Topic 8 Molecules of life (1) Flashcards
Everything is made of
matter
Life is organized into fundamental units, cells
What maintains it and what opposes this organization
energy is needed to maintain this, if not, entropy would cause the system to fall apart
Atoms and molecules
Everything is made of matter
Matter is made of elements
Elements are different types of atoms
Two or more join to make a molecule
What is life based on
Carbon based
Carbon
Oxygen
Hydrogen
Nitrogen
Elements that form the building blocks of molecules that are essential for life
Atomic mass
Mass of protons and neutrons
bottom right on periodic table
Atomic number
Number of protons
Top left in periodic table
Atomic structure
Protons and electron numbers are equal
Electrons are organized into shells. In reality these are clouds where they are likely to be found at a given time
Isoforms
Atomic number is the same but additional (or fewer) neutrons = isoform
Carbon dating
Nitrogen-14 decays to carbon-14 in the atmosphere due its loss of a proton and gain of a neutron using energy from cosmic rays in the atmosphere.
Organisms take in carbon-14 from the atmosphere ion proportion to its presence
This stops when an organism dies
C-14 > N-14 with t 1/2 5730
By comparing c-14 to n-14 in the body, the time since death can be calculated
Carbon-14 decays with a half life of
You believe an organism died 12000 years ago. Estimate the amount of c-14 you expect to find relative to the starting amount
12000 is appx 2x5730
Therefore 2 half lives
Hence 25% remaining
The bohr model and the octet rule
Reactivity of an atom is determined by the number of electrons in its last or valent shell
2,8,8
Tries to have a full outer shell by either losing, gaining or sharing electrons
Covalent bond
Shares a valent electron to form the bond
Ionic bond
Donates one (or more) valent electrons. Both atoms become charged.
Stay together by electrostatic forces
Bond types (5 things)
Covalent- share an electron pair - strong
Hydrogen - share an H atom - semi strong
Ionic - attraction of opposite charges via electron donation - semi strong
Hydrophobic interaction - interaction of nonpolar substances in the presence of polar substances - weak
Vaan der Waals attraction - interaction of electrons of nonpolar substances - very weak
Chemical reactions are based on random collisions
Increase temp or relative concentration you increase the probability of a collision happening with enough energy for a reaction
-273 degrees, no energy, absolute zero, no reactions
Irreversible reaction
One way (essentially)
One arrow
Reversible
two way, reaches and maintains an equilibrium
If you alter the amount of a product, you may drive the equilibrium in one way eg blood buffering
Covalent bond
Each atom shares electrons
In biological substances, up to 6 atoms are shared (in 3 pairs)
The strength of the bond increases with each pair
This also changes how much an atom may rotate around a bond and has a major effect on the molecules shape
Polar molecules have polar covalent bonds
When bonds form, sometimes the electrons stay closer to one atom of the molecule. This creates charged areas.
This may result in polar parts of a molecule
Covalent bond shape
Polar covalent bonds have unequal charge between atoms within a molecule because the covalent bond has resulted in electrons closer to one atom
If this does not happen it may be neutral, or non polar
Double bonds prevent rotation, single allow it
Ionic bonds
The more electronegative steals electrons from the donor atom. Then they stay electrostatically attracted to one another. These are often interrupted by water eg NaCl
Polar covalent and hydrogen bonds
Water makes polar covalent bonds within itself.
H+ areas of water are attracted to O- areas of others
This causes HYDROGEN BONDS
Breaking these turns ice to water and water to steam
Hydrocarbons
are composed of hydrogen and carbon
Water is special
as it is a liquid over livable temperatures
H bonds
Hydrophilic/phobic interactions
Phyllic between polar and polar
phobic between non polar and non polar
Means polar molecules are attracted to water and non polar ones are more to each other than water
Lipid bilayer
High heat capacity
Very important
Has the highest heat capacity of a liquid on earth
Takes a lot of energy to heat it
Takes a lot of energy to vaporize it
Stays as a liquid over a large range of temperatures
Great solvent
Water is a great solvent
Ions unstably bound by ionic bonds will be split up and form stable hydrated states with water molecules surrounding it
Water is cohesive and adhesive
Objects can float
Capillary action allows plants to draw water from the soil to leaves
Water as a heat sink
Oceans absorb all heat
Controls climate of earth
getting hotter
there is a limit to how much energy will be absorbed Water will expand as H bonds break and melt from ice
There will be less oxygen dissolved in water. More energy needed to maintain temp. Mess up habitats and food chains
