Intro to Metabolism Campbell Chapter 8 http://ag.ansc.purdue.edu/sheep/ansc442/semprojs/2003/spiderlamb/eatsheep.gif http://www.gifs.net
Section 8.1 An organism s metabolism transforms matter and energy, subject to the laws of thermodynamics PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Metabolism is the sum of an organism s chemical reactions Metabolism is an emergent property of life that arises from interactions between molecules within the cell http://www.encognitive.com/images/metabolic-pathways.png
A metabolic pathway begins with a specific molecule and ends with a product Each step is catalyzed by a specific enzyme BIOCHEMICAL PATHWAY VIDEO
Enzymes Macromolecules that serve as catalysts, a chemical agent that changes the rate of a reaction without being consumed by the reaction Mechanisms that regulate them balance metabolic supply and demand Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Metabolism Manages the material and energy sources of the cell. Two types of metabolic pathways: 1. Catabolic 2. Anabolic Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CATABOLIC PATHWAY (CATABOLISM) Break down pathway Release of energy by the breakdown of complex molecules to simpler compounds EX: digestive enzymes break down food Cellular respiration http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/nanoscience/sci_media/images/chemical_reactions_involve_making_new_combinat ions/53823-2-eng-nz/chemical_reactions_involve_making_new_combinations_full_size_landscape.jpg
ANABOLIC PATHWAY (ANABOLISM) Biosynthetic pathways consumes energy to build complicated molecules from simpler ones EX: synthesis of amino acids to form proteins Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
http://users.rcn.com/jkimball.ma.ultranet/biologypages/i/intermediarymetabolism.html Energy from catabolic pathways can be stored and used later to drive anabolic pathways i.e. Krebs Cycle connects the catabolic and anabolic pathways
Forms of Energy ENERGY = capacity to cause change Energy exists in various forms (some of which can perform work) The work of life depends on the ability of the cell to transform energy from one form into another
KINETIC ENERGY energy associated with motion HEAT (thermal energy) is kinetic energy associated with random movement of atoms or molecules Light is kinetic energy harnessed from light to perform work i.e. Photosynthesis
POTENTIAL ENERGY - energy that matter possesses because of its location or structure CHEMICAL energy is potential energy available for release in a chemical reaction i.e. glucose is high in chemical energy Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
On the platform, the diver has more potential energy. Diving converts potential energy to kinetic energy. Climbing up converts kinetic energy of muscle movement to potential energy. In the water, the diver has less potential energy.
THERMODYNAMICS = the study of energy transformations CLOSED system (EX: liquid in a thermos) = isolated from its surroundings OPEN system =energy + matter can be transferred between the system and its surroundings Organisms are open systems http://ag.ansc.purdue.edu/sheep/ansc442/semprojs/2003/spiderlamb/eatsheep.gif
The First Law of Thermodynamics energy of the universe is constant Energy can be transferred and transformed Energy cannot be created or destroyed The first law is also called the principle of conservation of energy http://www.pxleyes.com/photoshop-picture/4a3b747566555/remote-control.html http://www.suncowboy.com/solar101.php
The Second Law of Thermodynamics During every energy transfer or transformation entropy (disorder) of the universe INCREASES some energy is unusable, often lost as heat http://hyperphysics.phy-astr.gsu.edu/hbase/therm/entrop.html http://www.janebluestein.com/articles/whatswrong.html
First law of thermodynamics Chemical energy Second law of thermodynamics Heat CO 2 H 2 O ORGANISMS are energy TRANSFORMERS! Spontaneous processes occur without energy input; they can happen quickly or slowly For a process to occur without energy input, it must increase the entropy of the universe
Section 8.2 The free energy change of a reaction tells us whether or not the reaction occurs spontaneously PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Free-Energy Change ( G) can help tell which reactions will happen spontaneously Portion of a system s energy that can perform work when temperature and pressure are uniform G = H - T S G = change in free energy H = change in total energy (enthalpy) S = change in entropy (randomness) T = temperature (K) Only processes with a negative G are spontaneous Spontaneous processes can be harnessed to perform work
Free Energy and Metabolism Classification of Chemical Reactions based on Free-Energy Changes: 1. Exergonic 2. Endergonic Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Exergonic Reactions in Metabolism Release energy (- G) are spontaneous The magnitude of G represents the maximum amount of work the reaction can perform The greater the decrease in free energy, the greater amount of work that can be done Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Endergonic Reactions in Metabolism Absorb free energy from their surroundings Stores free energy in molecules + G Are non-spontaneous
Equilibrium and Metabolism Reactions in an isolated system eventually reach equilibrium Metabolic reactions are reversible and they would reach equilibrium if they occurred in isolation Systems at equilibrium are at minimum G and can NOT do work a cell that reaches metabolic equilibrium is dead! The constant flow of materials keeps metabolic pathways from reaching equilibrium and the cell continues to do work throughout its life. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Section 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A cell does three main kinds of work: Mechanical Transport Chemical In the cell, energy coupling, the use of exergonic processes to drive an endergonic one occurs.
