2ci: Amino Acid + Protein structure Flashcards
What are proteins
Polymers of amino acid monomers.
In what way do R groups vary
In size, shape, charge, hydrogen bonding capacity and chemical reactivity.
How are amino acids classified
According to their R groups: basic (+ charge), acidic (- charged), polar (hydrophilic), non-polar (hydrophobic)
acidic R groupsā¦
- negatively charged
- hydrophilic
- key component = carboxylic acid group COOH
Basic R groupsā¦
- end with a positively charged group
- hydrophilic
- key component of their R group is amine group NH
Polar R groupsā¦
- slightly charged
- hydrophilic
- key component: carbonyl, hydroxyl, sulfer, amine
Hydrophobic R groupsā¦
- hydrophobic
- do not have charges
- non- polar
- mainly consists of hydrocarbons
The wide range of functions carried out by proteins results fromā¦
The diversity of R groups
What is the primary structure
The sequence in which the amino acids are synthesised into the polypeptide (no folding)
What is the N-terminus and the C-terminus
Due to the make up of amino acids, there is an amino group at one end (N-terminus) and a C-terminus on the other end (C-terminus)
H2N- R - R - R - COOH
What is the secondary structure
Hydrogen bonding along the backbone of the protein strand results in the regions of the secondary structure.
Three types of secondary structure:
- alpha helix
- beta sheet
- turns
What are alpha helixes
Formed by twisting the polypeptide chain into a spiral/ helix and then stabilised with hydrogen bonding.
R groups stick out
What are beta sheets
Has parts of the chain running alongside each other, forming a sheet.
R groups sit above and below the sheet
Can be anti-parallel (chains run in opposite directions) or parallel (chains run in same direction)
What are turns
Turns reverse the direction of a polypeptide chain.
What is the tertiary structure
The polypeptide folds into a tertiary structure.
confirmation is stabilised by interactions between and R groups:
- hydrophobic interactions
- ionic bonds
- LDF
- hydrogen bonds
- disulfide bridges (covalent bonds between R groups containing sulfer)
What do hydrophobic interactions do
hydrophobic amino acids tend to cluster together on the interior of a protein, away from the surface (and away from the water)
What is the quaternary structure
Exists in proteins with two or more connected polypeptide subunits (which are linked by bonds between the R groups of the polypeptide chains.)
describes the spatial arrangement of the subunits.
What is a prosthetic group
A non- protein unit tightly bound to a protein and necessary for its function.
Eg haemoglobin- the ability of haemoglobin to bind to oxygen is dependant upon the non-protein haem group.
effect of increasing temperature (on a protein)
Disrupts the interactions that hold the protein in shape.
The protein begins to unfold and eventually becomes denatured.
Effect of changing pH
-charges on acidic and basic R groups are affected by pH.
- as the pH increases or decreases from the optimum, the normal ionic interactions between the charged groups are lost. it gradually changed the conformation of the protein until it becomes denatured.
