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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Can you consider a human as alive, or is it the cells on the body that are alive?

Sorry if this question seems strange, but in the recent time I have been interested in the question of what life is and how you can define life. My question: How long can individual cells live on a ...
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509 views

Does DNA contain information beyond protein synthesis?

It's well known that genetic information is stored in DNA. As far as I know, DNA only has information at the protein level. What about higher levels, such as organelles, cells, tissue, organs? Is ...
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428 views

Single long axon vs serial neurons

Based on the comments in this post and also this chat. For discussions and speculations please comment in the chat. The basic question is what is the advantage of having a single long axon such as ...
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697 views

What's the difference between growing cells in culture and cloning them?

The wikipedia page on Hela cells refers to George Gey being able "to isolate one specific cell, multiply it, and start a cell line." Later it says, "In 1955 HeLa cells were the first human cells ...
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why is AUG the initiation codon?

Is there any reason why AUG is the initiation codon ? Why is there a need for an initiation codon ? Can't translation start with different codons?
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144 views

What specific membrane adaptations do cells have for saline-rich environs?

Are the cells of marine animals and flora equipped with special ion exchange pumps to mitigate the effects of a saline-rich environment? Or have the cell's membranes adapted through structural ...
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222 views

Can a human cell live indefinetely in a controlled environment?

How long can a human cell live in a controlled environment, given all necessary nutrients, temperatures, mechanisms for waste removal, and other requirements are provided for? Put differently: Can a ...
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How fast do cancer cells divide, compared to normal cells?

This question suggests that we have, on average, 50-70 billion cell divisions per day. I just read that cancer cells divide more often and are therefore more prone to radiation. I am wondering, for ...
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755 views

Why aren't mitochondria and plastids considered symbiotes of eukaryotic cells?

Mitochondria and plastids have their own DNA, their own membranes, and their reproduction is not tied to the reproductive cycle of the host cell. However, they are considered to be organelles rather ...
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How can Valonia ventricosa cells get so big?

Valonia ventricosa are single celled algae that range between one and few centimeters. In rare cases they can reach sizes exceeding 5cm. They range from grass green, to dark green, and some are even a ...
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514 views

What is the difference between organelle membranes?

Cells and organelles are contained in lipid bilayers. I'm particularly interested in eukaryotic organelle bilayers and the biophysicochemical differences between them. Many papers assume a ...
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110 views

Pancretic Acinar Cell - ATP, calcium concentration data

I need to find a decent source of data for concentration of ATP and calcium in the pancreatic acinar cell. So far all I can find is ATP or calcium 'levels' based on fluorescence , which are not ...
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293 views

Contact Inhibition of Cell Division: Signaling Pathway

The following article refers to contact inhibition of cell division in epithelial cells, specifically MDCK cells: Collective and single cell behavior in epithelial contact inhibition. In their review ...
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947 views

X chromosome “weight”?

According to Wikipedia, the X chromosome has approximately 153 million base pairs, while the Y chromosome has only 60 million base pairs. Thus, the difference is roughly 93 million base pairs. My ...
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Are pulp cells (in oranges) normal plant cells?

Does a pulp cell contain all the elements that a 'normal' plant cell contains? I've searched for an hour to find more information about this but couldn't find anything useful. Is the pulp cell the ...
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375 views

Why should phospholipid non-polar tails be “protected” in the membrane bilayer?

lipids are arranged within the membrane with polar head towards the outer side and non polar tails towards inner side, this ensures that the non polar tail is protected from aqueous environment. My ...
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371 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.
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838 views

What determines the fate of a cell with respect to differentiation?

I have been reading about Townes and Holtfreter's work in 1955, in which cells are dissociated from a blastocyst in an alkaline solution then mixed together and spontaneously reaggregates based on ...
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Why aren't organelles considered alive?

I'm taking a 3-week Bio I summer course, and my textbook says the cell is the smallest/basic unit of life. I asked my professor why organelles aren't a living unit, and her reply was that they aren't ...
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Is “exhaustion” of the Hodgkin-Huxley membrane at constant stimulation a real phenomenon?

I was playing around with a simulation of the Hodgkin-Huxley model using their original parameters for the squid giant axon. By applying a constant stimulation current to the model in resting state, ...
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How do archaea relate to eukaryotes and bacteria?

I've read that they all share some genes, internal structure, and behaviour with each other, but with different degrees of overlap depending of what the function is. E.g., archaea have some eukaryotic ...
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190 views

How Do Large Ocean Viruses Form Their Own Organelles?

Several large viruses (Arslan 2011) form their own organelles within the amoebae they invade. How do these organelles form? Reference: Arslan, D., Legendre, M., Seltzer, V., Abergel, C., Claverie, ...
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539 views

To understand why satellite cells are genetically inactive in Barr body

DAPI is used as a stain for DNA heterochromatic and euchromatic regions. The Barr body is heterochromatic. In the slide of a normal human female cheek's somatic cells, there is apparently no other ...
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54 views

What is a positive epitope fragment

What is a positive epitope fragment? I found one paper on the subject: COBEpro: a novel system for predicting continuous B-cell epitopes by Michael J. Sweredoski and Pierre Baldi
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Where do lost membrane proteins go after exocytosis?

