3.1 Metabolism and Energy

Transcription

1 3.1 Metabolism and Energy

2 Metabolism All of the chemical reactions in a cell To transform matter and energy Step-by-step sequences metabolic pathways

3 Metabolic Pathways Anabolic reactions Build large molecules Catabolic reactions Break large molecules into smaller products

4 Energy All organisms continuously capture, store and use energy Cellular respiration releases energy from carbohydrates and other energy-rich molecules Functions: Survive Grow Reproduce Carry out daily activities Hummingbird heart rate: Over 1000 beats per min

5 Energy Capacity to do work 1. Kinetic energy: Energy of motion 2. Potential energy: Stored energy Can transform from one form to another

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7 Bond Energy Measure the stability of a covalent bond Forming bonds energy is released Breaking bonds energy is used Energy needed to break a bond is the same amount as the energy released when the bond was formed

8 Free atoms have more chemical (potential) energy than any compound Energy used Energy released Net Energy released

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10 Example: Cellular Respiration

11 Enthalpy Change ( H) change in the total energy of a system difference in the energy needed to break the bonds and the energy released when new bonds are form

12 Potential Energy Diagram Endothermic Reaction H is positive Energy is absorbed Exothermic Reaction H is negative Energy is released

13 Thermodynamics Study of energy changes in a system A system: Can be a whole organism or a set of reactants and products Biological systems are open systems (can exchange matter and energy with the surroundings)

14 First Law of Thermodynamics Total amount of energy in the university is constant Energy cannot be created or destroyed Energy can be transformed from one types into another and transferred from one object to another

15 Example: Cellular Respiration Transition State H is negative Energy is released Reactants Products Photosynthesis Reversed reaction Energy is absorbed

16 Entropy A measure of disorder Continuously increases as energy available to do work is progressively transformed into unusable heat (ie. energy available is decreasing) In chemical reactions, entropy increases when: 1. Solid reactants become liquids 2. Liquid reactants become gaseous 3. Complex molecules react to form simpler molecules 4. Solutes move with their concentration gradients

17 Second Law of Thermodynamics During any process, the universe tends towards disorder Only applies to closed system Living organisms remain organized because they use inputs of matter and energy to reduce entropy and thus stay alive

18 Gibb s Free Energy (G) Energy available to do work in any system (to break bonds and then form bonds) G = H TS In biological reactions, constant temperature, pressure and volume: ΔG = ΔH TΔS (used to predict whether a chemical reaction is spontaneous or not) G: Free energy H: enthalpy T: temperature S: entropy

19 Exergonic Reaction Endogonic Reaction H<0 and S>0 G<0 spontaneous reaction * Free energy is released in the form of heat H>0 and S<0 G>0 not spontaneous reaction * Energy must be supplied

20 Activation Energy Most spontaneous reactions still require an initial input of energy Biological catalyst (enzyme) reduces the amount of activation energy Activation energy

21 Thermodynamics and Metabolism When a molecule is broken down (catabolic reaction): Energy is released ( H <0) Entropy increases ( S >0) Exergonic (spontaneous) reaction When a molecule is built (anabolic reaction): Endergonic (non-spontaneous) reaction Coupled with catabolic reactions to get power Through the energy molecule: ATP (adenosine triphosphate)

22 Thermodynamics and Metabolism Catabolic reactions release energy Energy captured in ATP ATP used to power anabolic and endergonic reactions Bonds between the negative phosphate groups contain a large amount of energy Hydrolysis breaks these bonds and releases the stored energy to do work in the cell

23 Energy Dynamics of ATP The hydrolysis of ATP to ADP and P i is a highly exergonic reaction. Repulsion between negative charges on the neighbouring phosphate groups makes the bonds between the first and second and between the second and third phosphate groups unstable. When these bonds are broken, energy is released. inorganic

24 Coupled Reactions Use of ATP as a cycle Most cells only have a few seconds supply of ATP at any given moment Continuously produced