BIOCHEMISTRY FIRST AID

Question 1

What is located at the 3’ end of tRNA?

Answer 1

CCA - Can Carry Amino acids.

Question 2

What does the T arm of tRNA do?

Answer 2

T arm Tethers tRNA to ribosome, contains ribothymidine, pseudouridine, cytidine sequence necessary for ribosome binding

Question 3

What does the D arm of tRNA do?

Answer 3

D arm Detects tRNA by correct aminoacyl tRNA synthetase.

Question 4

B-thalassemia, Gaucher disease, Tay-Sachs disease, Marfan syndrome all have variations in what DNA synthesis process?

Answer 4

Splicing

Question 5

What molecule is needed to splice pre-mRNA?

Answer 5

snRNPs (small nuclear ribonucleoproteins) form spliceosome.

Cleavage at 5’ splice site, intron stays stuck to spliceosome in Lariat shape.

Question 6

Someone has dry skin, extreme light sensitivity, skin cancer. What issue with DNA repair do they have? What is the disease? What is this caused by?

Answer 6

Xeroderma pigmentosum - can’t repair DNA pyrimidine dimers caused by UV exposure.

Issue of
Nucleotide Excision Repair

Question 7

What disease is caused by failure of mismatch repair that should occur in the S phase of cell cycle?

Answer 7

Lynch syndrome: hereditary nonpolyposis colorectal cancer.

Question 8

What kind of DNA repair is defective in BRCA1 mutation?

Answer 8

Double strand homologous recombination

Question 9

What disease is associated with nonhomologous end joining double strand break repair?

Answer 9

Ataxia telangiectasia.

Question 10

What cell components/structures is actin involved in?

Answer 10

Actin = a microfilament along with myosin
Absorption = microvilli
Action = muscle contraction
Adherens = cell junction

Question 11

Microsatellite instability - failure of what mechanism?

What mutations may cause this?

Answer 11

Mismatch repair in S phase.

Causes Lynch Syndrome:
MLH1 and MSH2 mutations most often
Hereditary Nonpolyposis colorectal cancer.

Question 12

What drugs target microtubules?

Answer 12

Microtubules Get Constructed Very Poorly
Mebendazole - antihelminthic
Griseofulvin - antifungal
Colchicine - antigout
Vincristine/Vinblastine - anticancer
Paclitaxel - anticancer

Question 13

Increased Vimentin in an immunohistochemical stain would be found in what kind of tumors?

Answer 13

viMEntin - MEsenchymal tumors (sarcoma)

Also other non sarcomal tumors:
endoMEtrial carcinoma
renal cell carcinoma
MEningioma

Vimentin is in fibroblasts, endothelial cells, macrophages, etc.

FA 2018 p. 225

Question 14

Increased S-100 in an immunohistochemical stain would be found in what kind of tumors?

Answer 14

S-100 is from neural crest cells, found in:

Me1an00ma (melanoma), Schwannoma, Langerhans cell histiocytosis.

Question 15

Increased Desmin in an immunohistochemical stain would be found in what kind of tumors?

Answer 15

desMin - Muscle tumor

Rhabdomyosarcoma

Question 16

Increased Cytokeratin in an immunohistochemical stain would be found in what kind of tumors?

Answer 16

Epithelial cells

Epithelial cells (squamous cell carcinoma).

Question 17

Increased GFAP in an immunohistochemical stain would be found in what kind of tumors?

Answer 17

neuroGlia (astrocytes, Schwann cells, oligodendrocytes)

Astrocytoma, Glioblastoma

Question 18

Increased Neurofilament in an immunohistochemical stain would be found in what kind of tumors?

Answer 18

Neurons

Neuronal tumors - neuroblastoma

Question 19

Increased PSA in an immunohistochemical stain would be found in what kind of tumors?

Answer 19

Prostatic epithelium - prostate cancer

Question 20

Increased TRAP (tartrate resistant acid phosphatase) in an immunohistochemical stain would be found in what kind of tumors?

Answer 20

Hairy cell leukemia

“Hairy trap”

Question 21

Increased chromogranin and synaptophysin in an immunohistochemical stain would be found in what kind of tumors?

Answer 21

Neuroendocrine cells –small cell carcinoma of the lung, carcinoid tumor

Question 22

Which vitamin is involked in decarboxylation of alpha keto acids (carbohydrate metabolism)

CLUE: Pt presents with heart failure and peripheral neuropathy.

Answer 22

Thiamine (B1).

Causes beriberi (peripheral neuropathy, heart failure)

Wernicke-Korsakoff Syndrome

Question 23

Which vitamin that acts as a mitochondrial electron carrier such as FMN, FAD is deficient in angular cheilosis, stomatitis, glossitis and/or normocytic anemia.

Answer 23

B2 - riboflavin

Question 24

which vitamin is involved in transamination of amino acids (amino acid synthesis)?

Deficiency causes cheilosis, stomatitis, glossitis

Answer 24

B6 pyridoxine