There are 5 questions please answer all. A researcher growing cells in culture o
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Question
There are 5 questions please answer all.
A researcher growing cells in culture observed that the cells always divided once they reached a certain size. When she added more nutrients to the culture medium or adjusted the temperature of the growing chamber, the cells grew at different rates but always divided once they reached that certain size. Which statement explains these observations?
As they grow, cells require greater and greater quantities of nutrients from the environment, and they must reduce this requirement by dividing.
The increasing surface area of a cell as it grows larger increases the risk that small molecules that can harm the cell will pass from the environment into the cell interior.
The cell’s surface area increases faster than its internal volume as it increases in size, and this leads to an inability of the cell to feed itself.
Increasing cell size is accompanied by increasing cellular reactions, which produce more heat that threatens cell survival.
The figure below shows the procedure (A) and results (B) of an investigation using a technique called Fluorescence Recovery After Photobleaching (FRAP). The phospholipids of the cell membrane of a single cell were fluorescently tagged, resulting in uniform labeling of the fluorescent molecule across the membrane. The labeled cell was placed under a fluorescent microscope and observed as light from a laser was directed at a small region of the cell for a microsecond. The light bleached (i.e., damaged) the fluorescent molecules in that region so that the molecules were no longer able to fluoresce. In the time period following the bleaching event, recovery of fluorescence in the bleached region was observed and graphed. Which statement about cell membranes does these data support?
The data in the table below were collected during an analysis of neuronal cell membranes from fish of a single species transferred from a cold environment to a warm one. Which statement is consistent with these data and with what you know about membrane fluidity?
Membranes are more fluid at higher than at lower temperatures, so to maintain a constant fluidity, fish undergo a shift toward increased saturated fatty acid compositions with increasing temperature.
Fish adjust the fluidity of their cell membranes at high temperatures by increasing the number of double bonds in the fatty acid chains that make up their membrane phospholipid molecules.
More fluid membranes are formed at lower temperatures than at higher temperatures because of an increase in the ratio of saturated to unsaturated fatty acid chains in membrane phospholipids.
Exposure to higher temperatures results in a shift toward more unsaturated fatty acids in fish membrane phospholipids, which increases the membrane’s fluidity.
Addition of double bonds to fatty acid tails making up membrane phospholipids causes the membrane to become less fluid, so the ratio of saturated to unsaturated fatty acids increases in fish cell membranes as temperature increases.
You are characterizing the protein Par1, which is suspected to be involved in the embryonic development of the mouse. To study this protein, you isolate total protein samples from mice at the following four developmental stages: early embryos (EE), late embryos (LE), newborn pups (NB), and 3-month old adults (A).
You perform a Western blot, and probe the membrane for Par1 and a second protein, tubulin. Tubulin is a cytoskeletal protein expressed at constant levels throughout development and in the fully developed mouse. In this experiment, tubulin is being used as a loading control. Proteins used as loading controls typically have high and ubiquitous expression. Importantly, the expression level of the loading control should be consistent regardless of tissue or cell type or experimental conditions. Probing a western blot with an antibody against a loading control is an important control because it is used to indicate the equal loading of samples across all wells.
You observe the following on your blots:
Based on these results, which of the following statements is true?
There are 5 questions please answer all.
A researcher growing cells in culture observed that the cells always divided once they reached a certain size. When she added more nutrients to the culture medium or adjusted the temperature of the growing chamber, the cells grew at different rates but always divided once they reached that certain size. Which statement explains these observations?
As they grow, cells require greater and greater quantities of nutrients from the environment, and they must reduce this requirement by dividing.
The increasing surface area of a cell as it grows larger increases the risk that small molecules that can harm the cell will pass from the environment into the cell interior.
Efficiency of transport of materials within a cell decreases with size, thus limiting the maximum cell size.The cell’s surface area increases faster than its internal volume as it increases in size, and this leads to an inability of the cell to feed itself.
Increasing cell size is accompanied by increasing cellular reactions, which produce more heat that threatens cell survival.
