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This line is called an intercalated disc: it assists in passing electrical impulse efficiently from one cell to the next and maintains the strong connection between neighboring cardiac cells acne on chin buy cheapest dapsone. Nervous Tissues Nervous tissues are made of cells specialized to receive and transmit electrical impulses from specific areas of the body and to send them to specific locations in the body acne blemishes purchase dapsone 100 mg with visa. The main cell of the nervous system is the neuron acne wipes discount 100 mg dapsone with visa, illustrated in Figure 1036 Chapter 24 the Animal Body: Basic Form and Function 24 acne 3 step clinique purchase dapsone 100mg otc. Other glial cells that are not shown support the nutritional and waste requirements of the neuron. Why would a single layer of flat epithelial cells rather than cuboidal cells (cube-shaped) cells function more efficiently in diffusion? As diffusion of nutrients and gas is easier across a single layer of flat epithelial cells than cuboidal cells. As diffusion of only gases is easier across a single layer of flat epithelial cells than cuboidal cells. As active transport of nutrients and gas is easier across a single layer of flat epithelial cells than cuboidal cells. These professionals complete medical school education and follow it with an extensive post-graduate residency at a medical center. A pathologist may oversee clinical laboratories for the evaluation of body tissue and blood samples for the detection of disease or infection. Some pathologists perform autopsies to determine the cause of death and the progression of disease. For example, as an endotherm, your body temperature remains fairly constant around 37C or 98. If your temperature climbs above the set point, you sweat to cool off; if your temperature drops below the set point, you shiver to warm up. Your blood glucose levels also remain fairly constant because the liver removes glucose from the blood and converts it to glycogen; when the body cells require glucose, glycogen is broken down. Negative feedback mechanisms result in slight fluctuations above and below the set point. For example, if you were to consume a dozen jelly donuts, your blood sugar level would rise, and your pancreas would release insulin, a hormone involved in the conversion of glucose to glycogen, thus returning your blood glucose level to its appropriate set point. By comparison, positive feedback amplifies responses in the same direction, with the variable initiating the response moving the system even further away from the set point. There are fewer examples of positive feedback, but one is the onset of labor in childbirth when uterine contractions increase in strength with the secretion of oxytocin, another hormone. However, the loss of internal equilibrium due to positive feedback can be detrimental; for example, a small area of damaged heart tissue can precipitate a heart attack which, in turn, damages even more cardiac muscle. C 1038 Chapter 24 the Animal Body: Basic Form and Function Essential Knowledge Science Practice Learning Objective Essential Knowledge Science Practice Learning Objective Essential Knowledge Science Practice Learning Objective Essential Knowledge Science Practice Learning Objective Essential Knowledge Science Practice Learning Objective 2. Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). These changes might be in the level of glucose or calcium in blood or in external temperatures. Homeostatic Process the goal of homeostasis is the maintenance of equilibrium around a point or value called a set point. Positive feedback loops actually push the organism further out of homeostasis, but may be necessary for life to occur. Negative Feedback Mechanisms Any homeostatic process that changes the direction of the stimulus is a negative feedback loop. It may either increase or decrease the stimulus, but the stimulus is not allowed to continue as it did before the receptor sensed it. Specialized cells in the pancreas sense this, and the hormone insulin is released by the endocrine system. Insulin causes blood glucose levels to decrease, as would be expected in a negative feedback system, as illustrated in Figure 24. However, if an animal has not eaten and blood glucose levels decrease, this is sensed in another group of cells in the pancreas, and the hormone glucagon is released causing glucose levels to increase. Another example of positive feedback is uterine contractions during childbirth, as illustrated in Figure 24. The hormone oxytocin, made by the endocrine system, stimulates the contraction of the uterus.

