The rough ER is the portion of the ER that A) lacks ribosomes. B) is the oldest
ID: 88804 • Letter: T
Question
The rough ER is the portion of the ER that A) lacks ribosomes. B) is the oldest and was once the smooth ER. C) has ribosomes attached to it. D) is connected to the Golgi apparatus. E) is the site of steroid synthesis. If the organelles of an animal cell were separated by centrifugation, which organ would require the least amount of centrifugal force to sediment at the bottom of centrifuge tube? A) Mitochondria B) Nuclei C) Golgi apparatus D) Lysosome E) Chloroplasts The surface area-to-volume ratio of a cell A) increases with increasing volume of the cell. B) decreases with decreasing surface area of the cell. C) accounts for the size limit of cells. D) is of little significance in maintaining cell homeostasis. E) affects how molecules are distributed across the cell.Explanation / Answer
68) Microtubules and Microfilaments together constitute the cytoskeleton seen in the cytoplasm. Cytoskeleton helps in maintaining the internal organization and structure of the cells acting as a backbone to the cell.
Both the microtubules and the microfilaments are responsible for the several cellular processes like intracellular trnsport, movement of secretory vesicles etc.
Both the microtubules and the microfilaments are polarized with plus and minus ends.
Microtubules are involved in cell migration during cell division and microfilaments are involved in the movement of cells during processes like endocytosis , exocytosis etc.
Hence the options B, C, D and E are true.
Microfilaments are made up of proteins predominantly with Actin and the microtubules are made Predominantly with protein called Tubulin.
Hence the option A is false.
69) Endoplasmic reticulum is the network like structure which is helpful in the transport of proteins, synthesis of Lipids and their metabolism etc.
Endoplasmic reticulum is divided in to two types namely rough Endoplasmic reticulum and Smooth Endoplasmic reticulum.
Rough Endoplasmic Reticulum(ER) is so called due to the presence of ribosomes on its surface. The transport of Proteins take place through this rough ER.
Smooth Endoplasmic reticulum is so called because it lacks ribosomes. Smooth ER is useful for the synthesis of lipids and metabolism.
so the options A, B, D and E are incorrect. Option C is the correct one.
70) Centrifugation is the process of separating the mixture of compounds with different molecular sizes and densities.
The more denser the particle, the more quicker it gets separated from the mixture of compounds and gets sedimented fastly and those compounds with less weight are sedimented slowly.
More centrifugal force required to sediment the less dense particles.
So under centrifugation , with least centrifugal force, denser organelle will be sedimenting at a faster pace. Among the different organelles of the cell like nucleus, mitochondria, lysosomes, chloroplast, golgi apparatus, the most denser organelle is nucleus( constitutes nucleic acids Like DNA with heavy molecular weight). Remaining organelles are less denser than nucleus.
Hence the most Denser Nucleus will be sendimenting faster with least centrifugal force. So the correct option is B.
Remaining options A, C, D and E are incorrect because all these organelles are less denser than nucleus and they require more centrifugal force for sedimenting them at the bottom of the centrifugal tube.
71) The surface area to volume ratio is important in the maintenance of the cell functions and also Homeostasis.
The surface area to volume ratio is responsible for the differences seen in the animals living in the colder climates and those living in the warmer climates. This ratio of surface area and volume can best be explained by Bergmanns Rule.According to him large sized animals are found in colder climates and smaller ones in the hot climates.
The ratio of surface area to volume accounts for the size of the cell.hence the option C is correct.
Cell with Larger volume shows decreased ratio of surface area to volume.
cells with larger surface area shows increased surface area to volume ratio.
Hence the options A, B , D and E are incorrect.
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