Membrane lipids may

a. spontaneously flip-flop from one membrane leaflet to the other.

b. move laterally within one membrane leaflet.

c. aggregate with membrane proteins to form lipid rafts.

d. be unequally distributed in the two membrane leaflets.

e. be present in varying amounts in different cellular membranes

#Question id: 4012

#Unit 3. Fundamental Processes

Why is the methylguanosine cap added to mRNA before the poly(A) tail?

#Question id: 4013

#Unit 3. Fundamental Processes

The textbook states that the nucleotide sequence of splice sites is “highly conserved” and of “ancient origin.” How do we know this sequence is ancient?

#Question id: 4014

#Unit 3. Fundamental Processes

Operator constitutive mutants of the lac operon would

#Question id: 4015

#Unit 3. Fundamental Processes

When polymerase bind to promoter, it spontaneously undergoes a transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level. The rate -limiting step in basal level transcription

#Question id: 4016

#Unit 3. Fundamental Processes

Activators that stimulate this kind of promoter work by triggering a conformational change in either RNA polymerase or DNA; that is, they interact with the stable closed complex and induce a conformational change that causes transition to the open complex. This mechanism is an example of

#Question id: 4017

#Unit 3. Fundamental Processes

Which of the following sequences of events occurs when E. coli are released from catabolite repression by transfer to low-glucose medium?