METABOLISM: Energy and Enzymes

1. METABOLISM: Energy and Enzymes Outline - Chapter 6

2. Maintenance • Organic food • Plants Make ORGANIC FOOD for themselves and everyone else. • Heterotrophs eat other things. • Food – nutrients and energy

3. 6.1 CELLS AND ENERGY FLOW • Energy - Capacity to do work • TWO kinds • 1 Kinetic – motion • 2 Potential – stored • Chemical Mechanical Radiation Electrical

4. TWO Laws of Thermodynamics • 1st – Law of Conservation of energy – energy cannot be created of destroyed, only converted from one form to another. 2nd - Law of Entropy - Energy cannot be changed from one form to another without the loss of usable energy – generally, as heat.

5. 61.C Cells and Entropy The transformation of energy disorganizes the Universe • A measure of disorder, chaos • Entropy is always increasing.

6. Flow of Energy

7. 6.2 Metabolic Rxns and Energy Transformations. • Metabolism – sum of all reactions in cell • Reactions occur in a sequence • Products become reactants • Linked reactions form a metabolic pathway • Begins with a reactant, • Terminates with a particular end product “G” is EndProduct “A” is InitialReactant AB C D E FG Intermediates

8. Metabolic Reactions andEnergy Transformations • Some reactions are spontaneous • Free energy allows another reaction to occur. Free energy - energy available to perform work • Exergonic Reactions - Products have less free energy than reactants • Endergonic Reactions - Products have more free energy than reactants

9. Coupled Reactions Figure 6.4

10. ATP – Energy for cells. ENERGY () currency of cells – what you spend. FUNCTIONS OF ATP Chemical work – synthesize cellular components Transport Work - pump substances across plasma membrane Mechanical work – muscle contraction, cilia, flagella, chromosomal movement.

11. Coupled reactions • Energy released in exergonic reactions can be used to drive endergonic reactions. • Ex - ATP to ADP releases energy (is exergonic) that drives reactions. • The breakdown of ATP is coupled to subsequent reactions, but some of the energy is lost as heat.

12. 6.3 Metabolic Pathways and enzymes: Catalysts facilitate rxns: Enzymes - protein molecules function as catalysts. • Not used up in a reaction • E1 E2 enzymes in a rxn A + B  C + DE A-E are reactants, C and E are products.

13. Enzymes Protein molecules that function as catalysts • The reactants of an enzymatically accelerated reaction are called substrates • Each enzyme accelerates a specific reaction • Each reaction in a metabolic pathway requires a unique and specific enzyme • End product will not appear unless ALL enzymes present and functional E1 E2 E3 E4 E5 E6 A  B  C  D  E  F  G

14. 6.3a Energy of Activation • Without enough energy – no reaction • Energy needed for a rxn is • ENERGY OF ACTIVATION • CATALYST – Lowers activation energy. • Enzymes lower the energy of activation • They bring substrates into contact with one another.

15. Energy of Activation

16. 6.3b Enzyme-Substrate Complexes ACTIVE SITE – binds to substrate. • When Active site changes form to accommodate substrate – INDUCED FIT MODEL • Enzymes named for the substrates to which they bind. --ase ending.

17. Induced Fit Model

18. Degradation vs. Synthesis

19. Factors Affecting Enzyme Activity (1) • Substrate concentration • Enzyme activity increases with substrate concentration • More collisions between substrate molecules and the enzyme • Temperature • Enzyme activity increases with temperature • Warmer temperatures cause more effective collisions between enzyme and substrate • However, hot temperatures destroy enzyme • pH • Most enzymes are optimized for a particular pH

20. Factors Affecting Enzyme Activity:Temperature

21. Factors Affecting Enzyme Activity:pH

22. Factors Affecting Enzyme Activity (2) • Cells can affect presence/absence of enzyme • Cells can affect concentration of enzyme • Cells can activate or deactivate enzyme • Enzyme Cofactors • Molecules required to activate enzyme • Coenzymes are organic cofactors, like some vitamins • Phosphorylation – some require addition of a phosphate

