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mroman79 mroman79
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12 years ago
How do your results illustrate the importance of surface area:volume ratio in animal physiology ? Give examples . comparing animals and their organ system, which demonstrate the limitations of having a lower surface area :volume ratio. i need jelp answering this question for lab experiment on surface area to volume ratio. please help..
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wrote...
12 years ago
Without knowing really what your "results" are, I'll explain to you the importance of surface area to volume ratio.

The volume/surface ratio is frequently used to explain why cells are microscopic. As the cell grows the volume increases faster than the surface area, therefore materials cannot be exchanged adequately to service the cytoplasm. Look up the math for a sphere in regards to how the surface and volume increases as it gets larger.

It is also sometimes used to explain why cells undergo mitosis; they get too large for their own good, so to speak, and split, thus increasing surface area. (You can make it sound more scientific). To a lesser extent, you may also look into the benefits of having long projections, like villi in the small intestine, and microscopic root hairs.

To elaborate on the first part, take for example red blood cells.

Those are very small so they can have more surface area. Let's see the maths behind it: If all RBCs were had a cumulative volume of 8 and a side of 2, this is what the surface area would be.

  • 2x2x2 (lbh) = 8 cc
  • With a surface area of 2x2x6 = 24 sq cm.

NOW, if we take a volume of 8 again, with side 1 cm...

1x1x1 = 1 cc per RBC. So, 8 RBCs of side 1 will make a volume of 8.

BUT, surface area = 1x1x6 = 6 sq cm per cube surface area. And since there are 8 cubes, that's a total of 48 cm sq surface area.

Clearly, the surface area of smaller sized particles is greater. (Of course, RBCs aren't measurable in whole centimetres. we all know that, but its still true. Smaller the particles, more the surface area, hence more the efficiency). That's more efficient in matters of time, for example.
wrote...
12 years ago
1) In chemistry, the rate of reaction is higher when surface are to volume ratio is higher. eg. reaction betweencalcium carbonate and hydrchloric acid when finer particles are used as the surface area exposed for reaction is larger.
2) Gas diffusion of amoeba. Small organisms have large respiratory area ration over volume which is large enough for oxygen to diffuse in.
3) Absorption in the villi of the small intestine. same concept as above.
wrote...
12 years ago
Many reactions occur within the cell. Substances need to be taken into the cell to fuel these reactions and the wast products of the reactions need to be removed. When the cell increases in size so does its chemical activity. This means that more substances need to be taken in and more need to be removed. The surface area of the cell is vital for this. Surface area affects the rate at which particles can enter and exit the cell (The amount of substances that it takes up from the environment and excretes into the environment), whereas the volume affects the rate at which material are made or used within the cell, hence the chemical activity per unit of time.

As the volume of the cell increases so does the surface area however not to the same extent. When the cell gets bigger its surface area to volume ratio gets smaller. To illustrate this we can use three different cubes. The first cube has a side of 1 cm, the second 3 cm and the third 4 cm. If we calculate the surface area to volume ratio we get:

Cube 1
Surface area: 6 sides x 12 = 6 cm2
Volume: 13 = 1 cm3
Ratio = 6:1

Cube 2
Surface area: 6 sides x 32 = 54 cm2
Volume: 33 = 27 cm3
Ratio = 2:1

Cube 3
Surface area: 6 sides x 42 = 96 cm2
Volume : 43 = 64 cm3
Ratio = 1.5:1


As we can see the cube with the largest surface area and volume has the smallest surface area to volume ratio. If the surface area to volume ratio gets too small then substances won’t be able to enter the cell fast enough to fuel the reactions and wast products will start to accumulate within the cell as they will be produced faster than they can be excreted. In addition, cells will not be able to lose heat fast enough and so may overheat. Therefore the surface area to volume ratio is very important for a cell.
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