New answers tagged

1

If you are looking for a hard and fast answer, there is none. Life does not have a hard and fast definition, so it is impossible to identify something that everyone will recognize as both living and non-cellular. However, your question is answerable if you are interested in a summary of the state of the debate. All living organisms are made up of one ...


1

I know of an example in development biology. Here is an example where noise in retinoic acid gradients is required for the boundaries in the developing hindbrain to sharpen. A related result is that the zebrafish hindbrain has a protein to modulate noise, but does not reduce the noise to zero. Together these results show that noise in the retinoic acid ...


0

BOOKS If you want to learn about cells in detail from scratch to advanced level I recommend you two books: Molecular Biology of the Cell, 6th Edition. 2014. Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter http://www.garlandscience.com/product/isbn/9780815344322 Essential Cell Biology, 4th Edition. ...


2

The good ol'electron transport chain (ETC). Before beginning let us begin by looking at the structure of a mitochondrion and the purpose of the ETC. Take of note four things: The intermembrane space The matrix The electron transport chain proteins and ATP Synthase Now lets talk about the purpose of the ETC, essentially its job is to create a H+ ...


3

Yes. The structure of a cell is highly related to its function. For example, a plasma B cell (a type of immune cell) contains lots of ER and Golgi because its job is to secrete antibodies, which are proteins, in your body. It has to create a lot of proteins, so a plasma B cell has a lot of organelles that help create, assemble and secrete proteins. There ...


1

See this paragraph and image from The Cell: A Molecular Approach. 2nd edition.: During passive diffusion, a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane...Passive diffusion is thus a nonselective process by which any molecule able to dissolve in the ...


0

Density of a variety of cell types is rather well known. It can been measured directly by examining buoyancy (tendency to float) in liquids of known density, and also by microfluidic methods. But the results depend on the osmolality of the solution in which the cells are kept, since cells tend to "swell" (take up water) in low osmolality (hypotonic) medium. ...


1

The most common method of measuring glucose concentrations (in pretty much any sample) is an enzymatic assay based on the glucose oxidase enzyme. This method is reliable because the enzyme is known to be quite specific for glucose; it does not oxidize fructose, galactose, or any of the other common hexose sugars which can contaminate many other measurement ...


1

One more point to make that wasn't covered in the other answers - in some cases, free diffusion of reactants is desired in order to regulate cellular processes. For example, take amino acid synthesis. At least one of the enzymes in the synthesis pathways of the various amino acids is reversibly inhibited by the presence of the AA itself. Therefore, if AA ...


2

What are golgi? Stacked array in the cisternae which are ought to connect vesicles and tubules Made of >1000 different proteins Has the ability to transform/alter in response to a cellular stimulation such as mitosis Fragmentation of golgi during mitosis During interphase, the Golgi receives secretory cargo from the ER via the COP II vesicle ...


2

So, what is causing the higher degradation than usual? Is it the lack of the materials required to produce the receptor? Lack of materials is almost never the reason. Receptor turnover is actively controlled by different mechanisms. Ubiquitylation is one of the common mechanisms. Ubiquitylated receptors are internalized; these internalized receptors can ...


1

Organization of reactions occurs in both prokaryotic and eukaryotic cells. A very basic example of this would be that of multiprotein complexes such as fatty acid synthases and polyketide synthases. Organization of such complexes allows the substrate to be passed from one module to the other; in other words free diffusion of substrate is prevented. This kind ...


2

Okay, this is my first post on this site so please bear with me when it comes to the format of my response! To begin with I'm going to try and answer your question by clarifying some things. In prokaryotic cells I thought there were no organelles so does that mean that every reaction depends on the diffusion of the reactants throughout the cell and ...


4

You talk about memory loss. The hippocampus is involved in the formation and storage of memories and indeed one of the few places in the brain where new neurons are formed. The formation of new neurons here is indeed linked to the formation of memories (Coras et al., 2010). Hippocampal neurons do not lack centrioles (Dotti & Banker, 1991; Poppov & ...


1

What's interesting with this one is we don't really know very well the mechanism behind what's called chilling injury. It happens to a range of fruits, like bananas, peaches, avocado, or apples. The belief is that the chilling alters membrane permeability to storage vacuoles inside the plant cells. Try On Food and Cooking, pp.269, and Puig et al. (2015) for ...


2

BioNumbers is a good database for different values (numbers) in biological systems. From BioNumbers*: Volume of an alveolar macrophage ( Homo sapiens ) = 4990 (±174) µm3 Diameter of an alveolar macrophage ( Homo sapiens ) = 21.2 (±0.3) µm So, your thickness should be (assuming a circular shape of the cell): Volume/(pi×(0.5×diameter)2) = 14.15 (±1.52) µm ...


0

A promoter, in this context of biological regulation of gene expression, is not only a binding site for the RNA polymerase enzyme, but also the site where that enzyme initiates transcription of the RNA transcript of the adjacent gene (or operon). Typically, DNA sequences upstream (in the 5'-direction) are not transcribed, while the sequences downstream (in ...


2

Short answer: yes. It also includes unspecific leakage without the aid of uncoupling proteins, since the mitochondrial inner membrane is not entirely impermeable to protons. For example, protons might fall backward through the proton-pumping complexes, through other solute carriers, or through other openings or irregularities in the membrane.


1

Animal cells Generally all (animal) cells have different shapes because they do different things. Each cell type has a specific role which it has to play in order to assist the body in working efficiently and functionally. Thus their shape supports them to carry out these roles effectively. Look at (animal cells): Neurones Photoreceptors Immune Cells ...


2

What the article is saying, is that there are several respirasomes, each of which consists of multiple other mitochondrial complexes or cytochromes. The article makes an example of three commonly observed respirasomes when it says: The most common supercomplexes observed are Complex I/III, Complex I/III/IV, and Complex III/IV. So, the short answer to ...



Top 50 recent answers are included