1 Flashcards

Question

Do you know how to calculate the total magnification of a compound light microscope? Use an example to illustrate.

Answer 1

While optical lenses are typically a standard 10 times, objective lenses tend to vary more and come in sizes of 4, 10, 40, or 100 times magnification. With current technology, the maximum known magnification for light microscopes is 1000x, which is more than suitable for the most complex applications.

Answer 2

the resolution of objects: the ability to tell that two separate points or objects are separate. A low-resolution image appears fuzzy, whereas a high-resolution image appears sharp. Two factors affect resolution. The first is wavelength. Shorter wavelengths are able to resolve smaller objects; thus, an electron microscope has a much higher resolution than a light microscope, since it uses an electron beam with a very short wavelength, as opposed to the long-wavelength visible light used by a light microscope. The second factor that affects resolution is numerical aperture, which is a measure of a lens's ability to gather light. The higher the numerical aperture, the better the resolution

Answer 3

Contrast is the difference in light intensity between the object your are looking at and its background. You can enhance contrast by adjusting the light intensity and condenser when using a microscope or by subjecting your slides to different stains.

Answer 4

A brightfield microscope is the most commonly used type of microscope. It is a compound microscope that has two or more lenses that produces a dark image on a bright background. A brightfield microscope creates an image by directing light from the illuminator at the specimen. This light is differentially transmitted, absorbed, reflected, or refracted by different structures. In order to increase contrast and resolution, stains are often added to the specimen so it can be seen clearly through a brightfield microscope. A darkfield microscope is a brightfield microscope that has a small but significant modification to the condenser. It can often create high-contrast, high-resolution images of specimens without the use of stains. Darkfield microscopes are known to be better at viewing live specimens that can often be compromised or killed by stains.

Answer 5

Brightfield produces a dark image on a bright background, while Phase-contrast microscopes add a lot more complexity through light refraction and phase interference which produces greater contrast. It enables the viewer to see structures that might be invisible when seen through a typical brightfield microscope. Phase contrast microscopy is better at viewing granular details of living specimens because it can heighten contrast without staining or otherwise killing the specimen. I'm not totally sure I understand the physics of how the light is refracted and how that creates more contrast. If someone is able to explain in more simple terms that would be much appreciated!

Answer 6

Reason for electron microscopes being able to detect smaller objects than light microscopes is because electrons have shorter wavelength than photons. Therefore electron microscope could be used to observe biological and inorganic specimen. It's beams of electrons are used to illuminate specimen, mainly due it's wavelengths being much shorter resulting with much higher power compared to light microscope.

Answer 7

A scanning EM (SEM) - scanning electron machine is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The atoms of the sample then interact with the electrons, producing a great depth of focus. This bigger viewpoint can allow the viewer to image the whole specimen and things that would display patterns and the overall shape. The transmission electron microscope (TEM) can view thin slices of a specimen. It's used to image the interior of cells, the organization of molecules in a virus, and the structure of protein molecules.

Answer 8

The 5 I’s are Inoculation - to introduce a small amount of bacteria(the Inoculum) into fresh culture media which may or may not have nutrients to support bacterial growth Incubation - inoculated culture is placed in a temperature controlled incubator to stimulate human body temp of 37 degrees C Isolation - To give the patient the right medication to treat their infection, it is often necessary to isolate bacteria from a mixed culture to produce a pure culture of one bacterium. to getting a pure culture is the ability to get single colonies, which will only develop if the plating cell density is low enough. So all the isolating techniques include some form of serial dilution, are to get to the right cell density that can produce isolated colonies. Inspection - Inspection simply means to examine the microorganisms, either macroscopically observing the growth patterns in media and colony morphology, or microscopically observing the staining results for cell morphology (Figure 9). Both the colony morphology (color, texture, size, etc. of the colonies) and the cell morphology (shape, arrangement, etc. of the cells under microscope) hold clues to the identification of the microbes. Identification - Identification of the microorganism to the species level is the goal of most clinical microbiology labs. Identification is based on many criteria, including morphological data that we just talked about, and other biochemical, immunologic and genetic tests. Morphology alone is rarely enough. For example, you observe that the colonies of your bacteria on an agar plate is circular, with a smooth margin and white color. These colonies could be E. coli, Enterococcus fecium, Staphylococcus epidermidis

Answer 9

A pure culture is a bacterial culture of only one strain or species. Mixed culture means at least two different species of bacteria are in the culture, but these species are known and intentionally incubated. Contaminated culture means there are unknown species of bacteria in the culture and were unintentionally incubated.

Answer 10

Chemically defined or synthetic media has only known chemical ingredients. the recipe for the media is known and precise amounts of each chemical are added. The recipes are long since there is an exact amount of each ingredient added. An example is EZ medium. In comparison, complex media has at least one component that is not chemically defined usually some sort of natural extracts like blood, serum, meat extracts, or infusions. These come from plants animals or yeast. These recipes are much shorter since the natural medium contains many of the necessary nutrients and each ingredient is not added separately. The exact chemical nature of these medias are not known. Examples include nutrient broth, tryptic soy broth, and brain heart infusion.

Answer 11

All-purpose media support growth of a large variety of organisms. Examples of all-purpose media is tryptic soy broth (TSB), or tryptic soy agar (TSA). Enriched media contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms (organisms that cannot make certain nutrients and require them to be added to the medium). Examples of enrich media are blood agar, which contains blood from sheep, horse or rabbit added to the agar base; and chocolate agar, a modified blood agar. Selective media inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition. Example of selective media is MacConkey agar EMB agar, Mannitol Salt agar, MacConkey agar, and Phenylethyl Alcohol (PEA) MacConkey agar contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria. MacConkey agar is used to identify the Enterobacteriaceae. Enterobacteriaceae is species reside in the intestine, and are adapted to the presence of bile salts Differential media make it easy to distinguish colonies of different bacteria by a change in the color of the colonies or the color of the medium. Color changes are the result of end products created by interaction of bacterial enzymes with differential substrates in the medium or, in the case of hemolytic reactions, the lysis of red blood cells in the medium.

