Introduction to Metabolism

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Introduction to Metabolism

• Chapter 6

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Metabolism

• The totality of an organisms chemical processes.
• Concerned with managing the material and energy
  resources of the cell.

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Catabolic Pathways

• Pathways that break down complex molecules into
  smaller ones, releasing energy.
• Example Respiration

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Anabolic Pathways

• Pathways that consume energy, building complex
  molecules from smaller ones.
• Example Photosynthesis

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Energy

• Ability to do work.
• The ability to rearrange a collection of matter.
• Forms of energy
• Kinetic
• Potential
• Activation

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Kinetic Energy

• Energy of action or motion.

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Potential Energy

• Stored energy or the capacity to do work.

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Activation Energy

• Energy needed to convert potential energy into
  kinetic energy.

Activation Energy
Potential Energy
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Energy Transformation

• Governed by the Laws of Thermodynamics.

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1st Law of Thermodynamics

• Energy can be transferred and transformed, but it
  cannot be created or destroyed.
• Also known as the law of Conservation of Energy.

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2nd Law of Thermodynamics

• Each energy transfer or transformation increases
  the entropy of the universe.

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Entropy

• Measure of disorder.

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Summary

• The quantity of energy in the universe is
  constant, but its quality is not.

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Question?

• How do living organisms overcome Entropy?
• By using energy from the environment or external
  sources (e.g. food, light).

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Free Energy

• The portion of a system's energy that can perform
  work.

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Free Energy

• G H - TS
• G free energy of a system
• H total energy of a system
• T temperature in oK
• S entropy of a system

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Free Energy of a System

• If the system has
• more free energy
• it is less stable
• It has greater work capacity

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Chemical Reactions

• Are the source of energy for living systems.
• Are based on free energy changes.

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Reaction Types

• Exergonic chemical reactions with a net release
  of free energy.
• Endergonic chemical reactions that absorb free
  energy from the surroundings.

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Exergonic/Endergonic
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Biological Examples

• Exergonic - respiration
• Endergonic - photosynthesis

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Cell - Types of Work

• Mechanical - muscle contractions
• Transport - pumping across membranes
• Chemical - making polymers

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Cells use ATP as their energy source

• Adenosine Triphosphate
• Made of
• - Adenine (nitrogenous base)
• - Ribose (pentose sugar)
• - 3 phosphate groups

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Adenine
Phosphates
Ribose
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Key to ATP

• Is in the high energy bonds between the three
  phosphate groups.
• Negative charges on the phosphate groups repel
  each other and makes the phosphates unstable.

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ATP Cycles

• Energy released from ATP drives anabolic
  reactions.
• Energy from catabolic reactions recharges ATP.

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ATP CycleATP ADP P Energy
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ATP in Cells

• A cell's ATP content is recycled every minute.
• Humans use close to their body weight in ATP
  daily.
• No ATP production equals quick death.

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Redox reactions
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Oxidation - definitions

• Loss of electrons.
• Loss of energy.
• Loss of Hydrogens from Carbons.

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Reduction - definitions

• Gain of electrons.
• Gain of energy.
• Gain of Hydrogens to Carbons.
• Comment - be careful not to use reduction in
  lay terms.

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Redox reactions

• Reactions are usually paired or linked together.
• Many of the reactions will be done by
  phosphorylation.

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Phosphorylation

• Adding a phosphate group to a molecule.
• The phosphate group adds energy to the molecule
  for chemical reactions.

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ATP

• ATP energizes other molecules by transferring
  phosphate groups to them.. The process is called
  phosphorylation.

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Phosphorylation