Cell size and scale
learn.genetics.utah.edu
learn.genetics.utah.edu
Speaking of the carbon atom, there is no way that what seems to be its nucleus is even remotely to scale.
Rough estimates for diameter are based on molecular mass and density; density being variable. I'm curious how they did their calculations.
Diameter is a funny concept for atoms and molecules because electrons orbit at different distances around the nucleus probabilistically. The depiction of this carbon atom I think represents this, with the lighter color areas denoting areas of lower probability.
However, drawing such a diagram for a molecule isn't very pretty, because the orbitals for each atom in the molecule overlap. They probably drew the water molecule using intermolecular distances, and then filled in the distances so that each atom was a sphere. In actuality the electrons are found with some probability outside this area.
Carbon has both S and P orbitals whereas water has hybridized orbitals. This would mean both their carbon and water are drawn incorrectly.
Clearly they aren't drawing the orbitals for water, which I already stated.
But you're right, carbon is probably too big. Wolfram alpha says the diameter of carbon is 134pm, and we all know WA is right about everything.
"Thanks for your response to our website.
Depicting the size of atoms definitely has its challenges. We've been getting a lot of comments and feedback about this.
The radius of a carbon atom is not a measure of the size of its electron cloud, but rather the distance between the nuclei of two adjacent atoms. See http://www.chemguide.co.uk/atoms/properties/atradius.html The size of the carbon atom in our activity is based on its van der Waals radius (170 pm), not the covalent or ionic radius (around 77 pm). See http://www.webelements.com/carbon/atom_sizes.html
The sizes of the atoms in the water molecule have been adjusted to make them consistent with other atoms depicted in the activity, although the overall diameter of the molecule is the same.
Sincerely,
Sheila Avery Genetic Science Learning Center"
Neither sperm nor photoreceptors undergo cell division, so for all its existence its DNA exists in an undifferentiated mass inside the cell. DNA is long, but skinny, so it compacts quite nicely.
As an embryo, your gonads start in your chest and, through signals from your brain, end up in your pelvic region.
Erythrocytes (Red blood cells) are a great example of specialization. Before they become erythrocytes they have a nucleus. Their nucleus is ejected, their shape completely changes from spherical to flat-with-a-dimple and they are not a red blood cell. Obviously, erythrocytes cannot divide.