Proteins Flashcards
What are the monomers of proteins?
Amino Acids
What are the polymers that are combined to make proteins?
Polypeptides
How are dipeptides formed?
When two amino acids join together.
When are polypeptides formed?
When more than two amino acids join together.
What is the general structure of amino acids?
- Amino Group ( -NH2 )
- Carboxyl Group ( - COOH )
- Hydrogen Group ( - H )
- R Group, this is the variable side group, it can be one of 20 naturally occurring amino acids.
What reaction joins together amino acids?
Condensation reactions.
What bond is formed between amino acids?
Peptide Bonds
How are polypeptides formed?
- Amino acids are linked together by condensation reactions to form polypeptides.
- A molecule of water is released during the reaction.
How is the water molecule formed in the formation of polypeptides?
• -OH from the carboxyl Group of the first amino acid.
• -H from the amino group of the second amino acid.
These combine to form water.
Where does the peptide bond link two amino acids?
Between:
• Carbon of the first amino acid.
• Nitrogen of the second amino acid.
What reaction breaks down polypeptides?
Hydrolysis.
What is polymerisation?
Polymerisation is the process of reacting monomer molecules together in a chemical reaction to form polymer chains, in the case of protein, a polypeptide.
What are the four structures of a protein?
- Primary
- Secondary
- Tertiary
- Quaternary
What is the primary structure?
Sequence of amino acids in a polypeptide chain.
What is the primary structure determined by?
DNA
What does the primary structure determine?
Determines the shape of the protein, and therefore also determines its function.
What is the secondary structure?
- Hydrogen Bonds form in the polypeptide.
- Formation of bonds causes the long polypeptide chain to be twisted into a 3-D shape structure, which can be either: Alpha Helix or Beta Pleated Sheet.
What are the two structure that the secondary structure can twist into?
- Alpha Helix
* Beta Pleated Sheet
What bonds form between the amino acids in the polypeptide chain ( Secondary Structure )?
• Hydrogen bonds
How do the hydorgen bonds form?
- -NH and -C=O Groups on either side of every peptide bond.
* Due to the charges of the groups, they will form ionic bonds.
What is the charge of the -NH group?
H of -NH group has an overall positive charge
What is the charge of the -C=O group?
O of the group has an overall negative charge.
What occurs in the tertiary structure?
Alpha helix of the secondary structure. is twisted and folded even further to provide a more complex 3-D structure.
What are the bonds in the tertiary structure?
- Disulfide Bridges ( Very strong, not easily broken )
- Ionic Bonds ( Weaker than bridges, but broken by changes in pH )
- Hydrogen Bonds ( Weak but numerous )
( Tertiary Structure ) How do disulfide bridges form?
• When two molecules of the cysteine group come close, the sulfur atom i one cysteine bonds to the sulfur atom in the other.
( Tertiary Structure ) How do Ionic bonds form?
Formed between carboxyl and amino groups, that are not involved in forming peptide bonds.
What is the Quaternary Structure?
This structure is the way the polypeptide chains are assembled together, this applies to polypeptide chains with multiple polypeptides
What is the test for proteins?
Biuret Test:
• Place a sample of the solution into a test tube, and add an equal volume of sodium hydroxide solution at room temperature.
• Add a few drops of dilute copper ( II ) sulphate solution and mix.
• A purple colour indicates the presence of peptide bonds, and therefore indicates the presence of a protein.
• If it remains blue, there is no protein present.
What are some functions of proteins?
- Enzymes
- Antibodies
- Transport Proteins
- Structural Proteins.
What are structural proteins?
- They are physically strong.
* Consist of long polypeptide chains parallel to each other.
What is an example of transport proteins?
- Channel proteins in cell membranes.
- They contain hydrophobic and hydrophillic amino acids, which cause the protein to fold up and form a channel.
- These proteins transport molecules and ions across membranes.
What are antibodies?
- Proteins involved in the immune response.
* Consist of two light and two heavy polypeptide chains bonded together.
