Hydrogen bonds between different parts of the polypeptide chain result in which level of protein structure?
A. primary
B. secondary
C. tertiary
D. quaternary
Answer: B
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When a biologist narrowly defines species based primarily on minor differences, he or she is _________
Fill in the blank(s) with the appropriate word(s).
All of the following events occur during T-dependent activation of a B cell EXCEPT
A. an antigenic fragment held within an MCH Class II molecule of a dendritic cell binds to a specific T cell receptor on a naïve T-helper cell. B. specific cytokines from the T helper cells stimulate maturation and complete activation of the antigen-stimulated B cell. C. antigen within MCH class II molecule is presented by B cell to an activated T helper cell. D. antigen binds to specific B cell receptor molecules. E. antigen bound to the B cell receptor is internalized and transferred to an MHC class II molecule which then moves to the plasma membrane. F. There are no exceptions. All of these events occur during T-depedent activation of B cells.
Why do sex hormones and other steroids take much longer to produce their effects than nonsteroid hormones do?
A) Steroids are bigger, slower molecules. B) Steroids must usually be carried longer distances by the blood. C) Steroids must relay their messages via relay molecules. D) Steroids cause target cells to make new proteins, which takes time.
Which component of the human eye forms the iris?
A) sclera B) choroid C) retina D) pupil