Biological Molecules Great and Small

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Chapter 3
Biological Molecules Great and Small
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Key Questions

• How do organisms use carbon atoms decorated with
  functional groups to build basic molecules of
  life?
• What are the categories of building block
  molecules?
• What reactions link and unlink building blocks?
• How are fatty acids, polysaccharides, nucleic
  acids and proteins formed?

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Biological Molecules

• Size either small (MWlt300) or large (MWgt10,000)
• Organic molecules based on hydrogen and carbon
• Are built of subunits building blocks

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Subunits and Macromolecules

• Sugars
• Lipids
• Amino acids
• Nucleotides

• Polysaccharides
• Fats and cholesterol
• Proteins
• DNA and RNA

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Thinking About the Possibilities

• Examine the Nutrition Label from any snack food
• What class of biomolecule is not included on this
  label?
• Of the elements nitrogen, carbon and oxygen, are
  any contained in insignificant amounts?

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Carbon

• Carbon chains and rings are linked by single and
  double covalent bonds

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Carbon Rings

• Carbon rings can be flat
• Carbon rings can be boat or chair

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Chemical Interactions of Molecules

• Determined by
• Shape
• Charge distribution
• Interactions with water
• Interactions with other molecules

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Functional Groups

• Small groups of atoms
• Contribute to the chemical properties of a
  molecule
• Usually attached to the carbon backbone

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Examples of Functional Groups

• -CO carbonyl
• -COOH carboxyl
• -NH2 amine
• -SH sulfhydryl
• -PO4 phosphate

And the best darn functional group in the land. .
.
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-OH hydroxyl
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Shapes of Biomolecules

• Lipids do not form chains of subunits
• Proteins, nucleic acids and carbohydrates can
  form long chains
• Carbohydrate chains may be branched

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Carbohydrates

• Fundamental energy storage molecule
• Subunits are simple sugars monosaccharides
• Linked by dehydration condensation into
  polysaccharides

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Structure of Carbohydrates

• Chemical formula (CH2O)n
• For each carbon
• 1 oxygen
• 2 hydrogens
• Many hydroxyl groups make sugars hydrophilic

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Formation of Polysaccharides

• 2 sugars link to form disaccharide
• Several sugars oligosaccharide
• Long chains of sugars polysaccharide

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Carbohydrates and Energy

• Glucose is the basis of most energy releasing
  reactions
• Short term energy mono- and di-saccharides
• Long term energy storage glycogen in animals,
  starch in plants

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Carbohydrates and Structure

• Cellulose
• Structural support for plant cells
• Glucose polysaccharide with bonds in straight
  orientation
• Chitin
• Exoskeleton of arthropods
• Modified sugars in chains

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Carbohydrates in Plants
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Glycoproteins and Glycolipids

• Glycoproteins have short chains of sugars
  attached to proteins
• Glycolipids have short chains of sugars attached
  to lipids
• Both found on the exterior surface of cells