Metabolism An Introduction

Energy Every reaction that occurs in a living organism requires the use of Energy ◦ Energy = ability to do work Metabolism: capture and use of energy through catabolic and anabolic reactions ◦ Catabolic reaction = breaking apart molecules into simpler compounds  Eg. Protein  amino acids ◦ Anabolic reaction = building complex molecules out of smaller compounds  Eg. Glucose + glucose  maltose

Energy cont’d Cells need a constant supply of energy in order to live The nature of energy is important when considering metabolism In metabolism, ATP molecules are the cell’s source of energy ATP = energy currency

What does Energy look like? Energy used to do work takes on many forms ◦ Electrical, kinetic, thermal, light, sound The types of energy fall into 2 categories: 1.Kinetic energy- energy in MOVING objects  thermal (heat), mechanical, electrical 2.Potential energy- STORED energy  gravitational, chemical Ex. Roller coaster car Top: potential energy As drops: kinetic energy

Laws of thermodynamics (I) 1 st law: ◦ Total energy in a system always remains constant ◦ Energy is converted from on form to another Metabolism- in the context of biochemical reactions in living cells, energy is constantly changing form and thermal energy is generally lost from the organism

An interactive example r/ /animations/catalysis_energ y/catalysis_energy.htm r/ /animations/catalysis_energ y/catalysis_energy.htm

Free energy diagram #1 Energy changes are what drive all chemical reactions Free energy ( G) is the potential energy in a chemical reaction  energy available to do work #1- the reactants have a higher level of free energy than the products Glucose Carbon dioxide + water

Free energy diagram #2- a temporary state where both reactant bonds are breaking and product bonds are forming *intermediary step The activation energy (E act ) is the jumpstart needed for reactions to proceed  Needed to strain/break bonds #2 Ex. Racket ball turning inside out Glucose Carbon dioxide + water

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Free energy diagram #3- Decline in overall free energy as the free energy decreases in the reactants as they become products. #3 Glucose Carbon dioxide + water

Free energy diagram #4- Products have formed, the reaction is complete, the overall free energy has decline #4 G is negative Glucose Carbon dioxide + water An exothermic reaction

In a living organism/cell, G < 0 in a reaction is harnessed to do useful work, leaving less free energy available & more entropy What is entropy?

What are some words you would use to describe the change in this room?

Laws of thermodynamics (II) 2 nd law: ◦ The universe is constantly increasing in disorder  As energy changes forms, it becomes more disordered ◦ Entropy is a measure of disorder  Increased entropy = increase in disorder When thinking of chemical reactions, we must consider both energy AND entropy ◦ Text pg 61

Spontaneous vs Non-Spontaneous Reactions ◦ Chemical reactions occur spontaneously when both energy & entropy are favoured ◦ Chemical reactions may not occur spontaneously if energy is favoured but entropy is not ◦ In summary- cells favour spontaneous reactions

Less entropy More free energy More entropy Less free energy ATP ↔ ADP + Pi

Homework Pg 68 #1, 2, 3, 5, 6

Resources 32_ATP_and_ADP_cycle.jpg