Cell Function

CELL STRUCTURE AND FUNCTION All living things are made of the same basic building blocks, cells. A human is made of 65 trillion cells. Cells are everywhere, on you skin, in your blood, and even on your tongue. In fact, your blood is clear but red blood cells are what make your blood red. Most living things are made up of many cells but some are made of only one cell, like amebas, paramecium, fungi, protists, monerans, and bacteria. There are two basic types of cells, animal cells and plant cells. They have some common parts found in both and other parts that are unique to each. A cell membrane is found in both plant and animal cells. It is the structure that surrounds the cell and protects it. Plant cells have a cell wall, a rigid structure surrounding the cell membrane. Animal cells do not have a cell wall. Cytoplasm is the thick, jelly-like substance that makes up most of the cell. Vacuoles are fluid filled sacs in the cell. The vacuoles contain stored water or food that will be used by the cell. Cells also contain other small organs called organelles that carryout various cell functions. And then there is the control center of the cell, the nucleus, surrounded by a protective outer covering call the nuclear membrane. The nucleus contains the DNA, or chromosomes, that carries all the instructions on how a cell will function, live, and reproduce. Every cell needs to energy to live and reproduce. Plant and animal cells obtain energy in different ways. Animals can not make their own food. They obtain energy by taking in food, water, and oxygen and converting it to sugar. Sugar is the only food a cell can eat. Plant cells can make their own food from water and sunlight. This process is called photosynthesis. Both plant and animal cells use energy from the food they obtain to reproduce. All living things produce more living things. Cell reproduction is called mitosis. Mitosis is the process of a single cell dividing in two and then two more and so on. In mitosis, the pairs of chromosomes in the nucleus of the parent cell divide into two daughter cells. There are four phases of mitosis. In the first phase, the chromosomes are in a tangle and the nuclear membrane dissolves, or breaks apart. In the second phase, special fibers line up the chromosomal pairs. In the third phase, the fibers pull the pairs apart to opposite ends of the nucleus. In the final phase, the parent cell splits in two, creating two completely new daughter cells exactly like the parent cell.