Chapter 1.2 Enzymes and Metabolism PDF

ENZYMES & METABOLISM WEEK 2  Overview: The Energy of Life The living cell is a miniature chemical factory where thousands of reactions occur The cell extracts energy and applies energy to perform work Some organisms even convert energy to light, as in bioluminescence Biolum...

ENZYMES & METABOLISM WEEK 2  Overview: The Energy of Life The living cell is a miniature chemical factory where thousands of reactions occur The cell extracts energy and applies energy to perform work Some organisms even convert energy to light, as in bioluminescence Bioluminescence Firefly squid Mycena mushroom Metabolism and Thermodynamics Metabolism: totality of an organism’s chemical reactions An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics Emergent property of life that arises from interactions between molecules within the cell  Metabolic pathway Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting Product molecule  Catabolic pathways Anabolic pathways release energy by consume energy to breaking down complex build complex molecules into simpler molecules from compounds simpler ones E.g. Cellular respiration, the breakdown of E.g. The synthesis of glucose in the presence protein from amino of oxygen acids  Energy Energy is the capacity to cause change Energy exists in various forms, some of which can perform work Energy can be converted from one form to another  Forms of energy Potential energy is energy that matter possesses because of its location or structure Kinetic energy is energy associated with motion Thermal energy (heat) is kinetic energy associated with random movement of atoms or molecules Chemical energy is potential energy available for release in a chemical reaction A diver has more potential Diving converts energy on the platform potential energy to than in the water. kinetic energy. Climbing up converts the kinetic A diver has less potential energy of muscle movement energy in the water to potential energy. than on the platform. Chemical energy Thermal energy  LAWS OF THERMODYNAMICS Thermodynamics: the study of energy transformation 2 laws that govern energy transformation: – First law of thermodynamics – Second law of thermodynamics  1st Law of Thermodynamics Energy can be transferred and transformed but it cannot be created or destroyed Principle of conservation of energy  1st Law of Thermodynamics Chemical energy (a) First law of thermodynamics: Energy can be transferred or transformed but neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement  2nd Law of Thermodynamics Every energy transfer increase the entropy of the universe During every energy transfer or transformation, some energy is unusable, and is often lost as heat The more energy that is lost by a system to its surroundings, the less ordered and more random the system is; the measure of this randomness and disorder is known as entropy Spontaneous process that do not require energy input are energetically favorable and increase the entropy, or disorder, of the universe  2nd Law of Thermodynamics Heat co2 + H2O Second Figure 8.3 law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by- products of metabolism.  Entropy Entropy: a measure of randomness or disorder in a system High entropy: high disorder and low energy Order in the surrounding ↓ (entropy ↑) Order in a system ↑ (entropy ↓) CO2 ↑ O2 Figure 6.4  Measure of entropy: Gibb’s Free Energy Gibb’s free energy equation: G = free energy H = enthalpy / heat content T = absolute ΔG = ΔH – TΔS temperature (in Kelvin) S = entropy/disorder Only processes with a negative ∆G are spontaneous Spontaneous processes can be harnessed to perform work  Free-Energy Change, G A living system’s free energy – Is energy that can do work under cellular conditions The change in free energy, ∆G during a biological process – Is related directly to the enthalpy (heat content) change (∆H) and the change in entropy – Spontaneous process lowers the system’s ∆G (-ve ∆G) Free Energy, Stability, and Equilibrium Organisms live at the expense of free energy During a spontaneous process – Free energy decreases and the stability of a system increases At maximum stability – The system is at equilibrium A process is spontaneous and can perform work only when it is moving toward equilibrium  More free energy (higher G) Less stable Greater work capacity In a spontaneously change The free energy of the system decreases (∆G