The four most common elements found in living organisms are ________
A) nitrogen, oxygen, phosphorus, and carbon
B) carbon, oxygen, nitrogen, and hydrogen
C) carbon, oxygen, potassium, and calcium
D) oxygen, calcium, hydrogen, and carbon
B
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Answer the following statements true (T) or false (F)
1. IgA antibodies are involved in passive immunity. 2. RAG-1 is an enzyme involved in creating immunoglobulin light chains. 3. Hypermutation refers to the process by which immunoglobulin gene domains recombine to form a diverse array of antibodies. 4. The only cell type that can present antigens to helper T cells is the macrophage. 5. Cytotoxic T-cell activation requires the presentation of the same antigen by macrophages and (somatic) body cells.
Humans are an example of ____
a. bulk feeders b. deposit feeders c. fluid feeders d. suspension feeders e. bulk and fluid feeders
Which of the following types of transport does not require membrane proteins?
Facilitated diffusion Bulk Simple diffusion Active
Which of the following must occur in order to maintain a high pressure potential within guard cells?
A. Energy must be constantly expended. B. Stomata must take up more oxygen and less carbon dioxide. C. Water must exit guard cells by osmosis. D. Potassium ions must be actively transported out. E. The rate of transpiration must increase.