The cytoskeleton gives the cell its shape and structure while providing support. It is made up of 3 fibres: 1. Microtubules – long hollow tubes that act as movement tracks for organelles. 2. Intermediate Filaments – a little smaller than microtubules, give the cell its strength. 3. Microfilaments – tiny threads (the smallest of the 3) that allow the cell to move and divide.
The nucleus is the portion of the cell that contains DNA, deoxyribonucleic acid. The Nucleus has two important functions: 1. Protect the DNA from the cytoskeleton of the cell. 2. DNA must be available at the proper times. The nucleus also contains the nucleolus, an organelle that produces ribosomes.
Ribosomes are responsible for protein formation, and they form proteins by bonding together amino acids. Note: All proteins are just long chains of amino acids. Ribosomes themselves are made of proteins and RNA. You will learn more about RNA in Biology 30!
Endoplasmic Reticulum fills a large portion of the cytoplasm, and is a network of tightly folded membranes (sort of like the ones that surround the cell). Endoplasmic reticulum has numerous functions, including the productions of proteins and lipids (fats). ER can be rough (covered with ribosomes) or smooth (not covered with ribosomes).
The Golgi Apparatus also deals with protein synthesis, and is a bunch of folded up membranes. After leaving the ER, proteins often come to the Golgi Apparatus to be modified, sorted and packaged. Sometimes proteins are stored in the Golgi Apparatus for later use, whereas other times they are shipped off to other parts of the cell.
Vesicles are tiny sacs that are used for protecting certain things in the cell from chemical reaction until they are needed. Basically, vesicles separate materials from the rest of the cytoplasm and transport materials from place to place within the cell.
Mitochondria supply energy to the cell, turning the food you eat into useable energy for the cell. Strangely, mitochondria have their own unique DNA and ribosomes, which suggests that sometime ago, they used to exist alone in nature as prokaryotic cells. Mitochondria are shaped like a bean!
Vacuoles are fluid-filled sacs used for storage of material inside a cell. There are tiny vacuoles in both plant and animal cells. In plants cell only, however, there is also a large central vacuole which takes up most of the space. This central vacuole is responsible for holding water and supporting the overall structure of the plant. Sometimes a central vacuole also contains toxins used to discourage other creatures from ingesting the plant.
Animal Cells Lysosomes Note: there is still somewhat of a debate as to whether or not plant cells contain lysosomes. Centrioles – cylinder-shaped organelles made of microtubules that allow the cell to divide during mitosis. Plant cells Chloroplasts Cell Walls
Lysosomes are organelles that contain enzymes made for fighting invading bacteria and viruses. The contents of lysosomes are dangerous to other parts of the cell – if released, the contents would destroy parts of the cell they are meant to protetct. As a result, lysosomes are enclosed in a membrane.
Plant cells, in addition to having cell membranes around the cell, also have cell walls. Cells walls support the plant cell, giving it structure. They also contain holes for water to travel in and allow the cell to be rigid. This is why when you water a plant it gets strong and stiff again. Most of the wood in a tree is made from the cell walls of dead plant cells. Bacteria, algae and fungi cells mostly have cell walls, as well.
Chloroplasts are the organelle that take solar energy and convert it into energy-rich molecules that the cell (and other creatures) can use, known as photosynthesis. Chloroplasts, like mitochondria, also have their own DNA and ribosomes, suggesting that they too used to be prokaryotic cells that existed on their own. Chloroplasts are highly compartmentalized, containing stacks of disc-shaped sacs within an inner membrane.