Cellular Metabolism Energy as it relates to Biology

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Presentation transcript:

Cellular Metabolism Energy as it relates to Biology Energy for synthesis and movement Energy transformation Enzymes and how they speed reactions Metabolism and metabolic pathways Catabolism (ATP production) Anabolism (Synthesis of biologically important molecules)

Energy in Biol. Systems: General definition of energy: Capacity to do work Chemical, transport, movement First Law of Thermodynamics: Energy can neither be created nor destroyed Ultimate source of energy: Sun! 2 types of energy: Kinetic energy = motion examples ? Potential energy = stored energy Fig 4-2

Energy (E) Transfer Overview Figure 4-1

Potential Energy heat (~ 70% of energy Kinetic Energy WORK used in physical exercise) Kinetic Energy WORK

Bioenergetics = study of energy flow through biol. systems Chemical reactions transfer energy A + B C + D Products Substrates or reactants Speed of reaction = Reaction rate Initial force = Activation Energy

Potential Energy Stored in Chemical Bonds of Substrate can be . . . transferred to the chemical bonds of the product released as heat (usually waste) used to do work (= free energy)

Chemical Reactions p 93 Activation energy Endergonic vs. exergonic reactions Coupled reactions Direct coupling vs. indirect coupling Reversible vs. irreversible reactions

Activation Energy Fig 4-3

Endo- and Exergonic Reactions Which is which?? ATP + H2O ADP + Pi + H+ + Energy

Enzyme (= Biol. Catalyst) Some important characteristics of an enzyme: Enzymes are proteins  rate of chemical reaction by lowering activation energy is not changed itself It may change DURING the reaction does not change the nature of the reaction nor the result is specific Fig 4-6

Enzymes lower activation energy: All chemical reactions in body must be conducted at body temp.!! How do enzymes lower activation energy ?

Some more characteristics of enzymes: Usually end in –ase Inactive form: -ogen in few cases RNA has enzymatic activity (eg: rRNA  peptide bond) Isoenzymes may be produced in different areas of the body E.g., LDH

Active Site: Small region of the complex 3D structure is active (or binding) site. Enzymes bind to substrate Troponin I and T are structural components of cardiac muscle. They are released into the bloodstream with myocardial injury. They are highly specific for myocardial injury--more so than CK-MB--and help to exclude elevations of CK with skeletal muscle trauma. Troponins will begin to increase following MI within 3 to 12 hours, about the same time frame as CK-MB. However, the rate of rise for early infarction may not be as dramatic as for CK-MB. Troponins will remain elevated longer than CK--up to 5 to 9 days for troponin I and up to 2 weeks for troponin T. This makes troponins a superior marker for diagnosing myocardial infarction in the recent past--better than lactate dehydrogenase (LDH). However, this continued elevation has the disadvantage of making it more difficult to diagnose reinfarction or Old: Lock-and-key model / New: Induced-fit model

Enzyme-substrate interaction: The old and the new model Lock and Key: Induced fit:

Naming of Enzymes Kinase Phosphatase Peptidase Dehydrogenase mostly suffix -ase first part gives info on function Kinase Phosphatase Peptidase Dehydrogenase examples

Isoenzymes = different models of same enzyme (differ in 1 or few aa) Catalyze same reaction but under different conditions and in different tissues/organs Examples: Amylase LDH → importance in diagnostics (LDH) Lactate dehydrogenase  - Total LDH will begin to rise 2 to 5 days after an MI; the elevation can last 10 days. 140-280 U/L Normal Adult Range: 0 - 250 U/L Optimal Adult Reading: 125

Enzyme Activity depends on Proteolytic activation (for some) Cofactors & coenzymes (for some) Temperature pH Other molecules interacting with enzyme Competitive inhibitors Allosteric modulators

1) Proteolytic Activation Also Pepsinogen Pepsin Trypsinogen Trypsin

2) Cofactors & Coenzymes structure: Inorganic molecules (?) function: conformational change of active site structure: Organic molecules (vitamin derivatives, FADH2 ....) function: act as receptors & carriers for atoms or functional groups that are removed from substrate

3)

4) Molecules interacting with enzyme Competitive inhibitors: bind to active site Fig 4-13 block active site E.g.: Penicillin binds covalently (= irreversibly to important bacterial enzyme active site)

4) Molecules interacting with enzyme, cont’d Allosteric modulators (fig 4-14): bind to enzyme away from active site change shape of active site (for better or for worse) Special case: = end product inhibition

Allosteric Modulation

Reaction Rate Depends on Enzyme & Substrate Concentration

Reversible Reactions follow the Law of Mass Action

Three Major Types of Enzymatic Reactions: Oxydation - Reduction reactions (transfer of electrons or protons (H+)) Hydrolysis - Dehydration reactions (breakdown & synthesis of water) Addition-Subtraction-Exchange (of a functional group) reactions

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