Answer 12

Isolation is important because it can identify the bacteria that is responsible for causing disease. It is also important because it can help prevent the transmission of microorganisms. A pure agar culture plate is appropriate because it can be used to separate mixtures of bacteria, which allows us to observe colonies.

Answer 13

The most simple is wet mount, a specimen is placed in a drop of liquid with a cover slip on top. Wet mount is good for viewing live specimens. Hanging drop is used for viewing cell motility And fixed smear is as it implies, to fixed your specimen to the slide

Answer 14

If the chromophore is the positively charged ion, the stain is classified as a basic dye, a dye that will be absorbed by the negatively charged cells or organisms being observed, adding color to objects of interest to make them stand out against the background. Examples of basic dyes are methylene blue, crystal violet, malachite green, basic fuchsin, carbolfushsin, and safranin. If the negative ion is the chromophore, the stain is considered an acidic dye, which is absorbed by the background but not by the cells or organisms in the specimen if negatively charged. Negative staining produces an outline or silhouette of the organisms against a colorful background, but if the specimen is positively charged the dye will penetrate the molecules and structures. Examples of acidic dyes are eosin, acid fuchsin, rose bengal, and congo red.

Answer 15

Simple stain- requires one single dye and can reveal size and shape (Ex) Crystal violet, methylene blue and safranin. Differential stain- two dyes are needed. Requires a primary and counterstain and helps to see cell structure. (Ex) Gram staining, Acid fast stain, endospore stain and capsule staining.

Answer 16

Gram staining: differential staining procedure that involves multiple steps, an effective method to distinguish between bacteria with different types of cell walls. a few examples of bacteria used are Staphylococcus aureus and Escherichia coli (E.coli). acid-fast staining: is able to differentiate two types of gram-positive cells: those that have waxy mycolic acids in their cell walls, and those that do not. examples Mycobacterium tuberculosis endospore staining: uses two stains to differentiate endospores from the rest of the cell. example of microbes is Bacillus subtilis.

Answer 17

Gram staining: differential staining procedure that involves multiple steps, an effective method to distinguish between bacteria with different types of cell walls. a few examples of bacteria used are Staphylococcus aureus and Escherichia coli (E.coli). acid-fast staining: is able to differentiate two types of gram-positive cells: those that have waxy mycolic acids in their cell walls, and those that do not. examples Mycobacterium tuberculosis endospore staining: uses two stains to differentiate endospores from the rest of the cell. example of microbes is Bacillus subtilis.

Answer 18

Organic chemistry is the discipline devoted to the study of carbon-based chemistry, which is the foundation for the study of biomolecules and the discipline of biochemistry. Carbon is very important because it can form stable bonds with many elements including itself. Isomers are molecules with the same atomic makeup but different structural arrangement of atoms. Enantiomers are molecules that have the characteristic of chirality, in which their structures are nonsuperimposable mirror images of each other.

Answer 19

hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups hese groups play an important role in the formation of molecules like DNA, proteins, carbohydrates, and lipids.

Answer 20

Carbohydrates: glucose, galactose, fructose Protein: amino acids Lipids: triglycerides Nucleic Acid: nucleotides

Answer 21

A dehydration reaction is the formation of a polymer by removing water and linking together two monomers. It is important for dehydration synthesis to serve as a chemical basis for the building of larger macromolecules. An example is two glucose molecules forming together to form maltose. A hydrolysis reaction is opposite to a dehydration reaction, where the addition of water breaks down large molecules into their subunits. This synthesis plays an important role to your body by breaking down food into nutritious components. An example can be one maltose molecule splitting into two glucose molecules.

Answer 22

The main function of carbohydrates is long-term and short-term energy source. - Plants synthesize cellulose for cell wall components. - Animals and bacteria produce glycogen as their primary source of energy. - Starch is synthesized by plants and is their primary source of energy. Glycogen, cellulose and starch all need the monosaccharide glucose to be built.

Answer 23

Triglyceride is composed of one molecule of glycerol and three molecules of fatty acids Saturated fat has single bonds and is solid at room temperature Unsaturated fat contains double bonds and is liquid at room Temperature Phospholipids are the primary components of cellular membranes A phospholipid contains one molecules of glycerol, 2 fatty acids and a polar phosphate group It contains a polar head (hydrophilic) and two nonpolar tails hydrophobic) This is called amphipathic 2 layers of phospholipids form lipid bilayer, the structure of cell membrane Steroids are lipids that have a backbone of four fused rings Cholesterol is an important biological molecule that plays a key role in cell membrane structure Estrogen and testosterone are sex hormones Cholesterol is the basis of estrogen and testosterone When exposed to water, a single layer of phospholipids forms a micelle

Answer 24

Cortisol, our main stress hormone, allows our bodies to respond to threatening situations (or situations which we perceive as threatening). It augments our catabolism of glucose and our ability to heal our own tissue, amongst various other functions. Aldosterone is another steroid hormone in our bodies with the vital function of maintaining homeostasis via regulation of salts and water in our bloodstreams and tissues.

Answer 25

THe unique characteristics of the group allows these components to form hydrogen, ionic, and disufide bonds, along with polar/nonpolar interactions needed to form secondary, tertiary, and quaternary proteins structures Approximately 50 for polypeptides, 20 for oligopeptides Th number of monomers along with variety of possible R groups on each amino acid allows for a nearly unlimited diverse types of proteins

Answer 26

The major functions of proteins are providing structure, regulating body processes, transporting materials, balancing fluids, helping with immunity, and providing energy. this includes anti bodies, they are also a last resort source of energy once the body has ran out of carbohydrates and fats. There are 4 levels of protein structure organization, primary is first which is a chain of peptides, secondary is the local folding of the polypeptide chain into a sheet, tertiary structure is three dimensional because of side chain interactions, quaternary structure is a protein consisting of more than one amino acid chain.

