An Introduction to Metabolism

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to potential energy.

A diver has less potential

energy in the water

than on the platform.

Diving converts

potential energy to

kinetic energy.

A diver has more potential

energy on the platform

than in the water.

Slide 11

The Laws of Energy Transformation

Thermodynamics is the study of energy transformations

A closed system, such as that approximated by liquid in a thermos, is isolated from its surroundings

In an open system, energy and matter can be transferred between the system and its surroundings

Organisms are open systems

Slide 12

The First Law of Thermodynamics

According to the first law of thermodynamics, the energy of the universe is constant:

– Energy can be transferred and transformed, but it cannot be created or destroyed

The first law is also called the principle of conservation of energy

Slide 13

The Second Law of Thermodynamics

During every energy transfer or transformation, some energy is unusable, and is often lost as heat

According to the second law of thermodynamics:

– Every energy transfer or transformation increases the entropy (disorder) of the universe

Slide 14

Fig. 8-3

(a) First law of thermodynamics

(b) Second law of thermodynamics

Chemical

energy

Heat

CO2

H2O

+

Slide 15

Living cells unavoidably convert organized forms of energy to heat

Spontaneous processes occur without energy input; they can happen quickly or slowly

For a process to occur without energy input, it must increase the entropy of the universe

Slide 16

Biological Order and Disorder

Cells create ordered structures from less ordered materials

Organisms also replace ordered forms of matter and energy with less ordered forms

Energy flows into an ecosystem in the form of light and exits in the form of heat

Slide 17

Fig. 8-4

50 µm

Slide 18

The evolution of more complex organisms does not violate the second law of thermodynamics

Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases

Slide 19

Concept 8.2: The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously