Proximal tubular reabsorption

Reabsorbs 67% of the filtered Na+

Reabsorbs 67% of the filtered water

Reabsorbs 100% of the filtered glucose & amino acids 

Reabsorbs 85% of the filtered HCO3−

Reabsorbs most of the filtered phosphate, lactate, and citrate

TLS Online TPP Program

#Id: 3654

#Unit 3. Fundamental Processes

The translation machinery relies on the high fidelity of the aminoacyl-tRNA synthetases to ensure the accurate decoding of each mRNA.

TLS Online TPP Program

#Id: 3655

#Unit 3. Fundamental Processes

Certain archaebacteria lack a gene for CysRS. In these cells, Cys–tRNACys is produced by a ProRS (called ProCysRS).

TLS Online TPP Program

#Id: 3656

#Unit 3. Fundamental Processes

Certain proteins, such as the enzymes glutathione peroxidase and formate dehydrogenase, contain an unusual amino acid called selenocysteine, which is part of the catalytic center of the enzymes.

TLS Online TPP Program

#Id: 3657

#Unit 3. Fundamental Processes

Human proteome contains 25 selenoproteins. Selenocysteine, sometimes called the “twenty-first amino acid,”

TLS Online TPP Program

#Id: 3658

#Unit 3. Fundamental Processes

Selenocysteine is incorporated into proteins with the aid of a tRNA that interprets the UGA Stop codon as a Sec codon. tRNASec is initially charged with serine in a reaction catalyzed by the same SerRS that charges tRNASer.

TLS Online TPP Program

#Id: 3659

#Unit 3. Fundamental Processes

Instead, a dedicated protein (a special elongation factor) named SELB in complex with GTP is required to deliver Sec–tRNASec to the ribosome.