Answer 27

Hydrogen bonds are weak, peptide bonds are strong

Answer 28

URT - Upper Respiratory Tract Organs: Pharynx, Nasal Cavity Defenses: Mucosa-associated lymphoid tissue (MALT), including adenoids and tonsils Secreted antibodies (IgA) Lysozyme Surfacant Antimicrobial peptides (AMPs) called defensins Do they have normal biota? URT contains an abundant and diverse microbiota. LRT - Lower Respiratory Tract Organs: Bronchi Bronchioles Trachea Aveoli Defenses: Alveolar macrophages Mucociliary Escalator Do they have normal biota? It is unclear at this time if these small populations of bacteria constitute a normal microbiota or if they are transients.

Answer 29

Some respiratory defenses are the mucociliary escalator, the cough reflex, and alveolar macrophages(catches particles <2 µm that reach the respiratory units beyond bronchioles, rich in defense elements). The mucociliary escalator is made up of cilia and mucus. It moves mucus up and out of the lungs where it can be expelled by swallowing or coughing. Goblet cells are epithelial(line the internal and external surfaces of the body) cells that line and maintain many mucosal surfaces. They also secrete antimicrobial proteins, chemokines, and cytokines.

Answer 30

The signs and Symptoms of COVID-19 are mild cough, fatigue, fever/chills, muscle aches, headaches, difficulty breathing/shortness of breath, loss taste or smell, nausea/vomiting, diarrhea, runny nose, and/or sore throat. These symptoms could appear 2-14 days after contact exposure to a someone that has COVID-19. Patients that are affected severely from this virus could experience persistent paint/pressure on their chest, inability to wake or stay awake, trouble breathing, and/or having pale, gray, or blue-colored skin/lips/nails. Cytokine storm is known to damage the lung cells. By having the macrophages identify the virus, hence produces more cytokines. The more cytokines are produced the more it attracts the white blood cells, which could produce more cytokines, thus creating a cycle of inflammation and damage towards the lung cells. Acute Respiratory Distress Syndrome (ARDS) is where the air sacs becomes filled with fluid that leaks from tiny blood vessels within the lungs. Then shortness of breath begins to take place, hence lung failure. Often times patients with ARDS would have really hard time breathing to the point where they must required ventilator to assist with their breathing.

Answer 31

The Coronaviruses are a group of enveloped viruses that are highly pathogenic. The causative agent for COVID-19 is caused by SARS-CoV-2, a more pathogenic form than previously identified SARS-CoV (2002) and Middle East respiratory syndrome coronavirus (MERS-CoV, 2013). CoVs belong to the Coronaviridae family of order Nidovirales. They have been classified into four genera that include α-, β-, γ-, and δ-coronaviruses. Among them, α- and β- CoVs infect mammals, γ-coronaviruses infect avian species, and δ-coronaviruses infect both mammals and aves. It has a positive single-stranded RNA genome. The discovery of RaTG13 bat coronavirus in China suggested a high probability of a bat origin. Zhou et al. identified a closely related SARSr-CoV genome sequence, RaTG13, which shared a 96% whole-genome sequence identity with SARS-CoV-2, Whole genome sequences were obtained from five independent bats (Rhinolophus acuminatus) in a Thai cave yielding a single isolate (named RacCS203) which is most related to the RmYN02 isolate found in Rhinolophus malayanus. SARS-CoV-2 neutralizing antibodies were also detected in bats of the same colony and in a pangolin at a wildlife checkpoint in Southern Thailand. If bats can be found with antibodies fighting similar coronavirus strains, they believe the jump from origin host to human is not entirely surprising.

Answer 32

SARS-CoV-2 binds to the human ACE2 (hACE2) receptor on host cells. The life cycle of COVID starts like this. The first 5 days is the incubation period, where the virus starts to enter a healthy cell and start reproducing / duplicating itself. This happens inside the cell so the immune system won't respond. From 5-14 days after, the amount of virus in your system has started to hit levels where your immune system is alerted and releases cytokines to fight the infection. Usually by 14 days, a healthy host will not be infected. For those who are older in age or are immunocompromised, more severe symptoms may occur from day 14 - 21. Signs may include shortness of breath to pneumonia. If the patient is still showing symptoms, from day 21-60 is the time frame that there may be a chance that death might occur. Not all coronaviruses are pathogenic. Some like MERS-COV and SARS-COV can cause illness in humans and animals while other coronaviruses are harmless.

Answer 33

A: There are many variants of the SARS-CoV-2 virus, because the process of viral replication relies on RNA polymerase. RNA polymerase lacks the ability to "proofread" the replicated genome the same way that DNA polymerase can (Virology blog) which results in a higher rate of mutations. Any virus carrying a mutation is recognized as a variant. Depending on where the mutation occurs in the sequence of the virus, the properties can be changed. This includes the transmissibility. Changes to the spike proteins typically can increase transmissibility. For example a change to the amino acid sequence in the spike protein could allow the virus to bind more tightly to the ACE2 receptor, or reduce the binding between the spike protein and antibodies in our body generated by immune response or vaccination. The Delta variant was the dominant variant of summer 2021 and had high transmissibility rates. Researchers found that a specific mutation in the delta variant known as P681R mutation, allowed the delta variant to outperform all others and become the dominant variant. The P681R mutation specifically changes the amino acid sequence (proline into an arginine) in a very specific section of the spike protein known as the furin cleavage site.

Answer 34

SARS-CoV-2 is transmitted by exposure to infectious respiratory fluids. it has been estimated that SARS-CoV-2 has a R0 = 2-2.5 Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease. The spread of disease from person to person becomes unlikely when herd immunity is achieved. As a result, the whole community becomes protected — not just those who are immune.

Answer 35

To test for Covid 19, a swab sample is taken from the nose (nasopharyngeal), throat, or saliva. The sample is sent to the laboratory for testing. There are different type of test to detect the virus. The viral test also known as the nucleic acid amplification tests (NAATs) is a PCR based test that detects the viral genetic material. The antigen test is a rapid test and some can be done at home. The last method is the antibody test which looks for antibodies in the blood.

