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Unit 1 · Chemistry of Life Flashcards Cheat Sheet Essentials Visual Review MC Practice FRQ Practice

AP Biology Unit 1 Visual Review

A topic-by-topic visual walkthrough of Chemistry of Life — water and hydrogen bonding, the elements of life, and the four macromolecules that build every cell.

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TOPIC 1.1 Water Structure & Hydrogen Bonding O δ− H H δ+ δ+ Bent shape · ~104.5° · a polar molecule O H-bond Polarity is the root cause Oxygen is more electronegative, so it pulls the shared electrons closer — the O end is slightly negative (δ−) and each H end is slightly positive (δ+). Hydrogen bonds form between molecules The δ+ hydrogen of one water is attracted to the δ− oxygen of another. Weak alone, but powerful in huge numbers. Emergent properties of water • Cohesion & surface tension — water sticks to itself • Adhesion — sticks to other surfaces (capillary action) • High specific heat — resists temperature change • Universal solvent · ice floats (less dense than liquid) Evaporative cooling also comes from breaking H-bonds. Every life-supporting property of water traces back to one thing: its polarity and the hydrogen bonds it makes. The Review Hub · AP Biology Unit 1 TOPIC 1.2 Elements of Life THE SIX MOST COMMON ELEMENTS — "CHNOPS" C Carbon H Hydrogen N Nitrogen O Oxygen P Phosphorus S Sulfur Carbon is the backbone of life Carbon has 4 valence electrons, so it forms 4 stable covalent bonds — building long chains, branches, and rings. This versatility makes complex molecules possible. Functional groups add chemical behavior Groups attached to the carbon skeleton give molecules specific properties: hydroxyl (—OH), carboxyl (—COOH), amino (—NH₂), and phosphate groups are the key ones. Trace elements matter too Some elements are needed only in tiny amounts but are still essential — for example iron (Fe) in hemoglobin, and calcium, potassium, and sodium for nerve signaling and structure. Missing a trace element still disrupts function. A handful of elements — mostly C, H, N, and O — make up about 96% of all living matter. The Review Hub · AP Biology Unit 1 TOPIC 1.3 Introduction to Macromolecules mono mono → dehydration − H₂O mono mono covalent bond → hydrolysis + H₂O mono mono Monomers link into polymers — and back. Dehydration synthesis REMOVES a water to bond monomers · Hydrolysis ADDS a water to break them apart Carbohydrates monomer: monosaccharide energy & structure Lipids not true polymers glycerol + fatty acids energy storage & membranes Proteins monomer: amino acid nearly every cellular job Nucleic acids monomer: nucleotide store & transmit information Large biological molecules are built by dehydration synthesis and broken down by hydrolysis. The Review Hub · AP Biology Unit 1 TOPIC 1.4 Carbohydrates Monosaccharides — the monomers Simple sugars like glucose, fructose, and galactose. Glucose is C₆H₁₂O₆ — the cell's main quick fuel. General formula (CH₂O)ₙ — a 1:2:1 ratio of carbon, hydrogen, and oxygen. Disaccharides — two joined by a glycosidic bond Maltose (glucose+glucose), sucrose (glucose+fructose), lactose (glucose+galactose). The bond forms by dehydration synthesis — one water molecule is released. Polysaccharides — many monomers, two jobs Energy storage (α-glucose, easy to break down) • Starch — how plants store glucose (amylose & amylopectin) • Glycogen — how animals store glucose (highly branched, in liver & muscle) Structure (β-glucose, strong & rigid) • Cellulose — plant cell walls (indigestible fiber) • Chitin — fungal walls & arthropod exoskeletons The α vs β linkage between glucose units is what decides whether a polymer stores energy or provides structure. Same glucose monomer — the type of bond determines storage (starch/glycogen) vs. structure (cellulose). The Review Hub · AP Biology Unit 1 TOPIC 1.5 Lipids Hydrophilic head (phosphate) "water-loving" — polar, faces water Hydrophobic tails (fatty acids) "water-fearing" — nonpolar, hide from water amphipathic In water, phospholipids self- assemble into a bilayer — the basis of every cell membrane. Triglycerides (fats) 1 glycerol + 3 fatty acids. Long-term energy storage — more energy per gram than carbohydrates. Also insulation & cushioning. Saturated vs. unsaturated Saturated: no C=C double bonds, straight, solid (animal). Unsaturated: double bonds create kinks, liquid (plant oils). Kinks stop tight packing. Other key lipids Phospholipids — build membranes (the amphipathic bilayer above). Steroids — four fused rings; cholesterol & hormones. All lipids are nonpolar & hydrophobic. Lipids are defined by being nonpolar and hydrophobic — that's why they store energy and form membranes. The Review Hub · AP Biology Unit 1 TOPIC 1.6 Nucleic Acids DNA — ANTIPARALLEL DOUBLE STRAND 5' 3' 3' 5' AT GC CG TA AT base pairs held by hydrogen bonds The nucleotide monomer Three parts: a phosphate group, a five-carbon sugar, and a nitrogenous base. Nucleotides link into a chain with a sugar–phosphate backbone, joined 5' to 3'. Complementary base pairing Purines (A, G) pair with pyrimidines (C, T/U). A pairs with T (2 H-bonds); G pairs with C (3 H-bonds). In RNA, uracil (U) replaces thymine, so A pairs with U. DNA vs. RNA DNA: double-stranded, deoxyribose sugar, bases A/T/G/C. RNA: single-stranded, ribose sugar, bases A/U/G/C. Antiparallel strands run in opposite 5'→3' directions. Nucleic acids store and transmit genetic information — the base sequence IS the code (A–T, G–C). The Review Hub · AP Biology Unit 1 TOPIC 1.7 Proteins THE AMINO ACID MONOMER C amino carboxyl variable R group decides properties — H — Peptide bonds link amino acids Formed by dehydration synthesis between the carboxyl of one and the amino of the next. 20 different R groups. FOUR LEVELS OF STRUCTURE 1° Primary The exact sequence of amino acids, set by the gene (DNA). 2° Secondary α-helices & β-pleated sheets from backbone hydrogen bonds. 3° Tertiary Overall 3-D fold from R-group interactions (disulfide, ionic…). 4° Quaternary Two or more folded subunits together (e.g., hemoglobin). Structure determines function — and it's fragile A protein's shape lets it do its job (enzyme, transport, structure, defense, signaling). Heat or extreme pH can denature a protein — it unfolds and loses function, even though the primary sequence stays intact. The amino acid sequence folds a protein into a precise shape — and shape determines function. The Review Hub · AP Biology Unit 1
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Spend 30 seconds per slide before clicking next. Look at the diagram, then ask yourself: "Could I draw this from memory and explain it?"

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This is great for review the night before the exam — fast, visual, and covers everything you need to remember about Unit 1's chemistry.