Structure and Function in Proteins Flashcards
protein structure
the conformation and function of a protein depends on the protein’s 3D shape
what type of bonds holds proteins in their shape?
non-covalent bonds
rules in protein structure
flexible 3d shape for function but stable enough to not convert to another conformation and a.a.’s with side groups compatible with the environment (i.e. polar groups if in aq, non-polar groups if transmembrane protein)
peptide bond
the chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid (O=C-N-H)
alpha helix
secondary structure in which the spiral shape resulting from the coiling of a polypeptide in a protein’s secondary structure; maintained by hydrogen bonds b/w hydrogen from NH bond and O of carbonyl group (4 a.a. apart)
beta sheet
secondary structure (more rigid than alpha helix) in which the shape is maintained by hydrogen bonding b/w backbone groups; can be parallel or anti-parallel depending on orientation of strands
secondary protein structure
coiling or folding of a polypeptide due to H-bonding between amino acids
tertiary protein structure
occurs when certain attractions are present between alpha helices and pleated sheets; the α-helices and β-sheets, combined w/ irregular elements such as loops and turns, make up the tertiary structure of a protein
native conformation
the 3-dimensional form a protein should take to perform its function correctly; coded for in DNA
structural domain
stable conformation in a protein that can exist without the rest of the protein; may be a portion of the tertiary structure or the entire tertiary structure of the protein
quaternary structure
results from two or more polypeptide subunits
homodimer
when two polypeptides encoded by the same gene bind to each other to form a dimer
heterodimer
when two polypeptides encoded by different genes bind to each other to form a dimer
immunoglobulins
antibodies performing important defense functions in our bodies; Y structure with 2 light and 2 heavy chains held together by disulphide bonds and antigens are found at the ends of the Y
protein denaturation
when proteins are subject to temperature changes, pH changes or other conditions that disturb their stability
consequences of protein denaturation
structural changes/change in conformation due to disruption of hydrogen and ionic bonds
protonation and deprotonation
large change in pH could cause the addition or dissociation of a proton; loss or gain of a proton could cause the breaking of the hydrogen bonds that hold the protein in its proper conformation
hemoglobin HbA1c
gives a picture of what kind of conditions the RBCs have been exposed to over the last few months; the less well-controlled the blood glucose is and the higher the blood glucose, the more Hb will be “glycated”
protein modification
the process of affecting enzyme activity by covalently modifying it e.g. hemoglobin by glucose (increasing the HbA1c)
conservative change
an amino acid change usually within the same group, that does not affect significantly the function of the protein
non-conservative change
an amino acid change that significantly affects the function of the protein
consequences of non-conservative change in RBC
glutamate is replaced by hydrophobic valine and interacts w/ a hydrophobic pocket on another hemoglobin - formation of long strands of hemoglobin causing a sickle-shaped cell
