Final Exam Study Guide
Final Exam Study Guide BIOL 11100 - 001
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BIOL 11100 - 001
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This 11 page Study Guide was uploaded by Brianna Nemeth on Friday December 11, 2015. The Study Guide belongs to BIOL 11100 - 001 at Purdue University taught by Denise Lore Zielinski, Mark Edward Browning in Fall 2015. Since its upload, it has received 64 views. For similar materials see Fundamentals Of Biology II in Science at Purdue University.
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Date Created: 12/11/15
Focus Questions: Circulation 1. What kinds of animals need a circulatory system and why? What are the functional subdivisions of the human circulatory system? Animals with a diameter of more than 1 mm in need a circulatory system. This is because the functional limit to diffusion of gases is about 0.5 mm. The human circulatory system has a muscular pump, the heart, and an elaborate system of vessels. The vessels that lead away from the heart are called arteries, and they branch into smaller vessels called arterioles. The large vessels leading back to the heart are called veins, these also branch into smaller vessels called venules. Arteries and veins are connected by capillary beds where gas and fluids are exchanged. The progression is: arteries—>arterioles—>capillaries—>venules—>veins. 2. What are the two circuits of the circulatory system and what are their roles? The two circuits are the pulmonary circuit and the systemic circuit. These describe the route of blood to the lungs and back and to the body tissues and back respectively. The pulmonary circuit starts in the right ventricle that pumps deoxygenated blood to the lung where gas exchange can occur. The oxygenated blood returns to the left atrium of the heart via the only veins that carry oxygenated blood: the pulmonary veins. From the left ventricle, oxygenated blood is pumped via the systemic circuit to the rest of the body where gas exchange can occur leaving deoxygenated blood to be returned to the right atrium to begin the pulmonary circuit again. 3. What determines the direction of gas exchange in the lung and in the tissues? Both O a2d CO can c2oss the membrane as they are nonpolar, thus can move by simple diffusion. There is no active transport of O or CO , so2the 2 body must take advantage of concentration differences that arise due to the utilization and production of these gases. In the case of gases, we express concentrations as pressure (more accurately partial pressures). In the lungs, the pressure of O (Po ) in the air is much higher than the pressure in the lung 2 2 capillaries, so O e2ters the blood from the air. The pressure of CO (Pco ) in 2 2 lung capillaries is higher than the pressure of CO in the2air so CO moves fro2 the lung capillaries into the air. In the tissues, O is utilized lowering the Po in 2 2 tissue relative to the capillaries forcing O fro2 the capillaries into the tissues. The situation is reversed for CO , wh2ch is generated by tissues. This leads to higher Pco in2the tissue relative to the capillary forcing the CO from the2tissue into the capillaries. 4. Why do we need a carrier for oxygen in the blood? What are the characteristics of the oxygen binding curve of hemoglobin? How does this curve relate to the idea of structure and function? The solubility of O in2water is relatively low. To carry sufficient O at its 2 level of saturation in blood plasma would require extremely high flow rates. Instead of increasing the flow rate to deliver more oxygen, we use the O 2 carrier hemoglobin. The hemoglobin O binding curve is sigmoid shaped. This is indicative of 2 the cooperative binding of O . H2moglobin can bind 4 O molecule2 (one for each globin chain/heme group). Cooperativity means that the first O is slower2 to bind than the next two. The binding of the first O chan2es the shape of the molecule such that the next two O bind more readily. The last one binds more slowly than the second and third as there is now only 1 binding site remaining, so based on probability the last O wi2l bind more slowly despite the change in shape. The relationship of structure and function is nicely illustrated by the change in shape after initial binding leading to cooperative binding. This kind of alteration of shape due to binding of an effector is called an allosteric interaction, and hemoglobin is an allosteric protein. Note that not all allosteric interactions are cooperative, so these are different concepts. 