The primary polysaccharides associated with the plant cell wall are the
A) hemicelluloses.
B) extensins.
C) fibronectins.
D) pectins.
E) both choices A and D
E) both choices A and D
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Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones. Requirements for facilitated diffusion include
A. The carrier molecule must be specific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient. B. The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient. C. The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always against the concentration gradient, never with the gradient. D. The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier. The direction of movement is always against the concentration gradient, never with the gradient.
Which of the following groups of organisms demonstrated a sudden appearance in the fossil record
and continues to exhibit remarkable diversity today? a. ferns and mosses b. fungi c. algae d. flowering plants e. pines
Which one of the following events associated with the transmission of an impulse across a synapse occurs last?
A) Action potential arrives at an axon bulb. B) Neurotransmitter is released into the synaptic cleft. C) Chemically gated channels for sodium open. D) Calcium diffuses into an axon bulb. E) Neurotransmitter binds to receptors on the postsynaptic membrane.
According to the graph of U.S. municipal solid waste, which type of disposal method emerged in the late 80's?
A. Composting B. Recycling C. Combustion D. Sanitary Landfill E. Secure Landfill