1.6 - Proteins Flashcards
(28 cards)
What is an amino acid?
Amino acids arc the basic monomer units which combine to make up a polymer called a polypeptide
What can polypeptides be combined to form?
Polypeptides can be combined to form proteins.
How many naturally occurring amino acids are there?
There are 20 amino acids that occur in all living organisms. - evidence for evolution
What is the general structure of an amino acid?
H H
\ /
N
|
R - C - H
|
O = C - O
|
HWhat is an amino group?
amino group (-NH ) - a basic group from which the amino part of 2 the name amino acid is derived
What is a carboxyl group?
carboxyl group (-COOH) - an acidic group which gives the amino acid the acid part of its name
What is an R - Group?
a variety of different chemical groups. Each amino acid has a different R group. These 20 naturally occurring amino acids differ only in their R (side) group.
What do two amino acid monomers join to form?
A dipeptide.
How are the two amino acid monomers joined?
condensation reaction. The water
is made by combining an - OH from the carboxyl group of one amino acid with an - H from the amino group of another amino acid.
What is the bond that links two amino acids?
peptide bonds between the carbon of one amino acid and the nitrogen of another.
What is the process in which many amino acids are joined together?
Polymerisation = Polypeptide.
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain forms the primary structure of any protein.
What determines the sequence of amino acids in the primary structure of a protein?
DNA
What is the secondary structure of a protein?
Hydrogen bonds are formed and this causes the long polypeptide chain to be twisted into a 3-D shape - ⍺-helix or β-pleated sheet.
What is the tertiary structure of proteins?
The ⍺-helices of secondary structure can be twisted and folded even more to give a complex and specific 3-D structure.
What type of bonds help maintain the Tertiary Structure of a protein?
- Disulfide Bridges
- Ionic Bonds
- Hydrogen Bonds
What is a Disulfide Bridge?
A disulfide bridge is a strong bond that can form between two cysteines. The strength of disulfide bridges helps stabilize a protein. Disulfide bridges are especially common in proteins that are secreted from cells.
What is the Quarternary Structure of a protein?
A complex molecule that contains more than one polypeptide chain that are linked in various ways.There may also be non-protein (prosthetic) groups associated with
the molecules such as the iron-containing haem group in haemoglobin.
What determines the function of a protein?
The sequence of amino acids determines the 3-D structure of the protein. The 3-D shape then determines the function of the protein.
What is the test for Proteins?
The most reliable protein test is the Biuret test, which detects peptide
bonds.
Outline the steps of the Biruet Test.
- Place a sample of the solution w be tested in a test tube and add an
equal volume of sodium hydroxide solution at room temperature. - Add a few drops of very dilute (0.05%) copper(II) sulfate solution
and mix gently. - A purple coloration indicates the presence of peptide bonds and
hence a protein. If no protein is present, the solution remains blue.
You can simply refer to adding Biuret reagent to test for protein.
What are the two types of proteins?
- Fibrous
2. Globular
What are Fibrous Proteins?
Fibrous proteins, such as collagen, have structural functions. Fibrous proteins form long chains which run parallel to one another. These chains are linked by cross-bridges and so form very stable molecules.
What are Globular Proteins?
Globular proteins, such as enzymes and haemoglobin, carry out metabolic functions.
