What would be the effect of a complete block of the heart's electrical system at the atrio-ventricular node?
What will be an ideal response?
Answer: The atria could contract, but there would no ventricular contraction. (Not mentioned in this section: sometimes,the ventricular contraction will simply be delayed and less coordinated if a different location within the ventricle becomes a pacemaker).
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The direction of water movement across a cell membrane is determined in part by
A. the presence of transporter molecules. B. the levels of ATP in the cell. C. the concentration of solutes inside and outside the cell. D. the amount of pressure inside and outside the cell. E. the concentration of solutes and amount of pressure inside and outside the cell.
Cytotoxic T cells destroy cancerous cells by
A. forming the membrane attack complex. B. releasing vesicles containing perforin. C. activating natural killer cells. D. opsonization. E. secreting cytokines.
Animal body plans can evolve, because changes in genes that regulate development will alter body form. However, some factors limit the changes that can occur. Describe these factors
What will be an ideal response?
In the spiral staircase model of DNA, the rungs
are a. deoxyribose sugars. b. hydrogen bonds. c. nucleotide base pairs. d. phosphate groups. e. composed of all of these