Metabolism

Metabolism = anabolism + catabolism In a reaction, bonds between reactants break down and bonds between products form. Energy is absorbed when reactant bonds break (endothermic). Energy is released when product bonds form (exothermic). Drew's Metabolism Animation - Science is a Verb!

Catabolic Reactions Breakdown of complex substances. Examples: Break starch into glucose molecules Break glucose into carbon dioxide and water

Anabolic Reactions Build complex substances from smaller subunits. Examples: Protein is built from joining amino acids.

Metabolism = Anabolic + Catabolic reactions It is essential for living organisms to survive and it requires ENERGY Annie's 20 Animations - Science is a Verb!

Energy The ability to do work. Kinetic – energy in motion Potential – stored energy When energy is transferred from one place to another that is called WORK Energy Transformation on a Roller Coaster

1 st Law of Thermodynamics Energy is constant. It cannot be created or destroyed, only converted from one form to another. If an object gains energy, it does so at the expense or a loss in energy somewhere else in the universe.

Bond Energy: Measure of the stability of a covalent bond. (kJ) Equal to the min energy required to break one mole of bonds between two types of atoms. Equal to the amount of energy released when a bond is formed.

Potential Energy Diagrams Shows the change in potential energy during a chemical reaction.

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Metabolism Activation Energy The amount of energy needed to break the reactant’s bonds. Exothermic ΔH = - Endothermic ΔH = + The change in energy that occurs is called heat or enthalpy (ΔH)

Activation Energy: Energy needed to break bonds and is equal to the difference between the potential energy level of the transition state and the potential energy of the reactants. Transition State: Bonds within reactants are breaking (require energy) and the bonds between products are forming (release energy). The Cell Online: Chapter 3 - Animations

Exothermic reactions tend to occur spontaneously since products are MORE stable then reactants. Why would endothermic reactions occur if the products are LESS stable than the reactants? ENTROPY also needs to be considered. Spontaneous Reactions

Entropy A measure of the randomness of disorder in a collection of objects or energy; notated as S. The universe favors an increase in entropy. Examples: Deck of cards falling and scattering Dropping a glass and shattering it Diffusion

Exothermic Rxns (favoured) Endothermic Rxns (Not favoured) Increase in Entropy (favoured) Spontaneous at all temperatures  Not spontaneous at low temp.  Spontaneous at high temp. Decrease in Entropy (not favoured)  Not spontaneous at high temp.  Spontaneous at low temp.  Not spontaneous at all temperatures.  Proceeds only with a net input of energy. Spontaneous vs Non-spontaneous

Free Energy Energy that is available to do work. Also known as Gibbs free energy. ΔG = G(final) – G(initial) Exergonic Reactions – Spontaneous and involves a decrease in Gibbs free energy, ΔG is negative Endergonic Reactions – Not Spontaneous and involves an increase in Gibbs free energy ΔG is positive

The Laws of Thermodynamics First Law The total amount of energy in the universe is constant. Energy cannot be created or destroyed, but only converted from one form into another. Second Law Every energy transfer or transformation increases the entropy of the universe. * Entropy is a measure of the randomness or disorder in energy or in a collection of objects. Random, useless energy that cannot do work, e.g., heat.

2 nd Law of Thermodynamics Also known as the law of entropy. The entropy of the universe increases with any change that occurs ΔS(universe) > 0

Metabolic Reactions are Reversible When a reversible reaction reaches equilibrium ΔG value is zero and its free energy is zero. A cell whose reversible reactions have reached equilibrium is a dead cell.

ATP – Adenosine Triphosphate Primary source of free energy in living cells ATPase catalyzes the hydrolysis of the terminal phosphate Releases 31kJ/mol of energy Terminal phosphate is instable due to negative charges. Energy produced is use to attach phosphate group to another molecule (phosphorylation)

Adenosine Triphosphate (ATP) ATP is a nucleotide consisting of adenine, ribose and 3 phosphate groups.

Adenosine Triphosphate (ATP) ATP drives all cellular reactions by providing the energy that is needed.

Redox Reactions Chemical reactions involving the transfer of one or more electrons from one atom to another. Reducing Agent: The substance that loses an electron. Oxidizing Agent: The substance that gains an electron.

Redox Reactions Coenzymes are important in the creation of ATP. Working with special enzymes, coenzymes accept electrons and transfer them to other molecules. As oxidizing enzymes remove electrons from a substrate (oxidation) they pass them onto a coenzyme (reduction). Therefore the substrate loses electrons (oxidized) and the coenzyme gains electrons (reduced). When the reduced coenzyme passes the electron to another substrate, the coenzyme loses electrons (oxidized) and the substrate gains electrons (reduced). Coenzymes can carry electrons from one redox reaction to another.