2.1 proteins Flashcards
(40 cards)
What is a protein?
A macromolecule composed of amino acids joined by peptide bonds, folded into a 3D structure.
What determines a protein’s function?
Its 3D structure (tertiary/quaternary structure).
Name at least five protein functions.
Enzymes, receptors, structural proteins, adaptor proteins, hormones, motor proteins, antibodies, transport proteins.
Why can’t proteins be seen directly under a light microscope?
They are smaller (~3–6 nm) than the diffraction limit of light (~200 nm).
What method is commonly used to determine protein structure?
X-ray crystallography, producing electron density maps.
What does the electron density map allow?
Modeling of the protein’s atomic structure.
What are the common ways to represent protein structure?
Ball-and-stick (atoms and bonds), surface (shape), cartoon (secondary structure).
What colours represent oxygen and nitrogen in models?
Oxygen = red, Nitrogen = blue.
What are the four levels of protein structure?
Primary, secondary, tertiary, quaternary.
What is the primary structure?
The linear amino acid sequence.
What is the secondary structure?
Local structures like alpha helices and beta sheets stabilized by H-bonds.
What is the tertiary structure?
The 3D folding of the polypeptide chain.
What is the quaternary structure?
The association of multiple folded polypeptide chains.
What is the general structure of an amino acid?
Alpha carbon bonded to a carboxyl group, amino group, hydrogen, and R-group (side chain).
What forms a peptide bond?
A dehydration reaction between the carboxyl and amino groups of two amino acids.
What gives each amino acid its unique properties?
Its side chain (R-group).
How do amino acid side chains influence protein folding?
Through electrostatic interactions, hydrophobic packing, steric hindrance, and H-bonding.
What determines whether an amino acid is hydrophobic or hydrophilic?
Its chemical properties—e.g., polarity, charge.
What stabilizes secondary structures?
Hydrogen bonds between the peptide backbone.
Which amino acids favour alpha helices?
M, A, L, E, K, N.
Which amino acids favour beta sheets?
V, I, Y, C.
What is a dipole moment in an alpha helix?
A separation of charges along the helix axis that can stabilize negative charges.
What are parallel and antiparallel beta sheets?
Parallel: strands run in the same direction; Antiparallel: strands run opposite.
What is a motif?
A specific combination of secondary structures like beta-hairpins or helix-loop-helix.
