General Chemistry
Themes in bio
Evolution: Living organisms are modified descendants of common ancestors and leads to unity/diversity of organisms
Emergence: come out from whole; whole > parts
Levels of organization is hierarchy
Methods of investigating bio: scientific method * Hypothesis: testable explanation for observations based on available evidence (can be falsifiable) * Prediction: expectations from testing hypothesis * Theory: broad explanation with significant support * Law: statement of what always occurs under certain circumstances * Observation -> background -> hypothesis -> prediction -> experiment -> evaluate (ask new questions, repeat/verify experiments, revise predictions)
Basic chemistry
Electrons: 25 of 92 elements essential to life; -1 charge; move rapidly; determine how atom interacts * The further they are from the nucleus, the greater potential energy (usefulness) they have. * When they are excited, they have a lot of potential energy that can be used to do work (such as how photons are involved in producing ATP).
E- shell has e- PE
Valence shell: outermost shell where bonds between e- form
Part of atom (subatomic: proton, neutron, electron)
Formation of molecules * Chemical bonds: how atoms share e-; used to drive changes in bio. mol. -> energy -> change (energy is capacity to cause change) * Molecules: compounds with 2+ atoms like H2O * Emergent properties: compounds have different prop. Than elements (Na+ and Cl- -> NaCl)
Chemical bonds * Electronegativity: affinity for e- (atom attracting e- like O2); bond determined by difference; desire to fill valence * Covalent: sharing e- (
| Strength | Electronegativity | Interaction with water | intra/inter molecular | |
|---|---|---|---|---|
| Covalent (CH4, O2, nonpolar lipids) | Hard to break | <2 close to 0 | Don’t dissolve | Intra |
| Polar (H2O, HF) | Strong | < 2 | dissolve | intra |
| Ionic (NaCl, Na+, Cl-) | Weak | >2 | dissolve | intra |
| Van der Waals (DNA) LDFs, Hydrogen | Attractions between different molecules | H-bonds | Inter |
- Emergent properties of water * H-bonds: water is polar and bonds with other water mol. * Cohesive behavior * When H2O sticks to one another * Adhesion: H2O sticks to other polar things * Surface tension: measure of difficulty to break surface of liquid * Moderates temp * High specific heat: hard to change H2O temperature * High heat of vaporization: hard to change state bc water is stable * Expansion upon freezing * Ice floats: H-bonds more ordered and form air pockets; < dense than H2O (less mol. Compared to equal volume of liquid water) * Versatile as solvent * Hydrophilic: ions/salts/polar; hydrophobic: lipids/nonpolar
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