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Prokaryotes and Eukaryotic Organisms


Question 1

Part A

Bacteria are prokaryotes. They are single celled organisms that do not have a membrane-bound nucleus. The size ranges from 10 to 100 micrometres long from looking at them on a microscopic level. The bacteria can have a number of shapes that determine what it look like, its three shapes include; cocci, rods and spirilla. The cocci being a round shape of the bacteria, the rods having an oval shape and the spirilla having an spiral shape.

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In prokaryotes the energy is required from organic compounds. The molecules are referred to molecules comprising of carbon and hydrogen. The organic nutrients contain are carbohydrates (sugars, starches), lipids and proteins. More of the following are needed for bacteria nutrition. Nitrogen is needed to make amino acids, nucleic acids and ATP. Sulphur is required for the production of amino acids. Phosphorus to make nucleic acid acids and ATP. Water mainly comprised for the cytoplasm of 70%. Minerals like calcium, potassium, magnesium and iron to aid in allowing the enzymes to function. There are some hints of copper Bacteria’s obtain nutrition in different ways. Bacteria are nutritionally identified of what energy is required to be able to synthesise essential metabolites.

Autotrophic bacteria acquire nutrition from organic compounds. Carbon dioxide is usually used as the main source for carbon. Autotrophs will use hydrogen sulphide, ammonia or hydrogen gas to reduce the carbon in order to give the necessary sugars. An example of a bacteria that uses autotrophic nutrition is the nitrifying bacteria. They oxidize ammonia to make nitrites and nitrates.

Heterotrophs are another type of bacteria that want organic sources of carbon that include sugars, fats and amino acids. An example of a heterotroph bacteria is saprophytic bacteria. They get their nutrition from organic matter that is dead. By using enzymes, these bacteria can break down complex compounds and release energy using the nutrients. Saprophytic bacteria are mainly decomposers and have an essential role in the ecosystem by releasing simpler products that animals and plants.

Phototrophic bacteria take in light energy, then apply this in photosynthesis in order to make cellular energy. There are two kinds of phototrophs. Some which do not produce oxygen are anaerobic phototrophs, with others that do produce oxygen that are aerobic phototrophs. Autotrophs and heterotrophs can be phototrophs. Cyanobacteria is an example of bacteria that undergo photoautotrophic nutrition.

Chemotrophic bacteria attain chemical energy from their environment and translate it into adenosine triphosphate (ATP) for cellular energy. Chemotrophs gain energy from oxidation and reduction reactions of the inorganic compounds. These include hydrogen, ammonia, sulphide and iron. An example of the chemoautotroph bacteria is sulphur bacteria. The energy is produced by the oxidation of the hydrogen sulphide into sulphur and water.

Lithotrophs bacteria use reduced inorganic compounds as the electron donor (H-doner) in aerobic or anaerobic respiration.

Bacteria reproduce asexually by binary fission where the division occurs into two daughter cells after DNA replication of the parent. Binary fission is undertaken if the bacterial cells have grown to a fixed size. When the size is made the genetic material is from the replica of what each cell produces. These then have two DNA molecules that join to the cells membrane in the different locations.

Bacteria can also reproduce by budding as being another form of asexual reproduction. Some other types of bacteria reproduce from the budding technique. This occurs from when the mother cell forms a bud from one side with a nucleus also attached through the involvement of mitosis. The bud grows to a constant size to which it is the same to the mother cell. It then detaches itself from the mother that makes a different organism.

Although bacteria can undertake sexual reproduction in some circumstances. Where it contributes is from the genetic recombination is aided through conjugation. Conjugation happens to where the genetic material is transmitted between the bacteria by a tube known as the pilus. Transformation is another way of where the DNA is collected from the fragments of dead cells of the bacteria and are then transported through the cell membrane and fused to the genetic material of working bacteria. It can also be done through a technique called transduction. This occurs where the genetic material is transferred through bacteriophages. When bacteriophages come to the bacterial cell, it places its genetic material into the cell. It then results to forming more bacteriophages, the former one is then released. The host bacterial cell’s genetic material can then join to the DNA of any other bacterial cell from the invasion of new bacteriophages.

Bacteria can be identified using the gram staining technique. It is called a differential stain as it can be used to differentiate types of bacteria due to the differences they have in their cell wall. Where it gets distinguishes is the amount of pepitidoglycan a bacteria has. Therefore bacteria’s are then grouped into gram positive and gram negative. The differentiation happens as soon as the stain is added. The gram staining technique was developed by the Danish scientist Christian Graham.

Another staining technique that can be used to identify bacteria is Ziehl-Neelsen staining. This method is also referred to as acid-fast staining. The technique is important as some bacteria species typically Mycobacteria. These types of bacteria have waxy coats on their cell wall that prevents them from retaining the dye in gram staining. So the acid-fast staining procedure uses detergents that remove the waxy coat.

