## What is the relationship between cell size and diffusion rate?

The surface-to-volume ratio of a sphere is 3/r; as the cell gets bigger, its surface-to-volume ratio decreases, making diffusion less efficient. The larger the size of the sphere, or animal, the less surface area for diffusion it possesses.

How does size influence diffusion rate?

Mass of Particle: Heavier particles will move more slowly and so will have a slower rate of diffusion. Smaller particles on the other hand will diffuse faster because they can move faster.

### How might you explain the correlation between cell size and the rate of gas exchange?

As the cell grows, its surface area to volume ratio decreases, reducing the rate of gas exchange. This is because as the surface to volume ratio decreases, there is not enough surface area (cell membrane) for adequate gas exchange to occur in order to serve the needs of the internal contents (volume) of the cell.

Do larger or smaller cells diffuse faster?

Larger molecules diffuse through a cell membrane at a slower rate than do smaller ones.

#### Why do smaller cells diffuse faster?

Smaller cells have a much greater surface area to volume ratio allowing material to diffuse throughout the entire volume of the cell quickly and efficiently.

How does cell size and shape influence the diffusion of molecules?

As cell size increases, its ability to facilitate diffusion across the cell membrane decreases. This is because its internal volume increases at a faster rate than its external surface area. Therefore, the cell will divide to maintain the proper ratio and rate of diffusion to survive.

## Does diffusion increase with size?

When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared. When there is more volume and less surface area, diffusion takes longer and is less effective.

How does the size and nature of diffusing molecules affect the rate of diffusion?

Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly. The reverse is true for lighter molecules. Temperature: Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion.

### How does a large surface area increase gas exchange?

Large surface area: human lungs contain about 500 million alveoli, which creates a surface area around half the size of a tennis court. This speeds up diffusion because gases have more area over which to diffuse.

How does the size of molecules and surface area affect the rate of diffusion?

Surface area and thickness of the plasma membrane: Increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it. Distance travelled: The greater the distance that a substance must travel, the slower the rate of diffusion. This places an upper limitation on cell size.

#### What is the relationship of the size of the cubes to diffusion?

In other words, if the cube dimensions are doubled, the time it takes for the hydrogen ions to completely diffuse in more than doubles. When you triple the size, the time to diffuse MUCH more than triples.

Why does a larger surface area increase diffusion?

When a cell’s surface area increases, the amount of substances diffusing into the cell increases. As volume and surface area increase, the volume increases faster, so much so that the surface area available to allow substances in halves each time the cell volume doubles.