Protein Structure Flashcards
Proteins are
polymers of amino acid monomers
Structure of amino acids
Have the same basic structure, Carboxyl group and amine group differing only in R group present.
R group varies in size, shape, charge, hydrogen bonding capacity and chemical reactivity
Types of R groups
Basic(+)
Acidic(-)
Polar
Hydrophobic
Negatively charged acidic amino acids have
a COOH grouyp and are HYDROPHILIC
Positively basic charged amino acids are
Hydrophilic and have an AMINE group NH
Polar amino acids have
Hydrophilic groups like C=O OH NH
Hydrophobic amino acids hve
Hydrocarbon group
Primary structure
Sequence of amino acids
Secondary structure
Beta pleated sheets and alpha helices, resulting from hydrogen bonding along backbone
Tertiary
Polypeptide folded to form a more complex 3 Dimensional structure held together by interactions between R groups
Interactions between R groups
Hydrophobic interactions
LDF
Hydrogen Bonding
Ionic Salt bridge
Disulfide Bonds
Hydrophobic interactions
Hydrophobic R groups are mostly arranged to the inside of a protein
Ionic salt bridge
COOH and NH2 ionise to become COO- and NH3+ which strongly attract each other
Disulphide Bondss
covalent bonds between R groups containing sulphur
Quaternary
**Exists in proteins with two or more connected polypeptide subunits,
A prosthetic group
Non protein unit tightly bound to a protein and necessary for its function.
Example of a prosthetic group
The ability of haemoglobin to bind oxygen is dependent on the non protein haem group
What can the interactions of the R groups be influenced by
Temp and pH.
Temp on Protein stryucrure
Increasing temp disrupts interactions and the protein begins to unfold becoming denatured
pH on protein strucrure
Charges on acidic and basic R groups are affected by pH
as it increases from optimum, normal ionic interactions between charged groups are lost=gradually changing conformation of protein until its denatured
Ligand
Substance that can bind to a protein
Ligand binding
R groups not involved in protein can allow ligands to bind, Binding sites will have complementary shape and chemistry to ligand
Conformation of protein changes on bonding allowing functional change
in the protein
Allosteric interactions
. Binding of a substrate to active site of an allosteric enzyme increases affinity of other active sites for binding of subsequent substrate molecules.
can occur between spatially distinct sites
Allosteric enzymes
- Contain allosteric site
- Many Consist of multiple subunits(quaternary)
Modulators
Regulate activity of enzymes when they bind to the allosteric site
After modulator binds
Conformation of enzyme changes and this alters the affinity of the active site for substrate. Positive ones increase affinity, negativity decreases it.
Allosteric enzymes with multiple sub units show
Cooperativity in binding! so changes in binding at one sub unit alter affinity for remaining ones
Example of cooperativity
Binding and release of Oxygen in Haemoglobin
Changes in binding of oxygen at one SU alter affinity of remaining SUs of oxygen
Influence and physiological importance of temp & pH on binding of oxygen
A decrease in pH/increase in temp lowers affinity of haemoglobin for 02, so binding of 02 is reduced.
Decreased binding of oxygen to haemoglobin promotes
Increased oxygen delivery to tissue in actively respiring tissue.
What Do
protein kinases’
and protein phosphatases catalyse?
Kinases catalyse transfer of a phosphate group to other proteins
Phosphatases catalyse reverse reaction
Terminal phosphate of ATP is transferred to specific R groups
Phosphprylation brings about
Conformational changes which affect a proteins actvivity
proteins are activated/inhibited
The activity of many cellular proteins(enzymes receptors) is regulated this way
