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Midterm

BIOL 400 Study Guide - Midterm Guide: Cell Membrane, Mesophile, YogurtExam


Department
Biology
Course Code
BIOL 400
Professor
All
Study Guide
Midterm

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Short Answer Exam 2
Name:______________________________ ID#________________________________ Exam Code:111111
1. Previously we learned that proteins could be embedded in the plasma membrane to aid in transport of
large or polar molecules across the plasma membrane (depicted below). Based on the drawing and the
structures of the amino acids provided, identify which amino acid would be located in the following
positions in the space below. (6pts)
For each spot, identify one possible amino acid that could reside there. (1pt each)
R1____ Ser, Asp, Glu ______
R2_____ Ala, val, leu, Ile, gly
R3__ Ser, Asp, Glu ___
R4__ Ser, Asp, Glu _
Briefly explain your reasoning:
R1, R3 and R4 all face a polar environment so they would likely be polar amino acids. R2 faces the hydrophobic
interior of the membrane and would be a nonpolar amino acid. (2pts)
2. Below is a growth curve of E. coli (a mesophile) grown at two different temperatures. Answer the
following questions based on your analysis of this data.
3. Which culture represents growth at 37C and which is likely grown at 50? (2pts)
a. Culture A__37
b. Culture B__50_

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c. Explain what is happening to the proteins at the higher temperature. (2 points)
At higher temperatures the hydrogen bonding is disrupted and the proteins structure denatures. (1 pt for
mentioning H bonding, 1 pt for discussing denaturation or disruption to structure)
d. Some bacteria can grow at higher temperatures. How would their membranes differ from those
of mesophiles? (2 points)
Thermophiles need to have membranes that are less fluid (1pt) at high temperatures so they would have
more saturated fatty acids (1pt).
4. Brecken and Avery went home for fall break. Their mother went for a jog and the next day had sore legs
due to the build-up of lactic acid in her muscles. Avery told his mom it was due to the fact that her
muscles had undergone anaerobic respiration and produced lactic acid. Brecken corrected her brother
and explained that her muscles had undergone fermentation. Help Brecken explain the difference
between anaerobic respiration and fermentation to Avery and her mother. Be sure to include the major
differences between fermentation and anaerobic respiration. The following terms must be used for full
credit: glycolysis, recycling, NAD+/NADH, pyruvate, TCA, electron transport chain, terminal electron
acceptor, oxidative phosphorylation, substrate level phosphorylation and ATP. (10 points) In both
fermentation and anaerobic respiration a glucose molecule is oxidized into two molecules of pyruvate.
During this process, the electrons are added to NAD+ to form NADH. After the NADH is formed, ATP is
made via substrate level phosphorylation. In anaerobic respiration, the electrons are stripped away from
the pyruvate during the TCA cycle. The electron carriers NADH then takes the electrons to the electron
transport chain and then donates them to the terminal electron acceptor. In anaerobic respiration, this is
a molecule other than O2. The cell can make ATP via oxidative phosphorylation and the proton motive
force. If there is no terminal electron acceptor available, or ETC, then the cell can only gain ATP in the
steps of glycolysis. The problem is that NAD+ is in limiting supply so the cell must recycle the NADH to
NAD+ by dumping the electrons on another molecule. It can reduce pyruvate to lactic acid for example. (1
pt for each proper use of the term listed. Points 0.5-1 can be deducted for additional incorrect
information.)
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