scroll to top
Stuck on your essay?
Get ideas from this essay and see how your work stacks up
Word Count: 620
The Cell Theory 1 All living things are made of cells 2 Cells are the basic units of life 3 Cells come only from other cells Protocells One theory of the origins of cells states that the first life on earth consisted of several types of tiny protocells cell-like organisms These organisms were able to survive and reproduce in a very limited environment because of their simplicity Over time some of these protocells came together and shared their specialization in a symbiotic relationship These colonies of protocells eventually became the cells we know today Cell organelles components of cells with specific functions Cell membrane h A complex barrier of lipid molecules separating the cell from its external environment h These molecules can move apart to allow larger particles to move in or out of the cell h The selectively permeable cell membrane regulates what passes into and out of the cell Some substances like water move freely through the cell membrane by a process known as osmosis In osmosis particles move easily from an area of high concentration to an area of low concentration by molecular motion only Cells can push particles in the opposite direction from low concentration to high but it will take energy from the cell to do this Cytoplasm h A thick aqueous solution of salts surrounding the organelles inside the cell membrane h Nutrients and minerals spread through the cytoplasm to all parts of the cell h The constant motion of this gel-like substance is called cytoplasmic streaming Nucleus h The structure inside the cell that directs cell activities h Contains the DNA of a cell Cell wall h On the outside of some cells bacteria and plants this structure functions for support and protection h There are pores in the cell wall allowing substances to come
@Kibin is a lifesaver for my essay right now!!
- Sandra Slivka, student @ UC Berkeley
Wow, this is the best essay help I've ever received!
- Camvu Pham, student @ U of M
If I'd known about @Kibin in college, I would have gotten much more sleep
- Jen Soust, alumni @ UCLA