1. Describe microscope selections for specific examinations 2. Properties of Bas
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1. Describe microscope selections for specific examinations 2. Properties of Basic dyes . What is a differential stain, (example)? 4. How simple diffusion of water occurs (Mechanism)? 5. What are Facilitated diffusion and active transport? 6. Which macromolecule/s is/are found in the cell walls of all bacteria 7. Which molecules are associated with the cel wall of Gram-positive bacteria? 8. Against which bacteria Penicillin would be most effective? 9. Describe Extra-chromosomal DNA and it's location in bacteria? 10. Define Eukaryotic cells (with differences with Prokaryotic cells)Explanation / Answer
1. The different types of microscopes found are generally classified into:
These are the different typesof light microscopes. Other broad category of microscope is electron microscope, which is of the following types:
An electron microscope uses a beam of electrons instead of a beam of photons. While light microscopes can be used for viewing organisms that are alive, SEM and TEM both are required to prepare the specimen, fixation is required and also the specimen needs to be dehydrated. Electron microscopes can be used to observe specimens with a wide range of substances. In SEM, the sample needs to electrically conductive so that the electrons can bounce off it to create the image. SEM usually gives us the exterior view of the specimen concerned while TEM allows for incredible interior detail, they're often used in medical research. Thus specimens are often coated in a thin layer of gold or other metal. They are versatile but should be handled by professionals only.
2. The chemical substances that are used to stain organisms or biological specimens are known as dyes. Dyes may be acidic or basic. Properties of a basic dye are:
Crystal Violet, Methylene Blue, Safranin are examples of basic dyes.
3. Differential staining is the method of staining one single specimen with more than one chemical stain. Using different stains for the same specimen at the same time helps us to observe different part of the specimen more elaborately. For example, Gram staining in bacteria is a differential staining process. There are two stains involved here, namely, Crystal violet and Fuchsin or Safranin (the counterstain). This helps us to differentiate between Gram-positive bacteria and Gram-negative bacteria.
4. Simple diffusion of water is also known as osmosis. Here, water molecules diffuse through a selectively permeable membrane from areas of high water concentration to areas of lower water concentration.The water molecules simply move across the membrane along the concentration gradient of the solute molecule without the requirement of any energy. Hence it is also called passive transport. It is different from other types of diffusion because in other types we are concerned with solute molecules but in osmosis, we are concerned with water molecules.
5. Facilitated diffusion: a Facilitated diffusion is a passive form of diffusion where the solutes move down their concentration gradient with the help of Carrier proteins and channel proteins and do not require the expenditure of energy for this process.
Active transport: When solute molecules move across a membrane against its concentration gradient, that is, form low concentration to high concentration, with the expenditure of energy, it is known as active transport. active transport may be of two types, primary active transport and secondary active transport.
6. The macromolecule which is common to the cell wall of all bacteria is peptidoglycan.
7. Gram-positive bacteria retain the crystal violet stain because of the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away. So, the molecule associated with the cell wall of gram-positive bacteria is the peptidoglycan.
8. Penicillin can be effective against Gram-positive bacteria . This is because the Gram-negative bacteria have a lipopolysaccharide and protein layer surrounding the peptidoglycan layer of the cell wall, this penicillin from attacking the bacteria and inhibiting its growth. They can be used against staphylococci and streptococci infections.
9. Extrachromosomal DNA is the DNA that is found outside the nucleus of a cell. They are also called extranuclear DNA.Since prokaryotic organisms do not possess a membrane-bound nucleus like the eukaryotes, they contain a nucleoid region where the main chromosome is found. Extrachromosomal DNA in bacteria exists outside the nucleoid region as circular or linear plasmids.
10. Eukaryotic cells are cells that contain membrane-bound organelles like the nucleus, mitochondria, Golgi, plastids, etc.. On the other hand, prokaryotes are simple organisms which do not have membrane-bound organelles. The genetic material in eukaryotes is present inside the nucleus while in prokaryotes it is present in a structure that resembles the nucleus, known as the nucleoid. Cellular working of eukaryotic cells are much complex than prokaryotic cells and the cell walls of prokaryotic cells contain peptidoglycan but eukaryotic cells that do have cell wall do not have peptidoglycan, they have cellulose instead.
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