BIOC2000 Lecture Notes - Lecture 5: Helicase, Membrane Protein, Conformational Change
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As entropy increases there will be more useful energy to doâworkâ. True or false?
False. As entropy increases, there will generally be less usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. Imagine a car motor, which attempts toturn chemical potential energy into kinetic energy (movement). Lessefficient motors will get hotter for the same amount of fuelconsumed. When you drive a car you hope that most of the fuelenergy is converted into kinetic energy and not lost as heat(entropy). The hotter the car (and thus the more entropy) the lessefficient the ability to do âworkâ (the moving of the vehicle). |
| True. As entropy increases, there will generally be more usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. In most biological and mechanicalsystems it is heat energy which is captured to do useful 'work'.Heat energy, the random movement of molecules, and increases inentropy are central to doing useful work. |
Biological systems sometimes appear on the surface to break theSecond Law of Thermodynamics â by seemingly increasing the order inthe overall system. They donât. Why?
| a. Earth (and living things on it) are not a closed system. Thesun's constant input of energy in the form of photons is harnessedby living things to create internal order within themselves. Butwithout such a constant input of energy, most biological systems onearth would break down. |
| b. The Second Law tells us that no natural process can occurunless it is also associated with an increase in the entropy of theuniverse. A living organism (such as an animal or plant) brings inmatter and energy from its environment and uses this to creategreater order within its body: the processes of life. But it isimportant to keep in mind that all animals and plants are also partof a larger system of the environment around them. While creating asmall âpocketâ of order, the processes of life (metabolism,movement, etc..) releases heat into the environment â thusincreasing the entropy of the universe and following the2nd law. |
| c. Living things, by harnessing energy to create order (withinand around themselves) actually create a paradox in questionssurrounding the first and second laws of thermodynamics andseemingly violate many previously held assumptions. |
| d. Both a and b above are correct. |
When plants capture energy in the photons of sunlight andconvert that energy into the chemical bonds of organic molecules,are they creating new energy?
| No, the energy is being transferred from one form into another.But no new energy is being created. |
| No, the overall total energy is decreasing over time. |
| Yes, by capturing photons, the plants are creating newenergy. |
| Yes, by capturing photons, the plants are creating new energy -of a different wavelength. |
