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Transcript
Energy in living systems C-9-1 Photosynthesis is how plants obtain energy! ~ done by autotrophs They take CO2 and H2O and convert it to glucose and O2. The heterotrophs then take those products (glucose and O2) and use them for energy in cellular respiration Ex: There are several energy transferring reaction within photosynthesis: 1.) Using or making ATP – when ATP is split, it releases energy 2.) ATP synthetase – enzyme that makes ATP 3.) H+ pumps – actively pump in H+ ions to build up a concentration gradient ~ those will slip back through the synthetase and make ATP! Photosynthesis C-9-2 Factors that can affect photosynthesis are : Amount of CO2, temperature, and light intensity 3 steps: 1.) Plants harvest energy from the sun ~ thylakoids – contain chlorophyll - within the chloroplast Ex: Chlorophyll is a pigment that absorbs red and blue but reflects green and yellow ~2 types: chlorophyll a and chlorophyll b Also have carotenoids – absorb green and blue reflect red, orange and yellow ~ where we get the fall leaf colors! 2.) Light reactions produce energy ~ light comes in different wavelengths and energies: the longer the wavelength, the less energy it has Energy from these photons zaps the e- and gives it more energy *this energy is used in 2 different processes in the light reactions: a.) Making ATP: ~ excited e- get replaced by splitting H2O molecules - H donates its e- and is left with H+ - O isn't used anymore so it leaves as O2 gas ~ excited e- then goes down the e- transport chain to power a proton pump which brings in H+ ~ H+ creates a concentration gradient and it wants to slip out again - does this through the ATP synthetase! ~ATP is made from ADP b.) Making NADPH: ~ less excited e- continues down the etransport chain to the next chlorophyll molecule ~ gets zapped again - excited e- go down the second e- transp. chain to an e- acceptor call NADP+ ~ combines with H+ to make NADPH 3.) Dark reaction produces sugars Called the Calvin Cycle… a.) 6 CO2 are added to 6 5C molecules – yields 12 3C mol b.) use ATP and NADPH to power conversion to split the 12 3C into 2 3C mol. to go to sugar c.) other 10 3C use ATP to rearrange and regenerate the 6 5C at the start Like this: Cellular Respiration C-9-3 Energy that was made in photosynthesis can be used in cellular respiration by stripping the e- from the molecules built in photosynthesis. The e- have extra energy from the photon that hit it. Has 2 stages: 1. Glucose converted to pyruvate - produces small amount of ATP *occurs in the cytosol 2. O2 present = pyruvate and NADH used to produce lots of ATP : aerobic - needs O2 *occurs in mitochondria (eukaryotic cells); cell membrane in cells w/o mitochondria O2 not present = pyruvate converted to lactic acid or ethyl alcohol : anaerobic - w/o O2 Here's the flow chart: And the chemical reaction: C6H12O6 + O2 ---------- CO2 + H2O + 36ATP Glycolysis: *Sequence of enzyme-catalyzed rxns that converts a 6C glucose molecule into 2, 3C molecules of pyruvate. *This is an anaerobic reaction!! Here's how the flow chart works: *So at the end, we have 2- 3C pyruvates and 2ATP's After glycolysis, the pyruvate molecules are converted into a 2C fragment and a CO2 and H+ are also extracted. CO2 leaves the cell; H+ goes to a NAD+ molecule to be used later. The remaining 2C fragment (called an acetyl group) is attached to a coenzyme (coenzyme A) and forms acetyl-CoA. The acetyl-CoA gets either used in fat synthesis if there is enough ATP or it goes to be used in the Krebs Cycle to make more ATP. The Krebs Cycle: This is a repeating series of rxns that produces ATP, e- carriers, and CO2 Let's see how the cycle works! The Krebs Cycle must turn 2x for every glucose that is converted to pyruvate. Electron transport chains: *in the inner membrane of the mitochondria *as e- pass through an e- transport chain, p+ are pumped out of the inner chamber, the p+ build up outside and then rush back in via ATP synthetase thus making ATP **32 ATP's are made!!! *at the end of each e- transport chain, H+ are added to O forming H2O Without O2, Fermentation occurs! *instead of the e- getting carried away by NAD+, the e- remain attached to NADH *this takes up all available NAD+ and then glycolysis can't continue *SO the H+ must be attached to something else… - in animals = H+ gets attached back to pyruvate to form lactic acid *this is what causes your muscles to hurt when you work out! - in plants = H+ gets attached to CO2 from glycolysis to form ethyl alcohol *this is what causes bread to rise (CO2) and beer to become alcoholic (ethyl alcohol) *Yeast is the microorganism that performs this task!