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Size of cells - Coggle Diagram
Size of cells
Increasing the rate of diffusion
The cells size also impacts the rate of diffusion
The greater the difference in SA-to-V ratio the more substances it can diffuse
There are various ways that cells can increase the concentration gradient across their membranes in order to maintain a rapid rate of diffusion.
Plants cells
often carry out cytoplasmic streaming, a process in which the cytoplasm flows through the cell in a circular movement. The effect is to maintain a steeper concentration gradient because the materials diffusing into the cell are rapidly removed, keeping them at a lower concentration than if the cytoplasm was stationary.
Multicellular organisms
the circulatory system helps to increase the rate of diffusion. The blood circulation through the lungs rapidly removes oxygen that has diffused into the body, maintaining a steep concentration gradient. Similarly, at the tissues, blood flow removing a waste, such as carbon dioxide, also increases the rate of diffusion out of the body cells.
Inside a cell, the conversion of a diffused substance into another substance will lower its concentration, causing an increase in its rate of diffusion.
Surface-Area-to-Volume Ratio
Cells need a large surface area of membrane around the cell in relation to the volume of its cytoplasm.
This effects the efficiency of the cell due to the cell needing the membrane to uptake materials which fuel the chemical reactions that occur within the cytoplasm.
As the cells size increases so does its surface area and volume. However, its volume grows much faster than that of the surface area.
Overcoming problems associated with the SA-to-V ratio
Due to the restrictions, most cells are too small to see without a microscope.
However, some cells offset the low SA-to-V ratio.
In large algae cells, an insert vacuole fills the majority of the cell. This metabolically pushes the active cytoplasm to the outside of the cell, just beneath the plasma membrane.
Benefiting both the distance materials need to diffuse when moving and the active volume of the cytoplasm is less, therefore reducing the exchange that must occur across the membrane.
Multicellular Organisms
Some multicellular organisms the cell has to me a certain size to perform their specific tasks
The shape of an object can significantly change the SA-to-V ratio and cells often have specific that ensure they have the highest SA-to-V ratio
Spherical shapes have a relatively small SA-to-V ratio
Long, thin or flat cells have more membrane for a certain volume than spherical cells do. Such as roots of plants or hair.