 – Cellular Respiration - Overall – 2 ATP, 2 NADH Energy investment phase: 1 Importa1t regulatory step – phosphofructokinase regulate by enzyme Energy invested (2ATP) glucose splits Glucose fructose 1,6 biphosphate Energ
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