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Water and Life (3) & Carbon and the Molecular Diversity of Life (4) -…
Water and Life (3) & Carbon and the Molecular Diversity of Life (4)
Polar Covalent Bonds
Polar Covalent Bonds:
atoms that differ in electronegativity - electrons pulled closer to more electronegative, one slightly negative/positive,
ex: bond in H2O
Water:
Oxygen = more electronegative, covalent bonds closer, Hydrogen = less electronegative
Liquid (H2O):
weak hydrogen bonds, 1/20 as strong as covalent bonds, constantly reforming
Oxygen can form 2 hydrogen bonds
Charged regions in H2O molecule are due to polar covalent bonds
Polar Molecule:
Molecule with uneven distribution of charges in different regions within,
ex: H2O
4 Emergent Properties of Water
Cohesive Behavior
Cohesion:
linking together of molecules often by hydrogen bonds
Surface Tension:
measure of difficulty to stretch/break surface of water,
ex: high surface tension of H2O allows spider to walk on surface of pond
Adhesion:
clinging of one substance to another,
ex: water to plant cell walls
Adhesion and cohesion in plants
Ability to Moderate Temperature
Temperature and Heat
Kinetic Energy:
energy of motion,
ex: atoms and molecules
Thermal Energy:
kinetic energy due to motion of atoms/molecules, most random form
Heat:
thermal energy from one body of matter to another
Calorie (cal):
amount of heat required to raise temperature of 1 g of water by 1 degree celsius
Kilocalorie (kcal):
thousand calories, amount of heat energy to raise temperature of 1 kg of water by 1 degree celsius
Joule (J):
1 J = 0.239 cal, 1 calorie = 4.184 J
Temperature:
average kinetic energy of molecules in matter, independent of volume...thermal energy is total kinetic energy - dependent on matter
High Specific Heat
Specific Heat:
amount of heat that must be absorbed/lost for 1 g of a substance to change temperature by 1 degree celsius
H2O:
high specific heat, resists changing temperature, stabile ocean temperatures, organisms are able to resist own temperature change
Expansion Upon Freezing
Heat of Vaporization:
quantity of heat a liquid must absorb for 1 g of it to be converted from liquid to gas,
ex: H2O = 2260J/g - boiling pt
Evaporative Cooling:
surface of an object becomes cooler during evaporation, result of molecules with highest kinetic energy, liquid to gas
Floating of Ice on Liquid Water
Water is less dense as a solid than a liquid, allows life to exist under frozen surfaces
Versatility as a Solvent
Solution:
liquid that is a homogenous mixture of 2 or more substances,
ex: sugar dissolved in water
Solvent:
dissolving agent of a solution, water is the most versatile,
ex: water
Solute:
substance that is dissolved in a solution,
ex: salt/sugar
Aqueous Solution:
solution in which water is the solvent,
ex: sugar water
Hydration Shell:
sphere of water molecules around a dissolved ion
Hydrophobic and Hydrophilic Substances:
Hydrophilic:
having an affinity for water,
ex: sugars, salts, alcohol
Hydrophobic:
having no affinity for water, tending to form droplets of water,
ex: oil, fats, waxes
Solute Concentration in Aqueous Solutions
Molecular Mass:
sum of the masses of all atoms in a molecule; molecular weight,
ex: H2O = 18.016 amu
Mole (mol):
number of grams of a substance that equals its molecular or atomic mass in daltons; contains Avogadro's # of the molecules
Molarity:
measure of solute concentration, referring to the number of moles of solute per liter of solution, M = moles/liters
Acidic and Basic Conditions Affect Living Organisms
Hydrogen Ion:
single proton with a +1 charge, dissociation of a water molecule leads to generation of hydroxide (OH) and hydrogen (H) ion
Hydroxide Ion:
water molecule that has lost a proton, OH-
Hydronium Ion:
water molecule that has an extra proton bound to it,
ex: H3O+ commonly represented as H+
Acids and Bases
Acid:
substance that increases the hydrogen ion concentration of a solution,
ex: HCl
Weak acids are acids that reversibly release and accept back hydrogen ions,
ex: carbonic acid
Base:
substance that reduces they hydrogen ion concentration of a solution,
ex: NaOH
pH Scale
pH:
measure of hydrogen ion concentration equal to -log[H+] and ranging in value from 0-14, more acidic (0), more basic (14)
Buffers:
solution that contains a weak acid and its corresponding base, minimizes changes in pH when acids or bases are added to the solution
Acidification
Ocean Acidification:
process by which the pH of the ocean is lowered when excess CO2 dissolves in seawater and forms carbonic acid
Organic Chemistry
Organic Chemistry:
study of carbon compounds
Major elements of life are C, H, O, N, P, and S
Carbon Atoms
Formation of Bonds with Carbon
Valence:
bonding capability of an atom, # of covalent bonds that an atom can form which usually equals the # of unpaired electrons in its outermost shell,
ex: Sulfure has 6 valence electrons and usually forms 2 bonds
Carbon Skeletons
Length, Branching, Double Bond Position, and Presence of Rings
Hydrocarbons
Hydrocarbons:
organic molecule consisting only of carbon and hydrogen,
ex: CH4
Isomers
Structural Isomers:
1 of 2 or more compounds that have the same molecular formula, differ in the covalent arrangement of their atoms,
ex: pentane vs 2-methylbutane
Isomers:
one of 2 or more compounds have the same numbers of atoms of the same elements but different structures (different properties)
Cis-trans Isomers:
1 of several components that have the same molecular formula and covalent bonds between atoms, differ in spatial arrangements of their atoms; geometric isomer,
ex: x's on same side/x's on opposite sides
Enantiomers:
1 of 2 compounds that are mirror images of each other and differ in shape due to asymmetric carbon,
ex: L isomer/D isomer
Chemical Groups
Procceses of Life
Functional Groups:
specific configuration of atoms commonly attached to the carbon skeletons of organic molecules,
ex: alcohol group
Hydroxyl group, carbonyl group, carboxyl group, amino group, sulfhydryl group, phosphate group, methyl group
ATP
Adenosine Triphosphate:
adenine-containing nucleotide triphosphate that releases free energy when its phosphate bonds are hydrolized, drive endergonic reactions