WHAT DO MEMBRANES DO? –Membranes are essential boundaries that separate the inside from the outside; –Membranes regulate the contents of the spaces they enclose; –Membranes serve as a “workbench” for a variety of biochemical reactions; –Membranes participate in energy conversions. Why Are All Organisms Made of Cells?

Directions and Rates of Biochemical Processes

How Does Thermodynamics Predict the Direction of a Reaction? –The First Law of Thermodynamics The total amount of energy in any process stays constant. Energy cannot be created or destroyed, only converted from one form to another. So, energy may switch from potential to kinetic and back again, but it is neither created nor destroyed. »For example, the potential energy stored in the chemical bonds of ATP is converted into kinetic energy when it is split to allow a muscle contraction to occur.

Directions and Rates of Biochemical Processes How Does Thermodynamics Predict the Direction of a Reaction? –The Second Law of Thermodynamics In any process, the energy available to do work decreases. –For example, when ATP is split to allow a muscle contraction, only a fraction of the energy from ATP is converted into useful work.The rest of the energy becomes heat which is largely wasted energy.

∆G = G products – G reactants Exergonic ∆G < 0 spontaneous rx. Endergonic ∆G > 0

Chapter Six: How Do Organisms Supply Themselves with Energy

習題 p.120, 如果你專心唸書， 24h 要用掉 個 ATP 分子， 約重 40kg ，這個數字是怎麼得來的？ 有化學背景的同學 ，一定要做對 沒有化學背景的同學，做對會加分