Vijayalakshmi (1989 acne back discount 100mg dapsone mastercard, 2002) classifies the ligands used in affinity chromatography in two groups: biospecific and pseudo-biospecific acne quizlet discount dapsone 100mg line. Biospecific ligands interact with the target biomolecule through functional affinity acne wallet buy dapsone 100 mg with mastercard, exactly as happens naturally acne brand buy discount dapsone 100 mg on-line, for example in antigen­antibody, glycoprotein­lectin, and hormone­receptor interactions. Biospecific ligands provide high specificity and high adsorption capacities, with possibilities of achieving purification factors up to 1000-fold (Roper and Lightfoot, 1995). A common example of the application of biospecific ligands is the purification of monoclonal antibodies (mAbs) from cell culture supernatants using protein A and G as the ligands (Castilho et al. However, biospecific ligands are usually high cost molecules with a fragile three-dimensional structure. The interaction can sometimes be so strong that adsorbate desorption is only possible under drastic pH or ionic strength conditions. Pseudo-biospecific ligands, such as metal chelates, amino acids, and dyes are simpler and less expensive molecules with a structural affinity to biomolecules (group specificity). Since they have simpler structures, they can be immobilized by stable, well defined chemical reactions to the chromatographic matrix. Their disadvantages are their lower specificity, as compared with biospecific ligands. However, there are many examples of molecules obtained from animal cell cultures that have been successfully purified using pseudo-biospecific ligands (El-Kak and Vijayalakshmi, 1991; Atkins et al. Due to the central role of the ligand in affinity chromatography, some factors should be considered when selecting a ligand for the purification of a protein: (i) specificity: the ligand should be able to selectively recognize the target protein; (ii) reversibility: the ligand should form a reversible complex with the protein to be purified, and the complex should be resistant to the composition of the feeding stream or washing buffers, but easily dissociated during elution without denaturation; (iii) stability: the ligand should be stable under the conditions employed during immobilization and chromatography; (iv) immobilization feasibility: the ligand should contain a functional group suitable for covalent binding to the support, without affecting interaction properties with the protein. Many authors report their data in terms of the association constant (K A), which is equal to K D­1. After selecting the ligand, a suitable matrix should be chosen for its immobilization. The effectiveness of an immobilized ligand can be dependent on the matrix structure. The matrix should have high porosity and a suitable pore size, so that the target protein can access the ligands immobilized in its interior. It should be chemically stable during activation, ligand coupling, adsorption, elution, and regeneration. The matrix should also be mechanically resistant and rigid to allow suitable mobile phase flow, and should tolerate wide pH and temperature ranges. The matrix should have a uniform structure, possess high concentration of functional groups for ligand coupling, and should not promote non-specific adsorption. Widely used matrices are agarose and synthetic polymers also used in ion exchange and molecular exclusion chromatography. The ligand can be coupled to the solid matrix through spacer arms, especially when the ligand is small and stereo hindrance can affect its interaction with the target protein. The length of the spacer molecule is important and, also, it should have reactive ends enabling its coupling to the matrix and to the ligand. The spacer molecule should not interact with proteins and should preferably be hydrophilic. The coupling of a ligand to a matrix by means of a spacer arm is based on two general procedures, described in Figure 12. Once a suitable matrix is obtained, with the ligand coupled to it, and properly characterized with regard to ligand concentration, the effectiveness of the protein­ligand interaction can be evaluated. A sample containing the target protein is applied to the column, which is washed and evaluated for retained protein. One involves the elution by affinity based on the addition of high concentrations of a free ligand in the buffer. The eluted complex can later be dissociated by changing the buffer salt concentration or by the addition of a surfactant that decreases hydrophobic and van der Waals interactions, such as a non-ionic detergent. In this case, non-hydrophobic interactions between the protein and the immobilized ligand are broken, including biospecific ionic forces and other polar forces. Other elution methods are based on pH and 318 Animal Cell Technology (A) Activating agent * Spacer arm Ligand * (B) Ligand spacer arm Activating agent * * Figure 12.

