Each of the nine glycolytic intermediates between glucose and pyruvate is phosphorylated. The phosphoryl groups seem to have many functions such as,

a) The plasma membrane generally lacks transporters for phosphorylated sugars, the phosphorylated glycolytic intermediates cannot leave the cell

b) After the initial phosphorylation, further energy is necessary to retain phosphorylated intermediates in the cell, despite the large difference in their intracellular and extracellular concentrations

c) Phosphoryl groups are essential components in the enzymatic conservation of metabolic energy, Energy released in the breakage of phosphoanhydride bonds is partially conserved in the formation of phosphate esters such as glucose 6-phosphate

d) Binding energy resulting from the binding of phosphate groups to the active sites of enzymes lowers the activation energy and increases the specificity of the enzymatic reactions

which of the following functions shows Importance of Phosphorylated Intermediates?

#Question id: 1243

#Unit 4. Cell Communication and Cell Signaling

One form of receptor desensitization can be mediated by negative feedback involving phosphorylation of the receptor itself by a kinase activated downstream of a second messenger. The phosphorylated receptor likely:

#Question id: 1242

#Unit 4. Cell Communication and Cell Signaling

Rhodopsin, a light-sensitive GPCR whose role in vision is dependent on its phosphorylation status, is influenced in part by the protein arrestin.  Which of the following is TRUE with regard to rhodopsin and vision?

#Question id: 1241

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a common step in the opening/closing of ion channels by acetylcholine and rhodopsin binding to their receptors?

#Question id: 1239

#Unit 4. Cell Communication and Cell Signaling

GTPases serve in many signal transduction pathways and the presence of GTP or GDP dictates whether the pathway is on or off, respectively. Which of the following statements is TRUE regarding guanine nucleotide exchange factors (GEF) and the role in these signaling pathways?

#Question id: 1238

#Unit 4. Cell Communication and Cell Signaling

Which of the following can lead to loss-of-heterozygosity in a tumor-suppressor gene?

a. deletion of the normal copy                       

b. non dysjunction during mitosis

c. somatic mutation of the normal copy

d. mitotic recombination between a wild-type and mutant allele

#Question id: 1237

#Unit 4. Cell Communication and Cell Signaling

Arrange the following events in the proper order in which they occur during transduction of the Notch/Delta signaling pathway:

a. cleavage of Notch by TACE                                  

b. binding of Delta to Notch

c. translocation of Notch segment to the nucleus      

d. interaction of Notch with transcription factors     

e. cleavage of Notch by Presenilin 1