Energy and Metabolism Chapter 8

Energy

Energy

Energy

Metabolism All chemical reactions carried out by the cell

Metabolism Catabolic reactions: Break down large molecules into smaller substances Releases energy or is exergonic

Metabolism Anabolic reactions: Synthesis of large molecules from smaller substances Requires energy or is endergonic

Metabolism Biochemical pathways: Reactions in a cell that occur in sequence Product of one reaction becomes substrate in next reaction Pathways are highly regulated & coordinated Feedback inhibition: End product of a reaction inhibits the pathway from producing more.

Energy

Energy Bioenergetics: Analysis of how energy powers activities of living systems Growth, order, reproduction, responsiveness & regulation Require energy to happen

Energy Energy: Capacity to do work Kinetic energy Energy of motion Potential energy Energy of position or stored energy

Energy Kinetic energy: Potential energy:

Energy Most of the work done by living organisms is the transformation of potential energy to kinetic energy Thermodynamics:  Study of energy “heat changes”

Energy Sun main source of energy Energy from sun is used to combine smaller molecules to make larger molecules Energy is then stored in the chemical bond

Energy Redox(oxidation-reduction) reactions: Transfer of an electron or electrons Play a key role in flow of energy in biological systems An electron is passed from one atom to another energy is passed

Law of thermodynamics Laws of thermodynamics govern all energy changes in the universe.  First law of thermodynamics: Energy cannot be created or destroyed It can change from one form to another. (potential to kinetic) Total amount of energy stays the same

First law In living organisms: Eating transfers energy from bonds in food to organism Potential energy is transferred to kinetic energy

First Law Heat: random motion of molecules Heat can be lost during conversions Sun replaces energy that is lost as heat

Second law Second law of thermodynamics: Transformation of PE to heat (random motion of molecules). Entropy (disorder) in universe is increasing

Second law Energy transformations tend to proceed spontaneously Convert matter from a more ordered state to a less ordered More stable state.

Second law Entropy(s): Disorder in a system Enthalpy (H): heat content Free energy(G): Amount of energy available to do work in any system. Amount of energy available to break & then make other chemical bonds

Second law G=Gibbs free energy G = H - TS (T=Kelvin temp) G is positive than products have more energy than reactants Due to more energy in bonds or less randomness Endergonic reaction

Endergonic reaction

Second law G is negative products have less energy than reactants H is lower (bond energy) or S is greater- more randomness Exergonic: any reaction that releases energy

Exergonic reaction

Exergonic reactions

Energy

ATP ATP powers energy requiring processes in cell 1. Chemical work (making polymers) 2. Transporting substances across the membranes 3. Mechanical work Muscle movement, cilia

ATP Structure of ATP Ribose sugar Adenine 3 phosphate attached in a row

ATP

ATP

ATP ATP ADP Losses a inorganic phosphate Hydrolysis 7.3kcal/mole of energy is released.

Activation Energy Energy needed to initiate a reaction Exergonic & endergonic reactions both require activation energy. Reactions with higher AE tend to move forward more slowly

Enzymes Catalyst in living organisms Large three-dimensional globular protein

Enzymes Substrate: Molecule that is going to undergo the reaction Active sites: Specific spots on enzyme that substrates bind to. Enzyme-substrate complex: enzymes are bound to substrates with a precise fit. Induced fit: when the substrate causes the enzyme to adjust to make a better fit E+S ES E + P

Enzymes Only small amounts are necessary Can be recycled Specific Speeds up reactions Different types of cells have different enzymes Determine course of chemical reactions in the cell

Enzyme examples Lipase, protease Carbonic anhydrase CO2 + H2O H2CO3 Lactate dehydrogenase Lactate to pyruvate Pyruvate dehydrogenase Enzyme that starts the Kreb cycle

Enzymes Most enzymes are proteins RNA has been shown to catalyze some reactions Ribozymes: RNA catalysts are specific & speed up reactions

Enzymes Factors that affect rate of enzyme-catalyzed reactions 1. Concentration of the enzyme & substrate 2. Factors that affect the 3-D shape of the enzyme Temperature, pH, salt concentration & regulatory molecules

Enzymes Inhibitor: Binds enzyme & prevents it from working Occurs at end of a pathway to stop reactions Two types of inhibitors Competitive Noncompetitive

Enzymes Allosteric site: On/off switch for enzyme Allosteric site usually at a different location than active site Allosteric inhibitor: Binds at allosteric site & stops enzyme activity Activitors: Bind & increases activity

Enzymes Cofactor: Assists enzyme function (Zn, Mg, Cu) Coenzymes: Cofactors that are not proteins but are organic molecules Help transfer electrons & energy associated with electrons Vitamins are coenzymes NAD+ is an important coenzyme