Answer 36

Different types of vaccines work in different ways to offer protection. But with all types of vaccines, the body is left with a supply of "memory" T-lymphocytes as well as B-lymphocytes that will remember how to fight that virus in the future mRNA vaccines contain material from the virus that gives our cells instructions for how to make a harmless protein (spike protein) that is unique to the SARS-CoV-2. After our cells make copies of the protein, they destroy the genetic material from the vaccine. Our bodies recognize that the protein should not be there and build T-lymphocytes and B-lymphocytes that will remember how to fight the virus if we are infected in the future. Protein subunit vaccines include harmless pieces (proteins) of the virus instead of the entire germ. Once vaccinated, our bodies recognize that the protein should not be there and build T-lymphocytes and antibodies that will remember how to fight SARS-CoV-2 if we are infected in the future. Vector vaccines contain a modified version of a different virus such as adenovirus as a "vector" to deliver genetic material (spike protein gene) to our cells. Once the viral vector is inside our cells, the genetic material gives cells instructions to make the spike protein. This prompts our bodies to build T-lymphocytes and B-lymphocytes that will remember how to fight the virus if we are infected in the future.

Answer 37

In the early stages of infection, antivirals and interferons are good pharmaceutical options to treat COVID-19, because they interfere with the virus' ability so infect more host cells. This of course lowers the risk that the infection will progress to more serious stages and spread further throughout the body. Another treatment in early stages can be the use of neutralizing antibodies, either from recovered COVID-19 patients or man-made monoclonal antibodies, which mimic the role of human antibodies in the body. These antibodies bind to the spike protein on the virus. Because the spike protein is like a key the virus uses to attach to the ACE-2 receptor and enter the cell, antibodies can prevent infection by attaching to the spike protein and blocking entry. These antibodies also act as a flag to the immune system to kill the virus or infected cells they're attached to. During later, more serious stages of infection, the body's own immune response is the main cause of severe symptoms. This is often the result of a "cytokine storm" caused by over production of cytokines leading to inflammation and damage to lung cells. Sometimes this damage is irreversible. That's why reducing inflammation is the most important treatment at later stages. Medical professionals can administer anti-inflammatories such as corticosteroids to "calm" the immune system, reducing inflammation and limiting damage to lung cells. This not only improves recovery time, but can also potentially reduce the long term effects some patients experience due to damage to their lung cells.

Answer 38

The man dubbed the father of modern genetics is named Gregor Mendel. One of his greatest contributions is the discovery the fundamental laws of inheritance. In simple words, the law of inheritance states that each "parent" gives one allele that combines in the fertilization process. The chromosomal theory states "chromosomes are the vehicles of genetic heredity". In simple words, the theory explains that genes are units of inheritance that are responsible for our features and traits. There are multiple factors that enlightens us on how genetics works. One factor would be how dominate traits override the recessive traits. Another factor would be how genetic information is passed down. During cell division when egg and sperm meet, called meiosis, chromosomes are moved around and mixed, leading to offspring that is genetically diverse. Lastly, the fact that mutations can happen in chromosomes. This gives us insight on the diseases we may have because of misprinted genetic information.

Answer 39

Answer: Griffith had discovered that he could convert the R strain into the virulent S strain. After he injected mice with R strain cells and, simultaneously, with heat-killed cells of the S strain, the mice developed pneumonia and died. In their blood, Griffith found live bacteria of the deadly S type. The principle was able to transform a non-pathogenic bacteria into a pathogenic strain

Answer 40

Alfred Hershey and Martha Chase performed their own experiments in 1952 and were able to provide confirmatory evidence that DNA, not protein, was the genetic material (Figure 10.9). Hershey and Chase were studying a bacteriophage, a virus that infects bacteria. Viruses typically have a simple structure: a protein coat, called the capsid, and a nucleic acid core that contains the genetic material, either DNA or RNA. The particular bacteriophage they were studying was the T2 bacteriophage, which infects E. coli cells. As we now know today, T2 attaches to the surface of the bacterial cell and then it injects its nucleic acids inside the cell. The phage DNA makes multiple copies of itself using the host machinery, and eventually the host cell bursts, releasing a large number of bacteriophages. Hershey and Chase labeled the protein coat in one batch of phage using radioactive sulfur, 35S, because sulfur is found in the amino acids methionine and cysteine but not in nucleic acids. They labeled the DNA in another batch using radioactive phosphorus, 32P, because phosphorus is found in DNA and RNA but not typically in protein. Each batch of phage was allowed to infect the cells separately. After infection, Hershey and Chase put each phage bacterial suspension in a blender, which detached the phage coats from the host cell, and spun down the resulting suspension in a centrifuge. The heavier bacterial cells settled down and formed a pellet, whereas the lighter phage particles stayed in the supernatant. In the tube with the protein labeled, the radioactivity remained only in the supernatant. In the tube with the DNA labeled, the radioactivity was detected only in the bacterial cells. Hershey and Chase concluded that it was the phage DNA that was injected into the cell that carried the information to produce more phage particles, thus proving that DNA, not proteins, was the source of the genetic material. As a result of their work, the scientific community more broadly accepted DNA as the molecule responsible for heredity. Only the DNA of a bacteriophage (virus that infects bacteria) is needed to infect/hijack it

Answer 41

A nucleotide is the basic building block of nucleic acids (RNA and DNA). A nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base. The bases used in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T). There are two differences that distinguish DNA from RNA: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine.

