Cytoplasm

secretory vesicles

As proteins "tagged" for export accumulate in the golgi apparatus, the sacs swell.Then their swollen ends, filled with proteins, pinch off and form secretory vesicles which travel to the plasma membrane. When the vesicles reach the plasma membrane, they fuse with it, the membrane ruptures, and the contents of the sac are ejected to the outside of the cell. Mucus is packaged in this way, as are digestive enzymes made by the pancreas cell.

Cytoplasmic organelles

"little organs" are specialized cellular compartments, each performing its own job to maintain the life of the cell. Many organelles are bounded by a membrane similar to the plasma membrane. These membrane boundaries allow organelles to maintain an internal environment quite different from that of the surrounding cytosol. this compartmentalization is crucial to their ability to perform their specialized functions for the cell.

Inclusions

These are chemical substances that may or may not be present, depending on the specific cell type. Most inclusions are stores nutrients or cell products. They include the lipid droplets common in fat cells, pigments such as melanin in skin and hair cells, mucus and other secretory products and various kinds of crystals.

organelles

described in detail shortly are the metabolic machinery of the cell. Each type of organelle is specialized to carry out a specific function for the cell as a whole. Some synthesize proteins, others package the proteins, and so on.

microtubules

determine the overall shape of a cell and distribution of organelles, they are very important during cell division.

Endoplasmic reticulum

is a system of fluid-filled cisterns (tubules, canals) that coil and twist through the cytoplasm. It accounts for about half of a cell's membranes. It serves as a mini circulatory system for the cell because it provides a network of channels for carrying substances (primary proteins) from one part of the cell to another. Two forms of ER

cytosol

is semitransparent fluid that suspends the other elements. Dissolved in the cytosol, which is largely water, are nutrients and a variety of other solutes (dissolved substances)

Rough ER

is so called because it is studded with ribosomes. Because essentially all of the building materials of cellular membranes are formed either in it or on it, you can think of the rough ER as the cell's membrane factory. The proteins made on its ribosomes migrate into the tubules of the rough ER, where they fold into their functional three-dimensional shapes and then are dispatched to other areas of the cell in transport vesicles. Rough ER is especially abundant in cells that make and export proteins. The enzymes that catalyze the synthesis of membrane lipids reside on the external face of the rough ER, where the needed building blocks are readily available.

ATP

provides the energy for all cellular work, and every living cell requires a constant supply of ATP for its many activities. Because mitochondria supply most of its ATP, they are the powerhouses of the cell.

Intermediate filaments

strong, stable, roselike. they help form desmosomes and provide internal guy wires to resist pulling forces on the cell.

Centrioles

the paired centrioles lie close to the nucleus. They are rod-shaped bodies that lie at right angles to each other, internally there are made up of a pinwheel array of fine microtubules. Centrioles are best known for their role in generating microtubules, and during cell division, the centrioles direct the formation of the mitotic spindle.

Lysosomes

which appear in different sizes, are membranous bags containing powerful digestive enzymes. Because lysosomal enzymes are capable of digesting worn-out or nonusable cell structures and most foreign substances that enter the cell, lysosomes function as the cell's demolition sites. Lysosomes are especially abundant in phagocytes, the cells that dispose of bacteria and cell debris. As described above, the enzymes they contain are formed by ribosomes and packaged by the golgi apparatus. When lysosomes rupture, the cell self-digests.

Cytoskeleton

an elaborate network of protein structures extends throughout the cytoplasm. This network, acts as a cell's bones and muscles by furnishing an internal framework that determines cell shape, supports other organelles, and provides the machinery for intercellular transport and various types of cellular movements. From its largest to smallest elements, the cytoskeleton is made up of microtubules, intermediate filaments and microfilaments.

Golgi Apparatus

appears as a stack of flattened membranous sacs, associated with swarms of tiny vesicles. It is generally found close to the nucleus and is the principle "traffic director" for cellular proteins. Its major function is to modify and package proteins ( sent to it by the rough ER via transport vesicles) in specific ways depending on their final destination. In addition to its packaging-for-release functions, the Golgi apparatus pinches off sacs containing proteins and phospholipids destined for a "home" in the plasma membrane or other cellular membranes. It also packages hydrolytic enzymes into membranous sacs called lysosomes that remain into the cell.

Free radicals

are highly reactive chemicals with unpaired electrons that can scramble the structure of proteins, and nucleic acids. Free radicals are normal byproducts of cellular metabolism, but if allowed to accumulate, they can have devastating effects on cells.

Peroxisomes

are membranous sacs containing powerful oxidase enzymes that use molecular oxygen to detoxify a number of harmful or poisonous substances, including alcohol and formaldehyde. However, their most important function is to disarm the dangerous free radicals. Peroxisomes convert free radicals to hydrogen peroxide, a function indicated by their naming then converts excess hydrogen peroxide to water. peroxisomes are especially numerous in liver and kidney cells, which are very active to detoxification. Although peroxisomes look like small lysosomes, they do not arise by budding from the golgi apparatus. Instead they appear to replicate themselves by simplyy picking in half , as do mitochondria, but most peroxisomes appear to bus from the ER via a special machinery.

Microfilaments

are most involved in cell motility and in producing changes in cell shape. you could say that cells move when they get their act together.

Ribosomes

are tiny, bilobed, dark bodies made of proteins and one variety of the RNA called ribosomal RNA. Ribosomes are the actual sites of protein synthesis in the cell. Some ribosomes float free in the cytoplasm, where they manufacture proteins that function in the cytoplasm. Others attach to membranes, and the whole ribosome-membrane combination is called the rough endoplasmic reticulum.

Mitochondria

are usually depicted as tiny, lozenge-like or sausage shaped organelles, but in living cells they squirm, lengthen, and change shape almost continuously. the mitochondrial wall consists of a double membrane, equal to two plasma membranes, placed side by side. The outer membrane is smooth and featureless, but the inner membrane has shelflike protrusions called cristae. Enzymes dissolved in the fluid within the mitochondria, as well as enzymes that form part o the cristae membranes, carry out the reactions in which oxygen is used to break down foods. As foods are broken down, energy is released. Much of this energy escapes as heat, but some is captured and used to form ATP molecules.

cytoplasm

cellular material outside the nucleus inside the plasma membrane. It is the site of most cellular activities, so you might think of it as the factory area of the cell.

Smooth ER

communicated with the rough variety, it plays no role in protein synthesis. Instead is functions in lipid metabolism (cholesterol and fat synthesis and breakdown) and detoxification of drugs and pesticides. Liver cells are full of smooth ER.

three major elements of the cytoplasm

cytosol, organelles and inclusions