A known infectious disease caused by a bacteria is the one that can trigger harmful effects to the immune system this is the E.coli O157:H7. This forms a part of food poisoning by producing a toxin that damages the lining of the small intestine. E.coli infection can be developed if the strain of bacteria is ingested. The E.coli bacteria can cause an infection even if the smallest amount has been ingested into the body. Exposure to E.coli O157:H7 can come from sources of contaminated food or water. The infection of the E.coli O157:H7 bacteria can typically effect between three to four days with the symptoms showing as diarrhoea and abdominal cramping with some cases of nausea and vomiting. The E.coli O157:H7 is an infectious disease that can affect the immune system from functioning normally.

Fungi are eukaryotic organisms. This is where their DNA contains chromosomes that is surrounded by a membrane-bound nucleus in their cell. The membrane-bound organelles found in fungi include nuclei, mitochondria, Golgi bodies and ribosomes.

The size of a fungi can range from single-celled organism such as yeast to multicellular clusters like moulds or mushrooms. The unicellular organism that is yeast is small ranging from 4 to 12 µm. Sporophores are multicellular fungi that can vary immensely in size. Some can be microscopic and can hardly be visible to the naked eye and others are huge structures. Hyphae are among the smallest fungi that have structures varying from 2-10 µm in diameter. The part of the fungus that is visible is the fruiting body or sporophore. Within the largest of the sporophores are mushrooms, bracket fungi and puffballs. Some mushrooms can have a diameter of 20 to 25 cm and have a height of 25 to 30 cm. Bracket or shelf fungi can reach 40cm or more in diameter. A baracket fungus called Fomitiporia ellipsoidea has a fruiting body measuring 10.8 metres in length and between 82 and 88 cm in width. It can hold up to 450 million spores and weighed between 400 to 500 kg, this had made it the largest fruiting body. Puffballs can also range up to huge sizes. The biggest puffballs had measured to 150 cm in diameter.

Fungi are structured differently to the other eukaryotic organisms of plant and animal cells. They have a cell wall like plant cells do although their cell walls lacks cellulose and there are no chloroplasts.

A typical fungal structure has a mass of cells threaded together in a filament called a hypha. The cells in a hypha are separate from a cross-wall known as the septum. The hyphae normally form a big network of cells known as mycelium.

The Apical Vesicular Complex (APC) is located on the actively growing hyphal tip. These contains vesicles that surround the opaque structure called Spitzenkorper. Behind the APC there are many mitochondria.

The cell wall allows the fungal cells to hold its rigidity in order to prevent it from bursting by osmosis. Within the cell wall there are four main components. The chitin are microfibrils that make a high strength mesh in the cell wall. The glucans are polymers of glucose bound that are set in a pattern making them amorphous that helps the microfibrils to hold its place. Some proteins are in the water resistant hydrophobins that make a dehydration resistant layer when in contact with the air. And the melanin helps to prevent ultraviolet damage.

The Septum is a valve in line with hyphal cells to avoid loss of organelles. The pores in the septa let organelles and nutrients to freely flow when needed to.

The yeast cells appear to be round blobs under a microscope. They are small to look at as individual but can be seen as large clusters on other organisms. On the other hand moulds appear to have filament strands called hyphae. It is the hyphae that gives the mould colonies their fuzzy look.

Fungi obtain nutrients from other organisms as they cannot make their own food. Fungi absorb their nutrients using structures called hyphae. The hypha’s tip gives out enzymes that can break down food products in the soil. The hypahe

Virus is an akrayotic organism that has no membrane-bound nucleus. Their structure is laid out with its genetic material having a capsid as the outer protein coat for protection. With the genetic material and protein it differentiates them other virus-kind particles like prions and viroids.

Viruses have a relatively small size to prokaryotes and eukaryotes. Viruses can only be seen by an electron microscope. As the viruses are small organisms they are measured in the scale of nanometres. The size range is from 20 to 750nm that is comparatively small to the width of a human hair that is 45,000 times smaller. The resolution of a light microscope is limited to the ability of where it can see viruses so a scanning electron microscope is used to view most viruses.

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The virus structure is comprised of a genetic information molecule and a layer of protein which act as a protection for the genetic material. The organization of the protein layer and the genetic code is in a variety of appearances. In the centre of the virus it is comprised of nucleic acids that then join up the genetic coding in the form of RNA or DNA. The outer protein coat that is surrounds and protects the nucleic acid is a capsid.

From each individual virus come a number of different viral shapes. Most types of viruses have a polyhedral or multi-sided shape. This type of shape is like a cut gem of a diamond but does not reach a point as it is similarly shaped all around. Other types of viruses are shaped in spikey ovals with rounded corners.


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