Protein Structure And Types Flashcards
The sequence of amino acids in a polypeptide chain is called the […] structure of a protein
Primary
In a polypeptide there is always one end with a free amino group called the […] and one with a free carboxyl group called the […]
N-terminus, C-terminus
When does a proteins secondary structure form
When a chain of amino acids coils to form an alpha helix or folds into a beta pleated sheet
What bonding between the amine and carboxyl groups is needed for the proteins secondary structure to form
Hydrogen bonding
What happens for the protein to form it’s tertiary structure
The secondary structures fold up to form a precise 3D structure
What R group interactions are in the tertiary structure as
Hydrophobic and hydrophilic interactions (weak interactions between polar and non-polar R-groups, no actual bonds)
-Hydrogen bonds (weakest of the bonds formed)
-Ionic bonds (form between oppositely charged R-groups)
-Disulphide bonds/bridges (covalent bonds and the strongest, only form if the R-group contains sulfur atoms)
What can split the hydrogen bonds in the tertiary structure
High temperatures / altered pH
How do quaternary structure proteins form
Because of the interactions of the tertiary structures of the different subunits
What are multiple polypeptide chains called
Subunits
Haemoglobin is an example of a […] protein with a […] structure
globular, quaternary
Summary of each type of structure found in proteins
- The primary structure of a protein is the sequence of amino acids, joined by peptide bonds
• The secondary protein structure occurs when the sequence of amino acids are linked by hydrogen bonds in an alpha helix or beta pleated sheets
• The tertiary structure describes the folding of a polypeptide chain that result from the molecular interactions among the R groups of the different amino acids (H, disulphide, ionic bonds)
• The arrangement of two or more polypeptide chains in a protein make up its quaternary structure
Properties of globular properties
- compact
- water soluble
- roughly spherical in shape
How come globular proteins are water soluble
In their tertiary structure they fold so their hydrophobic R-groups are kept away from the aqueous environment, and the hydrophilic R-groups are on the outside in the aqueous environment
What are conjugated proteins
globular proteins that contain a non-protein component called a prosthetic group
Lipids combined with proteins =
Lipoproteins
Carbohydrates combined with proteins =
Glycoproteins
Metal ions and vitamins can also form […] groups
Prosthetic
Fibrous proteins characteristics
- tend to make strong long molecules which don’t fold into complex three dimensional shapes like globular proteins
Why do fibrous proteins have organised structures (due to…)
• Fibrous proteins being formed from long insoluble molecules
•This is due to the presence of a high proportion of amino acids with hydrophobic R-groups in their structure
•The amino acids sequence in the primary structure is usually quite repetitive, therefore it’s organised
Function of globular proteins
- acting as enzymes
- messengers
- transport molecules
-acting as hormones
Function of conjugated proteins
Provide structure and support for cells
Whats a prosthetic group
A non-amino acid unit e.g sugar or a nucleic acid
Haemoglobin is made from […] polypeptides, […] alpha and 2 […] subunits
4, 2, beta
Each haemoglobin subunit contains a […] group
Prosthetic haem
