Biochemistry comprehensive examination and answers 2024
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Course
BIOCHEMISTRY.
Institution
BIOCHEMISTRY.
Biochemistry comprehensive examination and answers 2024
which histone ties DNA-histone nucleosome beads into more condensed structures?
H1
is DNA acidic or basic?
acidic
what type of aa are histones made of? are they acidic or basic?
lysine and arginine; basic
is heterochroma...
Biochemistry comprehensive examination and answers 2024
Which histone ties DNA-histone nucleosome beads into more condensed structures? - ANSWER H1
Is DNA acidic or basic? - ANSWER acidic
What type of aa are histones made of? Are they acidic or basic? - ANSWER lysine and arginine; basic
Is heterochromatic more accessible or less accessible to TF? Euchromatin? - ANSWER less; more
If a cell has a hyperchromatic or condensed nucleus is it undergoing transcription etc? - ANSWER no
What are chromosomes? During what part of the cell cycle are they found? In what pathologic state would you see a lot of chromosomes? - ANSWER highly condensed forms of DNA; mitosis; neoplasia- highly dividing and thus hyperchromatic
What experiment is chromosomes used for? - ANSWER karyotyping
Are histones in heterochromatin or euchromatin more methylated? Which had more acetylated histones? - ANSWER heterochromatin; euchromatin
What does guanine have on it? - ANSWER a ketone
What does thymine have on it? - ANSWER a methyl Deamination of what pyrimidine makes what? - ANSWER cytosine to uracil
In what genetic code is uracil found in? In replace of what? - ANSWER uracil; thymine
How many bonds does a G-C connection have? What type of bonds? How about a A-T? - ANSWER 3 hydrogen bonds; 2 hydrogen bonds
What amino acids are required in purine synthesis? Which of these does pyrimidine synthesis require also? - ANSWER glutamine, aspartate, glycine; aspartate
What is the difference between a nucleotide and a nucleoside? - ANSWER nucleoside is just the ribose plus the base; nucleotide is the ribose plus the base but the phosphate bond
Is PRPP added later or first in pyrimidine synthesis? - ANSWER later
What is PRPP? How is it made? - ANSWER its the ribose; its made from PRPP synthetase using ribose 5 P from the HMP shunt
What is the precursor for both purines? - ANSWER IMP
What is the precursor for pyrimidines? - ANSWER orotate
Which intermediate is involved in both pyrimidine synthesis and the urea cycle? - ANSWER carbamoyl phosphate Why does a deficiency in ornithine transcarbamoylase (urea cycle enzyme) result in an increased production of orotic acid, the pyrimidine precursor? - ANSWER because carbamaoyl phosphate is involved in both urea cycle and pyrimidine synthesis
Is CPSII or CPSI involved in pyrimidine synthesis? - ANSWER CPSII
What three enzymes lead to orotic acid accumulation? What reactions are they involved in? - ANSWER ortinithine transcarbamoylase, orotic acid phosphoribosyltransferase, and orotidine 5 phosphate decarboxylase; urea cycle; last two are involved in conversion of orotic acid to UMP (adding PRPP to orotic acid)
What step in pyrimidine synthesis requires aspartate? - ANSWER carbamoyl phosphate to orotic acid
What are the clinical symptoms of orotic aciduria? - ANSWER increased orotic acid in urine, megaloblastic anemia, +/- hyperammonemia
How do you differentiate the causes of orotic aciduria? - ANSWER whether or not the patient is also hyperammonemia (if yes, then OTC def)
How do you differentiate causes of megaloblastic anemia? - ANSWER orotic aciduria megaloblastic anemia can not be corrected with folic acid or vit B12
How do you treat orotic aciduria? How does this work? - ANSWER oral uridine administration; provides nucleosides and provides feedback inhibition
What converts dump to dtmp? What drug blocks this? - ANSWER thymidylate synthase; 5-Flourouracil
What drug blocks ribonucleotide reductase? What does this enzyme do? - ANSWER hydroxurea; deoxygenates ribose What does ornithine transcarbamyolase do to carbamoyl phosphate? - ANSWER converts it to citrulline
What does 6 mercaptopurine do? - ANSWER 6MP blocks de novo purine synthesis
Other than thymidylate synthase, what else is required to convert dump to dtmp? - ANSWER N5N10 methylene THF
After N5N10 methylene THF donates a methyl for conversion of dump to dtmp what is it converted to? -
ANSWER DHF
What enzyme converts DHF to THF? What vitamin cofactor is used to transfer a methyl from an amino acid to DHF? What amino acid is that? - ANSWER dihydrofolate reductase; vitamin B12; homocysteine
What happens to homocysteine after converting a methyl? - ANSWER becomes methionine
How is THF converted to N5N10 Methylene? - ANSWER using serine (which turns into glycine after reaction)
What does methotrexate do? What step is this enzyme involved in? - ANSWER it inhibits conversion of DHF to THF by blocking dihyrdofolate reductase
What is the difference between methotrexate and trimethroprim? - ANSWER trimethroprim inhibits bacterial dihyrofolate reductase
What is adenosine/AMP converted to? Through what enzyme? - ANSWER inosine/IMP; adenosine deaminase
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