Enzymes function to:
A. react with other enzymes to form a product.
B. catalyze chemical reactions.
C. transport molecules and ions across membranes.
D. regulate messages between cells.
B. catalyze chemical reactions.
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The Hardy-Weinberg equation stats that p2 + 2pq + q2 = 1; the genotype frequency of heterozygotes is represented by
A. p2 B. 2pq C. q2 D. p2 +q2 E. p2 + 2pq
Answer the following statements true (T) or false (F)
1. Most plants transport sucrose over long distances through the xylem. 2. Vessels of the xylem are dead cells and therefore can transport water and minerals upward in the plant. 3. The Casparian strip prevents apoplastic movement through epidermal cells. 4. Plants that grow in salt marshes must have a mechanism for coping with potential osmotic stress in their cells. 5. When plants take up water and minerals these must pass through both a cell wall and a membrane.
Why does E. coli shut down the trp operon if tryptophan is available in the environment?
a. Synthesizing an amino acid takes energy so it is a waste of energy to make something that is already available. b. Environmental tryptophan is of higher quality than what the E. coli can make itself. c. The trp operon encodes genes that export tryptophan from the cell; if there is already tryptophan in the environment, further export isn't necessary. d. It doesn't shut down the trp operon but only lowers the level of trp operon activity. e. E. coli actually turns the trp operon on when tryptophan is present; tryptophan is an energy source for the cell, and there is no reason to make enzymes to degrade something that is lacking in the environment.
The scientist who first determined the complete amino acid sequence of a protein (insulin) was
a. Christian Anfinsen. b. John Kendrew. c. Linus Pauling. d. Frederick Sanger.