An Introduction to Metabolism
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Transcript of An Introduction to Metabolism
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An Introduction to Metabolism
Metabolism, energy and lifeEnzymesThe control of metabolism
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Metabolism
Metabolism- totality of an organism’s chemical reactions
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Metabolism
Catabolic pathways- release energy by breaking down complex molecules to simpler compounds
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Metabolism
Anabolic pathways- consume energy to build complex molecules from simpler compounds
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Energy
Energy- capacity to do work Kinetic energy- the energy of motion Potential energy- the capacity to do work,
energy stored as a result of its location or structure
Chemical energy- form of potential energy- stored in molecules as a result of the arrangement of the atoms
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Metabolism, energy, and life
Metabolism = anabolism + catabolism
Metabolic reactions are organized into pathways
Energy: kinetic and potential
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Thermodynamics
Thermodynamics- study of energy transformations
The First Law- the energy of the universe is constant
Energy can be transferred and transformed but it cannot be created or destroyed
“principle of conservation of energy”
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Thermodynamics
The Second Law- Every energy transfer or transformation increases the entropy of the universe
Entropy- the measure of disorder
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Free Energy- the portion of a system that can perform work It is available for work Symbol is G
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Exergonic reaction- “energy outward”Proceeds with a net release of free energyOccurs spontaneouslyEndergonic reaction- “energy inward”
absorbs free energy from its surroundingsnonspontaneous
Energy Coupling- the use of an exergonic process to drive an endergonic one
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Cells are kept alive with a flow of energyThe products of a reaction become the
reactants of the next reaction.
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Rube Goldberg Machine
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Cellular Work
1. Mechanical work 2. Transport work 3. Chemical work
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ATP
Adenosine Triphosphate Adenine bonded to riboseRNA has one phosphate group attached to riboseATP has three phosphate groups attached to ribose
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ATP to ADP
Phosphate bonds- broken by hydrolysis Without 3rd Phosphate Group= Adenosine
Diphosphate (ADP) and inorganic phosphate
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ATP + H2O → ADP + Pi
Test tube: Change in G = -7.3 kcal/molCell: Change in G= -13 kcal/mol
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ATP to ADP
Is this reaction Exergonic or Endergonic? Exergonic- ADP is more stable than ATP,
energy is released with the loss of Pi
Negative G value
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Phosphorylation
Pi is not transferred into solution, given to another compound
Compound receiving the Pi is phosphorylated.
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ATP cycle
ATP + H2O → ADP + Pi
Change in G =-7.3 kcal/molADP + Pi → ATP + H2O
Change is G = 7.3 kcal/mol
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Enzymes
Catalyst- chemical agent that changes the rate of a reaction without being consumed by the reaction
Enzyme- catalytic protein
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Activation Energy or “free energy of activation” – the energy required to break the bonds in the reactants
Symbol- EA
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Cellular issue with heat
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Induced fit hypothesis
Change in the shape of an enzyme’s active site, which is induced by the substrate.
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Enzyme-substrate complex
Substrate held by weak interactions- hydrogen and ionic bonds
R-groups of amino acid chain of the protein catalyze the substrate
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Lowering the EA
Active site • Stresses critical bonds that must be broken• Can provide a microenvironment
Ex: Acidic R groups form a pocket of low pH
• Brief bonding- covalent bonding between substrate and R groups
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Rate of reaction
Determined by the concentration of substrate and enzyme
Saturation point
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Temperature and pH
Optimal TemperatureOptimal pH
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Cofactors
Bind to active site permanently or loosely Inorganic Organic- coenzyme
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Inhibitors
Competitive inhibitors- block active site Noncompetitive inhibitors- bind to another
part of enzyme Types: poison, antibiotics
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When is it useful to inhibit enzymes?
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Allosteric regulation
Allosteric site- specific receptor site on enzyme away from active site
Can activate or inhibit
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Feedback inhibition
Most commonPathway switch off by its end product
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Cooperativity
Substrate induces enzyme to accept more substrates
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Multienzyme complex
Team of enzymes assembled together
Ex: Mitochondria in eukaryotic cells- enzymes for respiration are clustered together