Bio 160 Week 7 Notes
Bio 160 Week 7 Notes Bio 160
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This 10 page Class Notes was uploaded by Alex on Friday October 7, 2016. The Class Notes belongs to Bio 160 at University of Mississippi taught by SYMULA, REBECCA E in Fall 2016. Since its upload, it has received 62 views. For similar materials see Biological Sciences I in Biology at University of Mississippi.
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Date Created: 10/07/16
Bio photosynthesis Photosynthesis builds sugars using several reactions G=+686 kcal/mol Light is turned into energy through the chloroplasts Chloroplasts have two separate membranes and an intermembrane space just like mitochondria Membrane infolding is used to create compartments – think back to prokaryotes. They didn’t have organelles, but they had the infolding. Same concept Everything happens inside the chloroplasts. They will try to trick you! The stroma is INSIDE the chloroplast Chlorophyll is a molecule embedded in the membrane of the chloroplast. Specifically, in a protein called a photosystem Two different pathways- light reactions and light independent reactions Light independent reaction- Calvin Cycle Need to know how and where photosynthesis uses light, CO2, and water Which pathway plants use to produce oxygen (where, when, and how) Need to know when electron carriers become oxidized and reduced Photosynthesis is run to make SUGARS. Not ATP. Some ATP is made, but not enough to run the plant, just to fuel the Calvin Cycle. Photosynthesis takes place in the chloroplasts Thylakoid- can be inside the thylakoid or outside Stroma- outside of the thylakoid Thylakoid- pancakes | granum- stack of pancakes | stroma- syrup Chlorophyll is in a protein (photosystem is the name of the protein) Not all organisms that do photosynthesis have chloroplasts. We’re focusing on the ones that do Photosynthesis consists of two pathways Light reactions Happens within thylakoid membrane Creates a small amount of ATP, but a lot of NADPH Water is used, oxygen is produced Light-independent reactions Calvin Cycle Take carbon dioxide and make it into sugar (fixed) Light reactions occur across the thylakoid membrane Using the photosystems to capture light, convert light into chemical energy, and as a result, we will produce and electron carrier Transmembrane proteins- proteins that go all the way through Peripheral protein- a protein attached to the outside of the membrane Other type of protein- is embedded in the membrane The output of the light reaction- NADPH, a small amount of ATP, and oxygen We’re going to build a gradient again as well as oxidative phosphorylation Energy for photosynthesis comes from light Light behaves as a particle and a wave Light excites atoms and molecules Photon- an individual unit of light Some light is visible Normal state- ground state Excited state- when light hits it, it goes into a further orbital and creates energy because it is now more reactive Time between pulses- wavelength Longer wavelength- less energy Shorter wavelength- more energy See, the longer waveleng wavelength only waveleng Longer wavelength th has two crests in th means that less crests (the top of the the same amount curve) can pass of space while the smaller has three through a certain Some electrons won’t be excited except from certain wavelengths of light With chlorophyll, it is excited with visible light The particle properties of light will transfer energy When light hits something, it can go right through, absorbed, or reflected If it’s reflected or goes right through, it is not useful. There is no energy transfer Absorbed- actually doing the energy transfer When you see the color green, that is the color that is not being used/reflected Every color but green! Plants vary in how green they are and have different variants of green. That means they vary on the specific wavelengths they reflect! White- all visible light is being reflected Black- all visible light is being absorbed Pigment molecules absorb energy Chloryphyll is a lipid, very nonpolar Magnesium helps capture light There are many other pigments in a plant (when the leaves change in the fall, we see them) Chlorophyll a and b don’t have much difference between them, but need to know that there are two kinds photosystem Pigment molecules are part of a complex called a photosystem Transmembrane protein Many chlorophyll molecules associated with it Antenna system- all the chlorophyll molecules in a photosystem When a photon of light hits the thylakoid membrane, it excites a chlorophyll. Then, the chlorophyll transfers the energy around until it gets to the reaction center. Reaction center: light energy to chemical energy Chlorophyll- electron donor (becoming oxidized) Not all of the energy is used, some is released as heat or is lost Moves excited electron to an electron carrier REDOX REACTION NADP+ is the electron carrier Transports electrons to an electron transport chain NADP+ is an electron carrier NAD+ =NADP+ It simply just has an extra phosphate Made by e- transport. In cellular respiration, we just transfer the electrons, but in photosynthesis, the chain is used to MAKE NADP+ Oxygen released from photosynthesis comes from water Oxidize water and reduce carbon dioxide Electrons are transported in two ways Photosystems are organized in two ways: noncyclic transport and cyclic transport Non-cyclic transport has two photosystems. NADP+ (FINAL e- acceptor) This only happens in non-cyclic transport! The electrons from the chlorophyll are excited and taken away, it cannot be excited again. Water is used to help this problem. Water is split and the electrons are put back in the photosystem while the oxygen that is left over leaves Once the electron is excited from a photon, it goes to the transport It moves through the membrane to finally land in NADP+ Creates another hydrogen gradient and has ATP synthase Cyclic transport is the other kind Non-cyclic electron transport produces a few ATP and NADPH Two photosystems Photons hit both and excite both. Water comes