Biology Chapter 3

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rosylyn
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200898
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Biology Chapter 3
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2013-02-16 02:37:48
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Chapter 3 Notes
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  1. Properties of water
    • • Cohesion and adhesion
    • • Ability to buffer temperature changes
    • • Less dense as a solid than a liquid
    • • It is the solvent in our cells
    •      – Cells are 70-95% water
    •      – Life evolved in water
  2. Water is a polar molecule
    • The oxygen has a polar covalent bonds with the hydrogens

    • – Oxygen is delta-
    • – Hydrogen is delta+

    • Water molecules are held together by hydrogen bonds

    – The attraction of water molecules for each other is the reason for its special properties
  3. Hydrogen bonds between water molecules
  4. Water has cohesion and adhesion
    • • Cohesion
    • – Water molecules stick to each other
    • – Allows for surface tension of water
    • • Adhesion
    • – Water molecules stick to other substances(other than water)
    • • Why?
    • – Hydrogen bonds between water molecules
  5. Water has the ability to buffer temperature changes
    • • Can absorb and store heat
    • • Can release heat
    •          – Heat=total amount of kinetic energy (energy of motion)in a body of matter
    • • Why?
    •          – Heat is used to break the hydrogen bonds first
    •          – THEN, the heat increases molecular movement (which increases the temperature)

    • • Benefits for life
    •         – Moderates ocean temperature
    •         – Moderates cellular temperature
    •         – Moderates coastal climates
  6. Water is less dense as a solid(ice) than as a liquid
    • • 0 C is the temperature that liquid water becomes ice
    •      – Each water is hydrogen bonded to 4 other water molecules
    •      – The bonding arrangement prevents compaction
    •     – Therefore, ice is 10% less dense than liquid water

    • • Benefits
    •     – Frozen water is on the surface of lake’s etc. in winter
    •     – The surface is exposed to the sun’s heat and thaws in later seasons
    •      – If it sunk, bodies of water would permanently freeze
  7. Hydrophilic
    – Substances that are attracted to and can be dissolved in water

    – Polar and ionic substances
  8. Hydrophobic
    – Substances that avoid water and therefore cannot be dissolved in water

    – Non-polar substances
  9. Water soluble protein
  10. The pH scale
    • Water ionizes such that the molar concentration of H+ is 10-7 mole/liter

    – Mole= 6.02 x 1023 molecules

    – 1 molar solution = 6.022 x 1023 molecules/L

    • • pH = -log10 [H+]
    • – Note it is a logarithmic scale so each pH unit is a 10 fold difference in hydrogen ion concentration.

    • • Neutral pH is 7
    • – Example water

    • • Acidic pH is less than 7
    • – Acids increase [H+]    Example: HCl

    • • Basic pH is more than 7
    • – Bases decrease [H+] Example: NaOH
  11. pH Scale
  12. Buffers
    • Buffers- a substance that act as reservoirs for H+

    • – Minimize pH change–
    • -Accepts or donates hydrogen ions
    • • If pH increases it donates H+
    • • If pH decreases it accepts H+

    • H+ and 0H- are very reactive, so natural buffers areused in cells

    – Cells are very sensitive to pH changes• Common buffers used in biology experiments

    – Tris, MOPS, sodium phosphate

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