In vivo acne 11 year old cheap dapsone 100mg without a prescription, this form of death generally affects the neighboring cells and may result in inflammation acne out 100 mg dapsone with amex. Autodestruction occurs by activation of hydrolases when there is a lack of nutrients and oxygen acne studios purchase dapsone 100 mg fast delivery, followed by progressive disorganization and complete disintegration of the cell acne 10 days before period discount dapsone master card. Apoptosis, on the other hand, occurs through the activation of a biochemical program involving a cascade of cell components, which is internally controlled, requiring energy and not involving inflammation in vivo. The most frequently observed biochemical events during apoptosis comprise caspase activation, mitochondrial membrane permeation, leakage of diverse molecules from the mitochondria, nuclease activation, cytoskeleton destabilization, externalization of phosphatidylserine to the outer membrane, and protein interconversion. The determination of the cell growth profile is important to evaluate the specific characteristics of a cell line culture. Hence, knowing the growth curve of each cell line is important for establishing the most adequate inoculum concentration, prediction of the length of an experiment, and the most appropriate time intervals for sampling. Cell concentration in suspension can be determined through an optical microscope employing a hemocytometer for manual cell counting, or in a semi-automatic way using an electronic particle counter (such as a Coulter counter), as described in detail by Freshney (2005). Through dye exclusion (such as trypan blue), it is possible to determine viable cell concentration, that is the number of cells in a known sample volume capable of proliferating in favorable culture conditions. Other factors that impact the culture are medium composition, which can differ extensively between cell lines and is discussed in detail in Chapter 5, as well as susceptibility to hydrodynamic stress, as discussed in Chapter 7. Although the optimal pH value for cell growth does not vary too much for different cell lines, some normal fibroblasts proliferate well at a pH range between 7. Nevertheless, it is convenient to point out that most commercially available phenol red contains impurities that could influence cell behavior. Also, this compound can interfere with the interpretation of experimental data obtained by the use of fluorescence and absorbance techniques. Traditionally, culture media are buffered with sodium bicarbonate at a final concentration of 24 mM. This type of buffering is of low cost, non-toxic, and also provides other chemical benefits for the cells. In some situations, the utilization of a system with a higher buffering capacity is needed. In this case, organic buffers can be employed, and in this category, the most widely used is Hepes (N-2-hydroxyethylpiperazine-N9-2-ethanesulfonic acid). When using Hepes, a controlled gaseous atmosphere for mammalian cell growth is not required. Nevertheless, Hepes is relatively expensive, and is toxic for cells in concentrations above 100 mM. Given the osmolality of human plasma (290 mOsm/kg), it may be reasonable to assume that this is an optimal value for human cells cultivated in vitro, although it can be different for cells from other species. As a general rule, the optimal osmolality range for mammalian cells in culture is from 260 to 320 mOsm/kg, while for insect cells higher values are optimal, from 340 to 390 mOsm/kg. In laboratory and industrial practice it is important to verify the osmolality of all culture media after alterations in their basic formulation 26 Animal Cell Technology due to the addition of salt solutions, supplements, pharmaceuticals, and hormones, or large quantities of buffering agents. Also, metabolic transformations that occur during cell culture can cause osmolality changes. A slightly hypotonic culture medium can be more adequate for open cultures in multiple well plates or in Petri dishes to compensate for evaporation during incubation. To avoid large variations in osmolality during culture, the relative humidity of the culture environment should be maintained near to saturation. Insect cells grow at optimal temperatures of 26­288C, while cold-blooded vertebrate cells normally grow well at lower temperatures. Monitoring and controlling these gases in culture medium are essential for in vitro animal cell culture. Cultures vary significantly with respect to oxygen demand, but in general, for most cells, oxygen partial pressure conditions slightly below atmospheric pressure are preferred. Because of that, maintenance of dissolved oxygen concentration at a range from 30 to 60% for mammalian cells is important. Oxygen is frequently the first component to be limiting in high cell densities due to its low solubility in aqueous medium. Aeration should be performed gently and can be done by the following methods, either directly or in an isolated vessel: surface aeration, gas bubbling, diffusion through membranes, increasing O2 partial pressure and atmospheric pressure. For surface aeration of static cultures, in a closed system, a void volume 10 times larger than the culture medium volume is necessary for adequate oxygen supply. In agitated cultures with surface aeration, oxygen transfer is dependent on agitation rate and impeller geometry.

Predict how ecosystems in the northernmost land regions will be affected by human population change in the next 50 years skin care adha purchase 100 mg dapsone mastercard. Biodiversity of these northernmost regions will remain constant as humans will find other more habitable locations to house their growing numbers acne q-4 scale buy dapsone without prescription. The populations of organisms presently inhabiting these regions will shift as global warming causes many species to decline and new species to move in acne 5 months postpartum discount 100mg dapsone with amex. The carrying capacity of these regions for humans will decrease as the human population increases exponentially acne 60 year old woman buy dapsone 100 mg lowest price. Ecosystems can be expected to remain untouched by humans as new technologies are developed to sustain a growing population. A researcher is interested in investigating whether the croaking pattern produced by males in a frog species is a learned behavior or an innate behavior. A biologist hypothesizes birds of various species recognize the predator warning calls of other bird species. The biologist has established several feeders in a