Topic 2

Question 1

Second Law of Thermodynamics and Living Organisms

Answer 1

• Cell’s have a low entropy.
• As a result of chemical reactions within the cell, organisms release heat, CO2, and water.
• The released heat and gases spread out, increasing the entropy of the surroundings.
• The entropy in a cell can be low, because the entropy of the cell’s surroundings is always increasing.
• Low entropy in the cell is balanced by the increase in entropy in the cell’s surroundings.

Question 2

Why may someone think that life goes against the second law of thermodynamics?

Answer 2

• Organisms are highly organized, and energy is concentrated in complex molecules.
• This implies a low entropy, which goes against the second law of thermodynamics.
• However, life follows the second law of thermodynamics because the entropy of the cell’s surroundings is always increasing.

Question 3

Why do cell’s have a low entropy?

Answer 3

• Organisms can maintain a highly organized state because they are open systems. They constantly bring in energy and matter.
• This keeps a low-entropy state, because constant input of energy and matter allows the cell to maintain complex structures and processes.
• Organized, specific processes = low entropy.

Question 4

Why do living systems have to keep consuming energy?

Question 5

Why can’t we consume all the chemical energy produced by a plant through photosynthesis?

Question 6

Explain in thermodynamic terms why, if you stopped eating, you would die.

Question 7

Metabolism

Question 8

Catabolic Pathway

Answer 8

• A series of chemical reactions that result in the breakdown of larger, more complex molecules into smaller, less complex molecules.

large —-> small

• Energy is released when molecules are broken down.

ex.) Cellular respiration

Question 9

Anabolic Pathway

Answer 9

• A series of reactions that results in the synthesis of larger, more-complex molecules from simpler starting molecules.
• Also called biosynthetic pathways.
• Requires energy

ex.) Photosynthesis

ex.) The biosynthesis of specific carbohydrates, proteins, and nucleic acids are examples of anabolic pathways.

Question 11

ATP Structure