Eukaryotic+Cells

Eukaryotic cells are found in fungi, protists, plants and animals. Unlike prokaryotic cells, they contain far more structure and organization, using organelles ("small organ") that each do a separate task. This article will focus on animal and plant cells only. Each organelle will be put into one of four general categories: Manufacture, Breakdown, Energy Processing, and Suppor/Movement/Communication.

Starting with the manufactuerers, all eukaryotic cells have a **nucleus**. The nucleus controls the cells activities, as well as contains DNA as the cell's hereditar blueprint. Chromatin, DNA attached to proteins, floats around the nucleus. Surrounding the nucleus is a nuclear envelope, which is a double membrane with pores in it, allowing materials in and out of the organelle. Finally, in the nucleus, there is a nucleolus, which consists of chromatin, RNA, and proteins. This is the center where ribosomes are made.

The next manufacturer is **Rough Endoplasmic Reticulum (ER)**. Rough ER is a network of "sacs" with two main functions: 1) It produces membrane. Some proteins made from the ribosomes are put into the ER membrane, thus it enlarges and breaks off for other organelles. 2) It makes proteins that are secreted by the cell. They do this by: 1) The ribosomes studded along the side produce a polypeptide, where it is passed into the Rough ER. 2) The polypeptide becomes a glycoprotein when the ER adds sugar to it. 3) The glycoprotein hits the end of the ER, where a membrane surrounds it as it "buds off."  4) The glycoprotein gets sent off in a transport vesicle.


 * Smooth ER** is a continuation of Rough ER, but withouth the ribosomes studded along its membrane. The functions of smooth ER are: 1) To produce lipids, such as steroids and phospholipids 2) Enzymes within (in liver cells) help regulate the amount of sugar released from the liver into the bloodstream. 3) It stores Calcium ions, which are necessary in muscles, because they cause them to contract.

Continuing off from the Rough ER, the transport **vesicle** (like a car or taxi) comes to the **Golgi Apparatus**. The Golgi apparatus acts like a post office, by receiving vesicles from the ER and modifying them chemically. This modification seems to "mark" them and decide where they go. Then there's a shipping side of the apparatus, which sends the vesicles out to do whatever they're supposed to do.


 * Mitochondria** are energy processing organelles that turn energy from one form to another form such as in cellular respiration. This is when the energy taken from food we eat is converted to the chemical energy of ATP (adenosine triphosphate). ATP is used as the main energy to carry out cell work. There are two compartments within a mitochondrion. One is the inner membrane space that conatins a fluid compartment. This fluid compartment contains mitochondrial matrix where many of the chemical reactions are performed such as the cellular respiration. The inner membrane is folded many times with folds called cristae that contain ATP enzyme molecules to increase surface area and increase the ability to make ATP.

Another form of energy process are **chloroplasts** found only in plant and some protist cells. Chloroplasts convert solar energy into chemical energy stored in sugar. These organelles are like the "photosynthesizers" of these cells. There are three main compartments in chloroplasts: the space between inner and outer membranes, the stroma, and the space inside the grana. The stroma is a viscous or thick fluid within the membrane full of the grana. Grana are hollow disks and tubes where the organelle captures the solar energy.

Moving on to the general function of breakdown: First there are **lysosomes**. Lysosomes are basically sacs of enzymes, enclosed by a membrane. Lysosomes break apart nutrients, and also harmful bacteria (this happens in white blood cells). They also, however, break apart damaged organelles, and recycle the molecules to make a new one. Lysosomes are made by ER and the Golgi apparatuses.

Then there are also peroxisomes, which breakdown H2O2 and turn them into harmless chemicals the body can use. (I don't know much about these...)

Finally, for breakdown organelles, there are **vacuoles**. They can digest, like lysosomes, but they also can store chemicals. There are several different types of vacuoles: 1) Central vacuoles are found in plant cells, and they make up the majority of the cell. They can absorb water, which keeps the plant standing upright, and they can also store vital chemicals or waste products of cell metabolism.  There are also contractile vacuoles, which are star shaped, and they absorb water from the cell, and then pump it out.  This is necessary for protists, because they constantly absorb water from their environment, and they need to get rid of it, otherwise they could burst.