Which of the following is an example of specificity in G protein-coupled receptor signalling?

The image below left shows a cartoon representation of signalling through a specific receptor tyrosine kinase (RTK). Phosphorylation of downstream proteins is indicated by a "P" within a yellow circle. (This is the same pathway as the previous question.)

The image below right is experimental data on this pathway, obtained either in the presence or absence of several drugs, each affecting an unknown protein in the pathway. The upper panels show total protein and phosphorylation states of a number of key proteins in this signalling pathway. The lower image is of quantitative-RT-PCR for detection of expression of a known target gene at the end of this signalling pathway.

Separate experiments (not shown) concluded that none of these drugs had an effect on the activity RAS or RAF.

Which drug appears to be affecting the kinase activity of MEK but is still allowing transcription of the target gene?

The image below left shows a cartoon representation of signalling through a specific receptor tyrosine kinase (RTK). Phosphorylation of downstream proteins is indicated by a "P" within a yellow circle. (This is the same pathway as the previous question.)

The image below right is experimental data on this pathway, obtained either in the presence or absence of several drugs, each affecting an unknown protein in the pathway. The upper panels show total protein and phosphorylation states of a number of key proteins in this signalling pathway. The lower image is of quantitative-RT-PCR for detection of expression of a known target gene at the end of this signalling pathway.

Separate experiments (not shown) concluded that none of these drugs had an effect on the activity RAS or RAF.

Which drug appears to be affecting the kinase activity of MEK but is still allowing transcription of the target gene?

Which of the following fatty acids is expected to be least soluble in water?

The image below shows:

• (left) a region of a transmembrane protein with three different regions indicated by numbers, and;
• (right) a selection of different amino acids placed into four groups

Which group of amino acids would be more likely found in the primary sequence of the protein at position 3?

(If you are making a judgement call between several options, select the one that is most likely.)

The schematic diagram below represents two vesicles, each composed of a lipid bilayer.

The inner and outer leaflets of the bilayers are represented by different colours and are numbered.

If these two vesicles were to fuse with each other, which leaflet would end up merged with leaflet 4?

Shown below is the chemical structure of a glycerophospholipid, with several positions numbered.

When this lipid forms part of a lipid bilayer, which of the numbered positions is likely to be most exposed to water at the surface of the bilayer?

Shown below is a schematic diagram showing a lipid membrane with several associated proteins.

Treatment with high pH buffer enables proteins E, F and G to be removed from this membrane.

Which of the proteins shown in the image are peripheral membrane proteins?

Shown below is a schematic diagram of an integral membrane protein within a lipid bilayer.

Also shown are four hydropathy plots.

Which hydropathy plot is most consistent with the protein structure shown?

Shown below is a schematic diagram representing the primary structure of an integral membrane protein that traverses a cell membrane 4 times.

"N" and "C" represent the N- and C-termini of the protein.

Hydrophobic (red) and polar (blue) regions are colour coded.

When intact cells containing this protein in the membrane are treated with a chemical labelling reagent, the reagent reacts with lysine residues at the positions indicated by arrows.

Which regions of this protein are expected to protrude on the cytoplasmic side of the membrane?