5. Are all hemoglobins the same? What characteristics differ and how is this physiologically relevant? All hemoglobins are not the same. There are differences between species as well as developmentally within the same species. In humans, the fetal form of hemoglobin has a binding curve that is left-shifted relative to the adult form. There are also many different variants that can be found in different species. The example given in class was the Llama, which also has a left-shifted binding curve. Both of the left-shifted curves result in saturation at lower Po than2 non-shifted. In both cases, the left-shifted curve is an adaptation to lower O 2 environments. Focus Questions: Plant Transport 1. What types of conducting tissue do plants have? Is all of this tissue alive? Plants have two types of conducting tissue: xylem and phloem. The xylem tissue is dead, consisting of tracheids: cells that die leaving only hollow tubes made up primarily of cell wall material. The other type of conducting tissue, phloem, is alive made up of sieve tube cells. This difference in live and dead cells leads to differences in how water and solutes are moved in these two types of vessel. 2. How are plants able to move water without any pumping mechanism, or muscle tissue? Plants take advantage of basic chemistry to move fluids: plants move water based on water potential. Plants cannot pump fluids but can pump ions across membranes. This changes water potential and changes in water potential will lead to the movement of water. Water always flows from an area of high water potential to an area of low water potential. 3. What are the two pathways that allow water to enter the root? What distinguishes these two pathways? What is the Casperian strip, and how is it involved in these two pathways? The two pathways are the symplast and the apoplast pathways. The apoplast pathway is passive and involves water diffusing between cells by capillary action through the spaces between cell walls. This is called imbibition and can be thought of as similar to what happens when you put a paper towel on a puddle of water. This is a nonselective uptake of water into the root that does not actually enter cells and thus cannot reach the xylem. The apoplast pathway is prevented from reaching the stele, which contains conducting tissue, by the Casperian strip, which is a region of cell wall impregnated with a hydrophobic substance that acts like a gasket to seal off the stele. Water that eventually makes it into the xylem arrives by the symplast pathway. In this pathway, minerals are actively transported across membranes and water diffuses through the membrane due to changes in water potential. Once across the membrane, water and minerals can move between cells by specialized connections between cells called plasmodesmata. These connections allow the flow of cytoplasm between adjacent cells. Since the symplast pathway must cross the membrane, it enforces selectivity in uptake. Water and minerals can move from apoplast to symplast by simply crossing the membrane. 4. Trace the pathway of water from the soil into the xylem. What causes the movement of water from the soil to the xylem? Minerals are actively transported into the cells of the epidermis lowering the water potential in the cells causing water to enter the cells. Thus both water and minerals enter the symplast pathway with selectivity of mineral uptake by the root enforced by the plasma membrane. Water and minerals can then move through the cytoplasm of cells through the plasmodesmata connecting adjacent cells. This allows them to bypass the Casperian strip, which is outside the cells, and arrive at the pericycle of the stele. Water enters the xylem because the cells of the pericycle pump minerals outward into the stele lowering the water potential outside the cell. The Casperian strip keeps this solute containing water in the stele and water leaves the cells of the pericycle because of the difference in water potential. Thus water enters the xylem due to changes in water potential manipulated by the plant. 5. How do plants move water up the xylem? Is there any evidence for this model? Water moves up the xylem by a mechanism that involves tension and cohesion. This uses the properties of water to move it up the xylem. Water is lost from the leaf by transpiration creating tension in the column of water in the xylem. This is transmitted down the column by the cohesive nature of the water. We can tell that the water is being pulled up the xylem because the transpiring diameter of the xylem is less than the nontranspiring diameter, which we would expect if it is being pulled from above causing the xylem to collapse slightly. Also if we puncture the xylem, water does not squirt out as would be expected for water under pressure from below. Rather, the level falls as the diameter of the xylem increases due to the lack of tension. 6. What structure do plants use to control gas exchange? How does this function? Stomata control gas exchange. These are made up of two guard cells whose shape changes with water content. When the guard cells are full of water, the stomata are open, when they have less water, the stomata close. 