Changes in Matter

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Changes in Matter
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Chapter Eighteen The Chemistryof Living Systems

• 18.1 The Chemistry of Carbon
• 18.2 Protein, Fats, and Nucleic Acids

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Investigation 18A
Carbon and Its Chemistry

• What are some common molecules that contain
  carbon?

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18.1 The chemistry of carbon

• Carbon molecules come in three basic forms
  straight chains, branching chains, and rings.
• All three forms are found in important biological
  molecules.

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18.1 Carbohydrates

• All living things contain
• carbohydrates
• proteins
• fats
• nucleic acids

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18.1 Carbohydrates

• Carbohydrates are mainly composed of carbon,
  hydrogen, and oxygen in a ratio of about 121.
• Carbohydrates exist as small molecules, like
  glucose, and long-chain molecules, like starches.
  
• Table sugar is a carbohydrate called sucrose.

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18.1 Proteins

• Proteins are large molecules composed of carbon,
  hydrogen, oxygen, nitrogen, and trace elements.

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18.1 Fats

• Fats are medium-to-large nonpolar molecules that
  do not dissolve in water.

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18.1 Nucleic Acids

• Nucleic acids such as DNA store the genetic code
  that allows organisms to reproduce.

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18.1 Carbohydrates

• Carbohydrates are relatively small molecules used
  to store and transfer energy in living systems.
• Carbohydrates are classified as either sugars or
  starches.

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18.1 Carbohydrates

• Starches are long chains of simple sugars joined
  together.
• Cellulose is the primary molecule in plant
  fibers, including wood.

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18.1 Photosynthesis

• Photosynthesis is the foundation of the food
  chain on Earth.
• For every glucose sugar molecule produced, six
  molecules of carbon dioxide are removed from the
  air, and six molecules of oxygen are produced.

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18.1 Respiration

• Animals get energy and nutrients by breaking up
  glucose, starch, and other organic molecules.
• Cellular respiration breaks down glucose into
  water and carbon dioxide again, extracting energy
  in the process.
• Each cell converts the energy in glucose into
  chemical energy stored in molecules of ATP.

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18.1 The importance of water

• Liquid water is essential to life as we know it.
• The human body is typically between 60 and 65
  percent water by weight.
• Most of the chemical reactions that sustain life
  only work in solution.

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18.1 The importance of water

• There are 3 important characteristics of water
  that make it essential for life
• Water is a good solvent.
• Liquid water has a wide temperature range.
• Water has a high specific heat capacity.