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Mitochondria
These organelles are the power houses of the cell and contain the molecular machinery for the conversion of energy. This conversion changes glucose into adenosine tri-phosphate (ATP), the energy of every cell. Mitochondria are mostly protein, but some lipid, DNA and RNA are present. These generally cylindrical organelles have an outer membrane surrounding an inner membrane that folds a facility for the transport of enzymes.
Smooth ER lacks attached ribosomes and often appears more tubular than rough ER. Smooth ER allows the cell a certain ability to perform a variety of specialized functions. It is necessary for steroid sysnthesis, metabolism and detoxification of substances in the liver to take place in the smooth ER. Genes are the units of inheritance from parent to child. At a molecular level they hold the information necessary to direct the synthesis of cellular components. This is accomplished via the genetic code. Genes are units of deoxyribonucleic acid (DNA) contained within the chromosomes. DNA structure is that of a long, double-stranded helix. Each strand of the helix is made of repeating nucleotide bases of only four types: adenine, cytosine, guanine and thymine. It is the sequence of these nucleotides over the length of each individual chromosome added together that make up the human genome. The nucleotides are composed of a phosphate, a certain sugar, and one of the four bases.
Golgi complex
The Golgi is a curved membrane stack that concentrates and packages proteins for export or storage. It also adds directions for the destination of the protein package. Proteins made within the rough ER but are transported off in vesicles to the Golgi. There the vesicles fuse with the membrane and the components are further modified, concentrated and packaged. Therefore, the Golgi shows a polarity in that one side accepts incoming vesicles (convex) and the final product vesicles bud off the opposite side (concave]. In fact, scientists' studies have shown that the enzymes present within the Golgi are at different levels of the membrane stack.
Cell Wall
The Cell Wall is not found in animals cells, but is found in plant cells. It acts as a barrier and helps protect the cell and keep the shape of the cell. It is basically an extracellular structure surounding the plasma membrane. The primary cell wall is extremely elastic. meanwhile the secondary cell wall forms around the primary cell wall after growth is complete (after mitosis.
Lysosomes
Lysosomes are membrane bound vesicles containing more than 40 enzymes that can digest most biological macromolecules. These organelles are the sites of intracellular digestion that are more numerous in cells performing phagocytosis. The limiting membrane keeps the digestive enzymes separate from the cytoplasm. The most common lysosomal enzymes are acid phosphatase, ribonuclease, and deoxyribonuclease. The enzymes function mostly at pH 5 and are inactive at the pH of the cytosol (7.2). This taken with the limiting membrane protects the cell from digesting itself. Lysosomal enzymes are synthesized on the rough ER, trasferred to the Golgi for modification and packaging. The cellular machinery attaches a directional signal to the enzymes that allows the ER and Golgi to sort these proteins and separate them to forming lysosomes.
Primary lysosomes are small concentrated sacs of enzymes that are not digesting anything. Primary lysosomes fuse with a phagocytic vacuole to become secondary lysosomes where digestion begins. As the substances are digested the nutrients diffuse through the lysosomal membrane to the cytosol. Residual bodies are formed when indigestable things remain in the vacuoles. In cells with a long life span such as cardiac muscle cells, residual bodies are more numerous.
Lysosomes also participate in the turnover of cellular organelles. Cytoplasmic components become enclosed in a membrane that fuses with a primary lysosome. In bones, the lysosomal enzymes are released from osteoclasts to digest surrounding bone during the process of remodeling. Lysosomal enzymes are also involved in the process of inflammation.
Nuclear Membrane
The nuclear membrane is vital in all cells. It surrounds the nucleus which is the brain of the cell. The nuclear membrane is composed of two layers and has numerous openings for nuclear traffic.
Chloroplasts
Chloroplasts are organelles that are only found in plant cells. These are organelles that change light into food for the cell, called photosynthisis. The chloroplasts cannot convert light into food with out the chlorophyl, because the chlorophyl is the substance that changes the light into food for the cell. Because the chloroplasts have chlorophyl, the color of the plant cell becomes green, most of the time.
