Test 1 Quiz questions Flashcards
SDS is a detergent added to proteins to denature them prior to running on a gel. How does SDS work to denature proteins?
It disrupts hydrophobic interactions, thus disrupting tertiary and quaternary structure.
All of the following statements about allosteric regulation are correct EXCEPT:
Allosteric regulation occurs when an effector molecule binds to a protein and changes the proteins conformation.
GTP binding and hydrolysis gives 3 allosterically regulated conformations to proteins.
Allosteric regulation only regulates enzyme function.
Protein kinases and protein phosphatases are frequently involved in allosteric regulation.
Allosteric regulation only regulates enzyme function.
Allosteric regulation occurs when an effector molecule binds outside of a proteins binding site and causes the protein to change conformation and thus change it’s function. Allosteric regulation frequently effects enzymes, but many other proteins are regulated by this mechanism, including motor proteins. GTP binding and hydrolysis, as well as, phoshorylation are common mechanisms of allosteric regulation, but are not the only mechanisms
Studies conducted with a lysozyme mutant that contains an Aspartic acid→Asparagine change at position 52 and a Glutamic acid→Glutamine change at position 35 exhibited almost a complete loss in enzymatic activity. What is the most likely explanation for the decrease in enzyme activity in the mutant? (See Panel 2-5 for amino acid structures)
absence of a negative charges in the active site
Both amino acid changes are from an acidic R group to an uncharged polar R group, thus there is a loss of negative charges. Loss of enzyme activity suggests that these charges are required to either fold the protein correctly or for interaction of the substrate with the active site. Negative charges in the active site could produce either ionic or H-bonds, however the new amino acids can also H-bond.
Motor proteins use the energy in ATP to transport organelles, rearrange elements of the cytoskeleton during cell migration, and move chromosomes during cell division. Which of the following mechanisms is sufficient to ensure the unidirectional movement of a motor protein along its substrate?
A conformational change is linked to ATP hydrolysis.
C
Enzyme Q is normally activated by phosphorylation. A mutant of Enzyme Q can still bind to it’s substrate but is unable to form any product. Which of the following is a likely explanation for the inactivity of mutant Enzyme Q.
The mutant lacks a serine at the phosphorylation site.
Phosphorylation by kinase occurs only at serine, threonine or tyrosine amino acids.
The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer’s, Huntington’s, and Creutzfeld–Jacob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins?
They form protein aggregates.
Match the description with the level of protein folding.
Examples include alpha helix and Beta pleated sheet
Term to describe protein’s amino acid sequence.
The three dimensional final folded shape of a protein.
The modular folded unit that many larger single-chain proteins are composed of
Two or more polypeptide chains that form the functional protein
secondary structure
primary structure
tertiary structure
protein domain
quaternary structure
Enzymes that regulate many proteins by adding a phosphate to either serine, threonine or tyrosine are called _____________________.
kinases
The reaction below is catalyzed by the enzyme phosphoglucose isomerase. What would be the effect on chemical equilibrium if this enzyme was added to the reaction?
Conversion of fructose-6-P to glucosse-6-P
Equilibrium would not change
Place the non-covalent interactions in order of strongest to weakest.
- ionic
2.Hydrogen bonds - hydrophobic interaction
- Van der Waals
Which statement comparing covalent bonds to non-covalent bonds is true?
Covalent bonds share electrons while non-covalent bonds do not.
The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of_______.
chemical bonds
The amino acid lysine is capable of forming ________________bonds with other molecules and is __________________ in water.
ionic ; soluble
Match the Eukaryotic organelle or structure with its function.
stores DNA
contains enzymes that digest many macromolecules in the cell
contains metabolic enzymes and ribosomes
Is made up mostly of phospholipids
maintains cell shape
- nucleus
-lysosome
-cytosol
-plasma membrane
-cytoskeleton
