USMLE Biochemistry Videos & Books

2022-05-23 21:07:01 Educational objective: Xeroderma pigmentosum develops due to a defect in nucleotide excision repair. This disease is characterized by increased sensitivity to ultraviolet radiation and a high incidence of cutaneous malignancy. ओपन / कमेंट

2022-05-23 08:07:02 ओपन / कमेंट

2022-05-23 08:06:01 A 5-year-old girl is brought to the office by her mother because she is concerned that her daughter "sunburns too easily." The mother says the patient's skin becomes red and scaly with only minimal sun exposure. She first noticed the problem when her daughter was 7 months old during a trip to the beach.
The mother has since avoided exposing her child to excess sunlight, but finds it difficult now that the patient has begun kindergarten. Physical examination shows thin and hyperpigmented skin. She also has a few nevi on her hands that have been enlarging rapidly. ओपन / कमेंट

2022-05-22 23:59:01 Educational objective: The sequence of amino acids in a growing polypeptide chain is dictated by the interaction of the mRNA codon with the tRNA anticodon. tRNA that is mischarged with the incorrect amino acid (and not corrected by aminoacyl-tRNA synthetase proofreading) will incorporate the wrong amino acid into the growing polypeptide chain. ओपन / कमेंट

2022-05-22 23:04:34 ओपन / कमेंट

2022-05-22 23:03:47 In an experiment, erythrocyte precursor cells are incubated in a medium containing radiolabeled cysteine. These radiolabeled cysteine residues are attached to their appropriate tRNAs by the enzyme aminoacyltRNA synthetase. The bound cysteine residues are then chemically modified to form alanine. The end
product of this reaction is a tRNA molecule that contains the cysteine anticodon but is mischarged with alanine. ओपन / कमेंट

2022-05-18 21:41:01 Educational objective: The nucleolus is the site of ribosomal subunit maturation and assembly. RNA polymerase I functions exclusively within the nucleolus to transcribe the 4SS pre-rRNA gene, which codes for most of the ribosomal RNA components (18S, 5.BS, and 28S rRNAs). ओपन / कमेंट

2022-05-18 11:58:52 https://t.me/USMLE_AMBOSS ओपन / कमेंट

2022-05-18 07:40:22 ओपन / कमेंट

2022-05-18 07:40:21 A 58-year-old man comes to the office with a persistent dry cough. He has experienced an involuntary weight loss of 10 kg (22 lb) over the last 3 months. The patient drinks 2-3 beers daily and has a 40-packyear smoking history. Physical examination shows dullness to percussion over the right lower lung base. A
chest CT reveals a right-sided pleural effusion and a mass in the lower lobe of the right lung. Transbronchial biopsy of the mass demonstrates malignant cells with large nuclei that contain prominent, round, basophilic bodies as shown below. ओपन / कमेंट