Structure and Function in Proteins

Question 1

protein structure

Answer 1

the conformation and function of a protein depends on the protein’s 3D shape

Question 2

what type of bonds holds proteins in their shape?

Answer 2

non-covalent bonds

Question 3

rules in protein structure

Answer 3

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)

Question 4

peptide bond

Answer 4

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)

Question 5

alpha helix

Answer 5

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)

Question 6

beta sheet

Answer 6

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

Question 7

secondary protein structure

Answer 7

coiling or folding of a polypeptide due to H-bonding between amino acids

Question 8

tertiary protein structure

Answer 8

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

Question 9

native conformation

Answer 9

the 3-dimensional form a protein should take to perform its function correctly; coded for in DNA

Question 10

structural domain

Answer 10

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

Question 11

quaternary structure

Answer 11

results from two or more polypeptide subunits

Question 12

homodimer

Answer 12

when two polypeptides encoded by the same gene bind to each other to form a dimer

Question 13

heterodimer

Answer 13

when two polypeptides encoded by different genes bind to each other to form a dimer

Question 14

immunoglobulins

Answer 14

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

Question 15

protein denaturation

Answer 15

when proteins are subject to temperature changes, pH changes or other conditions that disturb their stability

Question 16

consequences of protein denaturation

Answer 16

structural changes/change in conformation due to disruption of hydrogen and ionic bonds

Question 17

protonation and deprotonation

Answer 17

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

Question 18

hemoglobin HbA1c

Answer 18

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”

Question 19

protein modification

Answer 19

the process of affecting enzyme activity by covalently modifying it e.g. hemoglobin by glucose (increasing the HbA1c)

Question 20

conservative change

Answer 20

an amino acid change usually within the same group, that does not affect significantly the function of the protein

Question 21

non-conservative change

Answer 21

an amino acid change that significantly affects the function of the protein

Question 22

consequences of non-conservative change in RBC

Answer 22

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