Chapter 6 Ground Rules Of Metabolism
Alcohol Dehydrogenase An enzyme Breaks down ethanol and other toxic alcohols Allows humans to drink
Metabolism Is the totality of an organism s chemical reactions Arises from interactions between molecules An organism s metabolism transforms matter and energy, subject to the laws of thermodynamics
Thermodynamics Is the study of energy transformations The First Law of Thermodynamics Energy can be transferred or transformed Energy cannot be created or destroyed The Second Law of Thermodynamics Spontaneous changes that do not require outside energy increase the entropy, or disorder, of the universe
1 st Law of Thermodynamics
2 nd Law of Thermodynamics
Living Systems Increase the entropy (disorder) of the universe Use energy to maintain order
Metabolic Pathways Have many steps Begin with a specific molecule, end with a different product Each step is catalyzed by a specific enzyme Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting molecule Product
Types of Metabolic Pathways Catabolic Pathways Break down complex molecules into simpler compounds Release energy Anabolic Pathways Build complicated molecules from simpler ones Consume energy
Energy Can be converted from one form to another
Free Energy Amount of energy available to do work Ex: cells store energy in chemical bonds The free energy change of a reaction tells us whether the reaction will occur spontaneously
Ex: When you walked into the room and sat in your chair, you could tell if someone was sitting there before you
Chemical Reactions
Metabolic Reactions Exergonic Reactions Spontaneous Release free energy
Exergonic Reactions
Metabolic Reactions Endergonic Reactions Non-spontaneous Absorbs free energy from its surroundings
Activation Energy (E A ) The initial amount of energy needed to start a chemical reaction Is often supplied in the form of heat by the surroundings in a system An enzyme catalyzes a reaction by lowering the E A barrier
Course of reaction without enzyme Reactants Course of reaction with enzyme E A without enzyme E A with enzyme is lower G is unaffected by enzyme Progress of the reaction Products
ATP The cell s energy currency Adenosine Triphosphate Powers cellular work by coupling exergonic reactions to endergonic reactions A cell does 3 main kinds of work: Mechanical Transport Chemical
Energy Release Energy is released when the bond between the terminal phosphate group is broken The negative charge on the PO 4 groups repel
ATP and Phosphorylation Endergonic reactions driven by the transfer of the phosphate to another molecule ATP Membrane protein P Motor protein Protein moved (a) Mechanical work: ATP phosphorylates motor proteins Solute P (b) Transport work: ATP phosphorylates transport proteins P Glu Solute transported + NH 3 + Glu Reactants: Glutamic acid and ammonia NH 2 P i P i P i Product (glutamine) made ADP + P i (c) Chemical work: ATP phosphorylates key reactants
Regeneration of ATP Catabolic pathways drive the regeneration of ATP from ADP and phosphate
Enzymes Speed up chemical reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction An enzyme is a catalytic protein E + S ES E + P
Conformational change!!!
Activation Energy Barrier Every chemical reaction between molecules involves both bond breaking and bond forming Ex: hydrolysis
Substrate Specificity of The substrate Is the reactant an enzyme works on The enzyme Binds to its substrate, forming an enzymesubstrate complex The active site Is the region on the enzyme where the substrate binds Enzymes
Induced Fit of a Substrate Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
Enzyme & Substrate fit like a lock & key (Shape specific) ph or temperature can change the active site shape on any enzyme Active site is where the reactants bind to the enzyme
Active Site Can lower the E A barrier by: Orienting substances correctly Straining substrate bonds Providing a favorable microenvironment Covalently bonding to the substrate
The Activity of an Enzyme Is affected by general environmental factors Temperature ph
Enzyme Cofactors Cofactors Non-protein enzyme helpers Ex: zinc, iron, copper atoms Coenzymes Organic cofactors Ex: vitamins
Enzyme Inhibitors Competitive Inhibitors Bind to the active site of the enzyme, competing with the substrate
Enzyme Inhibitors Noncompetitive Inhibitors Bind to another part of the enzyme, changing the function
Enzyme Regulation Regulation of enzyme activity helps control metabolism A cell s metabolic pathways must be tightly regulated
Allosteric Regulation When a protein s function at one site is affected by binding of a regulatory molecule at another
Cooperativity A form of allosteric regulation that can amplify enzyme activity
Feedback Inhibition The end product of a metabolic pathway shuts down the pathway
How to Name Enzymes Change the ending on the name of the substrate to ase Ex: Sucrose (substrate) Sucrase (enzyme) Lipid Lipase DNA DNAse Protein - Protease
Making Energy!! ATP 2008-2009 The point is to make ATP!
The energy needs of life Organisms are endergonic systems What do we need energy for? synthesis building biomolecules reproduction movement active transport temperature regulation
Where do we get the energy from? Work of life is done by energy coupling use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions digestion + + energy synthesis + + energy
Living Economy Fueling the body s economy eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids break them down digest = catabolism capture released energy in a form the cell can use Need an energy currency a way to pass energy around need a short term energy storage molecule ATP