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Energy Flow in the Life of a Cell-Life on Planet Earth-Chapter 4

By biology-medicine, From cbs.dtu.dk, Date: 2008-03-05 09:36:35

I. Energy and the Ability to Do Work

  • The laws of thermodynamics describe the basic properties of energy.Sun 16
  • Living things use the energy of sunlight to create the low-entropy conditions characteristic of life.

Chapter 4: Energy Flow in the Life of a Cell
Fire Wall


II. Energy Flow in Chemical Reactions

Glucose
  • Exergonic reactions release energy.
  • Endergonic reactions require an input of energy.
  • Coupled reactions link exergonic with endergonic reactions.
  • Chemical reactions are reversible.

    Glycolysis pathway

III. Controlling the Metabolism of Living Cells

  • At body temperatures, high activation energy makes spontaneous reactions proceed too slowly to sustain life.

  • Catalysts reduce activation energy.
    Activation Energy

  • Enzymes are biological catalysts.

    Shown below is a cartoon of the enzyme HEXOKINASE, which is responsible for the first step in glycolysis (the breakdown of glucose, as shown above). This enzyme catalyzes the formation of glucose-6-phosphate from glucose - the glucose is the very small molecule in the middle!

Hexokinase

IV. Coupled Reactions and Energy-Carrier Molecules

ATP

The "laws" of thermodynamics

Law # 1 - "The adiabatic work done on a system in taking the system from state 1 to state 2 is independent of the manner of doing the work and depends only on the initial and the final states of the system."

Q = U + W

where W = work done, Q = heat put into the system , U = internal energy of the system

"You can never get more energy out of a system than you put into it."

Law # 2 - "It is impossible for an engine working in a cycle to produce no other effect than that of extracting heat from a reservoir and performing an equivalent amount of work." (Kelvin Planck statement)

"It is impossible for refrigerator working in a cycle to produce no other effect than the transfer of heat from a colder body to a hotter body." (Clausius statement)

"Nature tends toward maximum randomness"
animated bomb
"your room will tend to get messy
unless you put energy into cleaning it up?

A little aside - there is actually a "zeroth law" of thermodynamics:

Law # 0 - Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other.