Explain two examples of diffusion in living organisms.   

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Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration. Particles can be atoms, ions, or molecules. When the particle is a water molecule, the diffusion process is called osmosis . Diffusion continues until the concentration of particles is equal in...

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Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration. Particles can be atoms, ions, or molecules. When the particle is a water molecule, the diffusion process is called osmosis. Diffusion continues until the concentration of particles is equal in both areas.

Diffusion and Nerve Cells

First, let’s review a little about nerve cell physiology. A nerve cell is called a neuron. The space between two neurons is called a synapse. Neurotransmitters are chemicals that diffuse across the synapse from the vesicles of one neuron to the receptors of another neuron. As neurotransmitters move from one neuron to another, they travel from an area of higher neurotransmitter concentration to an area of lower neurotransmitter concentration. Therefore, neurotransmitter molecules diffuse across the synapse.

Diffusion and the Placenta

First, let’s review a little about placenta physiology. The placenta enables nutrients, oxygen, and waste products to travel between the mother and the fetus. The blood from the fetus is high in `~CO_2` and waste products, but low in `~O_2` and nutrients. The blood from the mother is high in `~O_2` and nutrients, but low in `~CO_2` and waste products. Therefore, `~CO_2` and waste products will flow across the placenta by diffusion from the fetus to the mother. Similarly, `~O_2` and nutrients will flow across the placenta by diffusion from the mother to the fetus.

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