Shapes of cells

Shapes of cells Cells within the same organism show Enormous Diversity in: 1-Size 2-Shape 3-Internal Organization

1. Cell Size 1. A few types of cells are large enough to be seen by the unaided eye. The human egg (ovum) is the largest cell in the body, and can (just) be seen without the aid of a microscope. 2. Most cells are small for two main reasons: a). The cell’s nucleus can only control a certain volume of active cytoplasm.

b). Cells are limited in size by their surface area to volume ratio b). Cells are limited in size by their surface area to volume ratio. A group of small cells has a relatively larger surface area than a single large cell of the same volume. This is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface. As a cell grows larger at some point its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell's need

Limited in size by the RATIO between their Outer Surface Area and Their Volume. A small cell has more SURFACE AREA than a large cell for a GIVEN VOLUME OF CYTOPLASM

Why are cells small As cell size increases the volume increases much faster than the surface area. Cells obtain nutrients, gain information and rid waste through their plasma membrane. As cell size increases, a cell’s ability to exchange with its environment becomes limited by the amount of membrane area that is available for exchange

The smallest cells are known bacteria called mycoplasm, which diameters of between 0.1 and 1 micrometer. Most bacteria are 1 to 10 micrometer in diameter. Eukaryotic cell are typically 10 to100 micrometer.

2. Cell Shape Diversity of form reflects a diversity of function. THE SHAPE OF A CELL DEPENDS ON ITS FUNCTION.

sperm 1 µm Direction of swimming

Squamous cell

Cubical cell

Columnar cell