forest where birds come to feed regularly. They are spread out over a wide area, making it difficult to observe all of the boxes at the same time. Describe how the biologist can use this site to collect data to test his hypothesis. In addition, both species A and B use the same types of nesting materials and sites for building nests. A biologist observes that Species A and Species B primarily inhabit different regions of a forest in western Canada. During a forest fire that wiped out the region it inhabited, Species B fled to the region inhabited by Species A. Both the species will survive because of difference in needs for food and nesting space. Species A will increase in population whereas species B will remain same due to the overlapping needs for food and nesting space. Only one of these species will survive in this region due to the difference in needs for food and nesting space. Only one of these species will survive in this region due to the overlapping needs for food and nesting space. Himalayan blackberries are an invasive species that has spread in the forest of the Pacific Northwest. The plants develop thick tangles of cane covered with thorns that cover ground with a tight mat. Ecologists hypothesized that Himalayan blackberries displace native species of shrubs by reproducing faster and reducing areas available for growth. They recorded the density of blackberries and native salmonberries, a native shrub, along a creek for several years. The percentage areas of ground covered by blackberries and native shrubs were this OpenStax book is available for free at cnx. The biologist can use video cameras to record the behavior of birds coming to the feeders. The biologist can record the behavior of birds by comparing them with other birds using video cameras. Comparison of the total number of encounters shows that more birds responded to the eyespot, a trait that will likely be selected against in natural populations of the butterfly. Comparison of the number of birds attacking butterflies with and without eyespots suggests that the presence of an eyespot makes butterflies more visible to predators resulting in selection against the trait. Comparison of the number of birds fleeing from butterflies with and without eyespots indicates that the eyespot trait has been disfavored because this trait makes the butterflies stand out to predators. Comparison of the number of birds fleeing from butterflies with and without eyespots suggests that selection has occurred in butterflies in favor of the eyespot trait, which mimics a predator of the bird. Yellow buntings are birds that feed on butterflies, including Aglaisurticae, a species of butterfly that has bright circular coloring on its wing called an eyespot.

Using this fact acne zeno buy cheap dapsone 100mg on-line, justify the selection of these data shown in the graphs in the construction of a model of ocean photosynthetic productivity acne while pregnant buy dapsone 100 mg low price. Iron and molybdenum are two of 30 elements that are required by the chemical processes supporting life on Earth skin care yang aman order 100 mg dapsone with amex. Of these elements acne extractions generic 100mg dapsone with mastercard, the three most abundant in cells are also found in seawater in approximately the same concentrations. By increasing the mass of phytoplankton in the ocean, we may be able to compensate for the increasing concentration of carbon produced by the combustion of gas, oil, and coal. Select, with justification, the element or elements that, if added in large amounts to the ocean, could boost the growth of phytoplankton. Before implementing a large-scale geo-engineering effort to avert the effects of climate change due to carbon pollution, we must test the legitimacy of this solution. Describe a plan for collecting data that could be used to evaluate the effect of enrichment on phytoplankton productivity. Surface waters of the oceans lie to the left of the vertical 86 Chapter 2 the Chemical Foundation of Life this OpenStax book is available for free at cnx. Many of these critical nutrients are biological macromolecules, or large molecules, necessary for and built by living things. For example, the amino acids found in protein are needed to build healthy bone and muscle. The body uses fat molecules to build new cells, store energy, and for proper digestion. While all living things, including humans, need macromolecules in their daily diet, an imbalance of any one of them can lead to health problems. For example, eating too much fat can lead to cardiovascular problems, and too much protein can lead to problems with the kidneys. In fact, just the opposite may be true, because whole wheat contains more dietary fiber than other types of grains. Complex polymers are built from combinations of smaller monomers by dehydration synthesis, a chemical reaction in which a molecule of water is removed between two linking monomers. Both dehydration and hydrolysis reactions in cells are catalyzed by specific enzymes. Dehydration reactions typically require an investment of energy for new bond formation, whereas hydrolysis reactions typically release energy that can be used to power cellular processes. The four categories of macromolecules are carbohydrates, lipids, proteins, and nucleic acids. A learning objective merges required content with one or more of the seven Science Practices. D Essential Knowledge Science Practice Learning Objective Essential Knowledge Science Practice Learning Objective the process of evolution drives the diversity and unity of life. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids); each is an important cell component and performs a wide array of functions. In addition, they may contain hydrogen, oxygen, nitrogen, and additional minor elements. Most macromolecules are made from single subunits, or building blocks, called monomers. In doing so, monomers release water this OpenStax book is available for free at cnx. Hydrolysis Polymers are broken down into monomers in a process known as hydrolysis, which means "to split with water. Dehydration and hydrolysis reactions are catalyzed, or "sped up," by specific enzymes; dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy. These reactions are similar for most macromolecules, but each monomer and polymer reaction is specific for its class. For instance, carbohydrates are broken down by amylase, sucrase, lactase, or maltase. Proteins are broken down by the enzymes pepsin and peptidase, and by hydrochloric acid.

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