The figure below shows the procedure (A) and results (B) of an investigation using a technique called Fluorescence Recovery After Photobleaching (FRAP). The phospholipids of the cell membrane of a single cell were fluorescently tagged, resulting in uniform labeling of the fluorescent molecule across the membrane. The labeled cell was placed under a fluorescent microscope and observed as light from a laser was directed at a small region of the cell for a microsecond. The light bleached (i.e., damaged) the fluorescent molecules in that region so that the molecules were no longer able to fluoresce. In the time period following the bleaching event, recovery of fluorescence in the bleached region was observed and graphed. Which statement about cell membranes does these data support?
Membrane phospholipids interact noncovalently and are in constant flux. Some molecules are transported via simple diffusion through the phospholipid bilayer. Phospholipids are oriented in membranes with hydrophobic tails in and hydrophilic heads out. The cell membrane is composed of a lipid bilayer embedded with proteins. Some membranes have more proteins, where others are lipid-rich. 3.The data in the table below were collected during an analysis of neuronal cell membranes from fish of a single species transferred from a cold environment to a warm one. Which statement is consistent with these data and with what you know about membrane fluidity?
Membranes are more fluid at higher than at lower temperatures, so to maintain a constant fluidity, fish undergo a shift toward increased saturated fatty acid compositions with increasing temperature.
Fish adjust the fluidity of their cell membranes at high temperatures by increasing the number of double bonds in the fatty acid chains that make up their membrane phospholipid molecules.
More fluid membranes are formed at lower temperatures than at higher temperatures because of an increase in the ratio of saturated to unsaturated fatty acid chains in membrane phospholipids.
Exposure to higher temperatures results in a shift toward more unsaturated fatty acids in fish membrane phospholipids, which increases the membrane’s fluidity.
Addition of double bonds to fatty acid tails making up membrane phospholipids causes the membrane to become less fluid, so the ratio of saturated to unsaturated fatty acids increases in fish cell membranes as temperature increases.
You are characterizing the protein Par1, which is suspected to be involved in the embryonic development of the mouse. To study this protein, you isolate total protein samples from mice at the following four developmental stages: early embryos (EE), late embryos (LE), newborn pups (NB), and 3-month old adults (A).
You perform a Western blot, and probe the membrane for Par1 and a second protein, tubulin. Tubulin is a cytoskeletal protein expressed at constant levels throughout development and in the fully developed mouse. In this experiment, tubulin is being used as a loading control. Proteins used as loading controls typically have high and ubiquitous expression. Importantly, the expression level of the loading control should be consistent regardless of tissue or cell type or experimental conditions. Probing a western blot with an antibody against a loading control is an important control because it is used to indicate the equal loading of samples across all wells.
You observe the following on your blots:
Based on these results, which of the following statements is true?
Early embryos show greater expression of Par1 than late embryos. Par1 protein is likely required in the adult mouse. No conclusions can be drawn from these data because the loading control is not equally loaded. Par1 protein is expressed during embryonic development. Par1 protein expression is greater in newborn mice than embryonic mice.Explanation / Answer
The efficiency with which materials are transported within a cell decreases with size, thus limiting the cell size.
This is so because every cell in nature has a definite shape and size depending on the function it performs. This is fixed and the cell organelles and other intra cellular activities are dependent on this. So, no matter however favourable the external environment, cells will not grow larger than what is their fixed size.
2] Membrane phospholipids interact non-covalently and are in constant flux.
The cell membrane is highly elastic and selectively permeable i.e. it allows certain materials to enter and exit through it. It has protein molecules embedded in the lipid bilayer. So, all the other statements are true for plasma membrane in general. The phospholipid bilayer is held loosely with each other and is in constant flux.
3] Membranes are more fluid at a higher than at a lower temperature, so to adjust this fluidity , fish undergo a shift towards increased fatty acid compositions with an increase in temperature.
This helps the fish to adjust to the change in temperature and maintain the intra - cellular environment at the desired level.
4] Part one protein is expressed at the embryonic levels and to some extent in the new - born mouse but is not found in the adult.
This can be clearly infered from the results of the Western blot test. Tubulin is expressed at all stages.
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