Simple diffusion is the process by which a substance moves across a cell membrane from an area of high concentration to an area of low concentration. Substances that move by simple diffusion are able to diffuse directly across the phospholipid bilayer of the cell membrane. These substances are generally small and neutral, as large or charged particles cannot cross the phospholipid bilayer. Some examples of molecules that move by simple diffusion are carbon dioxide and oxygen.
Facilitated diffusion is the process by which a substance moves across a cell membrane from an area of high concentration to an area of low concentration with the aid of a membrane protein. Substances that move by facilitated diffusion are not able to diffuse directly across the phospholipid bilayer of the cell membrane. These substances are generally large and/or charged. They therefore travel through a protein channel in the cell membrane along their concentration gradient. Some examples of substances that can move by facilitated diffusion are glucose, sodium ions and chloride ions.
The similarities between facilitated diffusion and simple diffusion are:
They both involve the movement of a substance across a cell membrane along its concentration gradient (from an area of high concentration to an area of low concentration).
They are both examples of passive transport, as neither requires energy from the cell to move the substance across the membrane.
Answer:
Why is it thought that the majority of natural selection is stabilizing selection? Mutations produce extreme phenotypes, which are selected for. Artificial selection is the most common, which is a type of stabilizing selection. Most mutations are beneficial and produce intermediate phenotypes.
Explanation:
When insulin is deficient , GLUT4 transporters are not inserted into the cell membranes , glucose is not transported into the cells and the blood glucose concentration increases.
Insulin deficiency provides more amino acid and glycerol substrates for glucose synthesis ie increased gluconeogenesis .
With a deficiency of insulin, there is both increased hepatic glucose production through increased glycogenolysis and gluconeogenesis as well as decreased glucose use. The result is hyperglycemia.
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Plants have cell walls, so cytokinesis cannot go on with a cleavage furrow, but instead, a cell plate forms across the cell in the location of the metaphase plate.
There is no distinct groove along the cell plate as the cell divides because of the rigid nature of the cell plate or new cell wall.
A plant cell divides differently from an animal cell which forms a clear cleavage furrow because it only has a flexible cell membrane and not a rigid cell wall like plants.
The cell plate in plant cells is formed by membrane bound vesicles which migrate to the center of the cell where the metaphase plate used to be and fuse together to form a cell plate.
