Lesson 9.1 - Structure of proteins Flashcards
What elements do all proteins contain?
Hydrogen, Oxygen, Hydrogen, Nitrogen
What are peptides?
Polymers made up of amino acids
What forms a protein?
One or more polypeptides arranged as complex macromolecules.
What results in different amino acids?
The variable R-group.
Conditionally essential amino acids?
6: only needed by infants and growing children
Essential amino acids?
6: Can only be obtained by what we eat
Non-essential amino acids?
5: Can by formed from other amino acids in the body
Synthesis of peptides to form a dipeptide?
- Amino acids join when the amine and carboxylic acid groups connected to the central carbon atoms react.
- R-groups not involved at this point
- Hydrogen in amine group of one amino acid reacts with the hydroxyl group in carboxylic acid group of another amino acid.
- Peptide bond is formed between amino acids and water produced.
When many amino acids join together by peptide bonds?
Polypeptide forms.
What enzyme catalyses protein synthesis?
Peptidyl transferase.
How do long polypeptide chains form proteins?
The different R-groups interact with each other (R-group interactions). Form different types of bonds.
These bonds lead to long chains of amino acids forming complex structures (proteins).
Different R-groups?
Different combinations of R-groups lead to the formation of different proteins.
- Structure of proteins is specific to the function within living organisms.
Primary structure:
Specific sequence in which amino acids are joined in a polypeptide.
What directs the primary structure of proteins?
Directed by information carried within DNA.
Bonds involved in the primary structure?
Peptide bonds
What does primary structure influence?
- How polypeptide folds to give final shape.
What is the secondary structure of proteins?
The oxygen, hydrogen, and nitrogen atoms of the basic, repeating structure of the amino acids interact.
Role of hydrogen bonds in secondary structure of proteins?
Hydrogen bonds may form within the amino acid chain, pulling it into a coil shape called an alpha helix.
OR
Peptide chains can lie parallel to each other, joined by hydrogen bonds, forming sheet-like structures. Pattern formed by individual amino acids appears pleated (beta pleated sheet).
Summary of secondary structure?
Result of hydrogen bonds and forms at regions along long protein molecules. Depends on the amino sequence.
Tertiary structure
Folding of a protein into its final shape. It often includes sections of secondary structure.
How does tertiary structure work?
Coiling or folding of sections of proteins into their secondary structures brings R-groups of different amino acids closer together. Close enough to interact so further folding of these sections will occur.
What different types of interactions occur between R-groups?
- hydrophobic and hydrophilic reactions –> weak interactions between polar and non-polar R-groups.
- Hydrogen bonds –> weakest bonds formed
- Ionic bonds –> stronger than hydrogen bonds and form between oppositely charged R-groups
- Disulfide bonds/bridges - covalent and strongest of the bonds. Only form between R-groups that contain sulphur atoms.
Quaternary structure: result
Association of two or more individual proteins called subunits.
(Same as between tertiary structure). Just between proteins.
What types of subunits interact?
Can be identical or different.
Enzymes:
Consist of 2 identical subunits
Insulin:
Two different subunits
Hydrophobic and hydrophilic interactions:
Proteins are assembled in the aqueous environment of the cytoplasm.
The way proteins fold depends on whether the R-groups are hydrophobic or hydrophilic.
Hydrophobic groups are on the inside of the molecule (shielded from the water in the cytoplasm). Hydrophilic groups are on the outside of the molecule.
Catalyst for the reverse reaction (break down of peptide bonds)?
Proteases
The breaking down of peptide bonds?
Hydrolysis reaction –> water added
Reforms the amine and carboxylic acid groups.
Non-proteins in the quaternary structure?
Prosthetic groups
What is a protein with a prosthetic group called?
Conjugated proteins
