Cells: Constructing Living Things

Cells: Constructing Living Things — page 3 — The diversity of cells is mind-blowing They come in a huge array of sizes and shapes These characteristics are influenced by where a cell lives and what work it needs to do to survive The human body has an estimated 37 2 trillion cells A fruit fly has 50,000 cells Scientists recently discovered Cells of All Shapes and Sizes bacterial cells so tiny that 150,000 could fit into the tip of a human hair Cells can also be huge An ostrich egg yes it’s a single cell is about the size of a melon and weighs over three pounds 1 kilogram while a giraffe nerve cell can be several meters long 6

Cells: Constructing Living Things — page 4 — A cell’s size and shape can tell us a lot about what it does Unicellular organisms tend to be small Their size allows them to take up nutrients and reproduce quickly sometimes within minutes These things help them to adapt to new environments organism there can be hundreds of cell types Their many shapes and sizes help them carry out different life-supporting functions within that organism In a single multicellular Cell Power Nerve cells send signals from one part of the body to another They have a long thin shape with branches that reach out in different directions This allows them to communicate with other cells quickly and efficiently Skin cells can be wide and flat allowing fewer cells to cover a greater area They are also packed tightly together This allows them to form a smooth strong and stretchy barrier that protects the body from the outside environment 7

Cells: Constructing Living Things — page 5 — Inside Every Cell A Cell's Inner Workings For all their differences cells have certain fundamental things in common For starters all living cells use energy Energy gives cells the power they need to survive grow reproduce and defend themselves Without a source of energy a cell will eventually die Where do cells get energy from Some organisms like plants are producers They create their own energy-containing food in a process called photosynthesis Other organisms like animals are consumers They get their energy by eating plants or other animals Reaction Action Many chemical reactions go on inside a cell Together all of these reactions are called the cell’s metabolism Anabolic reactions store energy by building complex molecules out of simpler substances An example would be building carbohydrates out of simple sugar complex molecules down into simple substances An example would be breaking a complex carbohydrate down into simple sugars Catabolic reactions release energy for the cell to use by breaking 8

Cells: Constructing Living Things — page 6 — All cells contain DNA or deoxyribonucleic acid Amazingly all cells store their genetic information in the same way encoded in DNA The DNA in each cell contains all the information needed to build an entire organism It is like a master plan that tells a cell what to do what to make and when DNA Makes the Difference When scientists compared the DNA in humans to the DNA in chimpanzees and gorillas they found that we share approximately 99 percent of our DNA with chimpanzees and 98 percent with gorillas The remaining one or two percent is enough to make us as different as we are 9

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