the diffusion of water across a selectively permeable membrane.
cell cycle stages
-Prophase: the chromatin coils to form visible chromosomes.
-Metaphase: the chomosomes move to the equator of the spindle.
-Anaphase:the centromeres split and the sister chromatids are pulled apart to opposite poles of the cell.
-Telophase:two distinct daughter cells are formed, the cells separate as the cell cycle proceeds to the next interphase.
Three reasons why cell size is limited
1. Diffusion limits cell size. Diffusion becomes slow and ineffecient as the distances become larger.
2.DNA limits cell size. There is a limit to how quickly the blueprints for proteins can be copied in the nucleus and made into proteins in the cytoplasm. Cells cannot survive unless there is enough DNA to support the protein needs of the cell.
3. Surface area-to-volume ratio limits cell size. As a cell's size increases, its volume increases much faster than its surface area, resulting in the plamsa membrane not having enough space thought which oxugen, waste, and nutrients can diffuse. This would result in the cell either dying of starvation from lack of nutrients, or poisoning from excess waste.
The centromere connects the two sets of sister chromatids. Within the chromosome there is a supercoil. There is continued coiling within the supercoil. Also within the supercoil there are histones (H1), proteins. Rapped around the histones are longs strands of DNA called chromatins.
the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell.
the concentration of dissolved substances outside the cell is higher than the concentration insides the cell.
the concentration of dissolved substacnces in the solution outside the cell is the same as the concentration of dissolved substances inside the cell.
movement of materials through a membrane against a concentration gradient; requires energy from the cell.
the cell uses no energy to move the particles across the plasma membrane.
natural movement of particles
particles naturally want to move to areas of higher concentration.