Biology by Bradford
Biology by Bradford · AP Biology · Unit 1.2

Macromolecules & Carbohydrates

Every polymer in this course is built by the same reaction and broken by its reverse. Then one flipped hydroxyl decides whether the product feeds you or holds a tree up.

AP · U1.2CED 1.3–1.4Interactive lesson
Concept 01 · CED 1.3

One reaction, four families

Biology builds big molecules the boring way: the same reaction, over and over, with a different subunit each time. Learn it once and three of the four families come free.

Subunit

Monomer

Small and soluble. Monosaccharide, amino acid, nucleotide — the repeating unit that gives the polymer its name.

Build

Condensation

A covalent bond forms and a water molecule leaves. Anabolic, so it needs energy and an enzyme.

Break

Hydrolysis

Water is added across the bond and the chain splits. This is what digestion actually is.

CARBOHYDRATEmonosaccharideGLYCOSIDICPROTEINamino acidPEPTIDENUCLEIC ACIDnucleotidePHOSPHODIESTERLIPIDno true monomerESTERTHREE ARE TRUE POLYMERS · ONE IS NOT
Three of the four macromolecule families are genuine polymers — repeating identical subunits joined by a named bond. Lipids are assembled by the same condensation reaction but from unlike parts, one glycerol and three fatty acids, so they are not classed as polymers.
Diagram · interactive

Inside a glucose ring

Tap each part. Carbon 1 is the one to watch — it decides whether this molecule ends up as starch or as wood.

O123456OHC1OHC4CH₂OHC6OHOHC₆H₁₂O₆TAP A PARTα-GLUCOSE · OH BELOW THE RING AT C1
Diagram

Start at carbon 1

Tap the ring, carbon 1, carbon 4, the CH₂OH branch, the hydroxyl groups, or the molecular formula.

Signature interactive · CED 1.3

Build it, then break it

Step through the reaction that assembles every polymer you will meet this year — then run it in reverse.

Concept 02 · CED 1.4

Structure dictates function

Three polysaccharides, one monomer, three completely different jobs. The difference is entirely in the bonds.

Plant store

Starch

Amylose coils; amylopectin branches. Compact, insoluble, and hydrolysed back to glucose on demand.

Animal store

Glycogen

The same α-glucose, branched more heavily still. More free ends means faster release.

Plant structure

Cellulose

β-glucose forces straight chains that hydrogen-bond into cables. Strength, not storage.

Concept map · interactive

How it all hangs together

Tap a node to light up its connections. The pink dashed link is the one examiners keep coming back to.

join to formbuilt bybroken byopposite reactionslinks themsame formula1,4 and 1,6β-1,4 onlyno human enzyme fitsMonomersPolymersCondensationHydrolysisα-glucoseβ-glucoseStarch & glycogenCellulose
Concept map

Tap a node

Notice that α-glucose and β-glucose sit side by side: identical formula, opposite destinies.

Retrieval · drag and drop

Fill the gaps

Drag a term into a gap, or tap a term and then tap a gap. Two terms belong nowhere.

monomerscondensationhydrolysisglycosidicα-glucoseβ-glucosebranchedmicrofibrils peptide bondhydrophobic

Large biological molecules are polymers assembled from repeating . Joining two of them releases a water molecule in a reaction, and adding water to split the bond again is . In carbohydrates the covalent bond formed is called a bond. Starch and glycogen are polymers of , whereas cellulose is a polymer of . Glycogen is far more than amylose, so enzymes have many more free ends to work on. In cellulose, straight chains hydrogen-bond side by side into that give plant cell walls their strength.

Check yourself · AP-style

Six questions

Single best answer. You get the reasoning as soon as you commit.