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Introduction to Metabolism. Metabolism is the sum of an organisms chemical reactions Metabolism is an emergent property of life that arises from interactions.

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Presentation on theme: "Introduction to Metabolism. Metabolism is the sum of an organisms chemical reactions Metabolism is an emergent property of life that arises from interactions."— Presentation transcript:

1 Introduction to Metabolism

2 Metabolism is the sum of an organisms chemical reactions Metabolism is an emergent property of life that arises from interactions between molecules within the cell

3 A metabolic pathway begins with a specific molecule and ends with a product The product of one reaction is substrate of the next Each step is catalyzed by a specific enzyme BIOCHEMICAL PATHWAY BIOCHEMICAL PATHWAY VIDEO

4 ENZYMES THAT WORK TOGETHER IN A PATHWAY CAN BE Soluble with free floating intermediates Covalently bound in complex Attached to a membrane in sequence Concentrated in specific location

5 CATABOLIC PATHWAY (CATABOLISM) Release of energy by the breakdown of complex molecules to simpler compounds EX: digestive enzymes break down food ANABOLIC PATHWAY (ANABOLISM) consumes energy to build complicated molecules from simpler ones EX: linking amino acids to form proteins

6 Krebs Cycle connects the catabolic and anabolic pathways

7 Forms of Energy ENERGY = capacity to cause change Energy exists in various forms (some of which can perform work) Energy can be converted from one form to another

8 KINETIC ENERGY – energy associated with motion –HEAT (thermal energy) is kinetic energy associated with random movement of atoms or molecules POTENTIAL ENERGY = energy that matter possesses because of its location or structure –CHEMICAL energy is potential energy available for release in a chemical reaction

9 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.

10 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

11 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

12 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

13 Chemical energy Heat CO 2 First law of thermodynamics Second law of thermodynamics H2OH2O 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

14 Free-Energy Change ( G) can help tell which reactions will happen G = change in free energy H = change in total energy (enthalpy) S = change in entropy T = temperature G = H - TS Only processes with a negative G are spontaneous Spontaneous processes can be harnessed to perform work

15 Free Energy, Stability, and Equilibrium Free Energy- a measure of a systems instability Unstable systems (higher G) tend to change in such a way that they become more stable (lower G) A process is spontaneous and can perform work only when it is moving toward equilibrium Equilibrium is a state of maximum stability

16 Less free energy (lower G) More stable Less work capacity More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (G < 0) The system becomes more stable The released free energy can be harnessed to do work

17 Exergonic and Endergonic Reactions in Metabolism EXERGONIC reactions (energy outward) (- G) Release energy are spontaneous

18 Exergonic and Endergonic Reactions in Metabolism ENDERGONIC reactions (energy inward) (+ G) Absorb energy from their surroundings are non-spontaneous

19 Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions A cell does three main kinds of work: –Mechanical –Transport –Chemical In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction Overall, the coupled reactions are exergonic

20 Phosphate groups Ribose Adenine ATP (adenosine triphosphate) is the cells renewable and reusable energy shuttle ATP provides energy for cellular functions Energy to charge ATP comes from catabolic reactions

21 Adenosine triphosphate (ATP) Energy PP P PP P i Adenosine diphosphate (ADP) Inorganic phosphate H2OH2O + +

22 P i ADP Energy for cellular work provided by the loss of phosphate from ATP Energy from catabolism (used to charge up ADP into ATP ATP +

23 Endergonic reaction: DG is positive, reaction is not spontaneous Exergonic reaction: DG is negative, reaction is spontaneous G = +3.4 kcal/mol G = –7.3 kcal/mol G = –3.9 kcal/mol NH 2 NH 3 Glu Glutamic acid Coupled reactions: Overall DG is negative; Together, reactions are spontaneous AmmoniaGlutamine ATP H2OH2O ADP P i + + +

24 NH 2 Glu P i P i P i P i NH 3 P P P ATP ADP Motor protein Mechanical work: ATP phosphorylates motor proteins Protein moved Membrane protein Solute Transport work: ATP phosphorylates transport proteins Solute transported Chemical work: ATP phosphorylates key reactants Reactants: Glutamic acid and ammonia Product (glutamine) made + + +

25 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 ITS LIKE PUSHING A SNOWBALL UP A HILL... Once you get it up there, it can roll down by itself Free energy animation

26 Transition state CD A B EAEA Products CD A B G < O Progress of the reaction Reactants C D A B Free energy The Activation Energy Barrier

27 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)

28 Course of reaction without enzyme E A without enzyme G is unaffected by enzyme Progress of the reaction Free energy E A with enzyme is lower Course of reaction with enzyme Reactants Products ENZYMES ENZYMES work by LOWERING ACTIVATION ENERGY;LOWERING ACTIVATION ENERGY

29 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

30 ENZYMES Most are proteins Lower activation energy Specific Shape determines function Re-usable Unchanged by reaction

31 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 (ie. hydrogen and ionic bonds )

32 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

33 –General environmental factors, such as temperature, pH, salt concentration, etc. –Chemicals that specifically influence the enzyme See a movie Choose narrated Enzyme Activity can be affected by :

34 TEMPERATURE & ENZYME ACTIVITY Each enzyme has an optimal temperature at which it can function (Usually near body temp)

35 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.

36 pH and ENZYME ACTIVITY Each enzyme has an optimal pH at which it can function

37 COFACTORS = non-protein enzyme helpers EX: Zinc, iron, copper COENZYMES = organic enzyme helpers Ex: vitamins

38 SUBSTRATE CONCENTRATION & ENZYME ACTIVITY V MAX Adding substrate increases activity up to a point

39 REGULATION OF ENZYME PATHWAYS GENE REGULATION cell switches on or off the genes that code for specific enzymes

40 REGULATION OF ENZYME PATHWAYS FEEDBACK INHIBITION end product of a pathway interacts with and turns off an enzyme earlier in pathway prevents a cell from wasting chemical resources by synthesizing more product than is needed FEEDBACK INHIBITION

41 NEGATIVE FEEDBACK –An accumulation of an end product slows the process that produces that product B A C D Enzyme 1 Enzyme 2 Enzyme 3 D D D D D D D D DD C B A Negative feedback Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway

42 POSITIVE FEEDBACK (less common) –The end product speeds up production WW X Y Z Z Z Z Z Z Z Z Z Z Z ZZ Z ZZ Z Z Z Y X Enzyme 4 Enzyme 5 Enzyme 6 Enzyme 4 Enzyme 5 Enzyme 6 Positive feedback EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.

43 REGULATION OF ENZYME ACTIVITY ALLOSTERIC REGULATION proteins function at one site is affected by binding of a regulatory molecule at another site Allosteric regulation can inhibit or stimulate an enzymes activity Allosteric enzyme inhibition

44 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

45 Substrate Binding of one substrate molecule to active site of one subunit locks all subunits in active conformation. COOPERATIVITY another type of allosteric activation Stabilized active form Inactive form

46 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

47 COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme ENZYME ANIMATION Enzyme Inhibitors

48 NONCOMPETITIVE inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective ENZYME ANIMATION


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