SONGLyrical DNA
Bond, Fold, Function
A song about how proteins get their shape. The lyrics follow an amino acid from its basic structure and side chain chemistry through peptide bond formation, then up through the primary, secondary, tertiary, and quaternary levels of protein structure. Select any highlighted line to see the biology behind it.
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Interactive lyrics
Lines with a dotted underline and a + marker have an explanation. Select one and the science appears beside the lyrics. Everything else is ordinary lyric text.
Lyrics
One chain!
Four levels!
From amino acids to a protein,
Let's fold!
Verse 1
Different side chains make the molecule unique, all right!
Tiny little differences, but the impact is large!
Pre-Chorus
And the order of the sequence tells the protein where to go!
Chorus
Bond, fold, function, turn the music up!
Bond, fold, function, four levels in the light,
Primary, secondary, move it side to side,
Tertiary, quaternary, now we're unified.
Bond, fold, function, every shape is key,
Post-Chorus
Hey! Alpha helix, twist, twist, twist!
Hey! Beta sheet, pleat, pleat, pleat!
Hey! Side-chain chemistry,
Makes that protein move to the beat!
Verse 2
Backbone atoms interacting, bringing patterns to the chain,
Local folding builds the structure again and again!
Pre-Chorus
The polypeptide folds into a functional design,
Its three-dimensional structure is arriving right on time!
Chorus
Bond, fold, function, turn the music up!
Bond, fold, function, four levels in the light,
Primary, secondary, move it side to side,
Tertiary, quaternary, now we're unified.
Bond, fold, function, every shape is key,
Bridge
Hydrogen bonds help hold the pieces into place.
Build
What comes first?
Primary!
Backbone folds?
Secondary!
One chain, 3D?
Tertiary!
Multiple chains?
Quaternary!
Final Chorus
Bond, fold, function, turn the music up!
Bond, fold, function, four levels in the light,
Primary, secondary, move it side to side,
Tertiary, quaternary, chains are unified.
Bond, fold, function, now you know the key:
Outro
Amino acids, bond!
Polypeptide, fold!
Structure brings the function,
Now let the protein roll!
Concepts covered
General amino acid structureMost amino acids contain a central alpha carbon bonded to a hydrogen, an amino group, a carboxyl group, and a variable R group. The R group distinguishes one amino acid from another.
Amino acid side-chain chemistryR groups differ in polarity, charge, size, and reactivity. These properties determine which interactions each residue can form and strongly influence how a protein folds and functions.
Peptide bond formationA peptide bond links the carboxyl carbon of one amino acid to the amino nitrogen of another. Cells form these covalent bonds during translation, producing a polypeptide with a specific amino acid sequence.
Polymerization into a polypeptideJoining many monomers into one long polymer is polymerization, and each new amino acid is added to the end of the chain by a covalent peptide bond. That bond forms by dehydration synthesis, so the equivalent of one water molecule is lost every time the chain grows.
Structure determines functionA protein's job depends on its folded shape, because that shape sets which molecules it can interact with and how it can act. All four levels of structure contribute, so anything that changes the shape can change or destroy the function.
From linear chain to folded shapeA protein begins as a linear chain of amino acids, and the sequence of that chain determines the overall shape it folds into. Each level of structure, from local backbone folding to the packing of whole subunits, adds to that final three-dimensional form.
Primary protein structurePrimary structure is the linear amino acid sequence. Because the sequence determines the positions of chemically different R groups, changing it can alter folding, stability, and function.
Secondary protein structureHydrogen bonds between peptide-backbone atoms stabilize local patterns such as alpha helices and beta sheets. These interactions involve the backbone rather than the chemical identities of the R groups directly.
R group interactions during foldingAs the chain bends, R groups that sit far apart in the sequence are brought close together and can interact. Whether they attract, repel, or bond depends on their chemical properties, and those interactions set the structure and function of that region.
Tertiary protein structureTertiary structure is the overall three-dimensional shape of one polypeptide. It results from hydrogen bonds, hydrophobic interactions, ionic interactions, and disulfide bridges among parts of the chain.
Disulfide bridges and sulfurA disulfide bridge is a covalent bond between the sulfur-containing side chains of two cysteine residues. Sulfur is one of the elements used to build proteins, and because this link is covalent it holds distant parts of the folded chain firmly together.
Quaternary protein structureQuaternary structure describes how multiple polypeptide subunits assemble into one functional protein complex. Not every protein has this level of structure because some work as a single chain.
