Companion cells transport of photosynthetic products from producing cells in mature leaves to the sieve elements in the minor veins of the leaf. There are at least three different types of companion cells in the minor veins of mature, exporting leaves, All three cell types have dense cytoplasm and abundant mitochondria;

#Question id: 4148

#Section 3: Genetics, Cellular and Molecular Biology

Which of the following is true about the sorting pathway for proteins destined for incorporation into lysosomes or the plasma membrane of eukaryotic cells?

#Question id: 4149

#Section 3: Genetics, Cellular and Molecular Biology

Glycosylation of proteins inside the endoplasmic reticulum does not involve:

#Question id: 4150

#Section 3: Genetics, Cellular and Molecular Biology

Posttranslational glycosylation of proteins is inhibited specifically by:

#Question id: 4151

#Section 3: Genetics, Cellular and Molecular Biology

The signal sequences that direct proteins to the nucleus are:

#Question id: 4152

#Section 3: Genetics, Cellular and Molecular Biology

The pathway for polypeptides exported from E. coli includes the following steps, which occur in what order for correct export?

1.  A chaperone, SecA, binds to the polypeptide.

2.  A chaperone, SecB, binds to the polypeptide.

3.  ATP is hydrolyzed by Sec A.

4.  SecA pushes 20 amino acids of the polypeptide into the translocation complex.

#Question id: 4153

#Section 3: Genetics, Cellular and Molecular Biology

Ubiquitin-mediated protein degradation is a complex process, and many of the signals remain unknown.  One known signal involves recognition of amino acids in a processed protein that are either stabilizing (Ala, Gly, Met, Ser, etc.) or destabilizing (Arg, Asp, Leu, Lys, Phe, etc.), and are located at: