Which of the following is responsible for the alpha-helical structure of proteins?
a. hydrophobic interactions
b. nonpolar covalent bonds
c. ionic interactions
d. hydrogen bonds
e. polar covalent bonds
D
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Four of the following five events shuffles existing alleles into different combinations in sexually reproducing
organisms. Which one is the exception? a. changes in chromosome number b. mutation c. independent assortment of chromosomes d. crossing over e. fertilization
You isolate a crude fraction from the alien cells containing receptors for XFF. You perform a binding assay and plot the XFF receptors occupied (y-axis) at several XFF concentrations
You obtain a Michaelis–Menten-like simple binding curve that indicates a 1 XFF:1 receptor interaction and approaches a maximal level of binding you define as Bmax. From the curve you extrapolate the Kd for XFF binding as the concentration at which 50% of the receptors are bound. What value reflects the affinity of the receptor for the ligand? You have isolated a primary signal factor from the blood of a space alien, which you name XFF (for X-files factor). You also have isolated various types of alien cells which appear to interact with XFF. Based on preliminary data, you think that XFF could be similar to one of three compounds normally found in human blood: epidermal growth factor (EGF), epinephrine, or estrogen. A) Kd B) Bmax C) Kd ? Bmax D) 1/Bmax E) The affinity cannot be determined from the information available.
According to the fluid-mosaic model of the plasma membrane, a lipid bilayer is _____ and has the consistency of ______.
Fill in the blank(s) with the appropriate word(s).
Male guppies are known for their bright colors. Having bright colors attracts mates, but it also attracts predators. So in an environment with a lot of predators, male guppies have more dull colors. In an experiment, guppies were removed from an area
with predators to an area without predators. Over a period of 12 months the population became much more colorful. This is an example of a response to: A) disruptive selection. B) mutation. C) directional selection. D) stabilizing selection.