Transcript cellresp
I’ve Got the Power!! http://www.johnkyrk.com/glycolysis.html Photosynthesis Let the sun shine….. Hooray for photosynthesis!!!! The equations… • Cellular respiration-highly exergonic – C6H12O6 + O2 CO2 + H2O + ATP!! – Energy released thru oxidation of glucose • Photosynthesis-highly endergonic – Light + CO2 C6H12O6 + O2 – Light energy used to reduce CO2 • Stroma – ATP produced in stroma – Calvin cycle • Thylakoid membrane – Photosystems embedded – ETCs – ATP synthase • Thylakoid space – H+ conc. gradient Overview Produce energy Required for dark reactions “fix” CO2 into glucose Highly endergonic • Light independent reactions – Occur in thylakoid space & membrane – Light strikes chlorophyll – E- are boosted to higher energy level & travel down an ETC – Released energy captured to form ATP & NAPH – Water molecules borken apart to replace lost e- • Light independent reactions-carbon fixing – Uses energy captured in ATP & NADPH to reduce CO2 to sugar – Occurs in stroma Absorption pigments • Light energy must be absorbed to be of any benefit • Pigments absorb certain wavelengths of light, which causes altered structure • Chloroplasts contain several pigments – Chlrophyll-absorbs violet, blue, red – Carotenoids-absorb blue & green – Phycocyanins-absorb green What happens when chlorophyll absirbs light? • An e- becomes energized & moves to higher orbital • This is unstable-e- will normally release energy & • move back to its original orbital In photosynthesis, e- is captured by ETC What is a photosystem? • Located in thylakoid membrane • Composed of a reaction • center(chlorophyll), ,accessory(antennae) pigments, & an ETC PSI– – – – evolved 1st, cotains a dimer of chlorophyll, can operate independently of PSII, its ETC makes NADPH • PSII – Supllies e- to PSI – ETC produces ATP (photophosphorylation) • Accessory pigments absorb light & pass it chlorophyll •Only chlorophyll loses e- to ETCs Light causes e- to become energized in PSII Jump to higher level Water is split to replace e- E- captured by cytochromes in ETC Energy used to push H+ from stroma to space Gradient used to produce ATP in stroma E- end up in PSI, which has also lost eTo its ETC PSI ETC gives its e- to NAD-an e- shuttle, it carries e- to calvin cycle Cyclic e- flow-used when no NADP is available-(calvin cycle uses ATP faster than NADPH) This ETC shuts down No NADPH or O2 RuBP carboxylase CO2 is reduced RuBP is regenerated Totals-1 glucose molecule Requires: 6CO2 18 ATP 12 NADPH How many ATP do we get From 1 glucose in cell resp? Reverse reactions of glycolysis G3P In stroma C4 plants • During hot weather, stoma close to avoid water loss • Causes build up of O2 which favors photorespirationrubisco not selective • This inhibits calvin cycle • C4 plants have 2 adaptations to combat this – Bundle sheath cells in leaf interior-less PSII, so less O2 produced – PEP carboxylase-high affinity for CO2 despite O2 levls – Result is maintenance of high level of CO2, with a lower level of O2 CAM plants • Crusculacean Acid Metabolism • Open stomata at night-store CO2 as CA • During day, stomata closed-convert CA back to CO2 & photosynthesize Terminal phosphates Break off fairly easily Due to instability of Molecule-provide Enough energy for most Cellular reactions ADP AMP + Pi Coupled reactions-energy released from exergonic reactions drives endergonic reactions Nuclear fusion H He + Light energy EXERGONIC CO2 + H2O ENDERGONIC + O2 This reaction is endergonic Sometimes the breakdown Of ATP is coupled to An endergonic reaction This bond is Broken & the Energy released Drives the reaction This compound is Phosphorylated & Has energy •ATP is formed through the oxidation (breakdown) of glucose in a series of step wise reactions Redox (oxidation-reduction) Reactions • • • • • • e- pass from one atom/molecule to