University:
Ridge Point High School
Course:
Biology
Academic year:

2019
Views:

269

Pages:

2
Author:

Y. Mahon

CELL SHAPE AND SIZE The shape of the cell usually corresponds to its function. The human body consists of at least 1012 cells and these cells differ in shape and size. Cell size ranges from 5 – 15 microns (1micron = 0.001 ÿm). The cells with the smallest size are bacteria, while the largest cells are ostrich eggs, having a diameter of 30 – 80 ÿm. However, these cells have the same three basic structures, namely as follows. a. Plasma membrane, which divides the inside of the cell from the outside environment. Functions, among other things, help regulate the transport of materials between cells and their environment. The plasma membrane is a double layer of lipoproteins (fat and protein). b. The nucleus or core material contains genetic information in the form of DNA which plays a role in regulating cell activities and can carry out replication in cell reproduction. The nucleus is covered by a nuclear membrane whose arrangement is the same as the plasma membrane. The cell nucleus is generally located in the center of the cell. c. Cytoplasm, in which active chemical reactions occur in metabolic processes. The cytoplasm contains enzymes, proteins, fats, as well as special structures that have certain functions called organelles Why are cells generally small? Why couldn't cells be discovered before Robert Hooke? Cells are generally very small (microscopic), so we cannot see them with the naked eye. Cells were only discovered after the microscope was created because microscopes apart from having the ability to differentiate (resolving power) can also magnify the image of objects. The average cell in our body measures 10 – 100 ÿm, 1 ÿm = 10–9m. Generally, light microscopes are able to help our eyes to see objects as large as 0.0001 ÿm by using phase contrast or immersion oil