LZ

Bio Chapter 3

  • ==The Molecule that Supports all Life==
    • Water is the only substance that can exist in the natural environment in all 3 states
    • Water’s unique emergent properties make earth suitable for life
    • Structure of water allows it to interact with other molecules (be available for any large molecules’ broken and empty bonds)
    • Helps with the formation of different compounds/photosynthesis
    • It is an electron donor
  • ==Polar Covalent Bonds in Water Molecules Result in Hydrogen Bonding==
    • Electrons (overall charge) are unevenly distributed (more attracted to the oxygen ion), making it a polar molecule with dipoles
    • Its polarity allows it to interact and form hydrogen bonds with other substances
    • Water molecules have a small charge that attracts it to others like itself
    • COHESION: Attraction to others like itself
    • ADHESION: Attraction to different substances than itself
  • ==4 Emergent Properties of Water That Contribute to Life==
    • Cohesive behavior
    • Ability to moderate temperature
    • Expansion upon freezing
    • Versatility as a solvent
  • ^^The Cohesion of Water Molecules^^
    • Hydrogen bonds hold water molecules together, creating cohesion
    • Cohesion & adhesion allows the water in plants to move against gravity
    • Adhesion is in transpiration (as roots take up water to the leaves)
    • Capillary action = water going up a plant
    • Evaporation also pulls water upwards
    • Spheres take the least amount of energy (why water forms globs in space)
    • Tendency towards chaos/disorder + maintain energy (why it is a sphere)
    • Surface tension is the measure of how difficult it is to break the surface of a liquid
    • Water has an unusually high surface tension due to hydrogen bonding and cohesiveness
  • ^^Moderation of Temperature by Water^^
    • water absorbs heat from warmer air and releases that heat into colder air (why regions beside lakes are cooler = because water is absorbing the heat)
    • Water can hold onto heat for long periods of time & release/absorb a large amount of heat with only a slight change in its own temperature (changing its state)
    • %%Temperature & Heat%%
    • Kinetic energy = energy in motion
    • A lot of energy is required to break water’s hydrogen bonds (cohesion) in large numbers
    • Thermal energy = kinetic energy’s association with the random motion of atoms and molecules
    • Heat = thermal energy being transferred from one body to another
      • Enzymes are picky with pH and temperature (water has a huge temperature range)
    • A calorie (cal) is the amount of energy required to raise 1g of water by 1 degree C
      • Also the amount of heat released when 1g of water cools
    • Joule is another unit of energy
  • ^^Water’s High Specific Heat ^^
    • The amount of heat that must be absorbed or lost for 1g of that substance to change by 1 degree C.
    • Specific heat of water is 1 cal/(g x C)
    • Rubbing alcohol has a lower high specific heat = evaporates quicker
    • Water resists changing its temperature because of its high specific heat
    • Hydrogen bonding breaks = heat is absorbed
    • Hydrogen bonds form = heat is released
    • High specific heat limits water’s temperature fluctuations to which it can still sustain life
  • ==Evaporative Cooling==
    • Evaporation (vaporization) = transition from liquid to gas
    • The heat of evaporation = the heat required for 1g of a liquid to be converted into a gas
    • As the liquid evaporates, its remaining surface cools = evaporative cooling (the heat is released)
    • Helps stabilize temperatures in organisms and bodies of water
    • Ex. sweating (reduction of heat energy)
  • ==Floating of Ice on Liquid Water==
    • Ice floats in water because the hydrogen bonds are more “ordered”, making ice less dense than water
    • Water is densest at 4 degrees (ex. bottom of the lake)
    • If ice sank to the bottom of water bodies, the entire water body would freeze (ice formed at the top would keep sinking down)
    • Global warming is affecting water bodies (heatsinks), making them unable to properly absorb heat
    • Objects around it are then heating up (ex. icebergs)
    • Creating challenges for animals that rely on ice
  • ^^Water: The Solvent of Life^^
    • Aqueous solution = water is the solvent
    • Water is a versatile solvent due to its polarity
    • Ionic compounds can dissolve in water because its ions are surrounded by water molecules (ie. hydration shell/shield)
      • Ex. Glucose powder gets its molecules bent into rings when dissolved in water
    • Water can dissolve non-ionic polar molecules + very large polar molecules if they have ionic/polar regions
  • ==Hydrophilic and Hydrophobic Substances==
    • Hydrophilic = affinity for water
    • Hydrophobic = no affinity for water
    • Ex. oils because they have non-polar bonds
    • Oils and other non-polar molecules are the main substances for cell membranes
    • Ex. Phospholipid Bilayer
    • Hydrophilic heads allow the cell to live in the water/in the body
    • The charge on the heads attract it together (cohesion)
    • Hydrophobic tails: water-soluble materials can not bypass the tails unless there is a carrier/receptor that brings it inside
    • If tails were on the outside, we would not survive (the cell would not be able to survive in water) and we would be oil-based organisms
    • If there is a slight charge, it is hydrophilic, if there is no charge, it is hydrophobic and non polar
  • ==Solute Concentrations in Aqueous Solutions==
    • Molecular mass = sum of all atoms’ masses in a molecule
    • # of entities = avogadro’s number
    • Molarity (M) = # of moles of solute/L of solution
    • Ex. Vinegar in salad dressing = helps the hydrophobic vegetables to break down/have a change in pH
  • ==Acidic and Basic Conditions Affect Living Organisms==
    • A hydrogen atom in a hydrogen bond between 2 water molecules can shift between one and the other
    • Molecule that lost the proton = OH-
    • Molecule that gained a proton = H3O or H+
    • All enzymes are proteins, but not all proteins are enzymes
    • HCL is in stomach to lower pH (ex. of pepsin)
    • Amylase needs a neutral place to work (mouth)
    • Lower pH = more hydronium/hydrogen ions
    • High pH = more OH ions
    • When CO2 dissociates in water, it becomes carbonic acid or hydrogen carbonate
    • Changes in concentrations of H and OH can drastically affect the chemistry of a cell and affect the organism
    • Concentration of H and OH in pure water is the same
  • ==Acids and Bases==
    • Acid = increases the H concentration of a solution
    • Bases = reduces the H concentration of a solution
    • Strong acids and bases dissociate completely in water
    • Weak acids and bases reversibly release and accept back H ions but can still shift the H and Oh away from neutrality
    • Most bio fluids have a pH of 6-8
    • Inside intestine = 8 (water is absorbed, lining is thinner, and enzymes need s pH of 8)
  • ==Buffers ==
    • The internal pH of most living cells is close to 7
    • Buffers are substances that limit changes in concentrations of H and OH in a solution
    • Most buffer solutions contains a weak acid and its corresponding base, which combine reversibly with H ions
    • Weak acid and weak base to maintain good pH