Energy Transformation, Cellular Energy & Enzymes (Outline)

Transcription

1 Energy Transformation, Cellular Energy & Enzymes (Outline) Energy conversions and recycling of matter in the ecosystem. Forms of energy: potential and kinetic energy The two laws of thermodynamic and definitions Chemical reactions and energy transformation Biochemical metabolic reactions and pathways Coupling energy consuming biochemical reactions with the energy releasing reaction of ATP dissociation Types of cellular work that require energy (ATP) Role of enzymes in catalyzing biochemical reactions Biochemical composition of enzymes and the physical and chemical factors that regulate their activity Competitive and non-competitive inhibitors of enzymes.

2 Figure ENERGY FLOW Sun Inflow of light energy Outflow of heat Producers (plants) Consumers (animals) Leaves take up CO 2 from air; roots absorb H 2 O and minerals from soil Chemical energy in food Decomposers such as worms, fungi, and bacteria return chemicals to soil

3 Figure ENERGY FLOW Sun Inflow of light energy Outflow of heat Producers (plants) Consumers (animals) Leaves take up CO 2 from air; roots absorb H 2 O and minerals from soil Chemical energy in food Decomposers such as worms, fungi, and bacteria return chemicals to soil

4 Energy is the capacity to do work Kinetic energy is the energy of motion Potential energy is stored energy that can be converted to kinetic energy Chemical bonds are a form of potential energy that can be transformed to energize cellular work

5 The field of study of energy transformations is Thermodynamics The First Law of Thermodynamics Energy can not be created or destroyed, it can be transformed from one form to another The Second Law of Thermodynamics Energy transformations increase disorder or entropy of the universe, and some energy is lost as heat. Energy transformation is not 100% efficient

6 Heat Glucose + Oxygen Chemical reactions ATP ATP Energy for cellular work Carbon dioxide + water Figure 5.2B

7 Chemical reactions either store or release energy Endergonic reactions absorb energy and form products rich in potential energy Products Potential energy of molecules Reactants Energy required Amount of energy required Figure 5.3A

8 Exergonic reactions release energy and yield products that contain less potential energy than their reactants Reactants Potential energy of molecules Energy released Products Amount of energy released Figure 5.3B

9 Cells carry out thousands of chemical reactions some exergonic and others endergonic Cellular metabolism is the sum of all chemical reactions that take place inside the cell Energy coupling uses exergonic reactions to fuel endergonic reactions

10 ATP powers cellular work by shuttling chemical energy The energy in an ATP molecule lies in the bonds between its phosphate groups Adenosine Triphosphate Adenosine diphosphate Phosphate groups H 2 O Adenine P P P Hydrolysis P P + P + Energy Ribose Figure 5.4A ATP ADP

11 ATP hydrolysis is the main exergonic reaction used in cellular energy coupling ATP hydrolysis transfers a phosphate group to a molecule (phosphorylation). A phosphorylated molecule has a higher potential energy making it possible for the reaction to take place.

12 ATP is a renewable resource that cells regenerate ATP Energy from exergonic reactions ADP + P Energy for endergonic reactions Figure 5.4C

13 Types of Cellular Work ATP Chemical work Mechanical work Transport work Membrane protein Solute P + Motor protein P Reactants P P P Product Molecule formed Protein moved Solute transported P Figure 5.4B ADP + P

14 ENZYMES Proteins that function as catalysts for biochemical reactions Have a conformation (3D shape) that determines their specific binding to reactants (substrates) Lower the energy barriers of chemical reactions

15 For a chemical reaction to begin reactants must absorb some energy, called the energy of activation E A barrier Enzyme Reactants Products 1 2 Figure 5.5A

16 A protein catalyst called an enzyme can decrease the energy of activation needed to begin a reaction Energy Reactants E A without enzyme E A with enzyme Net change in energy Products Figure 5.5B Progress of the reaction

17 Enzymes, as proteins, have unique threedimensional shapes that determine which chemical reactions occur in a cell Each enzyme catalyzes a specific cellular reaction

18 The catalytic cycle of an enzyme 1 Enzyme available with empty active site Active site Substrate (sucrose) Glucose Enzyme (sucrase) 2 Substrate binds to enzyme with induced fit Fructose 4 Products are released H 2 O 3 Substrate is converted to products Figure 5.6

19 The cellular environment affects enzyme activity Temperature, salt concentration, and ph Some enzymes require non-protein components Cofactors- metal ions Coenzymes- organic molecules (vitamin derivatives) Enzyme inhibitors interfere with an enzyme s activity

20 A competitive inhibitor takes the place of a substrate in the active site A noncompetitive inhibitor alters an enzyme s function by changing its shape Substrate Active site Enzyme Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Figure 5.8 Enzyme inhibition

21 Many poisons, pesticides, and drugs are enzyme inhibitors