The study of cells: their physiological properties, structure, environmental interaction, division, life cycle, and death, as well as the organelles they contain. Also known as cytology.

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Which of the cell types commonly found in mammals has the greatest number of mitochondria?

This is basically a fun question, inspired by this answer on scifi.se. So, which cell type will have the greatest number of mitochondria? Obviously, I am talking about wild type, healthy individuals ...
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197 views

Number of spindle fibres during Metaphase?

During metaphase, the chromosomes are arranged on the equatorial plate and are attached to spindle fibres. After S phase, can the cell be said to attain the configuration of 4n? Also, during ...
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119 views

Macromolecule levels in daughter cells after fission

When a prokaryote undergoes binary fission, how are the non-DNA macromolecules distributed between the two daughter cells? This is motivated by comments on a previous question and a G+ discussion. I ...
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390 views

Intrinsic apoptosis in erythrocytes

With a lack of mitochondria, can red blood cells perform intrinsic apoptosis and do they have another way of generating cytochrome c to attach to a CARD domain and assemble the apoptosome? Or are ...
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72 views

How are chromatids correctly segregated during mitosis?

In my book this is described as happening by kinetochores depolymerising from their attached microtubule spindle, then being dragged towards the spindle's centrosome by a dynein protein. I can ...
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288 views

Primary cilia: what cell types have non-motile cilia that migrate?

My understanding is that there are two broad categories of cilia: motile and non-motile (also called primary. Examples of the former include sperm flagella and the cilia of epithelial cells that ...
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89 views

Can NSAIDs impact negatively the healing of tendons?

There are a number of articles regarding NSAIDs having a negative effect on healing conditions like tendonosis and tendinitis. From what I understand the channel through which they reduce inflammation ...
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86 views

number of RNA pol II molecules in a given human nucleus?

Does anybody have any estimate on the number of RNA pol II molecules in the nucleus of a given human cell? For example, how many RNA polymerase type II protein complexes would there be on average at a ...
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41 views

What is the fate of micronucleus DNA?

Micronuclei are cellular structures that are formed as a by-product of, usually, defective mitosis. The piece of chromosome in a micronucleus may, or may not contain a centromere and the DNA is ...
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RNA or ribosome, which one moves during translation?

During translation ribosomes decode the genetic information present in the mRNA and protein synthesis takes place. During this process which of those two does move, the ribosome or the mRNA?
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160 views

Problems understanding membrane potential

I understand that membrane potential is the difference of the extracellular and intracellular ionic charges, due to their concentrations. We say that the extracellular space has a charge of 0 and then ...
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156 views

Can botulinum toxin be grown or kept from denaturing in an UNWRAPPED 50 pound hay bale?

Botulinum toxin is the neurotoxin protein created when botulism spores grow. The requirements for growth and/or for keeping the toxin from denaturing would seem to be very difficult to create in bale ...
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151 views

How can a ligand be an integral membrane protein?

My background is in mathematics, and not biology, so please bear with me. I am currently working on a project involving the effects of Epidermal growth factor treatment (EGF) on cell migration. I am ...
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162 views

Studying effects of alcohol on cells

I am wondering about the logistics of a simple experiment with say 3 types of alcohols, and various concentrations of each, with a control(s) I would like to research the effects of alcohol on ...
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2answers
805 views

Can proteins move outside cells?

I am trying to learn about basic cell biology, and have what is probably an extremely simple question. So this is how I understand it so far: Proteins are made from amino acids. This process is ...
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3answers
97 views

What advantage does an enzyme serve over catalysis by the addition of heat energy?

I understand that an enzyme lowers the activation energy, allowing the reaction to run faster, however I am not sure, how it may be favorable during the addition of heat energy. Wouldn't that lower ...
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1answer
298 views

Why are certain aneuploidies more common?

