Download Lecture 06 Notes

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Energy storage wikipedia, lookup

Low-Income Home Energy Assistance Program wikipedia, lookup

Regenerative brake wikipedia, lookup

Zero-energy building wikipedia, lookup

Public schemes for energy efficient refurbishment wikipedia, lookup

World energy consumption wikipedia, lookup

Low-carbon economy wikipedia, lookup

Energy Charter Treaty wikipedia, lookup

Alternative energy wikipedia, lookup

International Energy Agency wikipedia, lookup

Internal energy wikipedia, lookup

Energy returned on energy invested wikipedia, lookup

Energy policy of the United Kingdom wikipedia, lookup

Energy efficiency in transport wikipedia, lookup

Energy in the United Kingdom wikipedia, lookup

Negawatt power wikipedia, lookup

Conservation of energy wikipedia, lookup

Energy policy of the European Union wikipedia, lookup

Gibbs free energy wikipedia, lookup

Energy Independence and Security Act of 2007 wikipedia, lookup

Energy applications of nanotechnology wikipedia, lookup

Transcript
Lecture 6 Notes – Metabolism: Energy and Enzymes Questions • What forms of energy are used by a cell? • How is energy used to drive biological processes within cells? • What might happen if insufficient energy is available for cells to function? Intro – chapter focuses on how cells perform work: energy, enzymes, membranes 6.1 Energy and the Cell Energy = the capacity to perform work Two types: 1. Kinetic energy = energy of motion a. Heat is kinetic energy – random movement of particles b. Light is kinetic energy 2. Potential energy = stored capacity to perform work as a result of location or structure a. Chemical energy – energy stored in arrangement of atoms in molecules b. Cell converts potential energy to kinetic energy to perform work Thermodynamics = study of energy transformations that occur in a collection of matter, or system 1. First Law of Thermodynamics = total amount of energy in universe is constant, energy can be transferred or transformed but not created nor destroyed 2. Second Law of Thermodynamics = every energy change results in increased disorder, or entropy, unusable energy is lost to surroundings as heat 6. 2 Chemical reactions store or release energy 1. Reactants vs. products: A + B  C + D 2. Free Energy – ∆G – amount of energy left to do work after a chemical reaction has occurred. 3. Endergonic reactions – require an input of energy equal to the difference in potential energy of reactants and products • Example = photosynthesis – uses energy of sunlight to form organic compounds • ∆G > 0 (draw picture) 4. Exergonic reactions – result in an output of energy equal to the difference in the potential energy of the reactants and products • Example = burning and cellular respiration – chemical energy of reactants is released to form energy-­‐poor products • Cellular respiration: glucose is burned to produce ATP, heat, CO2 and water • ∆G < 0 and reaction is spontaneous (draw picture) 5. Cellular metabolism = sum of endergonic reactions and exergonic reactions in cells 6. Energy coupling = the use of energy released from exergonic reactions to drive endergonic reactions ATP = adenosine triphosphate • Powers all forms of cellular work • Glucose contains too much energy – like using a $100 bill to buy a soda in a vending machine • Adenine (nitrogenous base) + ribose (5 carbon sugar) + three phosphate groups (all negatively charged) • Mutual repulsion of phosphate groups contributes to potential energy stored in ATP (like a compressed spring) • Energy stored in bonds between phosphate groups – bonds broken by hydrolysis • ATP + H2O  ADP + P + energy (exergenic reaction) • ADP = Adenosine diphosphate •
•
•
•
•
•
Phosphorylation = transfer of a phosphate group from ATP to some other molecule Most cellular work depends on ATP energizing molecules by phosphorylating them ATP drive all three types of cell work: chemical, mechanical, transport o Chemical work: phosphorylation of reactant molecules drive endergonic synthesis of product molecules o Mechanical work: transfer of phosphate groups to special motor proteins (myosin) in muscle cells cause proteins to change shape and pull on actin filaments, causing cells to contract o Transport work: phosphorylation of membrane proteins – movement across membranes ATP is produced from ADP during cellular respiration – breaking down glucose in exergonic reactions – phosphate is bonded to ADP – ADP is phosphorylated – endergonic reactions (energy storing) ADP + P + energy  ATP + H2O (endergonic reaction) 10 million ATP molecules consumed and regenerated by a cell each second 6. 