Explain the similarities and differences between diffusion, osmosis, facilitated diffusion and active transport.

All of them are transport systems that help the cells introduce or excrete substances. The difference is that each one is substance-specific and some require energy or carring proteins.

Explanation:

The cells transport is the action of move substances through cell membrane. In human cells, the membrane is selectively permeable, this means that membrane control which molecules can enter de cell. We can separate the cells transport in two groups: no energy need and energy need.  The transports that don’t need energy and moves through a gradient of concentration are: simple diffusion (molecules pass through cell membrane a favor of gradient, that is high to low concentration) like gas, alcohol molecules, and other no polar molecules. Facilitated diffusion, is like simple diffusion but need a protein channel to transport big or insoluble molecules.  And osmosis, molecules of water moves through cell membrane to high concentration to less concentration using specific protein channels called aquaporins.

The type of transport that need energy (ATP molecules) are the active transport, this is because molecules pass through cell membrane against gradient concentration (low to high concentration), like sodium-potassium bomb or glucose transport.

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the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus