Life and the Flow of Energy. Chapter 6. The Flow of Energy

Transcription

1 Life and the Flow of Energy Chapter 6 Metabolism: Energy and Enzymes Energy is the ability to do work Cells (and organisms) need a constant supply of Life on Earth is dependent on solar Solar The Flow of Energy Kinetic is the of motion Potential is stored When is converted, some will get lost as Kinetic is the of motion Potential is stored And can be converted to kinetic Chemical Mechanical

2 Two Laws of Thermodynamics sun CO 2 H 2 O 1. Energy cannot be created or destroyed, but it can be changed from one form to another Law of conservation of 2. Energy cannot be changed from one form to another without a loss of usable (Entropy increases when Energy is transformed) solar carbohydrate synthesis carbohydrate A leaf cell photosynthesizes Use solar to form carbohydrates Some is lost as Moose uses carbohydrates to power its muscles Some is lost as muscle contraction Entropy (Degree of Disorder) increases when Energy is transformed C 6 H 12 O 6 Glucose more organized more potential less stable (less entropy) CO 2 H 2 O Carbon dioxide and water less organized less potential more stable (more entropy) Energy Transformations and Metabolism Metabolism is the sum of all the chemical reactions that occur in a cell Catabolism breaking down molecules Anabolism building molecules

3 Energy Transformations and Metabolism A + B (reactants) C + D (s) Chemical reactions either store or release Endergonic reactions Absorb and yield s rich in potential Products Potential of molecules Reactants Energy required Amount of required Exergonic reactions Release and yield s that contain less potential than their reactants Metabolism is the sum of thousands of chemical reactions inside a cell powers nearly all forms of cellular work adenosine triphosphate P P P Potential of molecules Reactants Energy released Products Amount of released Energy from exergonic reactions (e.g., cellular respiration) ADP + P Energy for endergonic reactions (e.g., protein synthesis, nerve impulse conduction, muscle cont r action) P P + P a. adenosine diphosphate + phosphate

4 Energy Transformations and Metabolism Coupled Reactions The released by an exergonic reaction is used to drive an endergonic reaction ADP + P + a. breakdown is exergonic. ADP + P muscle contraction ADP + P c. Muscle contraction becomes exergonic and can occur when it is coupled to breakdown. b. Muscle contraction is endergonic and cannot occur without an input of. A + B coupling C + D Energy Transformations and Metabolism An is a protein catalyst It decreases the of activation needed to begin a reaction can be used for Chemical work Powers anabolism Transport work Supplies to pump substances across plasma membrane Mechanical work Supplies to make muscles contract, cilia and flagella beat, and so forth Free Energy of reactant not present present Progress of the Reaction of activation (E a ) of activation (E a ) of

5 Enzymes and Metabolic Pathways How Enzymes Function Enzyme binds substrate to form a complex A Metabolic Pathway is a series of linked Reactions (Also called substrates) E + S! ES! E + P substrate -substrate complex s substrate -substrate complex substrates -substrate complex active site active site Degradation The substrate is broken down to smaller s. Synthesis The substrates are combined to produce a larger.

6 The Enzyme changes shape upon binding to the Substrate (Induced fit). Enzymes are very specific. What affects Enzyme Activity? Temperature, salt concentration, and ph Some s require non-protein cofactors or organic molecules called cos Enzyme inhibitors block action active site substrate a. b. Enzyme activity increases as temperature rises Higher temperatures cause more effective collisions between s and substrates Enzyme may denature at high temperatures Each has an optimal ph Enzyme structure is ph dependent Extremes of ph can denature an by altering its structure Rate of Reaction ( per unit of time) Rate of Reaction ( per unit of time) pepsin trypsin Temperature C a. Rate of reaction as a function of temperature. b. Body temperature of ectothermic animals often limits rates of reactions. c. Body temperature of endothermic animals promotes rates of reactions ph

7 Enzymes and Metabolic Pathways Enzyme Inhibition Occurs when cannot bind its substrate Activity of almost every cell is regulated by feedback inhibition Enzyme Inhibition When is abundant it binds to the s active site and blocks further ion first reactant A A a. Active pathway altered site of due to binding of F E 1 site of where end F can bind E 2 E 3 E 4 E 5 B C D E E 1 end F end F first reactant A b. Inactive pathway E 1 end F Reactant A cannot bind, and no results. Enzymes and Metabolic Pathways Enzyme Cofactors Molecules which help function Inorganic cofactors are minerals Examples are copper and zinc Organic non-protein cofactors are called cos Vitamins are often components of cos A competitive inhibitor Takes the place of a substrate in the active site A noncompetitive inhibitor Alters an s function by changing its shape Competitive inhibitor Substrate Enzyme Normal binding of substrate Noncompetitive inhibitor Active site Enzyme inhibition

8 6.4 Oxidation-Reduction and Metabolism Photosynthesis Cellular respiration sun carbohydrate O 2 chloroplast CO 2 + HO 2 mitochondrion for synthetic reactions, active transport, muscle contraction, nerve impulse O 2 CO 2 Breathing Eating O 2 CO 2 Nutrients Cellular respiration Getty Images/SW Productions RF Human beings are involved in the cycling of molecules between chloroplasts and mitochondria Our food is derived from plants or we eat animals that have eaten plants Food nutrients and oxygen enter our mitochondria to produce Oxidation-Reduction and Metabolism Your diet is not all glucose Our food consists of carbohydrates, fats, and proteins Broken down into simpler molecules in digestion Can enter cellular respiration at various steps in the pathway to make Excess glucose can be used to form fatty acids Fatty acids and glycerol form lipids or fat