Types Of Cell Walls example essay topic

The cell is one of the most basic units of life. There are millions of different types of cells. There are cells that are organisms onto themselves, such as microscopic amoeba and bacteria cells. And there are cells that only function when part of a larger organism, such as the cells that make up your body. The cell is the smallest unit of life in our bodies. In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on.

All of these cells have unique functions and features. And all have some recognizable similarities. All cells have a 'skin', called the plasma membrane, protecting it from the outside environment. The cell membrane regulates the movement of water, nutrients and wastes into and out of the cell.

Inside of the cell membrane are the working parts of the cell. At the center of the cell is the cell nucleus. The cell nucleus contains the cell's DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside of the cell - small structures that help carry out the day-to-day operations of the cell. One important cellular organelle is the ribosome. Ribosomes participate in protein synthesis.

The transcription phase of protein synthesis takes places in the cell nucleus. After this step is complete, the m RNA leaves the nucleus and travels to the cell's ribosomes, where translation occurs. Another important cellular organelle is the mitochondrion. Mitochondria (many mitochondrion) are often referred to as the power plants of the cell because many of the reactions that produce energy take place in mitochondria. Also important in the life of a cell are the Lysosome. Lysosomes are organelles that contain enzymes that aid in the digestion of nutrient molecules and other materials.

There are many different types of cells. One major difference in cells occurs between plant cells and animal cells. While both plant and animal cells contain the structures inside the cell membrane the plant cell has a cell wall for support. Discussed above, plant cells have some additional specialized structures. Many animals have skeletons to give their body structure and support. Plants do not have a skeleton for support and yet plants don't just flop over in a big spongy mess.

This is because of a unique cellular structure called the cell wall. The cell wall is a rigid structure outside of the cell membrane composed mainly of the polysaccharide cellulose. As pictured at left, the cell wall gives the plant cell a defined shape that helps support individual parts of plants. In addition to the cell wall, plant cells contain an organelle called the chloroplast. The chloroplasts allow plants to harvest energy from sunlight. Specialized pigments in the chloroplast (including the common green pigment chlorophyll) absorb sunlight and use this energy to complete the chemical reaction: 6 CO 2 + 6 H 2 O + energy (from sunlight) = C 6 H 12 O 6 + 6 O 2 In this way, plant cells manufacture glucose and other carbohydrates that they can store for later use.

Organelles are small structures within cells that perform dedicated functions. As the name implies, you can think of organelles as small organs. There are a dozen different types of organelles commonly found in eukaryotic cells. Sch leiden and Schwann proposed the Cell Theory in 1838. They stated that all living things are made of cells; Cells are the basic units of life; and Cells come only from other cellsProtocells is one theory of the origins of cells states that the first life on earth consisted of several types of tiny proto cells, cell-like organisms.

These organisms were able to survive and reproduce in a very limited environment because of their simplicity. Over time, some of these proto cells came together and shared their specialization in a symbiotic relationship. These colonies of proto cells eventually became the cells we know today. There are two types of cells. They are: Prokaryotes are cells with no nucleus or organelles with membranes. Bacteria and blue-green bacteria are prokaryotic cells.

Eukaryotes are cells that contain a nucleus and organelles surrounded by a membrane. The cells of protozoa, algae, fungi, plants, and animals are eukaryotic cells. Microtubules, micro filaments & intermediate filaments make up The Cytoskeleton. The is unique to eukaryotic cells. It is a dynamic three-dimensional structure that fills the cytoplasm.

This structure acts as both muscle and skeleton, for movement and stability. The long fibers of the are polymers of subunits. The primary types of fibers comprising the are micro filaments, micro tubules, and intermediate filaments. Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin, which is the most abundant cellular protein. Microfilaments' association with the protein myosin is responsible for muscle contraction.

Microfilaments can also carry out cellular movements including gliding, contraction, and cytokinesis. Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein -- these subunits are termed alpha and beta. Microtubules act as a scaffold to determine cell shape, and provide a set of 'tracks' for cell organelles and vesicles to move on. Microtubules also form the spindle fibers for separating chromosomes during mitosis.

When arranged in geometric patterns inside flagella and cilia, they are used for locomotion. Intermediate filaments are about 10 nm in diameter and provide tensile strength for the cell. External cell movement is accomplished by cilia and the flagella. Cilia are hair-like structures that can beat in synchrony causing the movement of unicellular paramecium. Cilia are also found in specialize linings in eukaryotes.

For example, cilia sweep fluids past stationary cells in the lining of trachea and tubes of female oviduct. Flagella are whip-like appendages that undulate to move cells. They are longer than cilia, but have similar internal structures made of micro tubules. Prokaryotic and eukaryotic flagella differ greatly.

Both flagella and cilia have a 9 + 2 arrangement of micro tubules. This arrangement refers to the 9 fused pairs of micro tubules on the outside of a cylinder, and the 2 un fused micro tubules in the center. Dynein 'arms' attached to the micro tubules serve as the molecular motors. Defective dyne in arms cause male infertility and also lead to respiratory tract and sinus problems. Internal cell movement is possible because the acts as a 'track' on which cells can move organelles, chromosomes and other things. Some examples are: Vesicle movement between organelles and the cell surface frequently studied in the squid axon.

