Topic 2:1 - protein structure and function Flashcards
what is a protein?
a type of macromolecule. A polymer made up of many subunits (monomers) called amino acids
what links amino acids together?
peptide bonds
a length of linked amino acids is called:
a polypeptide chain. Some proteins consist of more than one polypeptide chain
what are the two main types of proteins?
- fibrous or structural
- globular
what determines how the polypeptide will fold into its unique 3-dimensional shape and function.
The unique sequence and number of amino acids in each protein determines how the polypeptide will fold into its unique 3-dimensional shape and function.
What are the 4 stages of protein structure?
- primary structure (1°)
- Secondary structure (2°)
- Tertiary structure (3°)
- Quaternary Structure (4°)
Not all proteins have all four stages of structure
describe primary structure
-The linear sequence of the number and type of amino acids joined together in each polypeptide chain is called the 1° structure.
-A small change (one amino acid absent or replaced) can destroy a protein’s function but it may not.
describe secondary structure
-The coiling or folding of localised sections of the polypeptide chain is called the 2° structure.
-Hydrogen bonds form between some of the amino acids to cause this folding. The most common folds produce an - helix or a - sheet and these result from an extremely regular sequence of amino acids.
describe tertiary structure
-The overall 3-D shape of the entire polypeptide is called the 3° structure. Folding already present due to 2°structure is retained but further folding occurs.
-The 3° structure forms spontaneously as a result of interactions between different kinds of amino acids (chemical attractions and repulsions) and the conditions present in the cellular environment in which the protein will be used e.g. pH
describe quaternary structure
If a protein consists of 2 or more polypeptide chains, then the quaternary structure is the complex structure composed of all polypeptide chains bonding together.
E.g. insulin and haemoglobin
What is a structural/fibrous protein?
Structural Proteins provide structural (mechanical) support within organisms (e.g. keratin in hair, collagen in skin and bone).
what is a globular protein?
-Have non-repeating amino acid sequences.
-Have irregular and unique shapes that are compact and roughly spherical.
-Usually soluble e.g. haemoglobin, insulin
-Always have at least 1°, 2° and 3° structures.
What’s an example of a globular protein?
haemoglobin and insulin
briefly describe proteins and binding / binding sites
Proteins contain specific binding sites.
These result from the unique structure of each protein.
Binding with other specific molecules involves complementary shapes and weak chemical interactions like hydrogen bonds between amino acids on different proteins.
list some examples of proteins with unique binding sites
-enzymes
-antibodies
-cell membrane receptors and hormones
briefly describe enzymes and their unique binding site
Enzymes- have an active site that binds to a specific substrate.
briefly describe the unique binding site in antibodies
Antibodies- complementary binding occurs between a specific antibody and a particular antigen on the surface of foreign materials (e.g. bacteria) facilitates the removal of pathogens.
briefly describe the unique binding site in cell membrane receptors and hormones
Cell membrane Receptors and Hormones- the binding between a hormone and its receptor on a target cell allows for communication in an organism.
What happens to proteins during denaturation?
During denaturation, the 3° and/or 2° structure of a protein is disrupted (i.e. the polypeptide chains unwind), binding sites are not produced and the protein cannot function.
can denatured proteins return to normal?
If it is gentle and the conditions are removed, some proteins regain their normal shape. Often denaturation is irreversible.
what is denaturation often caused by?
denaturation is caused by high temperatures (usually more than 50°C, e.g. cooking), pH and chemicals.
