Introduction to the Human Cell

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"Introduction to the Human Cell"
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Here goes, I am currently getting a 98.8% in my college bio class, so I hope I do my teachers justice!

All living things are made of cells, including humans. The cell can take many shapes, and the shapes determine the name the cell type can have. However, all cells in the human body are alike in most ways. They all have organelles, or small functional units, a cytoplasm, which is the liquid inside the cell, and a membrane. To begin with, the outermost portion of the cell-the plasma membrane.

The plasma membrane is made of two layers of phospholipids, which have a water loving-hydrophilic-end, as well as a water hating end-hydrophobic. The two lipids are arranged with their tails, the hydrophobic end, to each other, with the water loving ends facing out. The arrangement of the lipids enable the membrane to have selective permeability, which is what keeps things in and out that need to be kept either in or out. The membrane isn't rigid, either; it is fluid, in the respect that it can move and change shape to respond to pressure or changing environments. Also, the membrane can move to surround an object in order to take it in.

Next is the nucleus. The nucleus is the part of the cell that has the nuclear material-DNA. The nucleus is surrounded by a membrane of its own, as are all the organelles of the cell.

There are several organelles: ribosomes(not bound by a membrane); the Golgi apparatus; the endoplasmic reticulum; the mitochondria; microtubules and microfilaments. Also, if the cell is designed for movement, it can have cilia or a flagellum.

Ribosomes are the place that all proteins in the body are made. Every thing that is made up of protein-most of the body-is put together on the ribosome.

The Golgi apparatus is an organelle that packages materials in the cell for destruction, elimination, and transport.

The endoplasmic reticulum (ER) is made of two sections, rough with ribosomes, and smooth, without. Rough ER is where proteins are made and packaged for transport. The smooth is where lipids, steroids, and fatty acids are digested.

The mitochondria is where sugars are broken down to make ATP, the energy that all cells use to run.

Microtubules and microfilaments are the structure and support system for the cell. They form a scaffolding system that supports and maintains the cells shape.

A flagellum, or many cilia, are used to push cells around in a watery environment. They are mostly on single-celled cells, but sperm cells have a flagellum, and some cells in the lungs have cilia to propel mucus.

All cells are essentially the same. Their different shapes, sizes, and functions are due to differentiation, an event that occurs early in the cells life. Different genes in the human body are turned on or off, depending on the need for that cells function. When these genes are expressed stronger than others, they cause the cell's shape to change to fit that need.

Everything is made of cells; they are the building blocks of all life. While the shapes, sizes, colors, and functions can change from one area of the body to the other, they all have the same basic makeup.

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