Answer 42

The sugar-phosphate backbone forms the structural framework of nucleic acids, including DNA and RNA. This backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

Answer 43

Each molecule of DNA is a double helix formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four nitrogen bases: adenine (A), cytosine (C), guanine (G) or thymine (T). Duplication of the genetic information occurs by the use of one DNA strand as a template for formation of a complementary strand. In the early 1950s, American biologist James Watson and British physicist Francis Crick and British biophysicist Maurice Wilkins developed their model of the DNA double helix structure with the help of British Chemist Rosalind Franklin’s technique X-Ray crystallography. Franklin and her student produced images of DNA using X-ray crystallography. The famous “image 5” a remarkably clear and striking X-ray diffraction image of DNA. for RNA Uracil replaces Thymine, binds to Adenine

Answer 44

Hydrogen bonds stabilize the DNA double helix. Base Pairs A-T and C-G Adenine and Thymine Pair forms 2 H bonds Cytosine and Guanine forms 3 H bonds DNA denaturation- When (H) bonds are broken. Separating the double helix of DNA into a single strand

Answer 45

The main function of DNA (deoxyribonucleic acid) is to store the information needed to build and control the cell. The transmission of this information from mother to daughter cells is called vertical gene transfer and it usually occurs through the process of DNA replication. DNA is replicated when a cell makes a duplicate copy of its DNA, then the cell divides, resulting in the correct distribution of one DNA copy to each resulting cell. DNA however does not serve a structural role in cells. RNA (ribonucleic acid) molecules perform a variety of roles in the cell but are mainly involved in the process of protein synthesis (translation) and its regulation. RNA has three main types that are directly involved in protein synthesis which are messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA). DNA and RNA are quite similar to each other. The difference is that DNA molecules are typically long and double stranded and RNA molecules are much shorter and are typically single stranded. An image I saw from Openstax shows the structure difference of a DNA and RNA.

Answer 46

mRNA stands for messenger RNA and is the strip of genetic material copied from the DNA in the nucleus that is sent out into the cytoplasm for translation into a protein. rRNA stands for ribosomal RNA which makes up the ribosomes that help conduct protein synthesis. This mechanism joins with tRNA (transfer RNA), which string together amino acids coded for by the mRNA to build proteins.

Answer 47

The genotype is an organism's genetic information, while the phenotype is the observable physical traits or attributes. Genotype is the unique sequence of DNA. Is it distinguishable as it is unique to the cell. The two alleles present create the DNA for this organism, it is all part of the genetic makeup. Phenotype refers to the patient's clinical presentation or findings. What is observable. Genome is defined as the complete set of genes or genetic material present in a cell or organism.

Answer 48

Eukaryotic cells have a nucleus and chromosomes are located in the nucleus. While for Prokaryotic cells that lack a nucleus, chromosomes are found in the nucleiod. Eukaryotes cells wrap DNA around a protein called histones to help contain the DNA in a smaller space.Most prokaryotic cells do not contain histones so the compress DNA through supercoiling .

Answer 49

Greek philosopher Aristotle was one of the earliest scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle attributed the ability for nonliving material to give life, if that nonliving material contained pneuma ("spirit" or "breath"). Italian physician Francesco Redi, performed an experiment that refuted the idea that maggots spontaneously generate on meat left out in the open air. He used 6 containers, 2 were left open giving direct access to the meat, 2 were sealed preventing access, and 2 were covered by gauze. Maggots were found on the meat with the open containers, and on top of containers with gauze but not on the meat itself, but were not present on the sealed container. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation. Louis Pasteur ended the debate over spontaneous generation when he used a series of flasks with long, twisted necks. He would boil the broth inside the flask until it became sterilized, and predicted that as long as the swan neck prevented airborne microorganisms, that the flasks would remain sterile, and if the neck was broken that airborne microbes would be responsible for microbial growth within the flask. Pasteur articulated “Omne vivum ex vivo” (“Life only comes from life”).

Answer 50

All living things are composed of cells. Cells are the basic units of structure and function for living things. All cells come from pre-existing cells. Also, organisms grow by “adding on more cells” NOT by increasing the size of their cells. 2.7 billion years ago The hypothesis that eukaryotic cells evolved from a symbiotic association of prokaryotes—endosymbiosis—is particularly well supported by studies of mitochondria and chloroplasts, which are thought to have evolved from bacteria living in large cells. The endosymbiotic theory posits that some eukaryotic cell organelles, such as mitochondria and plastids, evolved from free-living prokaryotes. Available data indicate that the mitochondrial endosymbiosis initiated the evolution of the eukaryotic cell, as suggested by Margulis.

Answer 51

In the 1500's, Girolamo Fracastori was the first person to say that disease might be spread by "seed-like entities"; he categorized them by way of transmission. Agonisto Bassi theorized that disease in humans and animals was caused by microorganisms; he studied silkworms with disease caused by parasites. Louis Pasteur is accredited with the "germ theory of disease", which is defined as such: Many disease are caused by infections with many species of microorganisms, such as bacterial, viral, fungal, or protists. Joseph Lister was the first to apply the "germ theory of disease" to surgery. He developed antiseptic techniques through experimentation and clinical trials. The evidence that Lister's antiseptic techniques spoke for itself, and his techniques were widely accepted by surgeons around the world. Ignaz Semmelweis was a Hungarian doctor that studied childbed fever in two maternity wards. He discovered that women in one clinic where doctors were performing births were dying 5x faster than in another clinic with only midwives. This was because the doctors were performing autopsies, washing their hands and instruments with only soap, and then delivering babies. When Semmelweis ordered medical staff to clean with a chlorine solution as well as more vigorous hand-washing, the rate of disease in these women fell dramatically. Both Lister and Semmelweis showed that trying to kill as many disease-causing microorganisms by keeping standards of cleanliness prevents infection with their work, supporting the germ theory of disease.

Answer 52

John Snow was able to prove that cholera bacteria were being transmitted by contaminated drinking water. He was able to do this by plotting all of the affected people's locations on a map and saw most of the plots were in one neighborhood, which led him to find a contaminated water supply in that neighborhood. This proved that the bacteria transmission was not from the air or smell like others though at the time. Louis Pasteur did an experiment with a swan-neck flask that disproved spontaneous generation. The curve of the flask prevented outside air from entering the flask so no bacteria grew in the broth. When the neck of the flask was broken off bacteria was able to grow in the broth. Pasteur also discovered fermentation and proved that food spoiled because of bacteria contamination, not from spontaneous generation. Robert Koch found that a particular germ could cause a specific disease. He discovered this while studying anthrax. This led to the discovery of the causative agents for many bacterial infections. The first step in Koch's postulates is collecting microorganisms from an organism with the disease, not healthy individuals. Then the microorganism is isolated and grown in a pure culture. The cultured microorganism is then introduced into a healthy organism and the disease is reproduced. The pathogenic microorganism is then isolated and grown in a pure culture and should be identified as being identical to the original causative agent.

