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Biology Notes: Biomolecules, Water, and Bonding (Pages 1-3)

Page 1

  • Bonding in polar, non-polar and ionic compounds (quiz topics)

    • Polar compounds share electrons unevenly and can hydrogen bond and are hydrophilic.
    • Non-polar compounds share electrons evenly, have a lot of C-H bonds and cannot hydrogen bond so they are hydrophobic and don’t dissolve/mix with water.
    • Ionic compounds transfer electrons and are hydrophilic and do dissolve in water.

  • What is a hydrogen bond?

    • A hydrogen bond is a force between a positive hydrogen attached to a very electronegative element and a very electronegative element (F, O, N). (FON)
    • In shorthand: an H atom covalently bonded to F, O, or N forms a bridge to another electronegative atom via hydrogen bonding.

  • The three properties of water

    • Cohesion
    • Since water can hydrogen bond, water molecules stick to each other, causing surface tension.
    • This allows water molecules to be easily pulled up the stem of a plant since one water molecule pulls up the others because they stick together.
    • Adhesion
    • Since water can hydrogen bond, water molecules stick to other molecules that can hydrogen bond.
    • This allows water molecules to be easily pulled up the stem of a plant; water molecules can hydrogen bond to the inside of the stem, helping them to not fall back down.
    • Specific heat
    • Water has a very high specific heat, meaning you have to add a lot of energy to change the temperature of the substance.
    • This helps moderate the temperature of the Earth and living things because it can absorb a lot of energy without changing temperature.
    • Universal solvent
    • Since water has negative and positive ends, it can dissolve all substances that are polar or ionic.
    • This allows the water portion of the blood to carry dissolved molecules easily throughout the body.

  • Structure of water leads to those properties

    • (Note: The content above directly connects the hydrogen-bonding network and polarity of water to cohesion, adhesion, high specific heat, and solvent capabilities.)

Page 2

  • Biomolecules: chart prep

    • For each of the three biomolecules, make a chart (directly in your notes):
    • Proteins do not have types.
    • Atoms they contain
    • Building block (monomers)
    • Types
    • If they are hydrophobic or hydrophilic
    • All molecules that are lipids are hydrophobic. The rest are hydrophilic.
    • Identify them and their building blocks in pictures (more practice tomorrow). See slides on Google Classroom.

  • How each biomolecule is built and broken down using dehydration synthesis and hydrolysis

    • Dehydration synthesis: bonds are made between monomers by removing one less water than the number of monomers.
    • Hydrolysis: bonds are broken between monomers by adding one less water than the number of monomers to break each bond.

  • Filling out blanks in dehydration synthesis and hydrolysis reactions

    • See practice done as homework and reviewed in class.

  • Structural differences between starch and cellulose and how their properties differ

    • Starch is made with many
    • alpha glucose, which has the OH down on carbon 1, formed by dehydration synthesis.
    • Cellulose is made with
    • beta glucose, with the OH up on carbon 1.
    • This causes every other glucose to be flipped when bonded together, and because of the different structure, humans cannot digest cellulose but can digest starch.

  • Structural differences between an unsaturated and saturated fat and how their properties differ

    • Both are made by dehydration synthesis between 1 glycerol and 3 fatty acids.
    • However, unsaturated fats have at least one double bond between the carbons in the fatty acid tail.
    • The more double bonds there are, the lower the melting point and the more likely the fat will be a liquid because the bends from the double bonds prevent tight packing.

  • Structural differences between lipid and phospholipid and how their properties are different

    • A phospholipid has one of the three fatty acids bonded to the glycerol replaced by a polar phosphate group.
    • This makes the molecule have a hydrophilic head and two hydrophobic tails.
    • This arrangement is amphipathic.

  • Structure of an amino acid and how each amino acid differs from each other

    • Amino acids have a central carbon bonded to:
    • an amino group (
      • NH₂),
    • a hydrogen (H),
    • a carboxyl group (
      • COOH), and
    • an R group (varies among amino acids).
    • Variation in the R group gives all amino acids their distinct properties.

Page 3

  • The four types of amino acids and how they differ

    • Polar – hydrophilic
    • Non-polar – hydrophobic
    • Acidic: negatively charged
    • Basic: positively charged

  • Locate a peptide bond in a polypeptide

    • A peptide bond forms between the carbon of the carbonyl group of one amino acid and the nitrogen of the amino group of the next amino acid.
    • In structural notation, this bond is represented as a linkage between a C=O group and an NH group:
    • The bond is typically drawn as the bond between the carbonyl carbon and the amide nitrogen: - ext{C(=O)-N(H)-}
    • This is identified with a red line in the diagram.