Exocytotic vesicles take away membrane proteins and glycocalyx on the cell's plasma membrane surface. When those vesicles are released into the interstitial fluid and wherever else, where do they go? ...
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Intracellular lipid transport

I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved. Lipids can't always be integrated in a membrane though, the ...
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115 views

Cell Respiration and Oxidative Phosphorylation

Why and how does the proton travelling through the stalked particle in the inner mitochondrial membrane, cause a conformational change in the ATPase?
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645 views

How fast do different organs turn over cells?

It is said that the human body turns over all cells or molecules in 7 year cycles. This is not quite correct, because there are different organs changing at different speeds. My interest is what is ...
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Permeability of Plasma Membrane

I’m having trouble grasping why small polar molecules can cross the hydrophobic region of the membrane and not ions. Won’t the polar molecules be attracted to the watery extracellular medium and not ...
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410 views

How does skin healing work?

I stacked my bike and split my head right open. About three weeks later the scab falls off and the skin is sealed over, like magic! How does it all work? How does the brain know that part of the ...
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Multi-nucleated cells: advantages and examples?

This question arises because I saw that monocytes and leukocytes are commonly called 'mononuclear cells' in the scientific literature. The implication of course being that other immune sub-types are ...
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Is there a relationship between efficiency of cellular metabolism and warm-blooded-ness?

My BIO 101 book states that when human cells convert glucose to ATP, the process is only approx 35% efficient, and much of the potential energy is lost as heat. However, that heat is useful to us in ...
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232 views

When collecting cell lysates for a Western blot, how do I induce di-sulfide bonds?

I would like to conduct a simple dimerization experiment for some protein I'm collecting from a cultured cells. My thought is, that if I'm running a non-reducing, denaturing PAGE gel, then removing ...
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What is the difference between “dikaryotic” and “heterokaryotic” states in the sexual lifecyles of fungi?

Many fungi undergo a reproductive phase in which more than one genetically distinct nuclei (from 2 separate mating types) is present within the same cytoplasm. In the Ascomycota and Basidiomycota, ...
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115 views

What were the first neural systems like?

I'm curious about the origin of the neural network. I'm thinking perhaps once life evolved beyond the single cell organism, it needed a simple neural network to coordinate those cells, and cell ...
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494 views

What causes Paresthesia (Pins and Needles) at a cellular level?

I've looked it up in plenty of places like the Wikipedia page and such, and it is clear that the most common cause of Paresthesia is either a fair amount of pressure on a specific patch of skin ...
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208 views

What are the lifetimes of cellular components on organelle or molecular level?

I was thinking that even though I know how generally the cell works, I don't really have a feeling of how volatile it is. I want to know what is the lifetime/turnover rate of different constituents of ...
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647 views

How to Design an siRNA Experiment?

I'm going to undertake an siRNA experiment soon, but I have only read about them. I want to address the role an enzyme plays in processing a protein. From what I understand, I will need to pick two ...
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97 views

How do nuclear receptors locate each other to form a DNA loop?

Nuclear receptors can influence transcription far up- or downstream from their own binding sites by looping DNA (Rubina et al.; J Mol Bio 2004). I am not sure how exactly the receptors first attach ...
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133 views

If so many different hormones/molecules work by activating adenylyl cyclase, how do they have different effects?

It seems that many hormones and molecules work by activating adenylyl cyclase to convert $\text{ATP}$ to $\text{cAMP}$, such as adrenaline and glucagon. Both of these seem to bind to $\text G$ protein ...
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89 views

Gap junction turnover

Gap junction proteins, connexins, are known to form intercellular hemichannels, between two adjacent cells. These junctions are maintained cell adhesion proteins (cadherins), yet the turnover of ...
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160 views

What is the mechanism by which lamins regulate gene expression?

The heterochromatin is generally localized at the nuclear periphery (also near nuclear lamina), whereas active genes are preferentially found in the nuclear interior. Children with Hutchinson-...
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563 views

Are there any multicellular forms of life which exist without consuming other forms of life in some manner?

The title is the question. If additional specificity is needed I will add clarification here. Are there any multicellular forms of life which exist without requiring the consumption (destruction) of ...
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449 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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259 views

Does soap kill human cells?

I see many products, particularly hand soap and cleaning products, that claim to kill 99.9% or more of bacteria. This makes me wonder, if the chemicals are potent enough to break down bacterial cell ...
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19k views

Which human cells have the longest and shortest lifespan?

Which cells in a human have the longest lifespan? Which cell has the shortest lifespan?
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929 views

What is the main general difference between Mitosis and Meiosis?

I found such a clause: The general principle is that mitosis creates somatic cells and meiosis creates germ cells. However, I cannot agree. Each gametogonium needs to go through mitosis before ...
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226 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 ...
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Alternatives to trypsin for cell detachment?

I have ran out of trypsin and need to passage my cells (immortalized chondrocytes, C28/I2) today or tomorrow. I have been out of town and forgot to order more trypsin. I was wondering if there are ...
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Rate of cell division in humans

On average, how many cells divide each day in a human being? How long does a cell wait before dividing itself ? I have tried to look on the internet but surprisingly the answer is difficult to find.....