Cell Structure
Animal Cells
Cell (Plasma) Membrane
The cell membrane is what holds the cell together. It surrounds all the organelles of the cell and acts as a gate keeper. Because the cell membrane is the "gate keeper", it is said that the cell membrane is selectively permeable. This means that the cell membrane chooses what substances get to enter or exit the cell.
The cell membrane is made up of a lipid-bilayer. A lipid bilayer is an assembly of phospholipids into two layers. Phospolipds have heads that are hydrophilic, meaning they like water, and tails that are hydropohobic, meaning they hate water. When surrounded by water, phosopholibds align themselves into to layers so that the heads are facing out toward the water and the tails are facing inward toward each other and away from the water.
The cell membrane is what holds the cell together. It surrounds all the organelles of the cell and acts as a gate keeper. Because the cell membrane is the "gate keeper", it is said that the cell membrane is selectively permeable. This means that the cell membrane chooses what substances get to enter or exit the cell.
The cell membrane is made up of a lipid-bilayer. A lipid bilayer is an assembly of phospholipids into two layers. Phospolipds have heads that are hydrophilic, meaning they like water, and tails that are hydropohobic, meaning they hate water. When surrounded by water, phosopholibds align themselves into to layers so that the heads are facing out toward the water and the tails are facing inward toward each other and away from the water.
Among the phospholipids in the cell membrane, there are many proteins that are mixed in to the cell membrane. These proteins have a variety of functions and are what allows the membrane to be selectively permeable. Because these proteins "float" among the phospholipids, they are free to move and rearrange themselves around the membrane. This fluid like mobility of proteins is called the Fluid-mosaic model.
The Nucleus
The nucleus contains the cells DNA, which provides the instructions for how the cell carries out its functions. The nucleus is surrounded by a membrane of its own, called the nuclear membrane, which contains pores that allow proteins to enter the nucleus to act as messengers passing information back and forth from the cell to the nucleus. |
Cytoplasm
Cytoplasm is the fluid that gives shape and provides support to the cell. It is made up mostly of water
Cytoskeleton
The cytoskeleton is a network of protein filaments (microfilaments and microtubules) that are mixed in among the cytoplasm and give support and shape to the cell. Some of the cytoskeleton also helps to transport materials between different parts of the cell.
Vesicles
Vesicles are small sac-like structures that are used by the cell to store and transport materials between organelles. Vesicles are made up of phospolipids just like the cell membrane.
Lysosomes
Lysosomes act as the clean up crew of the cell. They break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell, and they break down old organelles that have outlived their usefulness to the cell.
Ribosomes
Ribosomes are small particles that are found throughout all cells. They are made of pieces of RNA and protein. Ribosomes read segments of DNA code to assemble amino acids into proteins.
Cytoplasm is the fluid that gives shape and provides support to the cell. It is made up mostly of water
Cytoskeleton
The cytoskeleton is a network of protein filaments (microfilaments and microtubules) that are mixed in among the cytoplasm and give support and shape to the cell. Some of the cytoskeleton also helps to transport materials between different parts of the cell.
Vesicles
Vesicles are small sac-like structures that are used by the cell to store and transport materials between organelles. Vesicles are made up of phospolipids just like the cell membrane.
Lysosomes
Lysosomes act as the clean up crew of the cell. They break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell, and they break down old organelles that have outlived their usefulness to the cell.
Ribosomes
Ribosomes are small particles that are found throughout all cells. They are made of pieces of RNA and protein. Ribosomes read segments of DNA code to assemble amino acids into proteins.
Endoplasmic Reticulum (ER)
The ER is where lipid and protein synthesis occurs. The ER has two parts, the smooth ER and the rough ER. What makes the ER rough is the attachment of ribosomes to it. The rough ER is the site where protein synthesis occurs. The ribosomes on the ER create proteins and deposit them in to the ER. The ER moves the proteins through its tubules to the smooth ER, which does not have ribosomes attached to it. The smooth ER then envelopes the proteins in vesicles and sends them through the cytoplasm to the Golgi Apparatus |
Plant Cells
Cell Wall
The cell wall is a strong supporting layer that wraps around the outside of the cell membrane of plant cells. Many prokaryotes have cell walls as well. The main function of the cell wall is to provide support and protection for the cell. The cell wall contains pores, called plasmodesmata, that allow water and other nutrients to pass from cell-to-cell. Cell walls are what allows plants to stand up and be rigid without having a skeletal system.
Vacuole/Central Vacuole
The central vacuole is a large sac inside a plant cell that is filled with mostly water. The purpose of the central vacuole is to provide assistance to the cell wall in maintaining a plants shape and structure. When the central vacuole is full, the pressure from the water inside helps to strengthen the cell walls. When a plant is not hydrated well enough, the vacuoles hold less water, which takes away from the strength of the cell walls causing the plant to wilt.
The cell wall is a strong supporting layer that wraps around the outside of the cell membrane of plant cells. Many prokaryotes have cell walls as well. The main function of the cell wall is to provide support and protection for the cell. The cell wall contains pores, called plasmodesmata, that allow water and other nutrients to pass from cell-to-cell. Cell walls are what allows plants to stand up and be rigid without having a skeletal system.
Vacuole/Central Vacuole
The central vacuole is a large sac inside a plant cell that is filled with mostly water. The purpose of the central vacuole is to provide assistance to the cell wall in maintaining a plants shape and structure. When the central vacuole is full, the pressure from the water inside helps to strengthen the cell walls. When a plant is not hydrated well enough, the vacuoles hold less water, which takes away from the strength of the cell walls causing the plant to wilt.
Chloroplast
Chloroplasts are disc-like structures that contain chlorophyl. Chloroplasts are like solar generators for plants because they convert sunlight into energy. A chloroplast has two membranes that surround a large number of tiny discs called thylakoids. Thylakoids are where photosynthesis takes place. The thylakoids are arranged into stacks called granum. The rest of a chloroplast is filled with stroma, a fluid that is similar to cytoplasm found inside cells. |