Introduction to Metabolism

Metabolism  Includes all of the chemical reactions in an organism.  Reactions are ordered in metabolic pathways (sequence of steps)  Each step is controlled by an enzyme that converts a specific molecule into a product.

Metabolism  Through metabolic pathways, the cell transforms and creates the organic molecules that provide energy for life.

Metabolism  Catabolic Pathways release energy stored in complex molecules through breaking down these molecules into simpler compounds. Proteins, Carbs & Lipids

Metabolism  Anabolic Pathways require energy to combine simpler molecules into more complicated ones. (Building up) Amino Acids Proteins

Metabolism  The energy released from catabolic pathways drives anabolic pathways in the cell. RESPIRATION BIOSYNTHESIS Glucose CO 2 + H 2 O Monomers Macromolecules CATABOLIC REACTIONSANABOLIC REACTIONS (Exergonic)(Endergonic) ATP

Forms of Energy  Energy is the ability to cause change.  Some forms of energy can do work such as moving matter against an opposing force.

Forms of Energy  Kinetic Energy is the energy of Motion.  Falling rocks, orbiting planets, air molecules.

Forms of Energy  Potential Energy is stored energy as a result of location or arrangement of matter.  A rock perched on ledge, standing on a diving board.

Forms of Energy  Chemical Energy is a form of potential energy stored in the arrangement of atoms in molecules.

Forms of Energy  Light Energy/ radiative energy carried by light.  Light can alter molecules in our eyes allowing us to see.  Light is the only energy we can see.

Forms of Energy  Energy can be converted from one form to another.  Plants convert light energy to chemical energy ( the potential energy of ATP).  When climbing up a hill kinetic energy of muscle movement becomes potential energy.

Thermodynamics  The laws of energy transformation.  1 st Law of Thermodynamics – the total amount of energy in the universe or any process remains constant. Energy can change form but can neither be created nor destroyed.

Thermodynamics  2 nd Law of Thermodynamics – in any process, the amount of energy available to do work decreases, such as when heat is released.  Heat is the random movement of molecules.  As a process occurs heat is the energy that can no longer do work.

Thermodynamics  An organism takes in large molecules to use for energy and releases Heat and smaller molecules like CO 2 and water into the environment.

Free Energy  Free Energy (G) is the energy available to do work  Each chemical has a certain amount of free energy.  Each chemical reaction involves a change in free energy. ∆G  ∆G = G products - G reactants

Free Energy  Exergonic reactions release energy and the free energy decreases. -∆G  Exergonic reactions occur spontaneously.  Downhill Reaction C 6 H 12 O 6 + 6O 2 6 CO H 2 O + ATP

Exergonic Reaction

Free Energy  Endergonic reactions absorb energy from the surroundings, and stores the free energy in molecules. +∆G  Endergonic reactions are not spontaneous and require ENERGY  Uphill Reaction

Endergonic Reaction

Exergonic vs. Endergonic

Free Energy  Free energy, energy available to do work depends on the concentration of molecules.  The greater the difference in concentration of molecules on either side of a barrier (Cell Membrane) the more work that can be done.

Concentration Gradient

Equilibrium  Eventually, in a closed system, reactions reach equilibrium and then can do no more work ∆G = 0.  A cell that has reached metabolic equilibrium is DEAD!  Metabolism as a whole is never at equilibrium.

Equilibrium  The constant flow of materials in and out of the cell is essential to LIFE.  As long as our cells have a steady supply of glucose, other fuels and oxygen and are able to get rid of waste, their metabolic pathways never reach equilibrium.

ATP  ATP (Adenosine triphosphate) powers cellular work by coupling exergonic reactions to endergonic reactions.  Exergonic reactions are used to power endergonic ones.  A cell uses ATP as immediate energy.

ATP  Structure of the ATP molecule

Hydrolysis of ATP  Can be hydrolyzed to ADP (Adenosine diphosphate) and an inorganic phosphate.  Releases 7.3 kcal of energy. ATP + H 2 O ADP + P i + ENERGY

Hydrolysis of ATP  In a cell, the free energy released from the hydrolysis of an ATP molecule is used to transfer the phosphate group to another molecule producing a phosphorylated molecule that is more reactive (less stable).  This phosphorylation forms the basis for almost all cellular work.

Hydrolysis of ATP  Phosphorylation of a Glucose molecule traps glucose inside of the cell.

Regeneration of ATP  A cell regenerates ATP constantly.  The formation of ATP from ADP and P i is endergonic (+∆G)  Cellular Respiration provides the energy for the regeneration of ATP.  Plants can also produce ATP using light energy.