Answer 53

It has two hydrophilic sides with the middle hydrophobic layer. This "sandwich" structure allows the phospholipids to form a micelle structure that allows separation between the inner cell environment and outer cell environment, so inside and outside the cell can be different. Since the middle layer of the membrane is hydrophobic, small and nonpolar molecules, such as carbon dioxide, can pass through the membrane. Water may use facilitated diffusion such as going through aquaporin to get in the cell faster. Potassium and Sodium are charged, so they cannot cross the membrane easily. They need to use sodium/potassium pump, which is a form of active transport, to cross the membrane.

Answer 54

The DNA molecules of bacterial chromosomes have a slightly different structure than those of eukaryotic chromosomes. Eukaryotes have a single circular chromosome, whereas bacteria have several linear chromosomes. Bacterial chromosomes have much more protein associated with the DNA than eukaryotes. Bacterial chromosomes are located in a nucleoid, a distinct cytoplasmic structure, in which double-stranded DNA is coated with histone-like proteins. Most bacteria appear to have a single large circular chromosome, but this is not universal. a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. That doesn't carry essential genes

Answer 55

A bacterial capsule is formed by many pathogenic bacteria that serves as protection against phagocytosis (when living cells ingest other cells). Its capsular coating blocks the mechanisms that phagocytes use to attach and engulf bacteria. This is important to us because it enhances the ability of bacteria to cause disease. Biofilm is film that are formed by free-living bacteria that protect a mature community of additional microbes with complex functions. Wherever you find a combination of moisture, nutrients, and a surface, you are likely to find biofilm.

Answer 56

Fimbriae are bristle like fibers filamentous, common with bacteria. It can be used for motility and also attachment to host cells. Fimbriae can also help with the formation of biofilms. Flagella are long whip shaped filamentous, common with bacteria. Flagella, used mostly for motility, but can be used to sense temperature and certain chemicals of interest in the environment. they can be present in prokaryotes and eukaryotes Function of flagella is locomotion. Flagella are appendages that go through the cell membrane. They are long and whip shaped. Function of fimbriae is surface attachment. Fimbriae are hollow extensions that go through the cells surfaces. They are shorter and involved in bacterial conjugation.

Answer 57

Multiple layers of skin cells in the epidermis act as physical barrier Stratum corneum contains dead cells that shed constantly taking bacteria attached with them Antimicrobial peptides (AMPs) and lipids act as chemical barriers Acidic pH of the skin acts as a chemical barrier Immune cells of the skin Normal microbiota of the skin Multiple layers of skin cells in the epidermis act as physical barrier Stratum corneum contains dead cells that shed constantly taking bacteria attached with them Antimicrobial peptides (AMPs) and lipids act as chemical barriers Acidic pH of the skin acts as a chemical barrier Immune cells of the skin Normal microbiota of the skin

Answer 58

Pseudomonas aeruginosa is an obligate aerobe, meaning it needs oxygen to survive. This explains why it often causes infection in the lungs of CF patients as there is an abundance of oxygen in the lungs. I did some more research on Psuedomonas infections in the lungs of those with cystic fibrosis and found it interesting that the bacteria is opportunistic meaning that they solely cause infection in those who are immunosuppressed or who have a condition such as cystic fibrosis.

Answer 59

P. aeruginosa has a larger genome than those of the two other major nosocomial pathogens Escherichia coli and Staphylococcus aureus that have an average size of 4,721 and 3,118 genes, respectively [33, 34]. The ubiquity of P. aeruginosa relies on its metabolic versatility and on the large range of its hosts.

Answer 60

The extrapolymeric substance (EPS), or glycocalyx, allows the bacteria to adhere to the host cells and makes it harder for the host to physically remove the pathogen The EPS not only allows for attachment but provides protection against the immune system and antibiotic treatments, preventing antibiotics from reaching the bacterial cells within the biofilm. In addition, not all bacteria in a biofilm are rapidly growing; some are in stationary phase. Since antibiotics are most effective against rapidly growing bacteria, portions of bacteria in a biofilm are protected against antibiotics.

Answer 61

P. aeruginosa can be detected through the use of cetrimide agar, which is selective for Pseudomonas species (Figure 21.17). Samples of blood or other body fluids are sent to the clinical labs for bacterial cultures. The production of blue-green pigments in colonies on agar plates (Figure 21.17b) is an indication of P. aeruginosa. Drug susceptibility tests are usually included because P. aeruginosa is known to be resistant to multiple antibiotics. keep their hands clean to avoid getting sick and spreading germs that can cause infections wash their hands with soap and water or use alcohol-based hand sanitizer, particularly before and after caring for wounds or touching a medical device remind healthcare providers and caregivers to clean their hands before touching the patient or handling medical devices allow healthcare staff to clean their room daily when in a healthcare setting

Answer 62

P. aeruginosa are resistant to pretty much all common antibiotics(antimicrobial agents), making it hard to treat it. This is due because of the low permeability of its outer membrane. There’s a test called ExAST which test cultures the germ and sees how sensitive it can be to different antibiotics. Also, the Zone of Inhibition is another test used to see the areas where the bacteria grows around the antibiotic that is being examined.

