BIOL 120 1st EditionExam # 3 Study Guide Lectures: 13 - 15Energy- Energy: the capacity to do work (flows into the biological world from the sun)- Laws of Thermodynamicso Energy cannot be created or destroyed, it can only change from one form to anothero Entropy (disorder) is continuously increasing (energy transformations occurring spontaneously to get matter from less stable to more stable andvice versa)Metabolism- It is the total of all chemical reactions carried out by an organism - Anabolic (making)o Expend energy to synthesis molecules- Catabolic (breaking down)o Harvest energy by breaking down molecules - Biochemical pathwayso Reactions occur in a sequence  product of one reaction is the substrate for the next- Feedback inhibitiono Shutting down enzyme activity by binding the end product of a pathway to the first sight because enough material is already present Turns backon once more is neededCellular Energy- ATP  main source of cellular energy - NADH  secondary source of energy o NAD + H+ 2e  NADH (reversible reaction)- Redox reactionso Reduced= an atom or molecule gaining an electrono Oxidized = an atom or molecule losing an electron o Oxidation and reduction events are always coupled Cellular Respiration-- STEPS:o Glycolysis: involves the initial oxidation and partial breakdown of Glucose (Glucose 6C to Pyruvic Acid 3C)  occurs in the cytoplasm It is a series of 10 reactions  Potential energy released is used to form ATP  All enzymes needed are found in the cytosol  Energy payoff phase- 6C is split into two pyruvates- 2 molecules of NAD form NADH- 4 molecules of ATP made and a net gain of 2 o Pyruvate processing:  pyruvate is oxidized to form acetyl CoA In the presence of O2 pyruvate produces acetyl CoA and NADH and CO2o Citric Acid Cycle  Acetyl CoA is oxidized to two CO2 molecules  Released potential energy is used to reduce NAD to NADH, reduce FAD to FADH2, Phosphorylate GDP to GTP (later become ATP) Completes glucose oxidation  for one glucose the citric acid cycle has to run twice  producing 6 NADH, 2 FADH, and 2 ATPo Electron Transport Chain and chemiosmosis compounds that were reduced in steps 1-3 are oxidized in reactions leading to ATP production occurs in inner mitochondrial membrane  O2 is the final electron acceptor  Oxidative phosphorylation- the energy released during this process is used to pump protons (H+) across the plasma membrane into intermembrane space - protons move through enzyme ATP synthase - Oxidative Phosphorylation: This mode of ATP production links the phosphorylation of ADP with NADH and FADH2 oxidation Chemiosmosis- ETC pumps protons from mitochondrial matrix into intermembrane space  used to make ATP ATP Synthase Structure- A structure that protons flow through that catalyzes the phosphorylation of ADP to ATP Energy Yield - Theoretical: 36 ATP - Actual: 30 ATP per glucose - Fuels for ATPo First use carbs, then fats and proteins as a last resort Aerobic vs. Anaerobic- Aerobic uses oxygen to produce ATP  more productive- Anaerobic does not use oxygen to produce ATP o Lactic Acid fermentation  occurs in muscle cells  Makes 2 ATP moleculeso Alcohol fermentation  occurs in yeast Makes 2 ATP Photosynthesis- Conversion of light energy into chemical energy - Stages:o Light dependent  Requires light Makes ATP and NADPH Occurs in thylakoid membrane  Chlorophyll a and b  green colors Carotenoids  red, orange and yellow pigments  Photosystem I  absorbs light at 700nm Photosystem II  absorbs light at 680 nm  Energy decreases as electrons are donated and the process repeats with added light energyo Light independent reaction Uses ATP and NADPH to synthesis CO2 Photosystems- Photosystem: a complex formed from chlorophyll molecules working together in groups - Antenna Complex/ light harvesting complexo Captures photons and channels them to reaction center chlorophylls - Reaction Centero Transmembrane protein o When a chlorophyll absorbs a photon of light an electron is excited to a higher energy level - Photosystem IIo Has a core of ten transmembrane protein subunitso Has 2 P680 chlorophyll o Reaction center contains 4 manganese atoms (needed for oxidation of water)o Has b6-f complex  Proton pump embedded in thylakoid membrane- Photosystem Io Reaction center has 12-14 protein subunitso Has two P700 chlorophyllo Accepts electrons to make NADP into NADPH - Chemiosmosiso Used to synthesis ATP o Calvin Cycle  catalyze the reaction of carbon fixation Types of photophosphorylation - Non- cyclic  (electrons flow in a non- cyclic manner) Energy gets lost and system is not constant  need a constant supply of electrons to replace lost energyo Also known as Z pathwayso Electrons come from photolysis of watero Generates NADPH, oxygen and ATP o Uses both Photosystem I and IIo Energy level of protons goes up and then transferred to electron acceptor because it is too much and keeps being transferred until I (energy slowly decreasing until reaches I and process continues)o Has 4 steps: Primary photoevent- Photon of light is captured by a pigment molecule Charge separation- Energy is transferred to the reaction center and an excited electron goes to an acceptor Electron Transport- Electrons move through carriers and reduce NADP to NADPH  Chemiosmosis- Makes ATP - Cyclic  electron flow stays constant with energy being received and removed simultaneouslyo Only uses photosystem IIo Generates ATP through the electron transport chain  doesn’t make oxygen Calvin Cycle- Also called C3 pathways of photosynthesis - Key step is attachment of CO2 to RuBP to form PGA- Uses rubisco to react with carbon and oxygen o Carboxylase  fixing carbon o Oxygenase  fixing oxygen- Light reaction provides ATP to run Calvin Cycle which makes glucose, fixes CO2 and regenerates RuBP- 3 Phases:o Carbon Fixation  RuBP (5C) + CO2  PGA (3C)o Reduction  PGA is reduced to G3P which is used to synthesis glucose  Extra sugar created is stored as starch o Regeneration of RuBPPhotorespiration - Carboxylation  favored under normal conditions- Photorespiration (oxygenase)  favored when stoma are closed in hot conditions - Stomatao Openings in leaves that control gas exchange o CO2 concentration is low during photosynthesis  et Co2 in Needed because the Calvin Cycle is constantly using up CO2 Other types of