Nucleus- the brain or control center of the cell. The Nucleus, a membrane-bound structure of a cell, plays two crucial roles in controlling the cell. The nucleus carries the cell’s genetic information that determines if the organism will develop, for instance, into a tree or a human; and it directs most cell activities including growth, metabolism, and reproduction by controlling protein synthesis. The presence of a nucleus distinguishes the more complex eukaryotic cells of plants and animals from the simpler prokaryotic cells of bacteria and cyanobacteria that lack a nucleus. The nucleus is the most predominate structure in the cell. It is typically round and occupies 10% of the cells total volume. The nucleus is wrapped in a double-layered membrane called the nuclear envelope. The space between the nuclear envelope layers is called perinuclear space. The nuclear envelope is attached to a network of membrane-enclosed tubules that extends throughout the cell called the endoplasmic reticulum. The nuclear envelope is perforated by many holes, called nuclear pores, that permit the movement of selected molecules between the nucleus and the rest of the cell, while blocking the passage of other molecules. The nucleus contains the nucleolus, which manufactures the organelle known as the ribosome, or the protein producing organism. Genetic information in the form of deoxyribonucleic acid(DNA) is stored in threadlike, tangled structures called chromatin within the nucleus. During the process of cell division known as mitosis, in which the nucleus divides, the chromatin condense into several distinct structures called chromosomes. Each time the cell divides, the heredity information carried in the chromosomes is passed to the two newly formed cells. The DNA in the nucleus also contains the instructions for regulating the amount and types of proteins made by the cell. These instructions are copied, or transcribed, into a type of ribonucleic acid(RNA) called messenger RNA (mRNA). The mRNA is transported from the nucleus to ribosomes, where proteins are assembled.
Nuclear Envelope- The nucleus is wrapped in a double-layered membrane called the nuclear envelope. The space between the nuclear envelope layers is called perinuclear space. The nuclear envelope is attached to a network of membrane-enclosed tubules called the endoplasmic reticulum. The nuclear envelope is perforated by many holes, called nuclear pores, whose job is to permit the movement of selected molecules between the nucleus and the rest of the cell, while blocking the passage of other molecules.
Chromatin- a collection of separate structures called Chromosomes. Within the nucleus the DNA is organized along with proteins into Chromatin. During Mitosis, the chromosomes condense into what is known as Chromosomes, which allows the genetic information of the previous cell to be passed on.
Chromosome- Chromosomes are the microscopic structure within cells that carries the molecule deoxyribonucleic acid. DNA is the hereditary material that influences the development and characteristics of each organism. In bacteria and bacteria-like organisms called archaebacteria, chromosomes are simple circles of DNA that float around in the cell. In more complex cells, or Eukaryotes, chromosomes are stored within a well developed and defined nucleus. In eukaryotic cells, chromosomes are highly complex structures in which the shape of the DNA molecules is linear, rather than circular. Chromosomes consist chiefly of proteins and DNA. Tiny chemical subunits called nucleotide bases form the structure of DNA. A sequence of these bases that are along a DNA strand will create a code for the production of a special protein also known as a gene. Genes occupy precise locations on the chromosome. Each cell contains enough DNA to form a thread extending about 2 m (about 7 ft). Proteins called histones play a key role in packaging DNA within chromosomes. Sections of the DNA molecule wind around clusters of histones to form units called nucleosomes, which resemble spools encircled with thread. Another type of protein, called nonhistone chromosomal protein, will continue to condense nucleosomes into compact structures. Chromosomes become most condensed when a cell is preparing to divide.
The chromosome structure ensures that even when the DNA is highly confined, it is still able to carry out cell transcription, or the production of messenger ribonucleic acid(mRNA). Messenger ribonucleic acid is the molecule that carries the DNA instructions to the sites where proteins are produced, indicating which protein is necessary to be made at that specific time. In addition, chromosomes permit DNA to replicate, or reproduce itself, but still keep the genetic information that is crucial and unique to that cell and that entire organism. The chromosomes of nearly all eukaryotic life forms contain two important structures: centromeres and telomeres. During cell division, the centromerevisible through a microscope as a knotlike structureconnects to an apparatus called the spindle. The spindle contains fibers that move the centromeres around, causing the rest of each chromosome to follow. This is necessary to make sure that chromosomes will be in the correct spot during mitosis, when a cell divides to give rise to two cells, or during meiosis, the process of cell division that creates eggs or sperm. Telomeres are specialized sequences of DNA that are found at the tips of chromosomes. Telomeres serve as a kind of protective cover that prevents the ends of chromosomes from attaching to the ends of other chromosomes. Scientists suspect that telomeres may influence the activity of nearby genes and may play a role in determining the life span of a cell.
Nucleolus- This is the most visible structure in the nucleus. It synthesizes molecular ingredients of ribosomes which will later become proteins.
Ribosomes- There are two different forms of Ribosomes, Free ribosomes, and bound ribosomes. Free Ribosomes are suspended in the cytosplasm, and their job is to carry out protein synthesis. Bound Ribosomes are attached to the outside of the endoplasmic reticulum. Bound Ribosomes usually synthesize proteins that are going to be shipped out of the cell. Even though their jobs are different, Bound and free ribosomes are structurally the same. The faster the organism can synthesize proteins, the more ribosomes they have in their cells.
Vesicles- membrane enclosed sacs.
Endomembrane system- Different membranes of the Eukaryotic cells, together are formed into one group called the Endomembrane system. These membranes are related either because their composition is the same or if they transfer segments of the membrane through the membrane of small vesicles. Despite the common system that they share, it does not mean that they are similar in structure or function, and only really need to be membranes to be considered in the Endomembrane system. Included in the endomembrane system is the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, the lysosomes, some kinds of vacuoles, and the plasma membrane. Even though the plasma membrane is not an ENDOmembrane, it is still in the group because it shares functions similar to the likes of edoplasmic reticulum and other internal membranous structures.
Endoplasmic Reticulum- There are two forms of Endoplasmic reticulum, rough and smooth, but together they form a membranous labyrinth so long and extensive that is accounts for more than half the total membrane in many eukaryotic cells. It does this by folding over and over itself many times thereby forming many membranous sacs. It consists of a network of membranous tubules and scas called cisternae. There are two distinct regrions of Endoplasmic reticulum that differ in structure and function. Smooth Endoplasmic Reticulum lacks ribosomes, and appears to have a smooth surface when looking under a light microscope or electron microscope. On the other hand Rough Endoplasmic reticulum consists of many ribosomes, which look bumpy and rough under a microscope, which was where Rough Endoplasmic reticulum got its name. Smooth Endoplasmic reticulum funtions in diverse metaolic processes like sythesis of lipids, and is found commonly in places such as the liver. Smooth Endoplasmic reticulum is used in the liver to detoxify poisonous substances. Rough Endoplasmic reticulum is important for protein synthesis because of its ribosomes. As discussed earlier, the ribosomes that are connected to the Rough Endoplasmic Reticulum differ from the ribosomes in the cytoplasm, for they are responsible for producing proteins that will eventually be shipped out of the cell. It is also responsible for producing membranes.
Golgi Apparatus- proteins from both the free and bound ribosomes of the cell are sent to the Golgi apparatus, the center of manufacturing, sorting and shipping in the cell. The Golgi apparatus is an organelle that resembles a stack of deflated balloons. The Golgi apparatus is filled with enzymes that allow it to finish the processing of the protein. These enzymes will add sulfur or phosphorus to certain regions of the proteins, or it might even chop off a small piece of the protein. Once it is completed, the protein leaves the Golgi apparatus and goes to its destination either inside or outside of the cell wall. The Golgi apparatus also produces ribosomes, by using 4 to 100 amino acids it has collected, known as a signal. This therefore showing the evolution that a Gogli apparatus was present before the ribosome, proving that the ribosome was produced to most likely make the process more efficient.
Lysosomes- the lysosomes is a small spherical organelle that functions as the cells recycling center and garbage disposal. A lysosomes is a membrane elcosed sac, filled with hydrolytic enzymes that the cells uses to digest macromolecules. Basically, the lysosome uses its powerful digestive enzymes to break down old worn out organelles, and put tiny particles of them back in the cytoplasm. The hope is that they will later be used to make new organelles. Lysosomes do the same thing to proteins, and hydrolyses them, along with lipids and other molecules. In fact, the lysosomes digestive power is so strong that it can destroy the cell that harbors it through a process called autodigestion. Lysosomes will also use the hydrolytic enzymes mentioned earlier to recycles the cells organic materials. Judging by the function of the lysosomes, it is most likely true that is was one of the last organelles to evolve, because its job is based around breaking down OTHER things in the cell, implying they had to exist before the lysosome was needed.
Mitochondria- the powerhouse of the cell. Shaped long and slender or like a bean, and is the place where enzymes turn the sugar glucose and other nutrients into Adenosine Triphosphate, or ATP, this process is also known as aerobic respiration. In this process glucose is broken down in the cells cytoplasm to form pyruvic acid which is transported into the mitochondrion. After going through the Kreb Cycle, the pyruvic acid reacts with water to form 10 hydrogen atoms. These atoms are then transported to the cristae of the mitochondrion by means of coenzymes. After going through the electron transport chain, the cell produces energy in the form of ATP. ATP then acts as an energy source for countless processes within the cell, including transport across the plasma membrane, the building and transport of proteins and lipids, the recycling of molecules and organelles, and the dividing of cells. Muscle and liver cells are so active that they required dozens, if not hundreds of mitochondria to meet with their energy needs. Mitochondria are unique for several reasons, the most obvious being that they contain their own DNA in the form of prokaryote-like circular chromosomes. Mitochondria also contain their own ribosomes which resemble prokaryote ribosomes, and divide independently of the cell. The evolution of the mitochondria can be explained by what some scientists call the endosymbiosis hypothesis. This hypothesis states that millions of years ago, prokaryotic cells that were capable of aerobic respiration were engulfed by other prokaryotic cells but not digested. The host cell than became dependent of the other cell where the host cell provided nutrients, and the engulfed cell provided the other cell with ATP. Therefore this is how the evolution most likely occurred.
Vacuoles- Found in both plant and animal cells, but serve a more important function in plant cells. A vacuole takes up most of the room in a plant cell, and takes up a much smaller amount of space in an animal cell. The Vacuole, a membranous bag, pushes the organelles and cytoplasm to the edges of the cell, in plants, it remains by itself alone in animal cells. The vacuole holds water, salts, sugars, proteins, and other nutrients. In plant cells, it also stores blue, red and purple pigments that give a flower its color. In plants, vacuoles also store plant wastes, that taste bitter to certain insects, thereby discouraging them from eating it.
Peroxisomes- a specialzed metabolic compartment bounded by a single membrane. Peroxisomes contain enzymes that transfer hydrogen from various substrates to oxygen-producing hydrogen peroxide. They grow by incorporating proteins and lipids.
Chloroplast- Found only in plants and eukaryotic algae. Structure in the cell where phosynthesis takes place. Chloroplasts are small disc shaped structures found most commonly in leaf cells so that they are closest to light. Being close to light is essential for photsynthesis to take place because the process involved the transformation of light energy into chemical energy used in the cell. Each chloroplasts consists of a double membrane, with a ground up material inside called the stroma. The stroma is crossed by a complex network of interconnected disks called thykaloids. Thykaloids will stack up like saucers into what is known as grana. Chlorophyll molecules, the molecules that actually absorb the light for photosynthesis are attached to the thykaloids. Chlorophyll is produced in the presence of light by small colorless organelles called proplastids. The evolution of the Chloroplasts is similar to that of the mitochondria, in plant cells. The self-reproducing ability of chloroplasts, their bacteria-like DNA and ribosomes, and their close similarity regardless of the type of cell they inhabit, suggest that they were once independent organisms that come to exist in symbiosis with the plant cell as host.
Cytoskeleton- Unlike Prokaryotic cells that are small, large Eukaryotic cells require support. The cytoskeleton is a large network of tubes made out of proteins, that support the cell and allow it to retain its desired shape. Protein tubes, filaments and fiber, cross all over the cytoplasm and hook on to organelles, and keep them in their place. The structure can also be used as a track for proteins and other items to travel across the cell. Scientist believe the cytoskeleton may have also evolved as a result of the nucleuss desire to have a structure that could keep the organelles where the nucleus wants them.
Cilia and Flagella- In Eukaryotic and Prokaryotic cells, these locomotive appendages that protrude from the cell help with movement. Swimming organism, usually move by means of Flagellum, a long tail like structure made of protein. Bacteria can have one, two, or many flagella to propell them in the water. But a Eukaryotic cell will have a longer and larger single flagellum. The cell with flagella propells itself by flapping around the flagella like a whip, in the same manner that a sperm cell with its flagella will propel itself toward a female egg. Movement in Eukaryotic cells also is accomplished by use of Cilia. Cilia are short hairlike proteins built by centrioles, which are barrel like structures located in the cytoplasm that assemble and break down protein filaments. The cell covered in the cilia appears to be hairy, and the cell propels itself by having all the hairs move like the oars of a boat and move where desired. But Cilia is not only used for movement, Cilia is found in humans to prevent dust, and smog from entering the lungs, and does this by sweeping them into mucus where they are swallowed, as opposed to inhaled.
Cell Wall- The most predominate feature that distinguishes plant cells from animal cells, is the cell wall. The Cell wall surrounds and protects the plasma membrane located within it, and helps it to maintain its shape. The pores in the cell wall allow objects to flow freely through the walls, into and out of the cell. The strength of the wall also allows for the central vacuole to be filled with water, or in a turgid state, without bursting. The strength of the cell walls is portrayed in the firmness of stems, leaves and flowers. It is also divided into a primary and a secondary cell wall.
Extracellular matrix- Functions in support, adhesion and movement and development. In animal cells like cell walls of plants. It also functions in a cells dynamic behavior. It Helps to control the activity of the genes in the nucleus.
Intercellular Junctions- integrate cells into higher levels of structure and function. The cell wall of plants are perforated by plasmodesmata which allow cytoplasm to pass through. This allows water and small solutes to pass freely from cell to cell.