Chromosomes
Cytoplasm
Cytoplasm is the gel-like material inside the cell membrane and outside the nucleus. Cytoplasm contains a large amount of water and many chemicals and structures that carry out the life processes in the cell. These structures that the cytoplasm contains are called organelles. The cytoplasm is the substance contained within the plasma membrane excluding, in eukaryotes, the nucleus. The cytosol makes up about 50% of the cell volume. It contains numerous cytoskeletal elements, organelles, vesicles and metabolic enzymes. The cytoplasm coordinates the movement of intracellular organelles, and provides a framework for the organization of enzyme pathways. All of the necessities of protein synthesis are found within the cytosol and it contains numerous enzymes that build large molecules and break down small molecules.
Cell Membrane
Cell Membrane is the thin and nearly invisible structure that surrounds the cytoplasm of the cell. It also connects the the endoplasmic reticulum, and the nuclear membrane. Each eukaryotic cell has as its boundary to the outside a cell membrane. The cell or plasma membrane is a lipid bilayer containing proteins, cholesterol, and oligosaccharides that functions as a selective barrier for entry and exit of substances. The plasma membrane, by limiting the transport of some things and facilitating the movement of others, helps to maintain the internal environment of the cell, which is different from the fluid outside the cell. Proteins are a very important part of the cell membrane and can be classified into two groups based on physical distribution. Integral proteins are within the cell membrane and may pass multiple times through the membrane. Peripheral proteins are loosely associated with membrane surfaces. On the external surface of the cell membrane are important parts of receptor molecules. Receptors are necessary to cellular signalling, adhesion, and recognition. The cell membrane is not static. It is changed by the addition of new membrane vesicles from the Golgi while removal takes place in the form of vesicles being formed and then fused with lysozomes for processing. This membrane trafficking is important in the cell function.
Peroxisomes
These are small oragnelles containing oxidative enzymes. Peroxisomes contain amino oxidases, hydroxyacid oxidase and catalase. Catalase protects the cell from hydrogen peroxide damage. Enzymes involved in lipid metabolism are also found in peroxisomes. Peroxisomal enzymes are synthesized on the free cytosolic ribosomes with a signal sequence that directs them to peroxisomes. As enzymes are added the peroxisome grows and then splits into two smaller peroxisomes.
Plastids
Plastids are cells that store specific things. They are large cytoplasmic organelles found in the cells of most plants, but they are not found not in animal cells. Plastids form small colorless bodies called proplastids and once formed, certain kinds of plastids can be converted into other types. There are three plastid categories- Leucoplasts (white or colorless plastids that store starch granules) , Chromoplasts (colored plastids that store pigment molecules) and Chloroplasts which are essential in the photosynthetic process.
Cytoskeleton
Within the cell is a complex network of filaments, anchor proteins, and protein motors that form a support and transportation scaffolding. This network provides shape to the cell and participates in cellular movement.
Nucleus
The nucleus is the major organelle of all cells, in which the chromosomes are separated from the cytoplasm by the nuclear membrane. The nucleus is a spherical, sometimes elongated structure that contains the genetic material, the DNA, of the cell. The highly organized chromatin within is enveloped by a nuclear membrane that contains numerous pores for the transport of large macromolecules and ribosomal subunits to the cytoplasm.
Nucleolus
This sperical structure within the nucleus is composed of DNA, RNA and protein. The DNA present is that which codes for RNA, known as nucleolar organizers. Proteins synthesized in the cytoplasm enter through the nuclear pores and become associated with the newly made RNA in the nucleolus. Afterwards the ribosomal subunits migrate to the cytoplasm. The nucleolus disappears during cell division but reappears in the final stage of mitosis.
Vacuole
The vacuole is a membrane - bound sacs for storage, digestion, and waste removal. The vacuole contains a large water solution. The vacuole is extremely large in plant cells but rather small in animal cells.