We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees
Which of the following has the lowest rate of diffusion across an artificial membrane? Why?
(a) glucose
(b) water
(c) glycerol
(d) ethanol
(a) Glucose will have a negligible degree of diffusion across the synthetic bilayer. Not only is it polar, it is also larger than other molecules that are able to diffuse across the membrane.
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How could you identify potential riboswitches with bioinformatics tools?
A) Advanced 3D modeling techniques of mRNA folding would be necessary because complementary nucleotide binding predictions would not be useful. B) Locate short regions of an individual transcript with several complementary sites. C) Identify homologous sRNAs in other organisms. D) Identify several complementary mRNAs encoded in the genome.
What is the difference between the blood types, A, B, and O?
A. A and B individuals have carbohydrate trees on the surface of red blood cells. O individuals do not have carbohydrate trees. B. For each blood type, A, B, and O, there is a different sugar attachment enzyme produced. C. A and B individuals have different modifications made to their carbohydrate tree. O individuals have no modifications made to their carbohydrate tree. D. The glycosyl transferase gene has a different mutation in A individuals than in B individuals. O individuals have no mutations in the glycosyl transferase gene. E. Two of these answers are correct. The glycosyl transferase gene mutations in A and B individuals prevent the removal of carbohydrate trees from the cell surface. O individuals have no mutations and therefore have no carbohydrate trees on the red blood cell surface.
Which neuronal structure has the greatest density of voltage-gated Na+ channels, resulting in the lowest threshold
potential along a neuron?
a. dendrites b. cell body c. axon hillock d. axon e. axon terminals
A population with an S-shaped growth curve is said to exhibit _____________ growth.
a. logistic b. density-dependent c. exponential