Answer 63

In order for a cell to manufacture these proteins, specific genes within its DNA must first be transcribed into molecules of mRNA; then, these transcripts must be translated into chains of amino acids, which later fold into fully functional proteins. in eukaryotes, while transcription occurs in the nucleus, translation occurs in the cytoplasm. For this reason, most of the cellular processes in the bacteria, including transcription and translation takes place in the cytoplasm of the prokaryotic cell. In fact, both transcription and translation in bacteria are coupled, i.e, both occur simultaneously. This is unlike that of eukaryotic cells, wherein transcription occurs in the nucleus and the mRNA is then taken to the cytoplasm for translation.

Answer 64

The primary functions of the nucleus are to store the cell's DNA, maintain its integrity, and facilitate its transcription and replication. The nucleolus is a prominent nuclear condensate that plays a central role in ribosome biogenesis by facilitating the transcription and processing of nascent ribosomal RNA (rRNA). Townhall

Answer 65

The cytoplasmic chromosome of eucaryotes are 80 S. They occur inside the cytoplasm of eukaryotes either freely or attached to ER. They contain 70s ribosomes in mitochondria and chloroplasts. Eukaryotic cells have evolved an endomembrane system, containing membrane-bound organelles involved in transport. These include vesicles, the endoplasmic reticulum, and the Golgi apparatus. Protein synthesis occurs in the cytoplasm on ribonucleoprotein particles, the ribosomes. rough endoplasmic reticulum (rough ER)

Answer 66

Endomembrane System Endoplasmic Reticulum: An array of tubules and cisternae (flattened sacs) connected with a single lipid bilayer. The spaces inside the cisternae are called the lumen. In a city, the ER would be a parts factory. Without the ER, the cell wouldn't have the proteins and lipids it needs for all of it's organelles. Rough ER: Bound on the cytoplasmic side of the membrane are ribosomes that make proteins that will be inserted into the membrane of the RER. Small sacs of these proteins will then bud off as transport vesicles from the RER membrane and travel to either the golgi apparatus, the plasma membrane, the membrane of another organelle, or out of the cell. Smooth ER: Does not have ribosomes, involved in the biosynthesis of lipids, carbohydrate metabolism, detoxification of toxic compounds within the cell Golgi apparatus: composed of membranous disks called dictyosomes, each having a single lipid bilayer, that are stacked together. Enzymes in the golgi apparatus modify lipids and proteins from the ER via transport vesicles, often adding carb components to them, producing glycolipids, glycoproteins, or proteoglycans. These new modified proteins and lipids leave the golgi apparatus via transport proteins and either fuse with the plasma membrane or the membrane of another organelle. In a city, golgi apparatus would be both a factory and packing plant. Without the golgi, the proteins and cells would be simpler and our cells wouldn't be as specialized and variable in terms of function. I.e. glycolipids and glycoproteins modified in the GA are often inserted into the plasma membrane and are important for signal recognition by other cells or infectious particles Lysosome: membrane bound organelles that contain digestive enzymes, usually used to break down food, damaged organelles, cellular debris, microorganisms, immune complexes. In a city, lysosomes would be recology. Without lysosomes, the cell couldn't break down potentially harmful and unnecessary particles.

Answer 67

Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell's biochemical reactions. Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP). Power plant If it stops everything in the cells dies from lack of ATP to power

Answer 68

There are three cytoskeleton molecules, the microfilaments, or actin filaments, the intermediate filaments, and the microtubules. Microfilaments allows for mobility within the cell, typically with cell division and vesicle transportation. It also helps with the rigidity of the cell. It's ability to depolymerize and repolymerize provides some cells with the ability to change its shape such as macrophages during phagocytosis. Intermediate filament plays no role in mobility within the cell, its sole purpose is to provide structural support to the cell and anchor organelles. Microtubules are hollow and they give structure to cilia and flagella. It also plays a key role in mitosis by pulling the two daughter cells away from each other to finalize mitosis. The microfilaments are the actin filaments. Only eukaryotes have cilia, and both prokaryotes and eukaryotes have flagella, but there are differences in their flagella.

Answer 69

Extracellular matrix (ECM) is the outermost layer of the cell. The ECM is made of proteins and polysaccharides including collagen, proteoglycan and hyaluronic acid. The main functions of glycocalyx are helping the cell adhere to surfaces, aids in the formation of biofilms, helps protect the cell and also acts as a signal sensor. There are two important types of glycocalyx, which are capsules and slime layers.

Answer 70

Both used flagella for motility. Eukaryotic flagella are structurally distinct from prokaryotic cells. Prokaryotic flagella is stiff and rotates. Whereas eukaryotic flagellum is whip like and more flexible, it is composed of 9 paralled pairs of microtubules surrounding a central pair of microtubules, allowing bending, referred to as a 9+2 array arrangement. Cilia are a external structure found in some eukaryotic cells, cilia are shorter than flagella and often cover the entire surface of a cell, although they use similar motility and are structurally similar to 9+2 array, they are compose of triple microtubules similar to a centriole.

Answer 71

These microbes include Bacteriodetes (especially the genera Bacteroides and Prevotella) and Firmicutes (especially members of the genus Clostridium). Methanogenic archaea and some fungi are also present, among many other species of bacteria. These microbes all aid in digestion and contribute to the production of feces, the waste excreted from the digestive tract, and flatus, the gas produced from microbial fermentation of undigested food. They can also produce valuable nutrients. Peyer's patches (Figure 24.5), detect pathogens in the intestines via microfold (M) cells, which transfer antigens from the lumen of the intestine to the lymphocytes on Peyer's patches to induce an immune response. The Peyer's patches then secrete IgA and other pathogen-specific antibodies into the intestinal lumen to help keep intestinal microbes at safe levels. Goblet cells, which are modified simple columnar epithelial cells, also line the GI tract (Figure 24.6). Goblet cells secrete a gel-forming mucin, which is the major component of mucus. The production of a protective layer of mucus helps reduce the risk of pathogens reaching deeper tissues.

Answer 72

Decades of research on virulence factor regulation in ETEC has revealed a variety of environmental factors that influence gene expression, including bile, pH, bicarbonate, osmolarity, and glucose. However, other hallmarks of the intestinal tract, such as low oxygen availability, have not been examined. Shiga toxins (Stxs) are considered the major virulence factors of EHEC involved in the pathogenesis of HUS. It is generally believed that after intestinal infection with EHEC, Stxs cross the intestinal barrier and bind to endothelial cells.

