Review of Last Class

Four Classes of Building Blocks

• Lipids

• Sugars – polysaccharides

• Nucleotides – nucleic acids

• Amino acids – proteins

Copyright 2001 by Harcourt, Inc.

Directions and Rates of Directions and Rates of Biochemical ProcessesBiochemical Processes

How Do Concentration (and Entropy) How Do Concentration (and Entropy) Affect Equilibrium?Affect Equilibrium?

reactant Areactant A product Bproduct B

more free energymore free energy less free energyless free energy

If the reaction isIf the reaction is exergonicexergonic (energy releasing), product B will begin to (energy releasing), product B will begin to accumulate.accumulate.As the amount of B increases, so does BAs the amount of B increases, so does B’’s free energy.s free energy.

Gradually, the difference in energy between the reactants and prGradually, the difference in energy between the reactants and products oducts decreases. When the free energy of B = the free energy of A, nodecreases. When the free energy of B = the free energy of A, no further further net movement occurs and the reaction is said to be in equilibriunet movement occurs and the reaction is said to be in equilibrium.m.

Chapter Six: How Do Organisms Supply

Themselves with Energy

Respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O

Photosynthesis

6 CO2 + 6 H2O C6H12O6 + 6 O2

CO2 + H2O C(H2O) + 6 O2

Reduction-Oxidation Reaction (redox reactions)

Oxidizing agent – electron acceptor, is reduced (more energy)

Reducing agent – electron donor, is oxidized

A– + B A + B–

H H H OH C H C OH H C O H C O H O C O

fully reduced fully oxidized

electronegativity

How Do Organisms Supply Themselves with Energy?

When NADWhen NAD++ accepts electrons and protons to become accepts electrons and protons to become NADH, is it being oxidized or reduced?NADH, is it being oxidized or reduced?

reducedreduced

When reduced, does the energy of a molecule When reduced, does the energy of a molecule increase or decrease?increase or decrease?

increasesincreases

Therefore, NADH is carrying some of the energy Therefore, NADH is carrying some of the energy originally stored in the carbon-hydrogen bonds of originally stored in the carbon-hydrogen bonds of glucose.glucose.

How Do Organisms Supply Themselves with Energy?

In looking at the process of glycolysis, what would we In looking at the process of glycolysis, what would we consider to be the essential ingredients?consider to be the essential ingredients?

A substrate to process--A substrate to process--glucoseglucose..

A number of A number of enzymes enzymes to change the molecule and assist to change the molecule and assist in its oxidation.in its oxidation.

Energy, in the form of Energy, in the form of ATPATP, to assist in the oxidation of , to assist in the oxidation of the glucose molecule.the glucose molecule.

An essential coenzyme, An essential coenzyme, NADNAD++..

How Do Organisms Supply Themselves with Energy?

Was oxygen a requirement for any part of glycolysis?Was oxygen a requirement for any part of glycolysis?

No.No.

If that is true, is glycolysis an aerobic or an anaerobic If that is true, is glycolysis an aerobic or an anaerobic process?process?

anaerobicanaerobic

習題p.120, 如果你專心唸書， 24h 要用掉 1025 個 ATP 分子， 約重 40kg ，這個數字是怎麼得來的？如果你 24h 不吃飯，只唸書，你的體重會減少 40kg 嗎？為什麼？