BIOL 1208 Chapter : Biol 1208 Written Assignment 1
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1. Humans with mutations in the AQP1 (aquaporin-1) gene do not produce the AQP1 protein. The absence of AQP1 causes an inability to ____ in these individuals.â
| a. | produce concentrated urineâ | |
| b. | ârecognize thirst | |
| c. | âmake large volumes of dilute urine | |
| d. | âcontrol sweating | |
| e. | âSalivate |
2. Two solutions of differing glucose concentration are placed in a container separated by a selectively permeable membrane that restricts large molecules like glucose, but allows the free diffusion of water. What will be the glucose concentration in the container after dynamic equilibrium has been reached?â
| a. | âThe water molecules will be evenly distributed in the container, with more glucose molecules on one side than the other. | |
| b. | âThe volumes of the solution will be different, with a higher volume on the side that originally contained the higher concentration of glucose. | |
| c. | âThe volumes of the solution will be different, with a lower volume on the side that originally contained the higher concentration of glucose. | |
| d. | âThe glucose concentration of the two solutions will be identical on both sides of the membrane, but the volumes will remain unchanged. | |
| e. | âThe volume and concentrations will be unchanged on both sides of the membrane. |
3. Which mutation is an example of an adaptation?â
| a. | A mutation results in decreased sperm count in humans.â | |
| b. | âA mutation is found to be the cause of Alzheimer's Disease. | |
| c. | âA mutation results in hairless cats, reducing allergies in humans. | |
| d. | âA mutation increases the size of tomato plants. | |
| e. | âA mutation renders an individual immune to HIV infection. |
4. The prokaryotic chromosome is comprised of a ____.
| a. | âhighly folded mass of a single, linear molecule of DNA | |
| b. | âloosely folded mass of a single, linear molecule of DNA | |
| c. | âhighly folded mass of a double, circular molecule of DNA | |
| d. | âhighly folded mass of a single, circular molecule of DNA | |
| e. | âloosely folded mass of a single, circular molecule of DNA |
5. Which methodology was used by researchers to identify the nuclear localization sequence?â
| a. | infection of cells in culture with viruses containing sequential deletions of amino acids in a protein known to localize to the nucleus, followed by microscopic determination of cellular localizationâ | |
| b. | âtreatment of cells in culture with pharmacological agents that inhibit the nuclear pore complex, followed by microscopic determination of cellular localization | |
| c. | âtransfection of cells in culture with mutant human proteins containing sequences believed to be required for nuclear localization followed by microscopic determination of cellular localization | |
| d. | âfluorescently labeling cells with known nuclear proteins and tracking changes in localization in the presence or absence of nuclear pore complex proteins | |
| e. | âtreatment of cells in culture with pharmacological agents that binds to the nuclear localization sequence and prevents nuclear transport, followed by microscopic determination of cellular localization27. Cells actively secreting enzymes would likely carry out more ____ than other cells.â |
6. Cells actively secreting enzymes would likely carry out more ____ than other cells.â
| a. | exocytosisâ | |
| b. | âosmosis | |
| c. | âendocytosis | |
| d. | âconjugation | |
| e. | âFractionation |
7. What is a function of prokaryotic common pili?â
| a. | âbiofilm formation | |
| b. | âtransfer of DNA | |
| c. | âprotein polymerization | |
| d. | âenergy production | |
| e. | âlipid synthesis |
yeast population dynamics
Procedure
1. Work in pairs on this lab, so 12 tubes per pair of students. And share a tube rack with one other pair of students
2. Turn on your spectrophotometer. It needs at least 15 minutes to warm up to give you good readings.
3. Add 5 mL of yeast extract solution (YECM) to each of 12 tubes. (The yeast extract provides vitamins and amino acids for yeast growth and will be the same for all cultures). The tubes should be labeled with your initials, treatment, and tube number. Tape or Parafilm down the lids of 3 tubes, and label them âCONTROLâ.
Do not touch the insides of the tubes or lids! Try to keep these as sterile as possible!!
4. Add 50 mL live yeast culture to each of the remaining 9 tubes.
5. Add the varying volumes of sugar and/or ethanol using Table 1 below.
6. Use Parafilm to close the tops of each tube, making sure the Parafilm is tight and no air can get in, and label each tube with the following:
Amount of sugar added (mL) Amount of ethanol added (mL)
Name of your group Tube number
| Table 1: setup yeast tubes (remember, 1 mL = 1000 mL) | ||||
| Tube number | Yeast culture medium? (5 mL) | Live yeast culture? (50 mL) | Sugar added (mL) | Ethanol added (mL) |
| 1 â control | YES | NO | 0 | 0 |
| 2 â control | YES | NO | 0 | 0 |
| 3 - control | YES | NO | 0 | 0 |
| 4 | YES | YES | 0 | 0 |
| 5 | YES | YES | 0.25 | 0 |
| 6 | YES | YES | 0.5 | 0 |
| 7 | YES | YES | 0 | 0.25 |
| 8 | YES | YES | 0.25 | 0.25 |
| 9 | YES | YES | 0.5 | 0.25 |
| 10 | YES | YES | 0 | 0.5 |
| 11 | YES | YES | 0.25 | 0.5 |
| 12 | YES | YES | 0.5 | 0.5 |
Procedure for measuring absorbance (in absorbance units, or AU)
7. Calibrate the spectrophotometer:
Turn on the spectrophotometer and let it warm up for 15 minutes. You will get erroneous results if you donât let it warm up first.
Be sure the spectrophotometer is set to read at the wavelength of 550 nm
With no tube in the spectrophotometer and the lid closed, use the left-hand knob to adjust the reading to 0% Transmittance/push zero button to calibrate
Insert a CONTROL tube (making sure it is clear, without bacterial contamination which would make it cloudy), and use the right-hand knob to readjust the spectrophotometer to 100% Transmittance.
When reading the absorbance, be sure to line up the needle on the spec with its reflection.
8. Immediately before reading any tube, vortex the tube so that the spinning column reaches the bottom of the tube for several seconds. This is critical! The yeast cells are heavy and will tend to sink to the bottom of the tube, so you must vortex the tubes to resuspend them: otherwise, your spectrophotometer readings will be erroneously low. If the vortex is not enough to suspend the pellet of yeast cells at the base of the tube, take a piece of Parafilm and cover the top of the tube, then cover this with your thumb and shake the tube vigorously. The pellet should dislodge and the yeast cells should be easily resuspended after doing this. Use a Kimwipe to wipe down the outside of each tube, to remove fingerprints and other smudges that could affect the absorbance reading. (COULD BE A POTENTIAL ERROR)
9. Record the absorbance (in absorbance units, AU) for the tube on your data sheet.
10. Repeat steps 5 and 6 for every tube.
11. Leave the spectrophotometer turned on for the next user.
Figures you should include are:
Average absorbance vs. time for the no ethanol (0 mL) treatment
Average absorbance vs. time for the 0.25 mL ethanol treatment
Average absorbance vs. time for the 0.50 mL ethanol treatment
Sugar added vs. average carrying capacity (K). Use different symbols to denote each of the three alcohol concentrations
A. After a limit, the increasing concentration of sugar decreases the carrying capacity and growth rate. This is because at higher sugar concentrations, the medium becomes hypertonic and the yeast cells loss water towards the medium.With increasing concentration of the ethanol, the carrying capacity and the growth rate decreases. Why does this happen?
B. Is there any interaction between the effects of adding sugar and alcohol on yeast?
C. why do some cultures not reach K?
D. What are the potential sources of error and assumptions made in this experiment?
E. What do these results mean in a more general (non-yeast) context?
