Which of the following BEST describes a cell using passive transport to maintain homeostasis? A. oxygen moving from a high concentration in the lungs to a low concentration in the blood

B. ATP is used to pump K+ ions out of the cell and Na+ ions into the cell to resting potential

C. a white blood cell uses a vesicle to engulf bacteria to help fight an infection

D. a transport protein moves amino acids from a low concentration in the blood to a high concentration in the small intestines.

Diffusion: the Simple and the Facilitated

Diffusion is the movement of particles down their gradient. A gradient is any imbalance in concentration, and moving down a gradient just means that the particle is trying to be evenly distributed everywhere, like dropping food coloring in water. This is what happened when we made our granola - a bunch of separate ingredients came together and spread out across the whole mixture. We call this evening-out moving “downhill”, and it doesn’t require energy. The molecule most likely to be involved in simple diffusion is water - it can easily pass through cell membranes. When water undergoes simple diffusion, it is known as osmosis.

Movement Across a Membrane and Energy

There are two major ways that molecules can be moved across a membrane, and the distinction has to do with whether or not cell energy is used. Passive mechanisms like diffusion use no energy, while active transport requires energy to get done.

Cartoon representing passive transport as rolling a boulder down a hill and active transport as rolling a boulder up a hill.

Explanation:

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the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.