Cytoplasmic streaming, movement of pigment vesicles for protective coloration and the Discharge of vesicle content for water regulation in protozoa Cell division -- cytokinesis Movement of chromosomes during mitosis and meiosis Cell organelles: components of cells with specific functions. Cell membrane. A complex barrier of lipid molecules separating the cell from its external environment... These molecules can move apart to allow larger particles to move in or out of the cell... The 'selectively permeable' cell membrane regulates what passes into and out of the cell. Some substances, like water, move freely through the cell membrane by a process known as osmosis.

In osmosis, particles move easily from an area of high concentration to an area of low concentration by molecular motion only. Cells can push particles in the opposite direction, from low concentration to high, but it will take energy from the cell to do this. Cytoplasm. A thick, aqueous solution of salts surrounding the organelles inside the cell membrane... Nutrients and minerals spread through the cytoplasm to all parts of the cell... The constant motion of this gel-like substance is called cytoplasmic streaming.

Nucleus. The structure inside the cell that directs cell activities... Contains the DNA of a cell. Cell wall (only in plants). On the outside of some cells, bacteria and plants, this structure functions for support and protection...

There are pores in the cell wall allowing substances to come in contact with the cell membrane... Types of cell walls: a. Primary cell wall - formed during cell growth, it is composed of parallel layers of cellulose and pectin. This structure allows the cell to expand as it grows.

While it does provide support, it is not nearly as strong as the secondary cell wall. b. Secondary cell wall - formed after cell growth stops, it is composed of interwoven cellulose and lignin fibers. This structure is very strong, but does not give. It gives plants their 'woody' characteristic.

Ribosome. The sites of protein synthesis in a cell... These small, spherical structures are the most numerous organelles in almost all cells... Some ribosomes produce protein to be used within the cell and some produce protein that is 'exported' to other parts of an organism. Endoplasmic reticulum.

A membrane system of folded sacs and tunnels in the cytoplasm... Rough 'ER' is covered with ribosomes. It is common in cells that export proteins and directs the proteins flow... Smooth 'ER' as few or no ribosomes. It functions as a pathway for molecules to follow. Golgi Apparatus.

A stack of membranes or sacs that acts to prepare substances for export from the cell... Once the Golgi apparatus has enclosed the final product in a vesicle, or pouch, the product is sent through the cell membrane. Mitochondria. Respiration centers of a cell... Large organelles scattered through most cells, they are most numerous in cells that use a lot of energy like liver and muscle cells. Lysosome.

Digestive centers of a cell... They produce many different types of enzymes and digest things from food particles to a cell's own worn out parts. Vacuole. Most common in plant cells, they are storage sites within a cell. Plastid.

Pigment producing organelle in cells. Genetics: DNA (acid) is a long molecule that is contained within almost all of our cells in a compartment called the nucleus. It is composed of individual units called bases. There are four types of bases, designated A (adenine), T (thymine), G (guanine), and C (cytosine).

Each DNA molecule is made of two individual strands paired together. Each strand consists of a series of the four bases. When the two strands pair up, an A on one strand is always across from a T on the other strand, and a C always pairs with a G. These A / T and G / C combination are called base pairs. The double-stranded molecule then twists like a coiled ribbon into a shape called a double helix. A piece of DNA millions of base pairs long - in conjunction with some proteins - is a chromosome. Each chromosome contains thousands of genes, each of which is several thousand bases long.

The sequence of bases in each gene contains instructions for making a single protein. Each protein serves a particular function in the body. For example, enzymes help us digest food, structural elements give our cells shape, and signaling molecules help the cells communicate with each other. Additional bases that come before the genes on a chromosome tell cells when each gene should be used, For example, these sequences might contain instructions that a protein for making hair should only be made in certain skin cells, and not by other cells of the body. Humans inherit 23 chromosomes from each of their parents for a total of 46 chromosomes. Of these, 44 are identical in men and women - these are called autosomes.

The remaining two chromosomes are called sex chromosomes, which are designated X and Y. Women inherit two X chromosomes, whereas men inherit one X chromosome from their mother and one Y chromosome from their father. Because of the way we inherit our chromosomes, we all have two copies of every gene that is contained on the autosomes. Depending on the combination of the genes we inherit, we end up with some traits that resemble our mother and others that resemble our father. Women have two copies of each gene on the X chromosome, while men have only the genes that they inherit from their mother on the X chromosome and only genes that they inherit from their father on the Y chromosome. Each gene is made up of a series of bases, and those bases provide instructions for making a single protein.

Any change in the sequence of bases - and therefore in the protein instructions - is a mutation. Just like changing a letter in a sentence can change the sentence's meaning, a mutation can change the instruction contained in the gene. Some mutations have little or no effect on the protein, while others cause the protein not to function at all.