Sponges have been abundant since the Cambrian period, especially in shallow coastal areas
a. True
b. False
ANSWER: True
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Which of the following statements about activation energy is not true?
A. The activation energy of a reaction is lowered by enzymes. B. The activation energy is the difference between the energy level of the ground state and the transition state. C. The activation energy is the difference between the free energy of the product of the catalyzed and uncatalyzed reaction. D. The activation energy represents an energy barrier to the transition from substrate to product. E. Activation energy is related to the rate of the reaction.
_____________________ can be defined as compulsive and repetitive behavior which can lead to impairment
Fill in the blank(s) with correct word
Respond to statements 112–116 with reference to the five types
of white cells listed below. a. macrophages b. helper T cells c. B cells d. cytotoxic T cells e. natural killer cells D 112. These cells kill tumor cells but are not B or T lymphocytes. M 113. These cells scavenge dead cells and attack bacteria directly. D 114. These cells destroy cells infected by viruses. D 115. These cells recognize cell surface antigens and initiate the proliferation of lymphocytes. M 116. Antibody production occurs in these cells.
Cells use exocytosis to
A) ingest nutrients. B) pump hydrogen molecules across the membrane. C) create new cells. D) release substances from the cell. E) move away from danger.