Energy Exchanges Exam: What to Study Here s what you will need to make sure you understand in order to prepare for our exam: Free Energy Conceptual understanding of free energy as available energy in a system Difference between spontaneous and nonspontaneous reactions Exergonic vs. Endergonic reactions and relationship to free energy availability Oxidation and Reduction: relationship to free energy availability Be able to calculate free energy equation problems
Exergonic vs. Endergonic Reactions Exergonic reactions Products < Reactants in terms of free energy available ΔG is negative Energy is released Spontaneous reaction System can do work Catabolic processes: molecules being broken down Ex.: Cellular respiration Endergonic reactions Products > Reactants in terms of free energy available ΔG is positive Energy is stored Nonspontaneous reaction System must have work done to it Anabolic processes: molecules being built from raw materials Ex.: Photosynthesis
Oxidation and Reduction Oxidation Loss of electrons Free energy is given off Reduction Gain of electrons Free energy is stored
Gibbs Free Energy The measure of free energy available in a system Know how to solve problems that use the equation Living organisms exist in an imbalance of free energy...when ΔG = 0, death occurs due to no free energy flow! Don t forget: temperature is in degrees K (273K + temp in degrees C)
Energy Exchanges Exam: What to Study Here s what you will need to make sure you understand in order to prepare for our exam: Cell Respiration AND Photosynthesis Organelles involved in process in both prokaryotes and eukaryotes Location of individual processes within these organelles Describe free energy flow in both processes Characterize each reaction as endergonic or exergonic Describe relationship between the two processes in terms of: Products and reactants Free energy flow Endergonic/exergonic reactions
Energy Exchanges Exam: What to Study Cell Respiration Importance of this process as a core process for all life on Earth: connections to evolution All organisms perform this metabolic process indicates common ancestry Endosymbiosis: mitochondria evolved from free-living bacteria that could oxidize organic compounds Where in cells it occurs: both prokaryotes AND eukaryotes Aerobic vs. Anaerobic respiration: Reactants and Products Location of each stage Movement of free energy: what is oxidized, what is reduced Use of alternative fuels by cells (not just glucose) as energy sources Advantage to this?
Location of Cell Respiration In prokaryotes: in the cytoplasm and on the cell membrane In eukaryotes: Cytoplasm: glycolysis Mitochondria: Krebs cycle in matrix Electron transport and oxidative phosphorylation: inner membrane of mitochondria and matrix
Goal of Cellular Respiration Move electrons from glucose to oxygen in a controlled manner using enzymes and co-enzymes (electron carriers) that releases a little bit of energy with each step--much more efficient!
Anaerobic Respiration Glycolysis: Splitting of sugar Takes place in cytoplasm Oxidizes glucose into pyruvate 2 ATP NET gain (made through substrate level phosphorylation) Does NOT require oxygen Fermentation: Occurs in the absence of oxygen Frees up NADH to accept more electrons from glucose (as NAD): keeps free energy flowing! Allows for oxidation of NADH back to NAD+ 2 forms of fermentation Lactic Acid Fermentation Occurs in organisms such as animals and some species of bacteria Alcoholic Fermentation Occurs in organisms such as yeast and other species of bacteria
Aerobic Respiration Krebs Cycle: can only happen if oxygen is present Oxidizes pyruvate, provides electrons that power the ETC and provide H+ gradient for ATP synthesis CO2 is given off as NAD and FAD are reduced to NADH and FADH2 Only yields 2 ATP total through substrate-level phosphorylation Must happen 2 times (once per pyruvate)
Oxidative Phosphorylation and Electron Transport Oxidative Phosphorylation Electrons from glucose are carried by NADH and FADH2 from the Krebs Cycle H+ ions are pumped across inner membrane to intermembrane space (from low concentration to high concentration AGAINST their concentration gradient) Proton-motive force provides energy to pump H+ ions (protons) across membrane Electrons from NADH and FADH2 are attracted to Fe+2 on cytochromes of ETC ETC creates a concentration gradient of H+ ions for chemiosmosis (H+ ions flow from high concentration to low concentration WITH their concentration gradient) Chemiosmosis powers the production of ATP by ATP Synthase as H+ ions flow through ATP synthase to produce ATP Oxygen acts as final electron acceptor and, combines with e- and H+ to produce water and to maintain the concentration gradient
Aerobic Respiration Other molecules can be used as fuel by cells Energy can be extracted from fats, proteins and nucleic acids Make sure you understand WHERE these molecules would enter the respiration process! Advantage to using other fuels?
