Insulin's sequence, helices, fold and zinc hexamer are drawn by bond type in this SC335 Unit 4 protein structure diagram, which ends on why the monomer is the active form. Searches like "sc 335 unit 4 assignment example", "sc335 unit 4 sample" and "sc335 unit 4 example" land here.
What a finished SC335 Unit 4 protein structure diagram looks like
Two pages of figure and two of annotation. Panel one gives the primary structure: the A chain of 21 residues and the B chain of 30, with three disulfide bonds drawn as bridges, two joining the chains at A7 to B7 and A20 to B19, one inside the A chain from A6 to A11. Panel two marks secondary structure: two short helices in the A chain, a central helix running from B9 to B19, and an extended strand near the B chain's end. Panel three shows the folded monomer with nonpolar side chains packed inward. Panel four draws the dimer, joined by paired strands at the B chain ends, and the hexamer, three dimers around two zinc ions held by histidine B10. Annotation lists each level's bonds, and a proinsulin inset shows the C-peptide removed.
How a SC335 Unit 4 example is structured
Each panel answers one question, which bonds hold this level, and the annotation keeps covalent and noncovalent bonds in separate lists so the two kinds are never blurred. Disulfides are placed deliberately: drawn at the primary level because they are covalent links fixed by the sequence, and discussed again at the tertiary level because they lock the fold. The diagram states its choice to treat the A and B chains as one monomer, since both come from a single proinsulin chain, while noting that some textbooks count them as quaternary. Quaternary structure is reserved for the dimer and hexamer, and the annotation explains that these assemblies protect insulin in storage granules and vials but must dissociate in the blood. A closing note connects that point to rapid-acting analogs, whose altered B chain ends pair less readily, without discussing any dosing.
Bond lists split by type
Covalent peptide and disulfide bonds sit in one column and hydrogen bonds, hydrophobic packing, ionic contacts and metal coordination in another, so no level's support is described vaguely.
Disulfides placed twice, on purpose
The three bridges appear on the primary panel as covalent features of the sequence and return in the tertiary annotation as the links that hold the fold together.
A stated choice about chains
Treating the A and B chains as one monomer is explained through proinsulin, with a sentence acknowledging textbooks that call the two-chain pair quaternary instead.
Zinc at the center
Two zinc ions coordinated by histidine B10 hold three dimers together, and the diagram labels that coordination as the bond class unique to the fourth panel.
An active form that comes apart
The monomer, not the hexamer, binds the receptor, so the diagram ends by showing assembly as storage and linking that to analogs designed to separate faster.
Where marks go in SC335 Unit 4
Levels labeled correctly but with no bonds named give up most of the credit a structure diagram carries, since the prompt asks what holds each level, not merely what it looks like. Disulfide bonds described as hydrogen bonds, or placed only in quaternary structure because they join two chains, draw accuracy comments wherever they appear. Secondary structure drawn with side-chain interactions instead of backbone hydrogen bonds misplaces the defining feature. Diagrams that present the hexamer as insulin's working form reverse the physiology. Panels contradicted by the annotation, a disulfide drawn at A7 to B7 and described elsewhere as A6 to B6, are treated as content errors rather than slips. Dosing remarks about analogs stray from the unit, and missing residue numbers take smaller amounts.
Get a SC335 Unit 4 example written to your instructions
Name the protein your SC335 Unit 4 prompt assigns, or say it is a free choice, and include the rubric plus any drawing format requirements. A free first custom diagram follows in 24-48h, drawn to those requirements, with every structural level annotated by the bonds that hold it.
SC335 Unit 4 questions, answered
Are disulfide bonds part of primary or tertiary structure?
Textbooks differ. Because disulfides are covalent and their positions follow from the sequence, some place them with primary structure; because they stabilize the fold, others treat them as tertiary. Either placement can earn full credit if your diagram states the choice and explains it. What costs marks is calling them hydrogen bonds or leaving them out entirely.
Does insulin have quaternary structure?
It depends on what counts as a subunit. The A and B chains come from one precursor chain and function as a single monomer, so many sources reserve quaternary structure for the dimers and zinc hexamers insulin forms in storage. Other textbooks count the two chains as quaternary. Say which view your diagram uses and why, and keep that choice consistent across panels.
Can the diagram be hand drawn?
Most sections accept a neat hand drawing that is scanned clearly, and some prefer it. What matters is accuracy: residues numbered, bonds labeled and panels matching the written annotation. Molecular viewers such as those linked from the Protein Data Bank can help you check a structure, but cite the source of any image you use rather than drawing over it.