7. What controls the amount of water in guard cells? How does this relate to environmental and physiological conditions? We discussed two environmental factors that affect this. The plant is sensitive to the amount of moisture in the soil such that if the soil moisture is low, abscisic acid is produced and this causes guard cells to lose water, which closes stomata. The other factor ties the stomata to the photosynthetic state of the plant. When plants are actively photosynthesizing, they need to exchange CO (and other gases). This is mediated by a sensing system that ties the level 2 of CO 2o the state of the stomata. Whe+ CO is lo2, as it would be in an actively photosynthesizing plant, K is transported into guard cells. This lowers y sn guard cells causing them to take up water opening the stoma. This process is reversed in plants with high CO . 2 8. Is transport in the phloem similar to transport in the xylem? What is the pressure bulk flow model? How does it operate? Transport in the phloem is fundamentally different from transport in the xylem in that it requires the participation of cells at both ends of any transport event. In the phloem, in photosynthetic areas sugars are actively transported into the phloem, reducing water potential in the phloem. Water follows the decrease in water potential and builds up pressure in the phloem. At the same time phloem cells in nonphotosynthetic areas remove sugars from the phloem increasing water potential in the cells such that water moves out. The loss of water from the phloem reduces pressure in the phloem. This has the effect of creating areas of higher water pressure in photosynthetic areas and reducing water pressure in nonphotosynthetic areas. This leads to the overall flow of water from areas of high pressure to areas of low pressure. This mechanism is called the pressure bulk flow model. Focus Questions: Hormones and Homeostasis 1. What are the two organizing principles of physiology we discussed in class? 1. Organisms show a hierarchical organization going from cells to tissues to organs to organ systems. This kind of organization leads to emergent properties where higher levels show new characteristics that are not evident at the lower levels. For example, cells can cooperate to form tissues which are capable of forming a protective barrier for the body, such as epidermis. 2. Organisms also exhibit the phenomenon of homeostasis. This is the ability to dynamically control the internal environment of a living organism despite fluctuations in the external environment. This is seen at multiple levels of the above hierarchy and results from the coordinated functioning of many interacting systems. 2. What is homeostasis and how does it act in living systems? What are set points and how does this relate to homeostasis? As stated above, refers to the ability to maintain a relatively constant internal environment despite a fluctuating external environment. This is seen in the maintenance of relatively constant internal temperature among homeotherms, blood glucose, blood pH, and plasma Ca level regulation, as well as other parameters. Set points refers to the level at which a physiological state is regulated through homeostatic control. This maintenance is dynamic and actual levels fluctuate around the set point. If levels rise above the set point, then there is a lowering response; if levels fall below the set point, there is a raising response. 3. What are hormones? Compare and contrast their function with neurotransmitters. Hormones are chemicals secreted by endocrine cells or glands, usually into the blood, for transport to a distant target. They are effective at extremely low concentrations. In order to generate a response in a cell, the target cell must have receptors for the specific hormone, either membrane-bound or intracellular. Neurotransmitters are also chemical signals that are secreted, but they are short- lived and act over a short distance (the synaptic cleft). 4. How do the hypothalamus and pituitary interact to regulate hormone production? The hypothalamus is a portion of the brain that integrates information about the physiological state of the organism. It generates appropriate inhibiting or releasing hormone and nerve signals to the pituitary. The pituitary is the brain structure below the hypothalamus and consists of an anterior and a posterior lobe. The posterior pituitary is part of CNS and is connected to the hypothalamus by axons from the hypothalamus. It receives neurohormones from hypothalamus and stores them until needed. The anterior pituitary is not part of CNS; it formed from an upgrowth of tissue from the palate. It receives hormonal signals from hypothalamus and in turn will secrete additional hormones that it made. These hormones have targets throughout the body are intended to regulate the variables the hypothalamus assessed. 5. What are stress hormones? Where are they produced and why are there different types? Stress hormones are those whose secretion is increased when an individual is exposed to stressors, such as perceived threat or increased demands, and whose actions are designed to mobilize energy stores, and increase efficiency and responsiveness. The stress hormones are produced by the adrenal gland on the kidney. The cortex produces the steroid hormone cortisol, and the medulla produces the non-steroid (catecholamine) hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones allow adaptive responses to stress exposure over different time scales. Adrenaline is involved in generating the ‘fight or flight’ responses; it causes an increase in heart and respiratory rates, increase in blood pressure, decrease digestive rates and an increase in blood glucose levels. Cortisol acts over a longer time scale. It can increase the mobilization of energy stores from fat, muscle and bone, suppress immune system function and suppress reproduction. 