Certain aneuploidies such as trisomy-21 (Downs syndrome), trisomy-18 (Edward syndrome), Turner syndrome (XO) etc are more common than others. I had a vague thought that it is related to chromosome ...
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2answers
130 views

Do changes in an organism's cell modify the genetic information it uses for reproduction?

What I'm actually interested about is whether a modification in one cell during the life of an asexually reproducing organism affects its genetic information? Which cell's genetic information is used ...
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235 views

Is this a grass cell?

I found this picture online claiming it was a grass cell. Clearly it is a cross section image but I was hoping you could tell me if this is actually grass, or something else if anything. Thanks!
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99 views

What is an operon?

What is an operon in a eukaryotic cell, and how does it regulate the expression of genes? I've already read Wikipedia, but it is not enough clear to me. Unfortunately my knowledge in genetics are very ...
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156 views

Free-flowing cells and those that are stuck together?

I've been thinking about the development of an embryo from the zygote stage. How is it that when cytokinesis takes place at that stage, the cells all stick together in a little ball, but later in ...
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109 views

During the process of correcting mutations via gene therapy, is the defective gene removed?

Just recently started learning about gene therapy, many websites explain that the corrected DNA can be added to the genome using a vector and all that. I just don't understand what happens to the ...
5
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1answer
758 views

What is the H+ gradient in mitochondria?

I would like to understand what the term H+ Gradient means. I googled this question and found terms such as chemiosmosis and ion gradient being tossed around. I am very new to biology and I do not ...
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2answers
4k views

Why was the Davson-Danielli model rejected?

According to my textbook, Davson-Danielli's model of a phospholipid bilayer sandwiched between two layers of globular protein was incorrect. The nonpolar protein portions would separate the polar ...
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2answers
97 views

Synthetic biology using existing cells

I was watching the video at this link: http://www.bbc.co.uk/news/science-environment-17436365 The speaker says that a cell is taken and its original DNA content is stripped out and replaced with ...
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118 views

Why does a “cascade” of events happen during signal transduction?

I've been watching some videos on signal transduction and it says that because there are enzymes being activated by the signal, then there is a "cascade" which happens afterwards...I don't understand ...
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34 views

How are the physiological properties of mitochondria measured?

this is my first question on BiologySE. I am a Physics and Mathematics student currently doing a project on cell growth simulation. I am doing literature survey and I have a question about cellular ...
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43 views

Why do epithelial cells arrest in response to serum?

Primary epithelial cells, for example human mammary epithelium, fail to proliferate (arrest) in serum-containing medium. Therefore, a common growth medium for epithelium contains pituitary extract ...
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104 views

Are There Exceptions to Animal Cells not Having Cell Walls?

In the January Issue of SciAm (discussing Haemophilia): When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the ...
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1answer
64 views

MHC restricted peptide

What is an MHC restricted peptide? I got this definition from wikipaedia, but cannot exactly extract what the phrase MHC restricted peptide means. MHC-restricted antigen recognition, or MHC ...
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872 views

How are lysosome membranes protected from the attack of hydrolases?

Lysosomes are a bit like the suicidal bags of cells. They help to clean cells, have an acidic pH and contain a large number of hydrolyzing enzymes. But why don't these hydrolyzing enzymes attack ...
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242 views

Significance of basal lamina for outer layers of epithelium

In stratified (not pseudostratified) epithelia such as the epidermis, what purpose does the basal lamina serve for the outer layer cells which do not even stand in contact with it? Also, how do these ...
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1k views

How does the Golgi Apparatus perform its function?

The Golgi Apparatus is an organelle with a great number of functions, I am particularly intrigued in the role it plays in packaging macromolecules and sending them to their target organelle or to ...
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1answer
55 views

Can methylation of a promoter induce gene expression in some rare cases?

