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

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