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Cells: The Basic Unit of Life Where does life come from?!? The answer may seem very obvious to us now, but people who lived long ago had some interesting ideas. Originally, people thought that life came from the heavens – mostly through rain. Later, as the world became more scientific, they thought that life must generate spontaneously.
This was disproved through a famous experiment where Aristotle placed a piece of meat in an open jar, and one in a closed jar. What do you think happen? What did the Prove?
The open jar quickly filled with maggotts, flies, and worms. • The closed jar didn’t get any insects. • This meant that life had to come from somewhere – it couldn’t generate inside the closed jar.
Eventually, with the invention of the microscope, people realized that all living organisms are made up of one or more cells. All of the cells that makes up plantshave the same structures inside. The cells that name up animals are also similar to each other, but slightly different than the plants.
Animal Cells • All animal cells have the same structures. • The first is the cellmembrane. • This is like, a gatekeeper, surrounding the whole cell and controlling the movement of materials into and out of the cell.
The Nucleus • The nucleus of the cell is like the ‘brain’ or the control center. • It directs all of the cells activities. Inside the nucleus is the nucleolus. • Also in the nucleus there are chromosomes which contain all of the genetic information (the stuff passed down by the parent cells). The chromosomes look like balled up strings.
Each chromosome contains many genes, which determine the specific characteristics of an individual. • The cytoplasm is the area of the cell where all of the ‘work’ happens. This is where nutrients are absorbed, transported, and processed. You could think of it like the blood of the cell.
Each Cell also has a number of organelles. These are kind of like our organs. The have a specialized purpose and do a specific job.
Plant Cells • Plant cells contain ALL of the structures and organelles found in animal cells, plus a few more. • Plant cells have a rigid cell wall that surrounds the cell membrane. This gives the cell protection and support.
Plant cells also contain larger vacuoles, which are spaces filled with liquids containing water, sugar, minerals, and proteins. • They also have chloroplasts which are organelles that are filled with chloroplasts. This gives plants their green color, and helps with photosynthesis.
