Cell Signaling

Cell signaling can best be defined as the process of cells communicating with each other and within the cell.  the three stages of cell signaling are reception, transduction, and response.  Some different ways cells receive signals are through G-proteins, ligands, tyrosine-kinase, and steroids and hormones.  All of these involve the phospholipid bilayer and its protein. 

Centrosome

Microtubules of the cytoskeleton grow from the centrosome.  The centrosome is located near the nucleus. In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring.  These centrioles replicate during cell division.  In cell diagrams, the centrosome resembles spider legs. 

Cytoskeleton

The cytoskeleton is a network of fibers that organizes the structures and activities of the cell.  It provides mechanical support and maintains the shape of the cell.  The cytoskeleton also provides anchorage for many organelles and helps with cell motility, including flagella and cilia.  The three types of fibers in the cytoskeleton are microtubules, microfilaments, and intermediate filaments.  Microtubules are the thickest fibers and move chromosomes during cell division.  Microfilaments are the thinnest of the fibers and are designed to resist tension.  Intermediate filaments are specialized in bearing tension and the most permanent of the fibers.

Mitochondria

Mitochondria are the sites of cellular respiration, generating ATP from the catabolism of sugars, fats, and other fuels in the presence of oxygen. They convert energy to forms that cells can use for work. Mitochondria are in almost all eukaryotic cells, outside of the endoplasmic reticulum. They have a smooth outer membrane and a folded inner membrane, called cristae. The cristae present ample surface area for the enzymes that synthesize ATP. The area enclosed by the cristae is called the mitochondrial matrix, which is a fluid-filled space with DNA, ribosomes, and enzymes.  They can move, change shape, and divide by themselves. They look like beans, leaves, or even a piece of meat.

Vesicles and Vacuoules

Vesicles and Vacuoles are membrane-bound sacs with varied functions. They look as they were described, like big sacs of empty space, but they do much more. There are 3 types: food vacuoles, contractile vacuoles, and central vacuoles. A food vacuole is from phagocytosis, and fuse with lysosomes. A contractile vacuole is found in freshwater protists, and they pump excess water out of the cell. The central vacuole, the most common vacuole, is found in many mature plant cells, right outside of the endoplasmic reticulum. Its functions include stockpiling proteins or inorganic ions, depositing metabolic byproducts, storing pigments, and storing defensive compounds against herbivores.  These vacuoles are made of fused membrane vesicles that are filled with water that contains organ and inorganic molecules. Vesicles are very small vacuoles that are formed in the Golgi and can carry proteins to other places in the cell. 

Lysosomes

The lysosome is an organelle surrounded by a membrane that digests macromolecules.  They can digest proteins, fats, polysaccharides, and nucleic acids.  Lysosomes function similarly as tiny stomachs in a cell, and are synthesized by the rough endoplasmic reticulum.  While lysosomes provide usable nutrients for the cell, they are also responsible for the destruction of cells.

Ribosomes

Ribosomes are small, round organelles, found both in the cytoplasm and attached to the rough endoplasmic reticulum.  They contain rRNA and proteins.  Ribosomes that are suspended in the cytosol produce proteins that function in the cell, and ribosomes that are attached to endoplasmic reticulum produce proteins that are exported. 

Smooth ER

The Smooth ER, or endoplasmic reticulum, contains many enzmes.  Smooth ER looks like a folded line but unlike the rough ER, smooth ER does not contain ribosomes.  Smooth ER contains enzymes that snythesize lipids that include, oils, phospholipids, and steroids.  Also some enzymes contained in smooth ER of liver cells can help to detoxify drugs and poisons.  The ER is continuous with the nuclear envelope and the cisternal space of the ER is continuous with the space between the two membranes of the nuclear envelope. 

Rough ER

The rough ER, or endoplasmic reticulum, are made of bound ribosomes that are attatched to the outside of the ER.  Rough ER is a membrane factory, many membrane bound proteins are synthesized directly into the membrane.  The rough ER looks like a lot of folded lines with small bums all over it.  The Rough ER contains enzymes that synthesis phospholipids.The ER is continuous with the nuclear envelope and the cisternal space of the ER is continuous with the space between the two membranes of the nuclear envelope. 

Golgi Apparatus

The Golgi finishes, sorts, and ships a cells products.  Cells that are specialized for secretion contain numerous golgi apparatuses. Golgi is made of  cisternae, these are flat sacs that look similar to a stack of pita bread.  The golgi has 2 sides, one that recieves materials called the cis side, and one that buds off vesicles that go to other sites called trans.  The Golgi can produce its very own macromolecules; such as pectin and noncellulose polysaccharides.

Nucleus

The nucleus is the “control center” of a cell.  It contains most of the genes in eukaryotes and is separated from the rest of the cell by a double membrane.  Much like the cytoskeleton, the nucleus has a nuclear lamina that maintains the shape.  Chromosomes form of chromatin when the cell is dividing.  Humans have 23 pairs of chromosomes.  Inside the nucleus, there is a region of densely stained fibers and granules, called the nucleolus. The nucleus is responsible for creating material (RNA) that is used in synthesizing proteins. 

Cytoplasm

The area between the plasma membrane and the nucleaus is called cytoplasm.it is a clear fluid that contains many vital parts of the cell.

Plasma Membrane

The plasma membrane is a barrier that allows passage of oxygen, nutrients, and wastes for the whole volume of a cell. It is made of a phospholipid bilayer with embedded proteins. The plasma membrane surrounds the cell like a barrier. It looks like a wall or barrier to regulate things going in or out. It contains many integral membrane proteins such as: integrins, cadherins, and desmosomes. These proteins perform different functions that regulate what goes in and out of the cell.

Hi my name is Mr. Cell

There are 2 types of cells: Prokaryotic and Eukaryotic. The location of chromosomes is one of the major differences between Prokaryotic and Eukaryotic cells. Eukaryotes have chromosomes in the nucleus and Prokaryotes have them in the nucleoid. All cells have some things in common. They all contain plasma membranes, cytosol, chromosomes, and ribosomes.