Activity: Identifying forms of energy

Activity: Identifying forms of energy

INTRODUCTION TO METABOLISM

Metabolism Metabolism is the sum of all chemical reactions in an organism Metabolic pathway begins with a specific molecule and ends with a product Each step is catalyzed by a specific enzyme

Metabolic Pathways Metabolic pathway divide into two categories: Catabolic pathway: release energy by breaking down complex molecules into simpler compounds n Ex. cellular respiration breakdown glucose to release energy Anabolism pathway: consume energy to build complex molecules from simpler ones n Ex. Synthesis of protein from amino acids

THERMOCHEMISTRY Energy

Types of Energy Energy: ability to do work Kinetic energy: energy of motion Examples: objects in motion, photons Potential energy: energy that matter possesses because of its location or structure Chemical energy is a form of potential energy because energy is stored up in the bonds of a molecule

Energy The greater the bond energy, the more chemically stable the bond. Bond stability is not related to chemical reactivity.

Thermodynamics Thermodynamics: study of energy transformations System: the matter under study Surroundings: everything outside the system Open system: energy and matter can be transferred between the system and surroundings Example: Organisms absorb energy in organic molecules and release heat and metabolic waste products Closed system: isolated from its surroundings (only exchange of energy)

First Law of Thermodynamics The total amount of energy in the universe is constant. Energy can be transferred and transformed, but it cannot be created or destroyed. Example: Plants transform light to chemical energy; they do not produce energy.

Energy Transformation Energy can be converted from one form to another Example: Climbing a slide Converting kinetic energy of muscle movement to potential energy Example: Sliding down Converting potential energy back to kinetic energy

Energy Transformation Where did the initial kinetic energy for climbing come from? Potential energy in food eaten earlier that was stored in the body Cellular respiration unleashes the potential energy in the foods that we consume

Energy Transformation Where did the chemical energy in food come from? from light energy by plants during photosynthesis

Energy Transformation Sunlight provides a daily source of free energy for the photosynthetic organisms in the environment. Nonphotosynthetic organisms depend on a transfer of free energy from photosynthetic organisms in the form of organic molecules.

Energy Transformation The quantity of energy is constant, but the quality is not. Organisms take in organized energy like light or organic molecules and replace them with less ordered forms, especially heat.

Second Law of Thermodynamics Energy transformation make the universe more disordered. C 6 H 12 O 6 + O 2 à CO 2 + H 2 O + energy n During Cellular respiration, cells convert about 40% of the PE from glucose into energy able to do work, remainder is lost as heat à increase the entropy of universe. Entropy: a measure of disorder, or randomness Order can increase locally in a particular system but the universe as a whole will trend towards randomization.

Heat Energy of random molecular motion; energy in its most random state Much of the increased entropy of the universe takes the form of increasing heat Living cells unavoidably convert organized forms of energy to heat. The metabolic breakdown of food ultimately released as heat even if some of it is diverted temporarily to perform work for the organism.

Gibbs Free Energy The energy that is able to perform work ΔG = G final G initial ΔG = G products G reactants

Gibbs Free Energy Exergonic Endergonic Energy Released Absorbed ΔG Negative Positive Reaction Spontaneous Nonspontaneous

Cellular Energy Energy transfer in a cell depends on bond energy. Energy is required to break bonds. Energy is released when forming bonds. Many reactions release heat, which dissipates.

Cellular Energy Cellular respiration: C 6 H 12 O 6 + 6O 2 à 6CO 2 + 6H 2 O + E Photosynthesis: E + 6CO 2 + 6H 2 Oà C 6 H 12 O 6 + 6O 2 require an equivalent investment of energy powered by the absorption of light energy

Equilibrium Equilibrium reactions convert back and forth with minimal energy. Equilibrium reactions: ΔG = 0

Equilibrium A system at equilibrium is at maximum stability. Example: In a chemical reaction, the rate of forward and backward reactions are equal. There is no change in the concentration of products or reactants. Reactions in closed systems eventually reach equilibrium and can do no work.

Equilibrium Cells are open systems which maintains disequilibrium A cell that has reached metabolic equilibrium has a ΔG = 0 and is dead! Metabolic disequilibrium is one of the defining features of life

Types of Cellular Work Transport work pumping substances across membranes against the direction of spontaneous movement Mechanical work contraction of muscle cells movement of chromosomes Chemical work driving endergonic reactions such as the synthesis of polymers from monomers

ATP Energy Currency of the Cell

Adenosine Triphosphate (ATP) In most cases, the immediate source of energy that powers cellular work is ATP Consist of 3 parts: 1. Base: Adenine 2. 5-C sugar: Ribose 3. 3 phosphate groups

ATP Hydrolysis Hydrolysis releases the end phosphate group: ATP à ADP + Pi ΔG is -30.5 kj/mol

Phosphate Bonds Referred to as high-energy phosphate bonds but are actually fairly weak covalent bonds Each of the three phosphate groups has a negative charge These repulsion contributes to the instability of this region of the ATP molecule. Their hydrolysis yields energy as the products are more stable Release energy when break Phosphate Bonds, Exergonic

Energy Coupling Energy from the hydrolysis of ATP is coupled to endergonic processes by transferring the phosphate group to another molecule. The phosphorylated molecule is now more reactive. This drives reaction to occur spontaneously

Energy Coupling and Work

Energy Coupling ATP hydrolysis does not occur on its own. Process is carried out with enzymes that can transfer the phosphate Pi group is recycled

Regeneration of ATP ATP is continually regenerated by adding a phosphate group to ADP (Reverse of ATP hydrolysis) In a working muscle cell the entire pool of ATP is recycled once each minute Over 10 million ATP consumed and regenerated per second per cell

Regeneration of ATP Regeneration is an endergonic process: investment of energy: ΔG = +30.5 kj/mol Energy for renewal comes from catabolic reactions in the cell

Cellular Respiration General Equation: Organic compounds + oxygen carbon dioxide + water + Energy Most often described as the oxidation of glucose: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6H 2 O + Energy (ATP + heat) Exergonic ΔG= 2870 kj per mol products store less energy than reactants reaction can happen spontaneously (without an input of energy)

http://www.mhhe.com/biosci/bio_animations/ MH01_CellularRespiration_Web/index.html http://www.youtube.com/watch?v=j7gptasv0sq