Thermodynamics notes

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THERMODYNAMICS

1.1. What is energy?

Energy is the capacity to do work.

Potential energy is stored energy. Kinetic energy is the energy of movement. Potential energy can be converted to potential energy.

1.2. What are heat and cold?

Heat is the transfer of thermal energy.

Cold is simply the absence of heat. A substance feels cold to us because it takes heat away from us.

Heat always flows from a warmer substance to a cooler substance. Heat, like all energy, spreads out or disperses over time.

1.3. The Laws of Thermodynamics

The laws of thermodynamics describe the quantity and the quality of energy.

The first law of thermodynamics states that energy can neither be created nor destroyed by ordinary processes.

Closed system, where energy can neither enter nor leave, the total amount f energy before and after the process will be unchanged. The first law is often called the law of conservation of energy, energy can be converted from one form to another.

The second law of thermodynamics states that when energy is converted from one form to another, the amount of useful energy decreases.

Entropy is a measurement of energy dispersal.

The highly organized, low-entropy stems that characterize life do not violate the second law of thermodynamics, because they are achieved through a continuous influx of usable energy from the sun, accompanied by an enormous increase in solar entropy.

2.1. Energy transformed during chemical reactions

Chemical reactions fall into two broad categories: in exergonic reactions, the reactant molecules have more energy than do the product molecules, so the reaction releases energy. In endergonic reactions, the reactants have less energy to do the products, so the reaction requires a net input of energy.

Exergonic and endergonic reactions y be coupled such that the energy liberated by an exergonic reaction drives an endergonic reaction.

3.1. Energy transported within cells

The energy released by chemical reactions within a cell is captured and transported within the cell by unstable energy-carrier molecules, such as ATP a the electron carriers NADH and FADH2.

Energy-carrier molecules are high-energy molecules that are synthesized at the site of an exergonic reaction, where they capture some of the released energy.

Many exergonic reactions in cells, such as breaking down sugars and fats, produce adenosine triphosphate ATP, the most common energy-carrier molecule in the body.

These molecules are the major reactions occurring at different places in the cell.