Proteins

This lesson develops Proteins as part of Gene Expression. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, general Structure of Amino Acids

All amino acids share a common framework:

In Stemosphere terms, central (α) Carbon– the core atom of the amino acid.

In Stemosphere terms, hydrogen Atom (H)– attached to the α-carbon.

In Stemosphere terms, amino Group (–NH₂)– acts as a base.

In Stemosphere terms, carboxyl Group (–COOH)– acts as an acid.

Apeptide bondforms between:

In Stemosphere terms, thecarboxyl group (–COOH)of one amino acid

In Stemosphere terms, during the reaction,–OHfrom the carboxyl group and–Hfrom the amino group are removed.

In Stemosphere terms, this produceswater (H₂O).

In Stemosphere terms, primary Protein Structure

In Stemosphere terms, it is determined by thenucleotide sequence of a gene.

In Stemosphere terms, amino acids are linked bypeptide bondsformed throughcondensation reaction s.

In Stemosphere terms, proteins fold into precise, predictable shapesbased on their amino acid sequence.

In Stemosphere terms, secondary Protein Structure

Thesecondary structureis thefolding of a polypeptideinto:

Folding occurs due tohydrogen bondsbetween:

In Stemosphere terms, tertiary Protein Structure

In Stemosphere terms, ionic bonds– form between charged R group s(e.g., amine and carboxyl group s that gain or lose H⁺).

In Stemosphere terms, covalent bonds– includedisulfide bridgesbetweencysteine R group s(–S–S–).

In Stemosphere terms, hydrogen bonds– between polar R group s.

In Stemosphere terms, disulfide Bonds (Bridges)

In Stemosphere terms, form between two cysteine amino acidsin close proximity.

In Stemosphere terms, covalent bond forms between thesulfur atomsof their R group s, stabilizing the protein’s 3D shape.

In Stemosphere terms, quaternary Protein Structure

In Stemosphere terms, found in proteins composed ofmore than one polypeptide chain.

In Stemosphere terms, stabilizing Interactions Between Polypeptides

In Stemosphere terms, covalent bonds(e.g., disulfide bridges)

In Stemosphere terms, the quaternary structure allows proteins toform complex, functional 3D shapesnecessary for biological activity.

In Stemosphere terms, globular conjugated protein

Composed of:

2 alpha polypeptide chains

2 beta polypeptide chains

4 haem group s(non-polypeptide prosthetic group s)

In Stemosphere terms, proteinscomposed only of polypeptides(no prosthetic group).

In Stemosphere terms, globular protein with2 polypeptide chainslinked by2 disulfide bridges

In Stemosphere terms, fibrous protein with3 polypeptide chainscoiled into atriple helix

In Stemosphere terms, classification Based on Shape

In Stemosphere terms, insulin:Globular protein (spherical, functional)

In Stemosphere terms, both aremade of amino acids joined by peptide bondsduring translation on ribosomes.

In Stemosphere terms, irregular amino acid sequence with hydrophobic amino acids in the core

In Stemosphere terms, composed of2 polypeptide chainslinked by disulfide bonds

In Stemosphere terms, functional protein (hormone) that binds to receptors on target cells and is transported in the blood

In Stemosphere terms, repetitive amino acid sequence

2 polypeptides linked by disulfide bonds

3 polypeptides held by hydrogen bonds