ATP (adenosine triphosphate) is the cell s renewable and reusable energy shuttle ATP provides energy for cellular functions Energy to charge ATP comes from catabolic reactions Adenine Phosphate groups Ribose
LE 8-9 Bonds between PO 3 are broken by hydrolysis It becomes ADP and releases energy P P P Adenosine triphosphate (ATP) H 2 O The reaction is exergonic P i + P P + Energy Inorganic phosphate Adenosine diphosphate (ADP)
Because hydrolysis releases energy, the PO 3 bonds of ATP are referred to as high-energy PO 3 bonds. The release of energy comes from the chemical change to a lower state of free energy ATP is useful because the energy it releases is greater that the energy most other molecules could deliver Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Endergonic reaction: G is positive, reaction is not spontaneous NH 2 Glu + NH 3 Glu G = +3.4 kcal/mol Glutamic acid Ammonia Glutamine Exergonic reaction: G is negative, reaction is spontaneous ATP + H 2 O ADP + P i G = 7.3 kcal/mol Coupled reactions: Overall G is negative; Together, reactions are spontaneous G = 3.9 kcal/mol
LE 8-11 ATP drives transport and mechanic al work it causes changes in shape and binding affinities of proteins ATP P Motor protein Mechanical work: ATP phosphorylates motor proteins Membrane protein Solute P P i Protein moved P i Solute transported ADP + P i a.) directly by phosphoryl ation Transport work: ATP phosphorylates transport proteins P Glu NH 2 + NH 3 + Glu P i b.) indirectly by binding of ATP Reactants: Glutamic acid and ammonia Product (glutamine) made Chemical work: ATP phosphorylates key reactants
ATP Energy for cellular work provided by the loss of phosphate from ATP Energy from catabolism (used to charge up ADP into ATP ADP + P i
Section 8.4 Enzymes speed up metabolic reactions by lowering energy barriers PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Every chemical reaction between molecules involves bond breaking and bond forming ACTIVATION ENERGY = amount of energy required to get chemical reaction started Activation energy is often supplied in the form of heat from the surroundings Free energy animation IT S LIKE PUSHING A SNOWBALL UP A HILL... Once you get it up there, it can roll down by itself http://www.chuckwagondiner.com/art/matches.jpg http://plato.acadiau.ca/courses/comm/g5/fire_animation.gif
LE 8-14 Free energy The Activation Energy Barrier A B C D Transition state A B E A C D Reactants A C B D G < O Products Progress of the reaction
CATALYST = a chemical agent that speeds up a reaction without being consumed by the reaction ENZYMES = biological catalysts, most enzymes are PROTEINS Exception = ribozymes (RNA) Ch 17 & 26
Free energy Course of reaction without enzyme Reactants E A without enzyme E A with enzyme is lower Course of reaction with enzyme G is unaffected by enzyme Products Progress of the reaction ENZYMES work by LOWERING ACTIVATION ENERGY;
ENZYMES LOWER ACTIVATION ENERGY BY Orienting substrates correctly Straining substrate bonds Providing a favorable microenvironment Enzymes change ACTIVATION ENERGY but NOT energy of REACTANTS or PRODUCTS http://sarahssureshots.wikispaces.com/focus+on+proteins http://www.ac-montpellier.fr/sections/personnelsen/ressources-pedagogiques/education-artistique/consultation-avis-du
ENZYMES Most are proteins Lower activation energy Specific Shape determines function Reusable Unchanged by reaction Image from: http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm
The REACTANT that an enzyme acts on = SUBSTRATE Enzyme + substrate = ENZYME-SUBSTRATE COMPLEX Region on the enzyme where the substrate binds = ACTIVE SITE Substrate held in active site by WEAK interactions (i.e. hydrogen and ionic bonds)
TWO MODELS PROPOSED: LOCK & KEY Active site on enzyme fits substrate exactly INDUCED FIT Binding of substrate causes change in active site so it fits substrate more closely http://www.grand-illusions.com/images/articles/toyshop/trick_lock/mainimage.jpg http://commons.wikimedia.org/wiki/file:induced_fit_diagram.png
Enzyme Activity can be affected by: General environmental factors: 1. Temperature 2. ph 3. salt concentration 4. Chemicals that specifically influence the enzyme Choose narrated See a movie http://www.desktopfotos.de/downloads/melt_cd.jpg http://www.nealbrownstudio.com/adm/photo/163_nb_fried_egg.jpg
TEMPERATURE & ENZYME ACTIVITY Each enzyme has an optimal temperature at which it can function (Usually near body temp) http://www.animated-gifs.eu/meteo-thermometers/001.htm
http://www.uic.edu/classes/bios/bios100/lectures/chemistry.htm Increasing temperature increases the rate of an enzyme-catalyzed reaction up to a point. Above a certain temperature, activity begins to decline because the enzyme begins to denature.
ph and ENZYME ACTIVITY Each enzyme has an optimal ph at which it can function
http://www.wissensdrang.com/media/wis9r.gif COFACTORS = non-protein enzyme helpers EX: Zinc, iron, copper COENZYMES = organic enzyme helpers Ex: vitamins http://www.elmhurst.edu/~chm/vchembook/595fadcoq.html
SUBSTRATE CONCENTRATION & ENZYME ACTIVITY V MAX Adding substrate increases activity up to a point
Section 8.5 Regulation of enzyme activity helps control metabolism PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
REGULATION OF ENZYME PATHWAYS GENE REGULATION cell switches on or off the genes that code for specific enzymes
REGULATION OF ENZYME PATHWAYS FEEDBACK INHIBITION end product of a pathway interacts with and turns off an enzyme earlier in pathway FEEDBACK INHIBITION prevents a cell from wasting chemical resources by synthesizing more product than is needed
NEGATIVE FEEDBACK An accumulation of an end product slows the process that produces that product A Enzyme 1 Negative feedback A Enzyme 1 B B Enzyme 2 C C Enzyme 3 D D D D D D D D D D D Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway
POSITIVE FEEDBACK (less common) The end product speeds up production W W Enzyme 4 Enzyme 4 X Positive feedback X Enzyme 5 Enzyme 5 Y Y Z Enzyme 6 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Enzyme 6 Z Z Z Z EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.
REGULATION OF ENZYME ACTIVITY ALLOSTERIC REGULATION = protein s function at one site is affected by binding of a regulatory molecule at another site can inhibit or stimulate an enzyme s activity Allosteric enzyme inhibition http://bio.winona.edu/berg/animtns/allostan.gif
SOME ALLOSTERIC ENZYMES HAVE MULTIPLE SUBUNITS Each enzyme has active and inactive forms The binding of an ACTIVATOR stabilizes the active form The binding of an INHIBITOR stabilizes the inactive form
COOPERATIVITY = form of allosteric regulation that can amplify enzyme activity Binding of one substrate to active site of one subunit locks all subunits in active conformation
Enzyme Inhibitors COMPETITIVE inhibitor = REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme ENZYME ANIMATION
Enzyme Inhibitors NONCOMPETITIVE inhibitors = bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective ENZYME ANIMATION