Practice Questions - Assignment Example

Practice Questions Insert Insert ANSWERS TO QUESTIONS Practice questions two The lipid bilayer that surrounds an aqueous solutionwith other units inside it serves as a boundary. As a boundary it serves the purpose of selective permeability. Selective permeability is the process by which a cell allows material into and out of the cell through the processes of diffusion, active transport and osmosis. These materials include essentials mineral salts that are actively required for different functions in the cell and waste products for excretion. The lipid bilayer is made up of a thin polar membrane that is also made up of two thin piles of lipid molecules. The lipid layer is the boundary that keeps ions, proteins and other molecules in relative position to each other. Regardless of the fact that the width of the boundary is only a few manometers, the boundary is impermeable to most to a majority of molecules that are water soluble. The bilayers are impermeable to ions and hence they allow the cells to control the level of salt concentration and also the pH by the process of pumping the ions across the membranes with the aid of proteins that are known as ion pumps.Naturally occurring bilayers are made up of phospholipids. The phospholipids are made up of a hydrophilic head and also two hydrophobic tails on each head. In situations where the phospholipids are exposed to water, they arrange themselves in particular manner. In this way, they form a two layered sheet whereby their tails point towards the center of the sheet. The center of the sheet is normally made up of little or no water. It contains sugars and/or salts that soluble in water but not soluble in oil. This specific arrangement brings about hydrophobic forces. The head groups for the phospholipids often change to meet certain demands by the cells. For example, they can change; the head groups can change the chemistry of the surface of the bilayer. An example, during immune response, the arrangement of the head group can be altered in order to mark cells that should be destroyed. It is important to note that the tails of the lipids can be changed in order to bring change to the properties of the membrane, for example, while determining the phase of the bilayer. The proteins that are embedded in any membrane serve three major functions. They may be grouped therefore in three major groups. They include channel proteins which serve the purpose of allowing substances access into or out of the cell. Marker proteins on the other hand, mark cells for instance during immune response. Lastly, receptor proteins receive signals that are often with the shape of a lock and key structure that allows the cell to change shape in order to fit different purposes. Lipids in the membrane store the energy that is required by the cell for various cellular activities and also provide for flexibility within the cell by changing shape. 2. Simple diffusion refers to the process whereby a substance passes through a membrane without the need for assistance form an intermediary such as an essential membrane protein. In this case the force that drives substances across the membrane is only the force of diffusion.Facilitated diffusion on the other hand, refers to a type of passive transport whereby substances are allowed to cross membranes with the aid of essential and equally special transport proteins. This is often due to the reason that some molecules and ions cannot go through the lipid bilayer of the membranes hence this method of transportation. Lastly, active transport refers to the method whereby substances are transported across membranes against the concentration gradient, that is, they move from a region of low concentration of the substance to a region of high concentration of the substance. 3. Biological membranes are described as fluid due to the hydrophobic integral components that includes lipids and membrane proteins that are known to move laterally or sideways throughout the membrane. In this sense, it means that the membrane is perceived as being fluid as compared to being a solid. Biological membranes are perceived as mosaic due to the fact that mosaics are made up numerous parts, biological parts tend to possess different types of macromolecules such as integral proteins, phospholipids, glycolipids, cholesterol and lipoproteins. 4. The great oxygenation event is the process whereby accumulation of oxygen has led to the evolution of the mitochondria in the cell. The sequence of events that led to this major environmental change includes the following processes. Photosynthesis, this process produced oxygen in the atmosphere before this major environmental change took place. Before the G.O.E chemicals and dissolved ions were used to capture any free existing particles of oxygen that was present. During the GOE the minerals were concentrated; therefore, the free existing oxygen could not be captured. Oxygen hence started to accumulate in the atmosphere. When the levels of oxygen started rose then the anaerobic inhabitants of the earths surface were wiped out due to the action of the cyanobacteria which produced toxic oxygen that was harmful to the anaerobic inhabitants. The free oxygen reacted with methane which led to the Huronian glaciations. From this moment on, the free oxygen has been important. According to Margulies cells have undergone evolution through a series of symbiotic partnership that involve different kinds of prokaryotic cells. The small partners are known to have invaded the larger host as a result they have evolved into three major parts that include the mitochondria, chloroplast and flagella. The evolution that took place took place discretely. 5. Life is supposedly known to have begun about 4.2 billion years ago, with organisms and simply structured organisms occupying the earth. Bacteria are also known to have lived during this period. It is through the evolution of free occurring oxygen that mitochondria and the chloroplasts have evolved. Due to the minute nature of the bacteria it is safe to conclude that in size, bacteria as compared to mitochondria and the chloroplast are equal in size. Bacteria reproduce by the process of active cell division, as such their structures as compared to the mitochondria and the chloroplasts are equal hence the two sets reproduce in a similar manner according to Margulies SET. The DNA consists of proteins; hence the structure of the DNA is similar in all organisms. The structure is similar but the contents of the DNA vary. It is for this reason that the DNA that is located in the mitochondria does not form linear chromosomes. It is believed that primitive cells had at least one method of nutrition that included absorption of organic materials that were present in the surrounding, inviginating food particles and also manufacturing their own food from materials that were available in the environment through the process of photosynthesis. However, the structure of the bacteria may vary slightly as compared to the eukaryotic cells. In this regard, they consist of membranes that are bi-lipid in structure. The mitochondria and the chloroplasts serve essential functions in any cell like producing energy and hence membranes that are structurally deprived of chloroplasts and mitochondria cannot make them de novo as the membrane can always acquire essential material for its survival through processes such as osmosis, diffusion and active transport. 