6. How does your body regulate blood sugar? What hormones are involved and what is their effect on blood glucose? Blood sugar is regulated by the action of antagonistic hormones. This means two hormones with functions that opposite each other. One acts to raise blood sugar and the other acts to lower blood sugar. The hormone insulin acts to lower blood sugar by causing cells to take up glucose, convert glucose to glycogen and to reduce the rate gluconeogenesis (glucose synthesis) in the liver. The hormone glucagon has the opposite effect: it acts to raise blood sugar by causing cells to convert glycogen to glucose, and to increase the rate of gluconeogenesis. These hormones act by binding to membrane receptors and initiating signal transduction cascades. Insulin acts through a catalytic receptor (see receptors Figure 9.7). 7. How can this regulation be overridden by the stress of extreme circumstances? What signaling pathways are involved in normal regulation and the override situation? The normal controls detailed above can be overridden by the action of the hormone adrenaline (epinephrine). Adrenaline binds to a G-protein coupled receptor that acts through the effector adenylyl cyclase to activate PKA. PKA then phosphorylates phosphorylase kinase that in turn phosphorylates glycogen phosphorylase. Glycogen phosphorylase cleaves glucose units off of the glucose polymer glycogen, adding a phosphate in the process to release glucose-1- phosphate. The end result is the secretion of glucose. This is all part of the “flight-or-fight” response to extreme stress and prepares the body for extreme actions. 8. How does the body regulate the level of Ca in blood plasma? Is the role of hormones in this case similar to the blood glucose case or different? What does this example add to our knowledge of homeostasis? The level of plasma Ca is maintained at a constant level of about 10 mg/ml. As this is an important signaling molecule, this regulation is critical to cells. The level of Ca is controlled by two hormones with antagonistic actions: ++ cal++tonin decreases plasma Ca and parathyroid hormone increases plasma Ca . This is similar to the case with blood glucose where we also had two hormones with antagonistic actions. The additional aspect of regulation observed in this system in the proportional response in the production of the hormones. The farther from the set point, the more of the appropriate hormone is produced. The closer to the set point, the less of the appropriate hormone is produced. Thus the response is graded: if a large deviation occurs there is a corresponding large response; if a small deviation occurs there is a correspondingly small response. This still involves negative feedback but allows finer control. Note that this kind of response is seen in most systems involving hormones, including the insulin, and glucagon example seen above. 9. In humans, how do gonads differentiate normally? During early embryonic development, males and females are indistinguishable. At 6 weeks post-fertilization Wolffian ducts (structures that will form male reproductive organs) and Mullerian ducts (structures that will form female reproductive organs) form. Wolffian ducts will inhibit Mullerian ducts when Sertoli cells in the testes secrete Mullerian inhibiting substance (MIS). If female reproductive anatomy is not inhibited by sex determining substances expressed from genes on the Y chromosome, the Mullerian system will develop. 10. What are endocrine disruptors? How do they work? What are their effects on sexual development? Endocrine disruptors are chemicals in the environment that interfere with normal endocrine signaling because they mimic effect of steroid hormones. Examples include DES and BPA. Early exposure to these chemicals during development causes males to have feminized reproductive organs, undescended testes and abnormal development of the penis and urethra. Early exposure in developing females causes abnormal development of the reproductive tract, including a T-shaped uterus, and an increased risk of developing uterine and cervical cancer. Focus questions: The immune system 1. What is the function of your immune system? Your immune system allows you to 1) prevent invasion by viruses, pathogens and parasites, 2) destroy viruses, pathogens, parasites that have invaded your body and 3) destroy abnormal (e.g. cancerous) cells that belong to your body. 2. How does your body recognize its own cells versus those of an invader? ‘Self’ markers, such as proteins or glycoproteins, on the plasma membrane of your own cells are identified by specific immune cells as belonging to your body. ‘Non-self’ markers are recognized as antigens by specific immune cells and stimulate a specific immune response. 