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USMLE
New FA Biochem 8
Question | Answer |
---|---|
"Chromatin structure: In the beads on a string analogy, what are the beads?" | "Start with a nucleosome core made up of an 8 histone cube (two each of positively-charged histones H2A, H2B, H3, and H4). Negatively charged DNA loops twice around nucleosome core." |
"Chromatin structure: In the beads on a string analogy, what is the string and how long is it?" | Histone H1 ties the nucleosomes together in a 30-nm fiber string |
Chromatin structure: What histones are included and which of these are not in the nucleosome core? | "H1 (only one not in the core), H2A, H2B, H3, and H4" |
Heterochromatin or Euchromatin: Which is more condensed? | Heterochromatin. Euchromatin is less condensed. |
Heterochromatin or Euchromatin: Which is less condensed? | Euchromatin. Heterochromatin is more condensed. |
Heterochromatin or Euchromatin: Which is transcriptionally active? | "Euchromatin (""eu"" means true, so think ""truly transcribed"")" |
Heterochromatin or Euchromatin: Which is transcriptionally inactive? | Heterochromatin |
Name the purines. | Adenine and Guanine |
Name the pyrimidines. | "Cytosine, Uracil, Thymine" |
Which base pair bond has 3 Hydrogen bonds? | Guanine to Cytosine |
Which base pair bond has 2 Hydrogen bonds? | Adenine to Thymine |
How many Hydrogen bonds does the Guanine to Cytosine pairing have? | 3 |
How many Hydrogen bonds does the Adenine to Thymine pairing have? | 2 |
Which amino acids are necessary for purine synthesis? | "Glycine, Aspartate, Glutamine" |
"In nucleic acids, what kind of substitution is a transition?" | "TransItion = Identical type (Purine for purine or pyrimidine for pyrimidine") |
"In nucleic acids, what kind of substitution is a transversion?" | "TransVersion = conVersion between types (Purine for pyrimidine or vice versa") |
What does it mean for genetic code to be unambiguous? | Each codon specifies only one amino acid. |
What does it mean for genetic code to be degenerate? | More than one codon may code for the same amino acid. |
What does it mean for genetic code to be redundant? | More than one codon may code for the same amino acid. |
Which amino acid is coded by only one codon? | Methionine |
"Trypsin cleaves peptides at which side of what residues?" | "C-terminal of lysine or arginine (the most basic amino acids)" |
"Cyanogen bromide cleaves peptides at which side of what residues?" | "C-terminal of methionine" |
"Pepsin cleaves peptides at which side of what residues?" | "C-terminal side of tyrosine, phenylalanine, and tryptophan (all have phenyl groups, these are the same bonds as chymotrypsin. Pepsin's action ceases when the NaHCO3 raises the pH of the intestinal contents)" |
"Chymotrypsin cleaves peptides at which side of what residues?" | "C-terminal side of tyrosine, phenylalanine, and tryptophan residues (all have phenyl groups, these are the same bonds as pepsin, whose action ceases when the NaHCO3 raises the pH of the intestinal contents)." |
"number of AAs in one turn of alpha-helix" | 3.6 |
"Amino acids that disrupt alpha-helix" | "proline, many charged AAs bulky side chains" |
"Which reagent sequentially removes N-terminal residues from a polypeptide?" | "Phenylisothiocyanate (Edman degradation)" |
"Which reagent sequentially removes C-terminal residues from a polypeptide?" | "Carboxypeptidase" |
"What kind of inheritance and mutation is the alpha-1-antitrypsin deficiency?" | "Autosomal recessive, single purine substitution (GAG to AAG)" |
"Anode: What does it attract?" | "Anions" |
"Anode: What does it contain?" | "Cations" |
"Cathode: What does it attract?" | "Cations" |
"Cathode: What does it contain?" | "Anions" |
"Inhibitors of electron transport from FMNH2 to Coenzyme Q" | "Amytal and Rotenone" |
"Inhibitors of electron transport from Cytochrome b to Cytochrome c" | "Antimycin A" |
"Inhibitors of electron transport from Cytochrome a+a3 to Oxygen" | "Cyanide, CO, and Sodium azide" |