Chapter 3: Carbon and the Molecular Diversity of Life – Study Notes

🧬 BIOLOGY MACROMOLECULES — FULL STUDY NOTES (LO 14–25)

🔵 LO 14 — Carbon & Molecular Diversity

Carbon is the backbone of life because it has 4 valence electrons, allowing it to form 4 covalent bonds.

Carbon forms:

• long chains

• branched structures

• rings

• double bonds

WHY THIS MATTERS:

These structures create molecular diversity, allowing all biological macromolecules to exist.

KEY IDEA:

Structure determines function

Organic molecules contain carbon and hydrogen.

🔵 LO 15 — Dehydration vs Hydrolysis

Dehydration reaction

• builds polymers

• removes water

• forms covalent bonds

Hydrolysis

• breaks polymers

• adds water

• used in digestion

KEY CONNECTION:

• dehydration = build

• hydrolysis = break

🔵 LO 16 — Macromolecules Overview (STRUCTURE → FUNCTION)

Carbohydrates

• Monomer: monosaccharides (glucose)

• Bonds: glycosidic

• Elements: C, H, O

• Function: quick energy + structure

WHY:

small + soluble → fast energy use

Lipids

• not true polymers

• glycerol + fatty acids

• mostly C and H

• Function: energy storage, membranes, hormones

WHY:

nonpolar → hydrophobic → energy storage efficiency

Proteins

• monomer: amino acids

• bonds: peptide bonds

• elements: C, H, O, N

FUNCTION:

enzymes, structure, transport

WHY:

function depends on 3D shape

Nucleic Acids

Nucleic acids

• monomer: nucleotides

• function: store genetic information (DNA/RNA)

✏️ DRAWING 1 — AMINO ACID

Must label:

• NH₂ (amino group)

• COOH (carboxyl group)

• H

• R group

• central carbon

KEY:

Amino acids join via peptide bonds (dehydration reaction)

🔵 LO 17 — α vs β Glucose

Glucose isomers

• α-glucose: OH down → starch + glycogen

• β-glucose: OH up → cellulose

WHY IMPORTANT:

small structural change → completely different function

✏️ DRAWING 2 — α vs β GLUCOSE

5

Must show:

• ring form

• OH position difference (C1)

• label α and β

🔵 LO 18 — Polysaccharides

• starch → plant energy storage

• glycogen → animal energy storage (highly branched = fast release)

• cellulose → plant structure (β-glucose, straight fibers)

• chitin → fungi + arthropods structure

KEY IDEA:

• storage = branched

• structure = strong fibers

🔵 LO 19 — Lipids

Triglycerides

• glycerol + 3 fatty acids

• energy storage

Phospholipids

Phospholipid

• hydrophilic head

• hydrophobic tails

WHY MEMBRANES FORM:

amphipathic molecules self-assemble in water

Steroids

Steroids

• 4 fused carbon rings

• hormones + membrane stability

✏️ DRAWING 3 — PHOSPHOLIPID

4

Must label:

• hydrophilic head

• hydrophobic tails

🔵 LO 20 — Saturated vs Unsaturated

• saturated: no double bonds → straight → solid

• unsaturated: double bonds → kink → liquid

WHY:

double bonds prevent tight packing

🔵 LO 21 — Amino Acids

Amino acids

Structure:

• amino group (-NH₂)

• carboxyl group (-COOH)

• R group

Peptide bond

• formed by dehydration reaction

🔵 LO 22 — Protein Structure

Protein structure

• primary = sequence

• secondary = α-helix / β-sheet (H bonds)

• tertiary = 3D folding (R interactions)

• quaternary = multiple chains

WHY:

shape determines function

🔵 LO 23 — Denaturation

Protein denaturation

Caused by:

• heat

• pH

• salt

RESULT:

protein unfolds → active site changes → no function

🔵 LO 24 — Nucleotides

Nucleotide

• phosphate

• sugar

• nitrogen base

Bases:

• DNA: A, T, C, G

• RNA: A, U, C, G

✏️ DRAWING 4 — DNA BASE PAIRING

6

Must label:

• A–T

• C–G

• sugar-phosphate backbone

• hydrogen bonds

🔵 LO 25 — DNA vs RNA

DNA RNA

DNA:

• double stranded

• deoxyribose

• stores genetic info

RNA:

• single stranded

• ribose

• helps make proteins