lecture notes based on the BIOL111 Molecules of Life Module
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Course
BIOL111: Molecules Of Life (BIOL111)
Institution
Lancaster University (LU)
Book
Biology
Lecture notes based on Molecules of Life 2022/23. 16 pages covering all 12 lectures. Basic information (e.g. GCSE/A-Level knowledge) may be skimmed over or not included. Specific information (e.g. examples of proteins or amino acids) are mentioned as they have been included in end of module tests, ...
,L1 – Energy, Elements, Atoms & Bonding
ENERGY
Energy Types:
1. Kinetic: energy gained or used due to motion
2. Potential: energy an object posses due to its position
3. Metabolic: energy gained or used in cells
a. Anabolism: constructive = complex molecules -> simple molecules + energy
b. Catabolism: destructive = simple molecules + energy -> complex molecules
ELEMENTS
Element: cannot be broken down by chemical reactions
• 92 naturally occurring elements
• Chemical symbols from Latin + German
• 25/92 elements essential to life:
o O, C, N, H = 96% living matter
o P (DNA backbone, cell membrane), S (cysteine + methionine), Ca (teeth, bones,
contraction), K (transporters, nerves)
• Trace elements: required in small quantities
o Fe = O2 transport
o I = produces thyroid hormones
ATOMS
Atom: smallest unit of matter which still retains all properties of an element
Relative mass: p + n = 1Da, e = 1/1840Da
Isotope: same atomic number, different atomic mass
Radioactive isotope: decays spontaneously
Matter: anything that takes up space + has a mass
Orbitals:
Atomic orbital: space around nucleus where electrons are present
• Each orbital contains <= 2 electrons
• Filler orbitals = more stable
1. 1S = 2e
2. 2S = 2e
3. 2P = 6e = 3x 2e
4. 3S, 3P, 3D, 4S, 4P…. 7S, 7P
1 = closer to nucleus
2 = further away from nucleus
Valence shell: outermost orbital
• Bonds: unpaired electrons in valence shell interacts with other unpaired electrons
• Lone pairs: electrons not involved in covalent bond
• Electronegativity: tendency of an atom to attract electrons
BONDING
Compound: substance consisting of 2 or more elements in a fixed ratio
➔ Has different chemical properties to elements
Bonding type:
1. Covalent bond: 2 atoms share electrons
, • Strong = 400kJ/mole
• O-H (440kJ) > C-C (350kJ)
a. Non-polar: equal sharing e.g. H2
b. Polar: unequal sharing e.g. O-H in H2O
2. Hydrogen bond: H atom bonds to electronegative atom
• Individually weak = 10-20kJ/mole
• e.g. H bonds between bases in DNA
3. Ionic bond: 2 atoms with different attraction for valence electrons bond
• Exchange electrons
• Form crystal
• Very strong = 700Kj/mole
4. Van der Waal forces: interaction between electron clouds
• Individually very weak = 0.5kJ/mole
• Very short range
L2 – Water, Concentration, Equilibrium, pH, Constants
WATER
• O more electronegative than H
• O-H = polar covalent bond 440kJ/mole
• Lone pairs in O = slight negative charge
• H nuclei = slight positive charge
Orbitals in Water:
• 2x unpaired electrons in 1s shells of H go to O’s unpaired electrons in 2x 2p shells -> 3 pairs of
electrons in 2p shells in O
• O2 = 1s, 2s, 2p, 2p, 2p -> 1s, Sp3
• 4 equivalent orbitals in balloon shape
Hybrid Orbital:
o Sp3 = (1) 2s orbital + (3) 2p orbitals
o Energetically favourable to have Sp3 instead of 2s, 2p, 2p, 2p
• Sp3 requires less energy than (3) 2p’s + more energy than 2s, 1s
Structure of Water:
• Tetrahedral arrangement = 109.5
• Lone pairs repel each other more than bonding pairs = 109.5 -> 104.5 between 2 H atoms
Delta Charges:
• 1 H2O molecules can bind to 4 other H2O molecules due to 2 delta +ve and 2 delta – ve
Hydrogen Bonds in Water:
1. High boiling point
2. Cohesive > Adhesive = Stick together more than other molecules
3. High heat of vaporisation:
• Evaporative cooling: hotter molecules on top layer evaporate -> lowers temp of
remaining molecules
Heat of Vaporization: energy to change state of 1g of water at 25C
4. Ice less dense than water:
• Ice has more gaps in structure + more H bonds than water
• Ice floats above water bodies -> ice insulates water
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