Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in the Life of a Cell What is Energy? Answer: The capacity to do work Types of Energy: 1) Potential Energy = Stored energy • Positional (stored in location of object) • Chemical (stored in bonds) • Electrical (stored in batteries) Potential energy can be converted to kinetic energy (& vice versa) 2) Kinetic Energy = Energy by movement • Light (movement of photons) • Heat (movement of particles) • Electricity (movement of charged particles) Figure 6.3 / 6.4 – Audesirk2 & Byers Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Laws of Thermodynamics: Describe the “quantity” (total amount) and “quality” Chemical Reaction: Process that forms or breaks the chemical bonds holding (usefulness) of energy atoms together 1st Law of Thermodynamics: (Law of Conservation of Energy) • Amount of energy in universe remains constant + + • Energy is neither created or destroyed Reactants Products • Energy can be converted (e.g., Chemical Heat) Types of Chemical Reactions: 2nd Law of Thermodynamics: • When energy converted, the amount of “useful” energy is decreased Exergonic: Endergonic: • No process is 100% efficient Reaction liberates energy Reaction requires energy to proceed Figure 6.2 – Audesirk2 & Byers Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells All chemical reactions require activation energy to begin: Cellular Respiration: (Exergonic) Energy required to “jumpstart” a chemical reaction • Must overcome repulsion of atoms due to negative charged electrons Energy in reactants > Energy in products Activation Activation Energy Repel Energy Photosynthesis: (Endergonic) Nucleus Nucleus Energy in reactants < Energy in products Figure 6.5 / 6.7 – Audesirk2 & Byers 1 Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Exergonic Reactions: Endergonic Reactions: (“Downhill Reactions”) (“Uphill Reactions”) Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Coupled Reaction: An exergonic reaction supplies the energy needed to Types of Energy-Carrier Molecules: drive an endergonic reaction 1) Adenosine Triphosphate (ATP) • Most common energy-carrier molecule How is Cellular Energy Carried Between Reactions? • Synthesized from adenosine diphosphate (ADP) Answer: Energy-Carrier Molecules Coupled ATP Reactions: Characteristics of Energy-Carrier Molecules: • Rechargeable Pick up energy Transport energy Drop off energy (Exogonic reaction) (Entergonic reaction) • Unstable (Short-term energy storage) • Function within a single cell Figure 6.8 / 6.9 / 6.10 / 6.11 – Audesirk2 & Byers Figure 6.13 – Audesirk2 & Byers Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Types of Energy-Carrier Molecules: Metabolism: Sum of all chemical reactions in a cell 2) Electron carriers (e.g., Nicotinamide Adenine Dinucleotide – NADH)) Reactions are linked in Metabolic Pathways • Donate high-energy electrons to other molecules Coupled Electron Carrier Reactions: Photosynthesis (Chloroplast) Cellular Respiration (Mitochondria) How do Cells Regulate Metabolic Reactions? 1) Couple exogonic / endergonic reactions together 2) Synthesize energy-carrier molecules 3) Regulate enzyme production / activity Figure 6.12 – Audesirk2 & Byers 2 Figure 6.14 – Audesirk2 & Byers Figure 6.15 – Audesirk2 & Byers Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells What are Enzymes? Enzymes = Biological Catalysts Answer: Molecules (proteins) that catalyze chemical reactions Unique Properties of Enzymes (compared to other catalysts): 1) Enzymes are specific (High Specificity) What are Catalysts? • Catalyze only one, or a few, chemical reactions • Structure dictates specificity Answer: Molecules that speed up chemical reactions Lower activation energy Active Site: Important Features: Location where substrate(s) can bind • Catalysts only speed up reactions that would occur spontaneously • Catalysts are not destroyed or altered in the reaction Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Enzymes = Biological Catalysts Enzymes = Biological Catalysts Unique Properties of Enzymes (compared to other catalysts): Unique Properties of Enzymes (compared to other catalysts): 2) Enzymes activity is regulated 2) Enzymes activity is regulated A) Regulate synthesis of enzyme A) Regulate synthesis of enzyme B) Regulate active state of enzyme (inactive vs. active form) B) Regulate active state of enzyme (inactive vs. active form) C) Feedback Inhibition: Regulate enzyme activity by [product] C) Feedback Inhibition: Regulate enzyme activity by [product] D) Allosteric Regulation: Regulate active site shape via small molecules Figure 6.17 – Audesirk2 & Byers Figure 6.16 – Audesirk2 & Byers Chapter 6: Energy Flow in Cells Chapter 6: Energy Flow in Cells Enzymes = Biological Catalysts Enzyme Activity can be Influenced by the Environment: A) 3 - Dimensional structure of enzymes due to hydrogen bonding Unique Properties of Enzymes (compared to other catalysts): • Factors affecting hydrogen bonding 2) Enzymes activity is regulated • pH (optimal = 6 – 8) A) Regulate synthesis of enzyme • Salt concentration B) Regulate active state of enzyme (inactive vs. active form) • Temperature C) Feedback Inhibition: Regulate enzyme activity by [product] B) Some enzymes require helper molecules D) Allosteric Regulation: Regulate active site shape via small molecules • Co-enzymes (bind with enzyme; assist in reaction) E) Competitive Inhibition: Regulate active site via molecular competition Example: B - vitamins (e.g., Vitamin B12) necessary for DNA synthesis Figure 6.18 – Audesirk2 & Byers Figure 6.19 – Audesirk2 & Byers 3.