lesson 1: EN, IMF's, H2O Flashcards
biochem big idea
understand how the unique structures and properties (functional groups, EN, polarity) of critical biological molecules impact their functions in the body
chem review
- rules of fundamental chem control cell activities
- structure determines function
- H, O, C, N make up 96% of weight in organism
- ionic vs covalent bonds
- properties determined by individual atoms
covalent bonds (intramolecular bonds)
- form when atoms share one or more pairs of valence electrons
- the strength of a covalent bond depends on the EN of the atoms involved
electronegativity (EN)
- the measure of an atom’s attraction to shared valence electrons
- the strength with which an element will attract a shared pair of valence electrons (e-) in a bond
- when EN is high (low), the element has a high (low) tendency to attract electrons in a bond and vice versa
- in covalent bonds, elements with high EN develop a slightly negative charge and elements with low EN develop a slightly positive charge
polar molecule
- molecules that develop a slightly negative or slightly positive charge
- unequal sharing of electrons between 2 atoms
non-polar covalent
difference in EN: 0-0.39
polar-covalent
difference in EN: 0.4-1.7
ionic
difference in EN: 1.71-4
a molecule’s biological function is determined by the 3 following factors:
- overall molecular shape
- overall molecular polarity
- types of bonds between atoms
intramolecular forces
- forces that hold atoms together within a molecule
- forces that exist within a molecule
- ie. ionic and covalent bonds
intermolecular forces (vanderwaal forces)
- can form between molecules
- forces of attraction between molecules
- there are 3 types: london forces, dipole dipole forces and hydrogen bonds
london forces
- weakest of the three
- exist between all atoms and molecules (including non polar ones)
dipole dipole forces
- stronger than london forces
- formed between the S+ and S- sides of polar molecules
hydrogen bonds
- a very strong dipole dipole force will form between H atoms and neighbouring N, O, or F atoms
- very important biologically (water, DNA, proteins)
- strongest force
- individually weak compared to covalent and ionic bonds but significant in large #’s
- crucial to the function of cells and other cellular processes
characteristics of water
- colourless, tasteless, odourless
- a polar molecule
- water has a very high specific heat capacity (4.18J/g *C) (result of hydrogen bonds, can absorb a lot of heat energy with minimal temp change, a lot of energy is needed to convert water from a liquid to a gas)
- ice is less dense than liquid water due to crystal formation so ice floats on water due to fewer/slower formations of hydrogen bonds
- water is densest at 4 degrees Celsius
cohesion
- water will form hydrogen bonds with other water molecules
- one bond is very weak but thousands of bonds become strong
adhesion
water molecules will also form hydrogen bonds with other polar molecules
why is water important?
- for temp regulation, moisture (eyes, lungs), lubrication (joints, saliva), chemical reactions, diffusion/osmosis and as a solvent
- properties of water (polar) drive the fundamental reactions to support life
could life exist without polar bonds?
no because they are what hold molecules together such as water which are essential to life
