All living things are made of the same basic building blocks, cells. A human ismade of 65 trillion cells. Cells are everywhere, on you skin, in your blood, andeven on your tongue. In fact, your blood is clear but red blood cells are whatmake your blood red. Most living things are made up of many cells but some aremade of only one cell, like amebas, paramecium, fungi, protists, monerans, andbacteria. There are two basic types of cells, animal cells and plant cells. Theyhave some common parts found in both and other parts that are unique to each. Acell membrane is found in both plant and animal cells. It is the structure thatsurrounds the cell and protects it. Plant cells have a cell wall, a rigidstructure 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 orfood that will be used by the cell. Cells also contain other “smallorgans” called organelles that carryout various cell functions. And thenthere is the control center of the cell, the nucleus, surrounded by a protectiveouter covering call the nuclear membrane. The nucleus contains the DNA, orchromosomes, that carries all the instructions on how a cell will function,live, and reproduce. Every cell needs to energy to live and reproduce. Plant andanimal cells obtain energy in different ways. Animals can not make their ownfood. They obtain energy by taking in food, water, and oxygen and converting itto sugar. Sugar is the only food a cell can eat. Plant cells can make their ownfood from water and sunlight. This process is called photosynthesis. Both plantand animal cells use energy from the food they obtain to reproduce. All livingthings produce more living things. Cell reproduction is called mitosis. Mitosisis the process of a single cell dividing in two and then two more and so on. Inmitosis, the pairs of chromosomes in the nucleus of the parent cell divide intotwo daughter cells. There are four phases of mitosis. In the first phase, thechromosomes 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 thirdphase, the fibers pull the pairs apart to opposite ends of the nucleus. In thefinal phase, the parent cell splits in two, creating two completely new daughtercells exactly like the parent cell. The two daughter cells will grow andeventually the process of mitosis will start again in each one. This is how allliving things grow and continue. In closing, it is important to remember thatall living things are made up of cells. Some have only one cell while othershave very complicated systems of many cells working together. Second, plant andanimal cells take in food, water, and oxygen in very different ways, but bothneed these substances to make the energy needed to live, grow, and reproduce.
Finally, every cell passes on their DNA to future generations through theprocess of mitosis. The DNA, in both plant and animal cells, contains all theinstructions needed for cell to grow and function.
