3.6b - Structure of Proteins Flashcards
What is a primary protein structure?
- Unique order in which amino acids are sequenced
- Order is directed by cellular genetic code (DNA)
- Bond - peptide
What is the secondary protein structure?
- Oxygen, hydrogen and nitrogen of the amino acids interact
- R-groups don’t interact yet
- The amino acids fold and coil into 2 shapes
- alpha helix - polypeptide chain fold to a helical shape
- beta pleated sheet - polypeptide chain arrange in parallell lines like a sheet of paper
- Hydrogen bonds hold the folding and coiling in place
What is the tertiary sequence?
- The folding of the protein into its final shape.
- This is where proteins of the secondary structure coil and fold.
- R-groups are brought closer together allowing for R-group interactions.
State the different R-group interactions.
Ionic bonding
Hydrogen bonds
Hydrophobic/hydrophilic interactions
Disulfide bridges
Describe the different R-group interactions
Ionic Bonding
- Between positive and negatively charged R groups (stronger than H-bonds)
Disulphide Bridges
- Strongest bond
- Covalent bonds between the R-groups containing sulfur atoms
Hydrogen Bonds
- Weakest bond between polar R-groups
Hydrophilic/Hydrophobic Interactions
- Proteins are assembled in the aqueous cytoplasm
- Hydrophobic R-groups assemble on the inside
- Hydrophilic R-groups assemble on the outside
- In a water soluble molecule that is.
What is a subunit?
Individual proteins (separate polypeptide chains) of the tertiary structure.
What i the quarternary structure?
Interactions between separate subunits
The interactions are the same as in tertiary sequences but they are between the protein molecules as opposed to within
Subunits can be identical or different
How do peptides break down?
The enzyme protease catalyses the reverse reaction (hydrolysis) using water to reform the separate aminoa acids with their amine and carboxyl groups.