to the first one to replenish electrons Two chains, between the two and then after the second Get ATP, but cannot fuel plant. But ir produces reduced electron carriers Non-cyclic electron transport occurs across the thylakoid membrane Once we generate a gradient, the gradient becomes acidic (thylakoid interior. Not intermembrane) Water is split into electrons and protons that are used for energy and NADPH We MAKE the electron carrier instead of simply using an electron carrier Inside of thylakoid is acidic NADPH and ATP are produced on the stroma side Save carbon dioxide for light independent reactions Cyclic electron transport produces ATP NOT NADPH To make a little more ATP than with non-cyclic Makes the gradient so we can use ATP synthase The electrons are excited and are moved to electron chain systems, but it goes back to the photosystem so we DO NOT NEED WATER Chemiosmosis generates ATP Bio- negative feedback Cellular respiration is regulated Glycolysis and cellular respiration produces a lot of ATP and intermediates. Option to store, or build macromolecules If we have enough ATP, we can shut off the process and create macromolecules or lipids Negative feedback regulates cellular processes When you produce one end product, the product can turn around and turn off the process in which it was made Ex: enzyme turns C into F. enzyme turns F into G. G can then go back and turn off the enzyme that turns C into F Allosteric activation- when a molecule binds with a enzyme and causes a shape change. Because it is activation, the active site opens so the enzyme can work Citrate is produced in the first step of the citric acid cycle Starts with Acetyl Coa and binds to Oxaloacetate and then a citrate to make citric acid You produce twice as much citrate with one molecule of glucose. Citrate can be easily converted to isocitrate Citrate has several impacts on respiration Formation of isocitrate Increase fatty acid metabolism, will make break down Acetyl CoA instead of sending it into the citric acid cycle Negative feedback- turns Acetyl CoA into a fatty acid and lowers the production of citrate At high concentrations, citrate will leave the mitochondria and work in the cytosol. Citrate and ATP inhibit PFK Citrate inhibits PFK used in the energy investing stage of glycolysis so the production of G3P would decrease since the product of the energy-investing stage is G3P PFK= phosphofructokinase This is the one that will actually be shut down if you’ve eaten too much sugar PFK is the enzyme we regulate glycolysis with (energy investing side of glycolysis) Citrate is an allosteric inhibitor to PFK (also an example of negative feedback!) ATP and NADH inhibit conversion of isocitrate NAD+ and ADP activate isocitrate dehydrogenase NADH and ATP inhibit isocitrate dehydrogenase They slow their own production, but once they get converted back to the previous form, they react accordingly remember, citrate is easily converted to isocitrate. So also increases the amount of citrate in the cell, therefore allowing it to conduct negative feedback when necessary. It’s all tied in together! Bio= end of photosynthesis You do not need to memorize the molecules or enzymes of glycolysis or the citric acid cycle You do not need to memorize the enzymes, but we talked avout a couple of specific ones such as kinases, isomerases, etc. need to be allosterically regulated Photosynthesis builds sugars using several reactions Water is split into electrons and protons that are used for energy and NADPH. The hydrogen is used to make the gradient, the electrons refuel photosystem 2 in noncyclic process and oxygen (O2) is a byproduct The Calvin cycle fixes CO2 in the stroma o NADPH and ATP are produced in the stroma o They are used to fuel the calvin cycle o This is a light independent reaction To “label” molecules to see how they are processed, they took an isotope of Carbon and saw where it was being used o What they learned is that carbon dioxide is fixated in plants and converted to sugar The calvin cycle has three processes o At the start of the calvin cycle, you start with 6 carbon dioxide o Immediately, its split into two G3P. o There are three proc esses The carbon fixation is the first part-it becomes a part of a 3 carbon molecule and binds to 3PG Reduction and sugar production- reduce G3P and build sugars Regeneration of RuBP- convert the sugars to recycle into RuBP o Use ATP in the last step o CO2 binds to RuBP using Rubisco (is an enzyme. The last name is carboxylase) o Carbon dioxide bonds with RuBP. Creates a 6 carbon molecule that is so unstable, it immediately splits into… o 2 3PG is made o 3PG is reduced to form sugars o 12 ATP are used to phosphorylate 3PG o 12 NADPH are oxidized to reduce 12 3PG to make 12 G3P o Sugars are made from G3P Anytime youre using a kinase enzyme- its substrate level phosphorylation Oxidative phosphorylation is using the hydrogen gradient to make ATP o G3P is used in glycolysis- it’s the product of the energy investing stage When G3P is already available, it can go straight into the energy harvesting reactions. Skip the energy investing stage altogether o G3P makes sugars and is recycled to form RuBP Need to go back and remake G3P. RuBP is essential so we recycle the rest to remake it 2 G3P can be used from 6 CO2 and the 10 other are used to make RuBP G3P can be used to make many things o Will be used to make sucrose, fatty acids, glycerol, starch, glucose, cellulose, and amino acids. o They can make their own triglycerides (storage of energy) o In a plant, the product of the Calvin Cycle can be used to build macromolecules Plants synthesize all of the molecules they need o Gluconeogenesis- making their own glucose One of the intermediates made in the citric acid cycle can be used to make amino acids therefore proteins. This is also reversible Photosynthesis is not 100% efficient nd o Energy is always lost between steps. 2 law of thermodynamics o Only 5% of the original energy is actually stored in the products of these processes
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