One of the consequences of large size in multicellular organisms is the increase

Question

One of the consequences of large size in multicellular organisms is the increased distance of internal cells from the outside space, and the practical limitation of simple diffusion as point. The time for diffusion can be estimated from this equation: ecanism for substances such as oxygen. This worksheet will illustrate that where x is the distance, t is the time and D is the diffusion coefficient (in units of cm2s). For a substance with a diffusion coefficient of 105 cm2s1 (O2 has a diffusion coefficient in water of about 2x105 cm2s1, and of about 1.3x105 cm' s in skeletal muscle), calculate the time to diffuse a distance of 1 m, 100 m, and 1 cm. Be mindful of units! Distance Time 100 m 1 cm Whst practical roblemo diffision distance pose far What practical problem does diffusion distance pose for multicellular organisms?

Explanation / Answer

The practical problem that diffusion distance pose for multicellular organisms is that as the organisms increase in size the distance with the external environment also increases. Due to long distances diffusion alone cannot provide the organism with the necessary nutrients or help in body processes.

The equation for estimation of time for diffusion is given as;

X2 = 2 D t --->(1)

where, X- distance

D- Diffusion coefficient

t- time

For 1 micrometer substituting the values in the equation we get,

(1)2 = 2 X 10 -5 X t

t = 1 ms

In this way we can calculate the time of diffusion

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