A virus, because it has a non-cellular structure.
the three accessory glands: the seminal vessicles, the bulbourrethhral gland, and the prostate
Answer: CHANNEL PROTEINS provide openings in the plasma membrane for substances to flow through without changing structure, and CARRIER PROTEINS allow passage of substances through the plasma membrane after undergoing a subtle change in shape.
Explanation: They are described thus:
A channel protein is a protein that allows the transport of specific substances across a cell membrane.
Carrier proteins are proteins that carry substances from one side of a biological membrane to the other. Many carrier proteins are found in a cell’s membrane, though they may also be found in the membranes of internal organelles such as the mitochondria, chloroplasts, nucleolus, and others.
In DIFFUSION AND FACILITATED DIFFUSION no energy is used. The one that needs a helper to get thing across is FACILITATED DIFFUSION.<span> Facilitated diffusion involves the diffusion of materials across the cell plasma membrane with the aid of membrane proteins such as carriers and channels. The process of diffusion does not need a carrier, the molecules to be transported just move on their own from the area of high concentration to the region of low concentration until the concentration in the space become uniform.</span>
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