Proteins pt2 Flashcards
Amino acid sequence determines
protein structure
Proteins are polymers of
amino acid monomers
Amino acids link by __________ _____ to form polypeptides
peptide bonds
How are amino acids classified?
according to their R groups
basic amino acids are
positively charged
acidic amino acids are
negatively charged
All types of amino acid R groups
basic, acidic, polar, hydrophobic
The diversity of R groups result in
the wide range of functions carried out by proteins
What is the primary structure?
The sequence in which the amino acids are synthesised into the polypeptide
What results in regions of secondary structure?
Hydrogen bonding along the backbone of the protein strand
Examples of secondary structures
alpha helices, parallel or anti parallel beta sheets, or turns
When the polypeptide folds into a tertiary structure this conformation is stabilised by
interactions between R groups: hydrophobic interactions; ionic bond; LDFs; hydrogen bonds; disulfide bridges.
Quaternary structure exists in proteins with
2 or more connected polypeptide subunits.
What is a prosthetic group?
A non-protein unit tightly bound to a protein necessary for its function
Interactions of the R groups can be influenced by
temperature and pH
The ability of haemoglobin to bind to oxygen is dependent upon the
non-protein haem group
The charges on acidic and basic R groups are affected by
pH
Key component of basic R group
NH2
Key component of acidic R group
COOH
Key component of polar R group
OH,NH3,SH
Key component of hydrophobic (non-polar) R group
Hydrocarbon
What is a ligand?
A substance that can bind to a protein
R groups not involved in protein folding can
allow binding to ligands
What happens as a ligand binds to a protein binding site?
The conformation of the protein changes. This change in conformation causes a functional change in the protein
Where do allosteric interactions occur?
between spacially distinct sites
Many allosteric proteins consist of
multiple units (have quaternary structure)
Allosteric proteins with multiple subunits show cooperativity in binding in which
changes in binding at one sub-unit alter the affinity of the remaining subunits
Allosteric enzymes contain a second type of site called
an allosteric site
What do modulators regulate?
The activity of the enzyme when they bind to the allosteric site
Following the binding of the modulator, what happens?
The conformation of the protein changes and this alters the affinity of the active site for the substrate
The binding and release of oxygen in haemoglobin shows
cooperativity
The binding of a substrate molecule to one active site of an allosteric enzyme…
increases the affinity of the other active sites for binding of subsequent substrate molecules.
The activity of allosteric enzymes can vary greatly with small changes in
substrate concentration.
What do positive modulators do?
increase the enzyme’s affinity for the substrate
What do negative modulators do?
reduces the enzymes affinity for the substrate
Changes in binding of oxygen at one subunit
alter the affinity of the remaining subunits of oxygen
What lowers the affinity of haemoglobin for oxygen so that the binding of oxygen is reduced
An increase in temperature or a decrease in pH
What will reduced pH and increased temperature do to actively respiring tissue?
it will reduce the binding of oxygen to haemoglobin promoting increased oxygen delivery to tissue
Adding a phosphate group adds
negative charges
Ionic interactions in the unphosphorylated protein can be
disrupted and new ones added
What do protein kinases do?
catalyse the transfer of a phosphate group to other proteins
What do protein phosphatases do?
catalyse the reverse reaction (removes a phosphate group from a protein)