6. Endosymbiosis is the process whereby cells and components of the cells change rapidly to the changes that occur in the surrounding. The theory of serial endosymbiosis on the other hand stipulates that eukaryotic cells have evolved through a series of events that have changed the environment. As a result of this, if endosymbiosis is false, then, the theory of the serial endosymbiosis will not be scientifically accepted. Cells that were capable of respiring aerobically were included into other cells that invaginated food. This particular relationship allowed respiration by symbiosis. This relationship, however, required that both the cell types reproduce at roughly the same rate and also the two cell types not to digest one another. From this it is safe to conclude that, if the action of the aerobic environment were not to take place then serial endosymbiosis would be impossible as other means of survival would have been adapted by membranes over time. Practice questions one 1. The means of height for the Dinkas and the Bostonians are equal because the Dinkas consist of males that have a fair height of 177 centimeters, when the average population has a majority of the population with little disparity regarding the height in regard with the shortest and the tallest males, it follows that the average population will be made of people with roughly the average height. On the other hand, the Bostonians is made of many males with varied heights. As a result of this phenomenon, there are many tall males; likewise there are many short males. This brings about an average that is similar to that of the Dinkas. Other statistical values that would be of essence to calculate would include thestandard deviation, the mean varying heights, the lowest value recorded and the relative and absolute extreme and standard variance. 2. Standard deviation provides information regarding how much variance there is from the mean or the average height of males. 3. The independent variables include the three male populations whereas the dependent variables include the heights of the three male populations. 4. Some variables must be standardized because the collection of data that was regarding the heights involved the combination of variables that are on different scales. In order to make each variable contribute to the mean or the average then there is need for standardization. 5. The null hypothesis regards heights of males changing in relation to location and hence the populations whereas the alternative hypothesis regards height in males being normally equal regardless of anyone’s background or community. 6. The null hypothesis in this case is that the future occurrences in the lives of people are independent of the education they acquire while they are growing up while the alternative hypothesis is that people tend to become more successful during the later stages of their lives when they have some educational background as compared to when they do not have some educational background. 7. The independent variable is the number of children in the study and location from which they were obtained from. In this case, they are 111 low income children from Chapel Hill. On the other hand, the dependent variables include the division criteria whereby half the children were enrolled into schooling while the other half was not enrolled and the outcome of their lives after attending preschool. The researcher standardized the results by grouping people with the same characteristics together. In this case, for example, the people who dropped out of school after preschool were disregarded. On the other hand, people who joined schooling at a later stage after not attending preschool were disregarded. 10. The researcher used brown snakes because the researching was seeking to validate the hypothesis that the color of the snake determines whether they are poisonous or not. 8. In response to the release of oxygen by photo-synthesizers, early prokaryotic organisms retreated to anaerobic habitats. 9. The independent variable is the rate of calcification whereas the dependent variable is the amount of carbonates The artificial king snakes were protected from predation by virtue of their size. It is common knowledge that animals naturally prey on each other in regards to their size. Smaller animals tend to preyed on by bigger animals; therefore the artificial snakes were protected from predation by their size. On the other hand, the researcher assumed that it would be difficult for animals to portray some level of cannibalism therefore, the artificial snakes could not be prayed on by the big snakes by the virtue of familiarity. Based on the experimental design the researchers wanted to find out whether, the color on the body of a snake determines whether they are poisonous or not. This nature would therefore help shed more light on whether the coloration on a snake would therefore warn animals on the dangerous nature of the snakes or whether the animals do not see a difference. I would support this hypothesis based on the fact that animals have used colors to survive. It is for this reason that prey often times have colors that may wade off predators and on the other hand, animals such as chameleons use color in order to prevent predation. Logically thinking, it goes without saying that snakes also have embraced this mechanism to protect themselves and also animals have learnt of this over time. The data supports the hypothesis. 9. All the following are parts of a prokaryotic cell accept the ribosomes. 10. The statement is true. Practice question three Chapter eight enzymes and metabolism 1. It is true that anabolic pathways consume energy to build up polymers from monomers. Metabolism can be grouped into catabolism or anabolism. Anabolic metabolism is the group of metabolic pathways that build up molecules from lesser units. 2. The second law of thermodynamics states that if no energy leaves or enters, the potential energy of the state will always be less than that of the initial state, therefore life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is balanced by an increase in the entropy of the universe. This is the answer that brings out the relationship between the second law of thermodynamics and living things. 3. Exergonic reactions refer to a type of chemical reaction whereby the variation in Gibbs free energy is negative hence signifying an extemporaneous reaction. Regardless of this fact, the reactions that take place at a rate that can be observed. Therefore the correct answer for the question is that the reactions are not considered spontaneous. 4. Enzyme catalyzed reactions refer to the catalysis of chemical reactions by particular proteins that are recognized as enzymes. The catalysis of biochemical responses in the cell is very vital because of the very low reaction rates of un-catalyzed reactions. Therefore the reaction is faster than the same reaction in the absence of the enzyme. Some of the factors that affect the rate of enzyme reaction in cells include temperature and the presence of enzymes among others. 8. Competitive inhibition refers to a kind of enzyme inhibition whereby the combination of the inhibitor to the active region of the enzyme prevents combination of the substrate and vice versa. On the other hand, non-competitive inhibition is a type of inhibition whereby the inhibitor lessens the action of the enzyme and binds similarly well with the enzymes whether or not it has now combined with the substrate. References http://www.4shared.com/office/bY2wuS2U/When_nitrate_reigns.html http://www.4shared.com/office/WtyYqK9T/How_cell_evolved.html   Read More