23. Factors Affecting Enzyme Activity (3) • Reversible enzyme inhibition • Inhibitor binds to an enzyme - decreases its activity • Competitiveinhibition – substrate and the inhibitor are both able to bind to active site • Noncompetitive inhibition – the inhibitor binds at the allosteric site • Feedback inhibition – End product inhibits the pathway’s first enzyme

24. Factors Affecting Enzyme Activity:Activation by Phosphorylation

25. Enzyme Inhibition • Enzymes can be prevented from acting: • Feedback Inhibition – when product concentration becomes great enough, it binds with allosteric site on enzyme and shuts down rxn. • Sometimes substrate binds to a non-active site (ALLOSTERIC) Site – shuts down process – no product is produced. • Poisons work by inhibiting enzymes.

26. Factors Affecting Enzyme Activity:Feedback Inhibition

27. Irreversible Inhibition • Materials that irreversibly inhibit an enzyme are known as poisons • Cyanides inhibit enzymes resulting in all ATP production • Penicillin inhibits an enzyme unique to certain bacteria • Heavy metals irreversibly bind with many enzymes • Nerve gas irreversibly inhibits enzymes required by nervous system

28. Enzyme Co-Factors • Inorganic ion or organic molecules (non-protein) that help enzyme work. • Organic non-protien molecules are – CO-ENZYMES – • VITAMINS are aprt of the structure of Co-Enzymes. So vitamin deficiency is bad – blocks enzymatic reactions.

29. Photosynthesis andCellular Respiration Cellular Respiration: Carbon dioxide+water+chemical energy Glucose+oxygen   C6H12O6 + 6O2 6CO2 + 6H2O Photosynthesis: Carbon dioxide+water+solar energy Glucose+oxygen  energy 6CO2 + 6H2O C6H12O6 + 6O2

30. 6.4a Photosynthesis • a series of rxns that transform solar energy into chemical energy in carbohydrates. • Hydrogen ions accompany electrons, so oxidation is a loss of HYDROGEN IONS • And REDUCTION is a gain of HYDROGEN ions. • In photosynthesis – H ions are transferred from water to Carbon Dioxide. • Water is OXIDIZED, Carbon dioxide is REDUCED.

31. 6.4b Cellular Respiration • C6H12O6 + 6O2 6CO2 + 6H2O + Energy • Glucose loses H+ so it is Oxidized. • Oxygen gains H+ - so it is Reduced. • Energy released from this process is used to make ATP.

32. CONNECTING CONCEPT CELL. RESPIR. USES AN ETS ELECTRONS ARE TRANSFERRED FROM CARRIER TO CARRIER WITH RELEASE OF ENERGY USED TO PRODUCE ATP

33. 6.4c Electron Transport System • Series of membrane-bound carriers that pass electrons (reducing) from carrier to carrier. • So carriers are Reduced, then Oxidized in turn. • To release Energy for the production of Carbohydrates or ATP.

34. Electron Transport Chain • Membrane-bound carrier proteins found in mitochondria and chloroplasts • Physically arranged in an ordered series • Starts with high-energy electrons and low-energy ADP • Pass electrons from one carrier to another • Electron energy used to pump hydrogen ions (H+) to one side of membrane • Establishes electrical gradient across membrane • Electrical gradient used to make ATP from ADP – Chemiosmosis • Ends with low-energy electrons and high-energy ATP

35. A Metaphor for theElectron Transport Chain

36. 6.4d ATP Production • Peter Mitche - British biochemist – Nobel prize in 1978 • Chemiosmotic theory of ATP production • H+ ions collect on one side of a membrane, being pumped there by certain carriers of the ETS. Yields ElectroChemical Gradient that provides Energy for ATP production. • The energy that the pumps use to maintain the H+ gradient comes from the breakdown of GLUCOSE.

37. Chemiosmosis

38. END