B1.2 Proteins Flashcards
The diagram in image B1.2.1 shows the structure of the protein CXCL12.
Which chemical group is found
at X?
A. NH2
B. NOH
C. COH
D. COOH
D
The image B1.2.2 shows the structure of the protein hemoglobin.
What level of protein structure bonds the α
and β chains together?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
D
What is found in insulin molecules?
A. Phosphates
B. Nucleotides
C. Peptide bonds
D. Glycerol
C
Which molecule in image B1.2.3 could be hydrolysed into amino acids?
C
Which of the molecules contain peptide bonds or are sugar molecules in image B1.2.4?
B
The diagram B1.2.5 shows a section through the melatonin receptor, with melatonin attached to its binding site. Darker grey areas show the surface of the protein and paler areas are internal. The membrane in which this receptor is located is also shown.
Draw one phospholipid molecule on the diagram to show a possible position in the membrane.
Go to the paper answer key for this. There’s no other way.
The diagram B1.2.5 shows a section through the melatonin receptor, with melatonin attached to its binding site. Darker grey areas show the surface of the protein and paler areas are internal. The membrane in which this receptor is located is also shown.
The receptor contains seven alpha helices and one other secondary structure. Deduce what this other secondary structure is.
beta pleated sheet/ beta-loop/ beta strands;
Reject ‘beta helix’
The diagram B1.2.5 shows a section through the melatonin receptor, with melatonin attached to its binding site. Darker grey areas show the surface of the protein and paler areas are internal. The membrane in which this receptor is located is also shown.
Discuss briefly whether amino acids on the surface of the protein are likely to be polar or non-polar.
polar/hydrophilic where exposed to the cytoplasm/to fluid outside cell/to
polar phospholipid heads;
non-polar/hydrophobic where exposed to the (core of the) membrane/hydrophobic tails (of phospholipids);
Proteins are an extraordinarily diverse group of carbon compounds that have a wide range of roles in cells.
Describe the structure of proteins, including features that are common to all proteins and features that vary.
a. composed of one or more polypeptides / some are single polypeptides others made of 2 or more polypeptide chains / all proteins consist of, at least, one polypeptide chain;
b. a polypeptide/protein is a chain of amino acids;
c. (chains of ) amino acids linked by peptide bonds;
d. twenty different amino acids/ amino acids have different R groups/ R groups can be hydrophilic/polar or hydrophobic/non-polar;
e. primary structure is the sequence/order (and number) of amino acids in the polypeptide;
f. any sequence/order of amino acids could b
e linked together hence many possible polypeptides/proteins;
g. secondary structure is the formation of
alpha / α helices and beta / β pleated sheets;
h. secondary structure stabilized by hydrogen bonding;
i. tertiary structure is the further folding of the polypeptide / tertiary structure is the three-dimensional (3-D) conformation/structure/shape of a protein;
j. tertiary structure stabilized by interactions / ionic bonds/hydrogen bonds/disulfide bridges
between R groups;
k. fibrous or globular are the two main classes of conformation/three-dimensional/ 3-D structure/shape;
l. conformation/three-dimensional (3-D) structure determined by amino acid sequence;
m. quaternary structure if two or more polypeptides are linked to form a (single) protein
OR
quaternary structure if a prosthetic group is linked (to form a conjugated protein);
Accept clearly annotated diagrams.
The diagram B1.2.6 shows the molecular structure of the amino acide leucine.
Draw a circle on the diagram to enclose the carbonxyl group.
Circle COOH
The diagram B1.2.6 shows the molecular structure of the amino acide leucine.
State one protein that acts as a hormone.
insulin/glucagon/ADH/oxytocin/leptin / other verified example;
The diagrams in image B1.2.7 represent the structure of a protein before and after it has become denatured.
State how many different types of amino acid there are, which can become part of a polypeptide when mRNA is translated.
20
The diagrams in image B1.2.7 represent the structure of a protein before and after it has become denatured.
Outline one cause of denaturation in proteins.
a. increase in temperature/heat;
b. change of pH;
c. salt;
d. heavy metals;
