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Unit 1 • Chemistry of Life

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Dashboard Unit 2 • Cell Structure & Membranes →

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Do first

Buffer logic: know how weak acid/base pairs resist pH swings; apply Henderson–Hasselbalch mentally.

Sketch dehydration vs hydrolysis arrows; connect to energy trade-offs.

Water properties (cohesion, adhesion, high specific heat) as a recurring MCQ anchor.

Functional groups: memorize polarity/charge and the shape cues (amine + carboxyl → amino acid behavior).

Bond Strengths

Hydrogen

Weak attraction between partial charges (e.g., between water molecules or DNA bases); easily broken for flexibility.

Ionic

Electrostatic attraction between charged ions; strong in dry environments, weaker in aqueous cytosol.

Covalent

Shared electron pair; strongest in cells and forms backbones of macromolecules (peptide, glycosidic, phosphodiester).

Van der Waals

Transient interactions between fluctuating charges; stabilize hydrophobic packing (lipid tails, protein cores).

Macromolecules

Carbohydrate

C, H, O

Monosaccharide (CnH2nOn) • Polysaccharides (starch, glycogen, cellulose)

Short-term energy, structure (cellulose), recognition (glycoproteins). Glycosidic bonds via dehydration; hydrolysis releases energy.

Lipid

C, H, O

No single monomer; fatty acids + glycerol backbone • Triglycerides, phospholipids, steroids, waxes

Long-term energy storage, membranes (amphipathic bilayers), hormones, insulation. Hydrophobic interactions drive bilayer formation.

Protein

C, H, O, N (±S)

Amino acid (central C, amine, carboxyl, R-group) • Polypeptides (enzymes, motors, receptors)

Catalysis, signaling, transport, structure, motion. Shape depends on primary sequence + H-bonds/ionic/hydrophobic forces.

Nucleic Acid

C, H, O, N, P

Nucleotide (sugar, phosphate, N-base) • DNA, RNA

Genetic storage, information transfer, catalysis (ribozyme), short-term energy (ATP). Phosphodiester bonds form sugar-phosphate backbone.

pH + Buffers

pH = -log[H⁺]; pOH = -log[OH⁻]; pH + pOH = 14.

Buffers = weak acid/base + conjugate pair. Greatest buffering near pKa; resists pH change on small acid/base additions.

Each pH step = 10× [H⁺] change; practice converting to concentration quickly.

Experimental Design

Positive control

Confirms the system can show an effect (validates detection works).

Negative control

Baseline with no treatment; expects no effect to reveal background noise.

Independent variable

Factor intentionally changed between groups.

Dependent variable

Measured response that depends on the independent variable.

Control variables

Kept constant to isolate the tested factor.

Standard deviation

Spread around mean; bigger SD = more variability.

SEM / SEM×2

Mean accuracy; SEM×2 approximates 95% CI. Non-overlap suggests real difference.

Error bars

Usually SEM or CI; overlapping bars hint at non-significant difference.

Isomers

Structural

Different covalent arrangement (e.g., chain vs branched); different properties.

Cis-trans

Same covalent bonds, differ around double bond (cis = same side, trans = opposite).

Enantiomer

Mirror images; not superimposable (L vs D amino acids).