3. What is a nonspecific immune response? A nonspecific immune response is one that does not require a specific antigen to stimulate it. It is a rapidly produced chemical and cellular responses to destroy or prevent the proliferation of the microbes that entered the body. 4. What is the inflammatory response and how does it benefit your body? Is it a specific or non-specific response? Inflammation is a non-specific response. When a pathogen enters the body through trauma to the skin or through a mucosal membrane, paracrine signals, such as histamine, are produced by the mast cells. These signals cause blood vessels to dilate. The larger diameter brings a larger supply of blood to the injured area, allowing other lymphocytes to reach the area. The signal also causes capillaries to become more leaky, so immune cells can exit and phagocytize the invaders. Fluid leaks out of the capillaries, causing swelling. The swelling puts pressure on neurons in the area, producing pain. Other proteins cause the temperature of the affected area to increase, producing redness. This heat can also help to kill the pathogens. 5. What types of molecules are antigens and antibodies? How are they produced and where would they be found? Antigens are the proteins or glycoproteins that initiate a specific immune response. They are found on the plasma membrane (or protein coat, for a virus) of pathogens. They are produced though translation and post-translational modification and inserted into the membrane. Antibodies are the proteins secreted by B cells that circulate in the blood plasma or lymphatic fluid. 6. What is the function of an antibody? What is the function of an antigen? Antibodies bind to antigens circulating in the body. The antigens served as ‘self’ markers to the pathogen, but serve as ‘non-self’ markers in the individual they are invading. Antibodies bind to antigens they are specific for, but do not kill them. The antigen-antibody complex can then be targeted for destruction by macrophages and phagocytes. 7. What is the function of B cells and T cells? Where are they initially produced? B and T cells are both white blood cells involved in specific immunity. The are both initially produced in the bone marrow. T cells go on to mature in the thymus gland while B cells mature in the bone marrow. 8. What is an antibody mediated immune response? Why does it take longer to kill off a specific invader upon first exposure compared to your second exposure to the same antigen? An antibody-mediated response is a specific one in which an antigen stimulates B cells to secrete antibodies. The initial exposure to the antigen also stimulates mitotic division within the B cell population that has the antibody specific to the invader. Some of these cells will remain dormant in lymph organs as memory cells. Because few cells initially produce antibodies in response to the first exposure, it takes longer for the pathogen to be destroyed. Upon a second exposure, a larger B cell population is ready to secrete antibody as well as to divide to produce more antibody secreting cells, so the immune response is more rapid. 9. What is the function of vaccines? Vaccines contain the minimum antigenic portion of the pathogen against whom the vaccine is directed. This is to prevent the person contracting a disease from the vaccine. The antigen stimulates the B cell antibody mediated response, resulting in a population of memory cells. When the vaccinated individual later encounters the pathogen, they are able to respond rapidly and secrete large quantities of antibodies to the antigens of the invader, leading to their destruction. 10. What is the difference between how B cells do their job compared to T cells? B cells never need to come in contact to the pathogen their antibodies are directed against, because the antibodies are secreted. T cells, however, are involved in cell-mediated responses. This means that they need to come in direct contact with the pathogen, to destroy the cell directly or to cause an infected cell to be destroyed. 11. What type of virus is HIV, what host cells does it infect, and how, and why is the infection so devastating? HIV is a RNA virus that infects helper T cells with CD4 cell surface markers. It has genes for reverse transcriptase, so it is able to integrate its genetic information into the host cell genome through reverse transcription. It is leads to immune system suppression and shut-down because it destroys the helper T cells that are evolved to help recognize and suppress other infections. Focus Questions: Waste and Water Balance 1. What are the three basic functions of the kidney? How do these relate to the functional regions of the nephron? The three functions of the kidney are: filtration, reabsorption and secretion. The purpose of filtration is to separate the soluble fraction of blood