Principles of Biochemistry Homework (Chapters 1, 2, 3)
What might be an effect if DNA nucleotide bases in a double helix were held together by covalent bonds rather than hydrogen bonds?
All of the above - Purified helices would require higher temperatures to melt apart the two DNA strands. - The helix would be more stable. - Replication of DNA, which requires separation of the two strands, would require a larger input of energy.
A solution of a weak acid contains 5 mM of the conjugate acid (HA), 2.5 mM of the conjugate base (A—), and 2.5 mM of H+. What is the Ka for this ionization?
1.25 mM
You prepare a solution with a proton concentration of 8.0 x 10—5 M. What is the concentration of hydroxide ion [OH—] in the solution?
1.25 x 10^—10 M
How many essential amino acids are hydrophobic?
6
The active site of an enzyme contains a critical cysteine residue. The enzyme is active only when the cysteine side chain is in its protonated form. The pKa for the R-group of cysteine is 8.18. What percentage of the enzyme is active when in a buffer at pH 7.18?
90.9%
Which amino acid would be positively charged at physiological pH?
Arg
Which of the following is NOT a characteristic that can vary between different amino acid side chains? A) hydrophobic character B) None of the above C) size D) shape E) charge
B) None of the above
In an electrostatic interaction, the strength of the bond is:
Both the first and third answers are correct. - proportional to the charges on the two interacting atoms. - inversely proportional to the distance between the two atoms.
Which of the following statements is TRUE of L amino acids but not of D amino acids. Please choose the correct answer from the following choices, and then select the submit answer button. A) They contain an amino group. B) They contain a carboxylic acid group. C) They contain a central carbon. D) None of these. E) They contain both an amino group and a carboxylic acid group.
D) None of these.
Which of the following would NOT be part of a complex carrying out the process of translation? Please choose the correct answer from the following choices, and then select the submit answer button.
DNA
Which of the following statements is true of BOTH DNA replication and DNA transcription?
During the process, the DNA double helix is separated into single-stranded regions.
Kwashiorkor is a particular form of malnutrition. The disease was first defined in the 1930s in:
Ghana.
When considering the chemical structure of ATP, which of the following statements is TRUE?
It contains the base adenine.
Which of the following amino acids contains a guanidinium group?
R
The side chain of an amino acid is also known as the:
R group.
Two amino acids are near each other in a protein structure. Both amino acids are alanine, the structure of which contains a methyl group. Which of the following statements regarding the interaction of the two alanine amino acids is CORRECT?
The amino acids may experience van der Waals interactions.
Which of the following statements is TRUE of water?
The electrons of water spend more time near the oxygen atom.
In a liver cell protein Q is present in the cytoplasm. Which of the following statements is TRUE of protein Q?
The gene encoding protein Q was expressed.
Which of the following statements is true of proteins but not true of lipids?
They are made of monomers.
Which of the following statements is true of lipids but not true of proteins or nucleic acids?
They have a typical molecular weight of 1300 g mol-1.
You are studying an enzyme isolated from lysosomes. It is most active at a pH of 5. Which of the following buffers would be the BEST choice to use in an enzyme activity assay for this enzyme?
an acetate buffer system
Which of the following does NOT have a double membrane?
an endosome
Which of the following has the lowest Ka?
bicarbonate
Ribosomes are made up of:
both proteins and RNA
A protein destined to be secreted by the cell will, at some point during its lifetime, be found in which of the following locations?
both the Golgi complex and transport vesicles
Cell-to-cell interactions are often dependent on unique _____ on the cell surfaces.
carbohydrates
Pairs of sulfhydryl groups in close proximity may form _____ bonds.
disulfide
Which amino acid has the simplest side chain?
glycine
Many biomolecules exist as polymers. Which of the following polymer(s) contains multiple branch points?
glycogen
Acetone contains which functional group(s)?
keto
The pKa of the carboxylic acid group of an amino acid is _____ than the pKa of the amino group.
lower
Which of the following is an essential amino acid?
methionine
The amino acid cysteine belongs to which functional group(s)?
sulfhydryl
During transcription, which of the following is NOT found associated with the RNA polymerase at some point during the process?
the RNA-RNA hybrid helix
There are two amino acids that begin with the letter "L." Of these, how many are essential amino acids?
two