Proteins: Structure and Function Flashcards
Select the one of the following statements that is NOT CORRECT
a. Fermentation and glycolysis share many common biochemical features
b. Louis Pasteur first discovered that cell-free yeast preparations could convert sugars to ethanol and carbon dioxide
c. Organic orthophosphate (Pi) id essential for glycolysis
d. 14C is an important toll for detecting metabolic intermediates
e. Medicine and biochemistry provide mutual insights to one another
b. Louis Pasteur first discovered that cell-free yeast preparations could convert sugars to ethanol and carbon dioxide
Selct the one of the following statements that is NOT CORRECT
a. the vitamin derivative NAD is essential for conversion of glucose to pyruvate
b. The term “Inborn errors of metabolism” was coined by the physician Archibald Garrod
c. Mammalian tissue slices can incorporate inorganic ammonia into urea
D. Realization that DNA is a double helix permitted Watson and Crick to describe the polymerase chain reaction
e. Mutation of the genome of a “model organisms” can provide insight into biochemical processes
D. Realization that DNA is a double helix permitted Watson and Crick to describe the polymerase chain reaction
Select the one of the following statements that is NOT CORRECT
The propensity of water molecules to form hydrogen bonds with one another is the primary factor responsible for all of the following properties of water EXCEPT: A. Its atypically high boiling point B. Its high heat of vaporization C. Its high surface tension D. Its ability to dissolve hydrocarbons E. Its expansion upon freezing
D. Its ability to dissolve hydrocarbons
E. Its expansion upon freezing
Select the one of the following statements that is NOT CORRECT
a. The side-chains of the amino acids cysteine and methionine absorb light at 280 nm
b. Glyxine is often present in regions where a polypeptide forms a sharp bend, reversing the direction of a polypeptide
c. Polypeptides are named as derivatives of the C-terminal aminoacyl residue
d. The C, N, O and H atoms of a peptide bond are coplanar
e. A linear pentapeptide contains four peptide bonds
a. The side-chains of the amino acids cysteine and methionine absorb light at 280 nm
Select the one of the following statements that in NOT CORRECT
a. Buffers of human tissue include bicarbonate, proteins, and orthophosphate
b. A weak acid or a weak base exhibits its greatest buffering capacity when the pH is equal to its pKa plus or minus one pH unit
c. The isoelectric pH (pI) of lysine can be calculated using the formula (pK2 + pK3)/2
d. The mobility of a monofunctional weak acid in a direct current electrical field reaches its maximum when the pH of its surrounding environment is equal to its pKa
e. For simplicity, the strengths of weak bases are generally expressed as the pKa of their conjugate acids
d. The mobility of a monofunctional weak acid in a direct current electrical field reaches its maximum when the pH of its surrounding environment is equal to its pKa
Select the one of the following statements that is NOT CORRECT
a. If the pKa of a weak acid is 4.0, 50% of the molecules will be in the dissociated state when the pH of the surrounding environment is 4.0
b. A weak acid with a pKa of 4.0 will be a more effective buffer at pH 3.8 than at pH 5.7
c. At a pH equal to its pI, a polypeptide carries no charged groups
d. Strong acids and bases are so named because they undergo complete dissociation when dissolved in water
e. The pKa of an ionizable group can be influenced by the physical and chemical properties of its surrounding environment
c. At a pH equal to its pI, a polypeptide carries no charged groups
Select the one of the following statements that is NOT CORRECT
a. A major objective of proteomics is to identify all of the proteins present in a cell under different conditions as well as their states of modification
b. Mass spectrometry has largely replaced the Edman method for sequencing of peptides and proteins
c. Sanger reagent was an improvement on Edman’s because the former generates a new amino terminus, allowing several consecutive cycles of sequencing to take place
d. Since mass is a universal property of all atoms and molecules, mass spectrometry is ideally suited to the detection of posttranslational modifications in proteins
e. Time-of-flight mass spectrometers take advantage of the relationship F=ma
c. Sanger reagent was an improvement on Edman’s because the former generates a new amino terminus, allowing several consecutive cycles of sequencing to take place
Why does olive oil added to water tend to form large droplets?
Self-association in an aqueous environment as a large droplet minimizes the surface area in contact with water, and hence the number of water molecules whose degrees of rotational freedom are restricted
What distinguishes a strong base form a weak base?
Strong bases and acids dissociate essentially completely in water, NaOH as Na+ and OH-. By contrast, a weak acid such as pyruvic acid dissociates only partially in solution
Select the one of the following statements that is NOT CORRECT
a. Ion-exchange chromatography separates proteins based upon the sign and magnitude of their charge at a given pH
b. Two-dimensional gel electrophoresis separates proteins first on the basis of their pI values and second on their charge-to-mass ratio using SDS-PAGE
c. Affinity chromatography exploits the selctivity of protein-ligand interactions to isolate a specific protein form a complex mixture
d. Many recombinant proteins are expressed with an additional domain fused to their N- or C-terminus. One common component of these fusion domains is a ligand-binding site designed expressly to facilitate purification by affinity chromatography
e. Following purification by classical techniques, tandem mass spectrometry typically is used to analyze individual homogeneous peptides derived form a complex protein mixture
e. Following purification by classical techniques, tandem mass spectrometry typically is used to analyze individual homogeneous peptides derived form a complex protein mixture
Select the one of the following statements that is NOT CORRECT
a. protein folding is assisted by intervention of specialized auxillary proteins called chaperones
b. Protein folding tends to be modular, with areas of local secondary structure forming first, then coalescing into a molten globule
c. Protein folding is driven first and foremost by the thermodynamics of the water molecules surrounding the nascent plypeptide
d. The formation of S-S bonds in a mature protein is facilitated by the enzyme protein disulfide isomerase
e. Only a few unusual proteins, such as collagen, require posttranslational processing by partial proteolysis to attain their mature conformation
e. Only a few unusual proteins, such as collagen, require posttranslational processing by partial proteolysis to attain their mature conformation
Select the one of the following statements that is NOT CORRECT
a. Posttranslational modifications of proteins can affect both their function and their metabolic fate
b. The native conformational state generally is that which is thermodynamically favored
c. The complex three-dimensional structures of most proteins are formed and stabilized by the cumulative effects of a large number of weak interactions
d. Research scientists employ gene arrays for the high-throughput detection of the presence and expression level of proteins
e. Examples of weak interactions that stabilize protein folding include hydrogen bonds, salt bridges, and van der Waals forces
d. Research scientists employ gene arrays for the high-throughput detection of the presence and expression level of proteins
Select the one of the following statements that is NOT CORRECT
a. Changes in configuration involve the rupture of covalent bonds
b. Changes in cinformation involve the rotation of one or more single bonds
c. The Ramachandran plot illustrates the degree to which steric hindrance limits the permissible angles of the single bonds in the backbone of a peptide or protein
d. Formation of an alpha helix is stabilized by the hydrogen bonds between each peptide bond carboxyl oxygen and the N-H group of the next peptide bond
e. In a beta sheet the R groups of adjacent residues point in opposite directions relative to the plane of the sheet
d. Formation of an alpha helix is stabilized by the hydrogen bonds between each peptide bond carboxyl oxygen and the N-H group of the next peptide bond
Slect the one of the following statements that is NOT CORRECT
a. The a2b2y3 denotes a protein with seven subunits of three different types
b. Loops are extended regions that connect adjacent regions of secondary structure
c. More than half of the residues in a typical protein reside in either a helices or B sheets
d. Most B sheets have a right-handed twist
E. Prions are viruses that cause protein-folding diseases that attack the brain
E. Prions are viruses that cause protein-folding diseases that attack the brain