another H+ may also be lost or gained as a result Molecule which loses the e- (H+) is oxidized Molecule which gains e- (H+) is reduced Must always occur together The transfer of an e- to a more electronegative atom releases energy Na + Cl Na+ ClNa is oxidized Cl is reduced C6H12O6 + 6O2 6CO2 + 6H2O During cellular respiration….. •Glucose is oxidized, oxygen is reduced • e- shift from glucose to highly electronegative O2 •Energy released a little at a time No matter what food is taken in It can be fed into this process At some point! The Reactions……. So what’s really important about glycolysis? 1. Takes place in cytoplasm 2. With or without oxygen 3. Every living thing on the planet does it 4. Starts with 6C glucose 5. Ends with 2, 3C pyruvates 6. Gross 4 ATP 7. Net 2ATP, & 2 NADH Nicotinamide adenine diphosphate, aka NAD, is an electron shuttle So what happens next? That depends on whether or not O2 is present!!! •W/ O2, Kreb’s cycle & ETC •W/O O2, fermentation Fermentation • In the presence of O2, • NADH carries its e- to the ETC NAD is regenerated for use during glycolysis – W/o this regeneration, glycolysis would stop!! • If no O2 is present, fermentation regenerates NAD, & keeps glycolysis active Hooray for Fermentation! Used by anaerobic microorganisms (bacteria, yeast), & to make human foods • Used by human • • • muscles during vigorous exercise (oxygen debt) Allows muscles to continue working w/o oxygen Build-up forces muscles to slow down until intake of O2 catches up Lactic acid eventually breaks down • • • • Outer membrane permeable to most small molecules Inner membrane only permeable to ATP & pyruvate Matrix-enzymes, water, Pi-parts of Kreb’s & ETC Cristae-kreb cycle enzymes, ATP synthetase, ETC embedded in folds •Intermediate Step-what’s important… link between glycolysis & Kreb’s moves pyruvate into mitochondria (sometimes ACTIVE transport) happens twice per glucose (2 pyruvate) start w/ 2 pyruvate end with 2 acetyl CoA net 2 NADH, 2 CO2 (by-product) To Krebs cycle oxidized Series of redox Reactions which Completely finishes The oxidation of glucose So Dunbar, help us out here! What’s important? • Each glucose requires 2 turns • • • • • of cycle (2 pyruvates) Takes place in matrix & cristae Oxaloacetate is regenerated Start w/ 2 acetyl CoA End w/ oxaloacetate Net, per glucose – – – – 2 6 2 4 ATP NADH FADH2 (another e- shuttle) CO2 (by-product) – – – – 4 ATP 10 NADH 2 FADH2 6 CO2 • TOTALS SO FAR THE BIG PAYOFF!!!! • Totals so far… – – – – 4 ATP 10 NADH 2 FADH2 6 CO2 • But I thought you could get • 38 ATPs from just 1 glucose!! What’s the deal yo? MOST OF THE ATP COMES FROM THE ELECTRON TRANSPORT CHAIN!!!! So what is it, anyway???? • A collection of molecules • • • • embedded in the cristae Molecules are proteins called cytochromes- they can accept & pass on e- (just like NAD) – Heme group alternates between reduced & oxidized state NADH & FADH2 drop off e- to 1st cytochrome, & these are passed down the chain Each cytochrome in the chain is more electronegative than the one before it The last e- acceptor is O2 (the most electronegative of all!!!) 2. Conc. Gradient set up-water behind a dam H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ cristae 1. Energy released as emove closer to O2-used to pump H+ into intermembrane space 4. Energy created from H+ moving thru enzyme provides energy to Phosphorylate ADP (chemiosmosis) 3. H+ MUST pass thru here How does this enzyme work? Think pinwheel! 1. Rush of H+ turns the rotor which spins the rod 2. Turning of rod activates catalytic sites 3. Each NADH makes 3ATP, each FADH2 makes 2 ATP • • • 10 NADH30 ATP 2 FADH2 4 ATP SO………….. TA-DAAAA!! The last thing! • How does a cell/organism control how much ATP is made? – Second step of glycolysis controlled thru biofeedback – Phosphofructokinase is an allosteric enzyme!!!