from the cells and large proteins in blood. This filtrate is then further processed to produce waste and reclaim important components. The important components are reclaimed by reabsorption. This refers to the movement of molecules out of the filtrate where they can be picked up by capillaries and returned to the bloodstream. Secretion refers to the active secretion of toxic compounds from the blood into the filtrate for removal as waste. The major functional regions of the nephron are the glomerulus and the tubule system. The tubule system consists of the proximal and distal convoluted tubules (PCT and DCT), which are joined by the loop of Henle, and the collecting duct, which loops back down next to the loop of Henle and moves the filtrate out of the kidney. The glomerulus and the PCT and DCT are all in the cortex of the kidney and the loop of Henle extends down into the medulla. Filtration takes place in the glomerulus with the filtrate collected by Bowman’s Capsule; reabsorption and secretion take place in the tubule system. 2. Where does filtration occur? What provides the pressure for this process? Filtration occurs in the bed of capillaries called the glomerulus. These are the only capillaries in the body that have an arteriole going in and coming out. The artery that feeds the glomerulus is the afferent arteriole and it has a larger diameter than the efferent arteriole that exits the glomerulus. This difference in diameter leads to pressure across the glomerulus that forces fluid out of the capillaries and into Bowman’s capsule where it can enter the tubule system. 3. How does reabsorption occur? Where in the nephron does it occur? Give an example of this process. Reabsorption is confusing as it involves active and passive transport of materials out of the tubule system. This sounds like secretion but is in fact reabsorption as the material that leaves the tubule system is returned to the blood stream through the peritubular capillaries and vasa recta. The peritubular capillaries surround the PCT and DCT and the vasa recta surrounds the loop of Henle. Glucose and amino acids are actively transported out of the proximal convoluted tubule and essentially all of these molecules are reabsorbed here. Salts are reabsorbed at various points along the tubule system, and the reabsorption of water is complex, taking place at a number of sites. 4. What is secretion and how is it different from reabsorption? Where does this occur? Secretion is the active transport of materials into the tubule system. This allows the body to move substance from the blood into the tubule system selecti+ely. To+ic substances are handled this way as well as the important ions H and K . The difference between secretion and reabsorption is entirely in the direction of transport: secretion is into the tubule system, and thus out of the body eventually, and reabsorption is out of the tubule system, and back into the bloodstream. 5. What is the role of the loop of Henle in water reabsorption? How does this relate to the structure of the kidney? How does this relate to the function of the collecting duct? The loop of Henle acts to create a region of very low water potential (high solute concentration or high osmolarity) in the deep medulla of the kidney. This is due to the differential permeability of the different parts of the loop to solutes and water. This acts as a so-called “counter-current multiplier system.” This is because solutes are pumped out going down the loop and then diffuse out going back up. The flow of fluid being in the opposite direction is the countercurrent part and acts to amplify the effect. The end result of this is a gradient of increasing osmolarity (decreasing ψ ) soving down the loop and peaking in the deep medulla. The importance of this is that the collecting duct runs through this region of the medulla and allows a last chance to reabsorb water before the filtrate exits the kidney. 6. What is the hormonal control over blood volume and osmolarity? How does this relate to kidney function? The hormone antidiuretic hormone (ADH) acts to control the permeability of the collecting duct to water. The levels of ADH are sensitive to both blood pressure and to blood osmolarity. Thus ADH can act to control blood osmolarity. The action of ADH is to increase the permeability of the collecting duct to water: in the presence of ADH water channels (called aquaporins) are inserted into the wall of the collecting duct making it permeable to water. In the absence of ADH these pores are removed making it impermeable to water. So in the presence of ADH, water is reabsorbed in the collecting duct due to the low water potential in the interstitial fluid created by the loop of Henle. This results in concentrated urine and is a response to low blood pressure or high blood osmolarity. In the absence of ADH the collecting duct wall is not permeable to water and dilute urine is produced. This is the case in terms of normal blood pressure and blood osmolarity.
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