Ion channels that permit ions to pass between the interior of the cell and the extra-cellular medium are an important part of a living cell. There are multiple mechanisms that happen in an ion channel, but the simplest is that ions flow through the cell preferentially in one direction as a result of diffusion arising from a difference of ion concentrations on the inside and outside of the cell.
As a first model of an ion channel, let's see how it would behave if the flux through the open channel were simply due to diffusion arising from a concentration difference. We'll model the open channel as a cylinder.
Part (a) A typical ion channel radius is about 1 nm (nanometer), and the thickness of the cell membrane is about 7 nm. The concentration of Na+ ions inside a mammalian heart cell is about 0.6 ions/nm3, and in the fluid surrounding the cell is about 6.0 ions/nm3. The diffusion constant for ions is about 109 nm2/s (nanometers2/second). If the channel were just an open cylinder, how many ions per second would flow through the channel?
Part (b) Is the flow from the inside to the outside or from the outside to the inside?
Part (c) What is responsible for the flow of the ions through the channel in this model?
Part (d) Can this "diffusion constant, D " be the same constant as in the other Fick's law equation?

the correct answer is: d. the saltine and pretzel are made of flour, yeast, and baking soda, and salt. the pecan contains no flour but it does contain fats. the pecan is a nut that can be consumed as a healthy snack. first of all, pecans are a source of fat (monounsaturated fat), but they provide less fat than some other nuts. pecans are a rich source of dietary fiber, manganese magnesium, phosphorus, thiamin, vitamin e…

transcription is a process in which information is rewritten. it is something our cells must do, in a more specialized and narrowly defined way. in biology, transcription is the process of copying out the dna sequence of a gene in the similar alphabet of rna. it needs to happen in the nucleus because that's where the dna is. dna is always inside the nucleus unless the cell is dividing.

transcription is the first step in gene expression, which involves copying a gene's dna sequence to make an rna molecule. transcription is performed by rna polymerases. it has three stages: initiation, elongation, and termination. rna molecules must be processed after transcription in eukaryotes.

explanation:

long version:

the protein synthesis consists two processes which are, transcription and translation. transcription takes place in the nucleus. it uses dna as a template to make an rna molecule. rna then leaves the nucleus and goes to a ribosome in the cytoplasm, where translation occurs. transcription is the first part of the central dogma of molecular biology: dna → rna. it is the transfer of genetic instructions in dna to messenger rna (mrna). during transcription, a strand of mrna is made that is complementary to a strand of dna.  

these three stages are:

  initiation: in which   is the beginning of transcription.occuring when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

    elongation: in which is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

    termination: in which is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

answer///multiple alleles;