Energy Exchanges Exam: What to Study Photosynthesis Leaf Structure: know where parts of PS occur; their role in PS process Importance of this process as a core process for all life on Earth: connections to evolution as well as importance of process as provider of free energy from the Sun Light and Pigments Endosymbiosis: chloroplasts evolved from free-living blue-green bacteria Action vs Absorption Spectra Light-dependent vs. Light-Independent reactions: Reactants and Products Location of each stage Movement of free energy: what is oxidized, what is reduced Adaptations for prevention of photorespiration: C4, CAM photosynthesis
Leaf Structure Know where photosynthesis takes place in the leaf: palisade layer Stomata allow CO2 to enter leaf Vascular bundle carries products of PS to other parts of the plant
Chloroplast Structure Know where the different parts of photosynthesis take place in the chloroplast: stroma: Calvin cycle thylakoid: light-dependent reactions Contain chlorophyll (that has electrons excited by light--very important!)
Chlorophyll and other pigments Know the difference between action spectrum and absorption spectrum Absorption spectrum: what wavelength of light is the pigment absorbing? Action spectrum: what wavelengths of light can PS occur at? Electrons on chlorophyll get excited by the sun and will move up energy levels to travel down electron transport chains
Visible Light Spectrum Remember that light behaves as a particle and a wave Light is sent to Earth from the Sun as photons (small packets of light--particles) The wavelengths of light we see are a part of the visible light spectrum Longer wavelengths have less energy; shorter wavelengths have more energy available Colors of the visible light spectrum that we see are visible because that color is reflected back to our eyes So...plants are green because green light is reflected back to us; they absorb every other color of the spectrum with varying efficiency
Goal of Photosynthesis Move electrons and hydrogen from water to CO2 in a controlled manner using enzymes and co-enzymes (electron carriers).
Light Dependent Reactions Photosystem II: Non-cyclic photophosphorylation Water is split through photolysis into H+ ions, electrons and O2 gas is released Excited electrons from Photosystem II are sent through the ETC, ending up in Photosystem I Electrons from PS2 are replaced by electrons from hydrolyzed H2O Electrons move down ETC, create proton-motive force that pumps H+ ions from stroma into thylakoid lumen (hollow space) H+ ions flow back through ATP synthase from lumen into stroma: chemiosmosis Photosystem I: Cyclic Photophosphorylation Excited electrons from Photosystem I are sent back through the ETC if more ATP is needed Electrons cycle back into Photosystem I NADP+ is reduced to NADPH
Light Independent Reactions The Calvin Cycle 3 Main Steps a. Fixation of CO2 b. Reduction of 3GP to G3P c. Regeneration of RuBP Occurs in stroma 3 carbon carbohydrate is produced as a result--this means plants can produce other carbohydrates, not just glucose
Adaptations for Photosynthesis: C4 and CAM These help plants avoid photorespiration: fixation of O2 instead of CO2 CAM: temporal separation of carbon fixation Calvin cycle happens at a different time of day than C3 plants C4: spatial separation of carbon fixation Location of Calvin cycle is NOT in the spongy mesophyll as it is in C3 plants
Energy Exchanges Exam: What to Study Energy and Matter BioGeochemical Cycles Water, Nitrogen, Carbon Primary Productivity Net Primary Productivity, Gross Primary Productivity Trophic Levels 10% Rule Food Chains and Webs Ecosystems Limiting Factors Density-Independent vs. Density-Dependent Biotic and Abiotic Factors
Trophic Levels 10% Rule
Biotic vs Abiotic Factors
Math Skills for this Exam Be able to interpret standard error bars--what do they mean when they overlap? What do they mean when they don t overlap? Be able to calculate a mean Be able to calculate a rate of reaction Be able to calculate Gibbs Free Energy equations given the variables for the equation Understand the significance of the standard deviation for a data set Be able to calculate productivity