3 Enzyme functions Metabolic pathway – series of linked reactions – each step catalyzed by enzyme – small steps instead of large jump – maximizes cell efficiency Enzymes = large protein molecules that function as biological catalysts, a chemical that speeds up reactions without being consumed (end with –ase suffix) Ribozymes – special enzymes that use RNA instead of proteins – involved in synthesis of RNA and synthesis of proteins at ribosomes Energy of activation = amount of energy put into an exergonic reaction before reaction occurs (Mexican jumping bean analogy)  Enymes lower activation barrier Specific enzymes catalyze each cellular reaction Enzymes (types of proteins) have unique 3-­‐D shape – shape determines the chemical reaction it catalyzes Substrate = reactant in enzyme-­‐catalyzed reaction Substrate binds to active site on enzyme  this causes a slight change in shape of enzyme called an induced fit  this promotes chemical reaction  substrate changes into product and is released & enzyme is unchanged One enzyme may act on thousands or millions of substrate molecules per second. Factors that affect way enzymes work  Substrate concentration -­‐ increases enzyme activity as substrate concentration increases – until all enzyme active sites are full  Optimal pH – change in pH alters ionization of side chains (R groups) – H+ ions can interfere and denature (alter shape of) enzyme  Salt ions interfere with some of the chemical bonds that maintain protein structure  Temperature -­‐ affects molecular motion – high temps may denature proteins o Changing coat colors in animals  Cofactors = non-­‐protein helpers – may be inorganic, such as ions of zinc, iron, copper Coenzymes = organic cofactors -­‐ often vitamins or made from vitamins Enzyme inhibitors block enzyme action Irreversible -­‐ Inhibitors attach to enzyme be covalent bonds – irreversible – toxins and poisons Reversible -­‐ Inhibitors attach by weak bonds (hydrogen bonds) Competitive inhibitor – binds at active site Noncompetitive inhibitor – binds at some other site Feedback inhibition – type of inhibition whereby enzyme activity is blocked by a product of the reaction catalyzed by the enzyme – prevents too much product Poisons, pesticides, drugs = enzyme inhibitors Cyanide = inhibits production of ATP during respiration Nerve gas sarin = inhibits enzyme acetylcholinesterase – transmission of nerve impulses Pesticide malathion – inhibits enzyme acetylcholinesterase Antibiotic penicillin inhibits enzyme that builds bacterial cell walls Painkillers aspirin and ibuprofen inhibit enzyme to produce pain 6.4 Organelles and the Flow of Energy Photosynthesis – 6CO2 + 6 H20 + energy  C6H12O6 + 6 O2 • Chloroplasts • Hydrogen (H+ and e-­‐) are transferred from water to CO2 forming glucose • Redox reaction = oxidation (loss of electrons) + reduction (gain of electrons) • Requires high-­‐energy electron-­‐carrier molecule or coenzyme called NADP+ (nicotinamide adenine dinucleotide phosphate) • Reduction of NADP+: NADP+ + 2e-­‐ + H+  NADPH Cellular Respiration – C6H12O6 + 6O2  6CO2 + 6H2O + energy • Mitochondria • Glucose loses electrons (oxidized) and oxygen gains electrons (reduced) • Need a coenzyme, NAD+ (nicotinamide adenine dinucleotide) • Reduction of NAD+: NAD+ + 2e-­‐ + H+  NADH • And reduction of FAD, FAD + 2e-­‐ + 2H2  FADH2 Electron Transport Chain • Hindenburg disaster: 2H2 + O2  2H2O + BOOM! • Oxygen has super high electronegativity – as electrons fall toward oxygen energy is released (electrons at lower potential energy level when closer to nucleus) – in mitochondria • In chloroplasts the electrons fall toward a chlorophyll a complex with even higher electronegativity than oxygen • ETC: Series of membrane-­‐bound carriers that pass electrons from one carrier to another via redox reactions – more control of energy release than Hindenburg disaster • High energy electrons in and low energy electrons out • Energy is released as electrons lose energy and energy is capture to make ATP ATP Production • ATP synthesis • Peter Mitchell, 1978 theory of ATP production in mitochondria and chloroplasts • Chemiosmosis – in thylakoids of chloroplasts and in cristae of mitochondria o Electrochemical gradient across membrane powers ATP production o ATP Synthase – enzyme synthesizing complex that makes ATP from ADP + P • Draw it for photosynthesis and mitochondria