Chapter 4
Cell Structure
By Boundless
![Thumbnail](../../../../../figures.boundless-cdn.com/18581/square/figure-04-00-00.jpeg)
A cell is the smallest unit of a living thing and is the basic building block of all organisms.
![Thumbnail](../../../../../figures.boundless-cdn.com/18582/square/figure-04-01-01ab-new.jpeg)
Microscopes allow for magnification and visualization of cells and cellular components that cannot be seen with the naked eye.
![Thumbnail](../../../../../figures.boundless-cdn.com/20244/square/l-cell-in-three-dimensions.jpg)
Cell theory states: living things are composed of one or more cells; the cell is the basic unit of life; cells arise from existing cells.
Cell size is limited in accordance with the ratio of cell surface area to volume.
![Thumbnail](../../../../../figures.boundless-cdn.com/18589/square/figure-04-03-04.jpeg)
A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions.
![Thumbnail](../../../../../figures.boundless-cdn.com/18595/square/figure-04-03-02.jpeg)
The plasma membrane is made up of a phospholipid bilayer that regulates the concentration of substances that can permeate a cell.
![Thumbnail](../../../../../figures.boundless-cdn.com/20009/square/0318-nucleus.jpeg)
Found within eukaryotic cells, the nucleus contains the genetic material that determines the entire structure and function of that cell.
![Thumbnail](../../../../../figures.boundless-cdn.com/18599/square/figure-04-03-07.jpeg)
Mitochondria are organelles that are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule.
![Thumbnail](../../../../../figures.boundless-cdn.com/18600/square/figure-04-03-08.jpeg)
Although they are both eukaryotic cells, there are unique structural differences between animal and plant cells.
![Thumbnail](../../../../../figures.boundless-cdn.com/31889/square/ggdcj9gcsgondhug8udv.jpg)
Vesicles and vacuoles are membrane-bound sacs that function in storage and transport.
![Thumbnail](../../../../../figures.boundless-cdn.com/18603/square/figure-04-04-02-new.jpeg)
The endoplasmic reticulum is an organelle that is responsible for the synthesis of lipids and the modification of proteins.
![Thumbnail](../../../../../figures.boundless-cdn.com/18604/square/figure-04-04-03.jpeg)
The Golgi apparatus sorts and packages materials before they leave the cell to ensure they arrive at the proper destination.
![Thumbnail](../../../../../figures.boundless-cdn.com/18605/square/figure-04-04-04.jpeg)
Lysosomes are organelles that digest macromolecules, repair cell membranes, and respond to foreign substances entering the cell.
![Thumbnail](../../../../../figures.boundless-cdn.com/19992/square/0316-peroxisome.jpeg)
Peroxisomes neutralize harmful toxins and carry out lipid metabolism and oxidation reactions that break down fatty acids and amino acids.
![Thumbnail](../../../../../figures.boundless-cdn.com/18606/square/figure-04-05-02.jpeg)
Microfilaments, which are the thinnest part of the cytoskeleton, are used to give shape to the cell and support all of its internal parts.
![Thumbnail](../../../../../figures.boundless-cdn.com/18608/square/figure-04-05-04ab.jpeg)
Microtubules are part of the cell's cytoskeleton, helping the cell resist compression, move vesicles, and separate chromosomes at mitosis.
![Thumbnail](../../../../../figures.boundless-cdn.com/18610/square/figure-04-06-01.jpeg)
The extracellular matrix of animal cells holds cells together to form a tissue and allow tissues to communicate with each other.
![Thumbnail](../../../../../figures.boundless-cdn.com/18613/square/figure-04-06-04.jpeg)
Intercellular junctions provide plant and animal cells with the ability to communicate through direct contact.