midterm 1 summary

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Midterm 1 Learning objectives 1. Describe what is meant by growth in a unicellular organism. Growth = growth of the population due to cell duplivcation 2. Calculate the approximate number of cells in a growing population based upon the initial number of cells. N*2^n where N= initial #, n = number of generations 3. Identify the following phases on a growth curve graph: lag phase, exponential phase, stationary phase, death phase. Contrast the phases in terms of division rate, cell composition, and cell viability. Lag phase - adaptation to growth conditions, no division. Synthesis of RNA and proteins Exponential growth – cell division (doubling) while growth and resources are unlimited Stationary phase – growth slows due to lack of resources. Growth=Death rate Death phase – Death rate > growth rate, lack of nutrients. 4. Predict the response in cell growth to environmental conditions. Change of nutrient = additional lag phase Lack of nutrient = stationary phase then death Worse nutrient = less steep exponential phase More nutrients = longer time till stationary phase 5. Remember the pattern of electronegativity of O, N, C S P H atoms O>N>S=C~H=P 6. Recognize whether a molecule or group on a molecule is polar, hydrophobic, neutral, or amphipathic. Polar – has polar bonds Hydrophobic – has no polar bonds Amphipathic – a large molecule with both polar and non polar groups (separated) 7. Describe why water is termed a polar molecule. Differences in electronegativity creates partial charges on H (+) and O (-). This is called a polar bond (permanent dipole). 8. Describe the process of diffusion and the consequences of diffusion for cells. Diffusion allows materials to cross into/ out of the cell according to a concentration gradient. Diffusion alone can not enable cells to maintain internal composition different from its environment Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.
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9. Recognize the types of interactions that can form between polar and non-polar molecular groups on molecules. Covalent bond – sharing electrons between two atoms Polar interactions: - Ionic bonds – form between positively and negatively charged molecules/ groups - Hydrogen bonds - (permanent dipole-permanent dipole) electroststic attraction between polar bonds. Groups usually include O, N or S - Permanent dipole-induced dipole – electronegative groups induce a charge on non polar groups due to electronegativity differences. For example, O e- will repel H e- in a nonpolar group and create a partial + charge on the H, if the groups are close to one another. Non polar interactions: - Van der Waals – (induced dipole-induced dipole) interactions that depend on molecule size and proximity 10. Describe why phospholipids are amphipathic.
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