Bio Exam 2 Key

Bio Exam 2 Key - Name _ Lab (Please circle): Tues Wed Time:...

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Name ____________________________ Lab (Please circle): Tues Wed Time: 9:30 11:30 1:30 3:30 Biology 195Z – 10/21/08 EXAM II Please put your name on the first two pages of the exam and completely fill in your PURDUE ID NUMBER on the scantron sheet. This exam consists of three sections and is worth 100 points plus 6 points of extra credit in the multiple choice section (Part III). There are two questions in Part I and one question in Part II. PART I: Answer BOTH of the following questions in a few sentences on the exam sheet. 1. (6 pts) The plasma membrane of a cell is permeable and described as a fluid mosaic. Describe three molecules that contribute to the mosaic nature of the membrane and describe the function of each. The membrane is composed of lots of different molecules, that’s why it is considered a mosaic. The membrane is also flexible and never becomes solid, so material can pass through. Some components are: 1) phosphatidyl choline makes up the majority of the membrane. 2) cholesterol adds to stability for other molecules such as proteins and produces rafts where diffusion is more likely to occur. 3) glycolipid markers: on outer membrane are used in ‘self’ recognition by the immune system to prevent attack by one’s own immune cells. 4) glycoprotein markers: on outer membrane are used in ‘self’ recognition by the immune system to prevent attack by one’s own immune cells. 5) Proteins form channels that allow large or hydrophilic molecules to pass through the membrane. 2 (8 pts). a) What is the function of replication and where does it occur? Replication ensures that DNA will be copied exactly and put in new cells as cells divide or that the DNA of a parent will be put into sperm and eggs to be passed to offspring. It occurs in the cell’s nucleus. b) Briefly describe three sequential steps (they must be in the correct order) that occur during DNA replication. Identify where each occurs and include any molecules that are necessary to carry out these steps. Helicase unwinds strands by breaking hydrogen bonds to form replication bubbles. RNA primers bind. DNA polymerase helps covalent bond formation between nucleotides being added to the new strand The leading strand is synthesized continuously (5’ to 3’) The lagging strand is synthesized discontinuously in Okazaki fragments (because polymerase only joins sugar to adjacent phosphate. DNA ligase helps covalent bond formation between adjacent fragments (We did not spend much time on polymerase removing primers or error checking)
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Name ____________________________ Lab (Please circle): Tues Wed Time: 9:30 11:30 1:30 3:30 Part II: (11 pts) Answer the following essay question. Put your answers on the exam sheet,
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Bio Exam 2 Key - Name _ Lab (Please circle): Tues Wed Time:...

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