29 Questions
What can form a diffusion barrier similar to the nuclear pore?
A dense network of unstructured proteins
What type of bonds form between adjacent cysteine side chains?
Covalent disulfide bonds
What is a common feature of protein assemblies?
Multiple protein-protein contacts
What is the shape of the protein coat or capsid of many simple viruses?
A hollow sphere based on an icosahedron
What is the function of the capsid in viral structures?
To enclose and protect the viral nucleic acid
What is a characteristic of protein subunits in viral capsids?
They are composed of identical protein molecules
What is the approximate diameter of the tomato bushy stunt virus (TBSV)?
33 nm
How many identical copies of the capsid protein are present in the TBSV?
180
What is the purpose of the proteolytic enzyme in insulin assembly?
To cleave the proinsulin into insulin after it has folded into a specific shape
What is the function of the short amyloid fibrils formed by peptide hormones of the endocrine system?
To store the hormones in an inactive form
What is the name of the extensively studied yeast prion protein?
Sup35
What type of bonds are disrupted in the insulin protein that cannot spontaneously re-form efficiently?
Disulfide bonds
What is the shape of a typical antibody molecule?
Y-shaped
What happens when colliding molecules have poorly matching surfaces?
They form few noncovalent bonds
What is a characteristic of enzymes within a functional class?
They are highly specific and catalyze a single type of reaction
What happens to the rate of reaction when the enzyme molecule is saturated with substrate?
It reaches a maximum value
What does the Km of an enzyme represent?
The concentration of substrate that allows the reaction to proceed at half its maximum rate
How do enzymes accelerate chemical reactions?
By decreasing the activation energy
What is the role of lysozyme in the catalysis of polysaccharide chains?
To cut the polysaccharide chain, which is its substrate
What is the function of coenzymes in enzyme-catalyzed reactions?
To assist in enzyme-catalyzed reactions such as hydrolysis
What is the result of the conditions created in the microenvironment of the lysozyme active site?
An impressive increase in hydrolysis rate
What type of molecule is attached to rhodopsin in the eye?
A lightsensitive molecule called retinal
What is the central atom of the heme ring?
Iron
What is the purpose of a multienzyme complex in cells?
To increase the rate of cell metabolism
What is the effect of conformational coupling between two separate binding sites?
Reciprocal effect on each other's binding
What do GAP and GEF regulate in GTP-binding proteins?
The type of nucleotide bound
What is the function of covalent modification patterns in cells?
To provide specific meanings to the cell
What is a characteristic of motor proteins?
Random back-and-forth wandering
What is a common feature of heme groups in hemoglobin?
Tightly bound to each of the four polypeptide chains
This quiz covers the structure and function of proteins, including intrinsically disordered polypeptide chains, disulfide bonds, and protein assembly into large structures.
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