Can methylation of a promoter induce gene expression in some rare cases? I've read somewhere that methylation of an intron can induce gene expression (eg. Igf2). How is that even possible? Thank ...
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41 views

Regarding cellular self-destruction

I heard and read telomere 'health' or 'length' ( if that's right ) has alot to do with cell 'health'. If telomere 'abilities' are 'restored' to a 'healthier' status then the cell it is in functions as ...
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280 views

Time spent in phases of cell cycle

I am looking for references to papers containing the time intervals spent in different phases of the cell cycle (ej., G0, G1, S, G2, M for eukaryotes) for different cells. In particular, I am ...
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2answers
102 views

Are fish roe unicellular?

Are roe (fish eggs, caviar, etc.) single cells? I have tried looking this up on google (sadly, to no avail), and I am guessing they might be multicellular (like bird eggs) or consist of one cell plus ...
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2answers
119 views

What percentage of a cell's volume is occupied by protein?

I was looking at one of David Goodsell's illustrations of a cell: And it seems to suggest a very crowded picture of the intracellular environment. Just how crowded are cytoplasms? What percentage ...
5
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1answer
839 views

Chromosome and chromatid numbers during cell cycle phases

A diploid cell in G1 has 6 chromosomes. How many chromosomes and how many chromatids are present in each of the following stages? Here is what I am guessing G1: 6 chromosomes ; 6 chromatids G2: 6 ...
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1answer
253 views

Cell proliferation limit and senescence of embryonic stem cells and fibroblasts

I am trying to understand the importance of proliferation limits and cell senescence. In particular, I would like to compare the proliferation limit of Embryonic Stem cells (ES) and fibroblasts (which ...
5
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1answer
166 views

Which cells are responsible for the extracellular matrix remodeling?

I am studying a case of tendinopathies induced by an alteration of how the extracellular matrix is being remodeled. From my understanding there has to be a careful balance of MMP (metallproteinases) ...
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2answers
95 views

How extensive is CD47?

CD47 aka the "don't eat me" signal has recently been claimed to be expressed on all tumor cells. This doesn't seem to corroborate with other cell-biology experiments. On what other cells is CD47 ...
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2answers
104 views

Does polyploidy always isolate the polyploids from the diploid source population?

I am receiving conflicting information while researching polyploid speciation. On the one hand, some sources state that a polyploid can only reproduce sexually with polyploids having the same number ...
5
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1answer
42 views

Spatial learning in microorganisms

Has there ever been an experiment performed that demonstrated a form of 'spatial memory' in a unicellular organism? I'm imagining something analogous to the classic 'rat in maze' experiments, but ...
5
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1answer
52 views

Do non-enzyme catalysed reaction pathways exist?

Can their be a kind of chemical reaction pathway in a cell, that is catalyzed or regulated but NOT necessarily by enzymes? I could not find anything on Google. I have almost no background in biology, ...
5
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1answer
145 views

Mechanism of Muscle Growth

According to this video (sorry for the poor reference but it represents my level of understanding in physiology), muscle grow as a consequence of repairing micro-lesions. How are these micro-lesions ...
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1answer
98 views

How does a Na+/H+ antiporter drive osmosis in this “osmotic motor”?

This recent paper in Cell describes a cancer cell using osmotic pressure to move in confined spaces. The cell preferentially inserts Na+/H+ antiporters in the leading membrane. I want someone to ...
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3answers
404 views

Aerobic vs anaerobic respiration comparison

The following graphs compare glucose decomposition in yeasts (in anaerobic vs aerobic conditions respectively) My question is, why doesn't the first one look like a straight line as the second one ...
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1answer
149 views

Can in the case of multiple sclerosis (MS), a too high osmotic pressure in the nerve, lead to a high intracellular concentration of potassium?

Can in the case of multiple sclerosis (MS), a too high osmotic pressure in the nerve, lead to a high intracellular concentration of potassium, and also lead to 'pumping up' of nerve cells, which then ...
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114 views

Creating a cell, not from another cell. Will it be possible?

If some time in the future, we can know exactly what a cell (for example simple prokaryote bacteria) contains, (I mean, exactly which molecules, the shape of them, the density of each, everything), ...