234 Answered Questions for the topic Cell Biology

03/26/19

Why do ribosomes associate with rough endoplasmic reticulum but not other membranes?
As far as I am aware, all eukaryotic membranes consist of a lipid bilayer. Smooth endoplasmic reticulum (ER) and rough ER are distinguished by the presence of ribosome on the rough ER surface, but... more
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03/26/19

Amino acid profile of GPCRs?
> You are studying cellular signalling through a newly identified GPCR. Specifically you’re working on a pair of newly identified GPCRs, GPCR-A and GPCR-B. Each binds the same small ligand, but... more
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03/26/19

Photosynthesis: What Powers the Splitting of Water?
The splitting of water is an endergonic (non-spontaneous) reaction, and thus would require energy (chemical work to be done) in order to happen. In Photosystem II, an enzyme catalyzes this... more
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03/20/19

Blebbistatin effect on vesicles?
Blebbistatin is a drug that specifically inhibits the assembly of myosin in the cytoskeleton. What effect would you expect blebbistatin to have on intracellular vesicles?  The formation of vesicles... more
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03/19/19

True or False. A promoter is necessary for RNA polymerase binding, with the codon start and stop sites defining the transcriptional unit.
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03/19/19

What happens to the precursor protein's signal sequence after it is cleaved?
Where does this signal sequence "go" after it has been cleaved by signal peptidase and what is its next function?
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03/19/19

Why is contractile vacuole absent in parasitic protozoans but present in free living protozoans?
I know that contractile vacuole helps in osmoregulation of protozoans and some nitrogenous wastes are also excreted through it. Since contractile vacuole plays an important role in protozoans, why... more
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03/18/19

How does Cro protein expressed by lambda phage kill its host?
I read that the DNA segment of lambda phage integrated in host DNA could switch between lysogenic state where cI represses the expression of *Cro* and lytic state where *Cro* expression takes over... more
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03/18/19

How do single-celled predators chase other cells?
From my understanding, single celled organisms have been seen avoiding, and chasing, potential food or other organisms.How do they accomplish this? They do not have eyes or ears or a nervous... more
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03/18/19

What is the purpose of the outer mitochondrial membrane?
The purpose of mitochondria is to generate ATP, utilising a chemiosmotic gradient across the inner mitochondrial membrane. Protons are pumped out of the mitochondria into the intermembrane space,... more
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Cell Biology Biology

03/18/19

How does sugar enter neurons if they don't use insulin?
I heard somewhere that as opposed to other cells, neurons do not use insulin to get their sugar supply.Why is that? What is the alternative mechanism? I assume sugar can't just enter the cell... more
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03/18/19

How much of the jejunum is bypassed during gastric bypass?
There is both long and short limb gastric bypass surgeries (along with several other variations on intestinal bypass procedures). How much of the jejunum is bypassed with a long-limb and short-limb... more
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Cell Biology Botany Chloroplasts

03/18/19

Do all cells of a plant contain chloroplasts?
If the answer is no, then how do plant cells tell whether they need to keep chloroplasts or not? What kind of signals are used, and how are chloroplasts eliminated?
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Cell Biology Biology Metabolism Cancer

03/17/19

Energy metabolism in Cancer cells?
The TCA cycle intermediate Isocitrate dehydrogenase commonly undergoes point mutations in cancers. This allows IDH to reduce a-Ketogluterate to 2Hydoxygluterate, causing a reduction in pVHLs... more
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03/17/19

What is the purpose of requiring two separate binding systems for the antibody response?
I've read that in most cases, B-cell activation requires helper T-cells. This requires antigen binding by both antibodies and T-cell receptors, using two different antigen-binding proteins,... more
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Cell Biology Biology

03/16/19

Reason behind formation of different shapes of cell?
I have always wondered how cells are modified to give them a specific shape. On what specific part of a cell does gene regulation act for giving the shape ?
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Cell Biology Biology

03/16/19

Stardust or the elements in our bodies?
How do we know we are made of stardust? As our cells divide, are our atoms repurposed from existing materials or spontaneously generated? Do we consume materials after we are born that contain... more
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Cell Biology Biology Homework Osmosis

03/16/19

What happens to the red blood cell in CaCl₂ solution?
Here's the problem:One red blood cell is placed in a hypertonic solution of NaCl, another isplaced in a solution of CaCl2 equimolar with the NaCl solution. Whatwould you expect to happen and why?My... more
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Cell Biology Biology

03/16/19

Red blood cells?
How can we classify red blood cells while they lack nucleus? From my point of view i find it difficult to be classified as we have all cells with nucleus, even prokaryotic cells which have no... more
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03/16/19

Do mitochondria contain the genes to specify themselves?
My book says : "Mitochondria contain their own genetic material so when a cell divides, the mitochondria replicate themselves under the control of the nucleus."The book means that the mitochondria... more
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Cell Biology Biology Gene Expression

03/16/19

Name two reasons why it is impossible to determine a gene's nucleotide sequence from the amino acid sequence of the polypeptide?
I can only think of one reason, which is because different codons can specify the same amino acids. However I am having trouble thinking of another reason.
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03/15/19

Knockout and knockdown of gene?
Out of curiosity, I got this question whether knocking out (deletion) of a gene on one side and knocking down (RNAi) of the same gene on the other side will affect the cell in a similar manner or... more
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03/15/19

Are all functions of a human cell known?
Please bear with me as I'm intruding into your world from a computer science background. In programming, once you have created a program, you know all functions of that program. Thus, 100%... more
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Cell Biology Biology Botany

03/15/19

Why higher plants lack centrioles?
Why do plant cells not have centrioles?
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03/15/19

Enzyme Inhibition in relation to Aspirin?
I see that aspirin (in part) works by inhibiting cycloxygenase isoenzymes and that this inhibiting is irreversible. I've had a few classes mentioning this topic in passing, but never with depth.I... more
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