Answer 73

ETEC stands for Enterotoxigenic E. coli which is the causative agent of most traveler's diarrhea. Symptoms are relatively mild with watery diarrhea. This is usually self-limiting, but if needed, fluoroquinolones, doxycycline, rifaximin, TMP/SMZ is given and antibiotic resistance is sometimes a problem. This is usually diagnosed using a culturing or PCR test. EHEC stands for Enterohemorrhagic E. coli. EHEC causes intestinal inflammation and diarrhea. This is the most dangerous strains because this strain can cause an epidemic. EHEC can cause disease ranging from relatively mild to life-threatening. Symptoms include bloody diarrhea with severe cramping, but it does not cause any fever. This is self-limiting, but it can lead to hemorrhagic colitis and profuse bleeding which one possible complication is HUS (Hemolytic Uremic Syndrome which causes a serious disease that affects the kidneys and blood clotting system). Antibiotics are usually not recommended due to the risk of HUS

Answer 74

Enteric bacteria are bacteria that commonly live in the intestines of humans and animals with no harm to the host or even be helpful to the host. However, they can still sometimes cause infections under the right conditions. O and H refer to certain antigens that cause pathogenicity in enteric bacteria. O refers to the O side chain of the lipopolysaccharide and H is the flagella. This particular strain of E. coli can cause serious harm to the host in the form of diarrhea and GI illness.

Answer 75

The patient stool sample is sent to laboratory to test for the presence of E. coli bacteria. If blood is present in the stool. Bacteria be cultured to identify specific toxins Such as following: Shiga toxin-producing E. coli (STEC): This is the bacteria most commonly known for E. coli food contamination. This strain is also called enterohemorrhagic E. coli (EHEC) and verocytotoxin-producing E. coli (VTEC). Enterotoxigenic E. coli (ETEC): This strain is commonly known as a cause of travelers’ diarrhea. Enteroaggregative E. coli (EAEC). Enteroinvasive E. coli (EIEC). Enteropathogenic E. coli (EPIC). Diffusely adherent E. coli (DAEC). The treatment for E. coli - Most infected persons will recover within a few days, without requiring any specific treatment. Maintain hydration and electrolytes. Drinking fluids and consuming electrolytes and rest are the treatment. IV fluids may be required for the most severe cases. The hemolytic uremic syndrome due to Shigella poisoning may require hospitalization, intravenous fluid replacement, blood transfusions, or dialysis. Antibiotics may increase the number of toxins and the risk of hemolytic uremic syndrome, so they are used in only rare cases. They are never used if there’s any suspicion of an enterohemorrhagic E. coli infection. Antidiarrheal medications are also discouraged. They can slow down movement in the colon, also lead to an increase in the concentration of bacterial toxins in the intestines and increase the duration of the infection. No antibiotic is used when Shiga toxin-producing bacteria are present in STEC. In ETEC, under rare cases, antibiotics are used for certain traveler’s diarrhea and infant diarrhea only in cases of fever or persistent diarrhea.

Answer 76

Ribosomes are constructed from protein and ribosomal RNA (rRNA). Eukaryotic ribosomes are larger than prokaryotic ribosomes. Both types ribosomes are made of two subunits. Eukaryotes have complete ribosomes that are 80S, prokaryotes have complete ribosomes that are 70S. (Svedberg "S" as a unit of measure) The prokaryote ribosome is made of a small subunit 30S and a large subunit 50S. Eukaryotic ribosomes are comprised of the small subunit 40S, and the large subunit 60S. (These numbers do not add up to the size of their complete ribosomes, these measures are when they are apart)

Answer 77

Another name for TB was “phthisis” in Ancient Greece, “Tabes” in Ancient Rome, “Schachepheth” in Ancient Hebrew. It was also referred to as “ the white plague” due it would cause paleness in the patients. According to the World Health Organization, over six million men, 3.4 women, and 1.2 children have been exposed to TB About a quarter of the global population is estimated to have been infected with TB bacteria,

Answer 78

Primary TB - Bacteria enters the lungs, Tubercles are present causing tissue damage Secondary TB - The tubercles start to liquify and spread to the lungs which can cause severe symptoms such as fever, coughing, weight loss and chest pain Extrapulmonary TB- Common in young children, the tubercles start to rupture later spreading bacteria to the pulmonary capillaries. Once spread to the capillaries other organs may be compromised

Answer 79

Mycobacteria are called acid-fast bacilli because they are a group of rod-shaped bacteria (bacilli) that can be seen under the microscope following a staining procedure where the bacteria retain the color of the stain after an acid wash (acid-fast). mycolic acid The acid-fastness of Mycobacteria is due to the high mycolic acid content of their cell walls, which is responsible for the staining pattern of poor absorption followed by high retention.

Answer 80

Some mechanisms that M. tuberculosis uses to survive within macrophages include: inhibiting the fusion of phagosomes with lysosomes; inhibiting the release of acid from lysosomes; and protection from reactive oxidation radicals (Figure 4). As a result, the bacteria continue to multiply inside the macrophages.

Answer 81

There are two main tests that are used to diagnose TB. The first one is TB skin tests or TB blood tests. There are several ways to treat TB depending on the severity of the disease. Treatment can last from 4 to 9 months. Physicians can prescribe antibiotics depending on the regimen picked for the patient and also it depends on the drug susceptibility results. Sometimes the antibiotics will not work which will cause the patient to develop DR TB or drug resistant TB. Furthermore, it also is possible to develop more than one type of DR TB such as MDR(Multidrug resistant) or XDR TB(Extensively drug-resistant). MDR is a more serious subtype where the patient usually is resistant to more than one drug. Then XDR TB is a more serious subtype, but its rare to develop it. Nonetheless, it usually affects patients with very weak immune systems.

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