Around 1838, an animal physiologist, Theodor Schwann, and a botanist, Matthias Schleiden, put forth the unprecedented work on the concept of cells as the building blocks of all living organisms. From that point forward, cell theory has grown into the foundations of modern era biological research without which none of today’s discoveries would be possible.
We now know that there are a myriad of different cell types, with outstanding capabilities and functions. Regardless of how different all types of cells may be, there are common characteristics to all of them, along with established differences as well.
Whether we are looking at multicellular organisms or those containing one single cell, all of them will be manifesting the same features necessary to support life. We will go over certain similarities and characteristics of the animal and plant cells, in order to gain a better understanding of each. In that context, the last few paragraphs we will be focusing on the primary differences between plant cells and animal cells.
The size of plant cells usually ranges from 10-100 µm, which is a range that is bigger than animal cells. The primary function of these cells in plants is to carry out the process of photosynthesis via chloroplast which gives them their color. The cells themselves maintain their structure thanks to cellulose that make the walls of the cells. These cell walls aren't found in cells within the animal kingdom - we'll look at that in just a bit.
There are several different small structures inside the cell itself, called organelles, each with a specific function. These organelles are found in both types of cells discussed here, with many of them identical in function. Here are some of the most important ones that we find in plant cells:
Plasma Membrane - makes sure the structure of the cells remains intact and consequently keeps the cell content from spilling out. It also enables molecule movement via osmosis and diffusion.
Cell wall - different from a membrane by being found only in plant cells where it encompasses the cell membrane. The cell wall is firm but completely porous at the same time.
Chloroplasts/plastids - also found only in plant cells, these organelles enable photosynthesis when exposed to sunlight. Plastids are a group name for various kinds of chloroplasts that differ in color.
Vacuoles - provide structural integrity to the cell but also contain a variety of liquids or solids. These organelles are responsible for the colors we see on flowers.
Cytoplasm - the enzymes found within these structures are at the helm of all metabolic processes that happen inside.
Animal cell size ranges from 10-30 µm, which makes it obvious that plant cells can be much bigger, clearly, depending on the plant. The primary difference from plant cells is that animal cells don’t contain chloroplast nor structurally important cell walls.
It is obvious why animal cells lack in chloroplast, as there is no process of photosynthesis that generates food for the cells - animal cells create their energy via different process. But the interesting question is why exactly do they lack cell walls.
The primary theory is that the main "culprit" for the absence of cell wall is the evolution itself. Unlike plants, animal kingdom evolved to have more complex cells that are specialized to a greater extent and are able to sustain the structure of the cell without the cell wall. Obviously, just like plants cells, they also contain organelles with a variety of functions:
Plasma membrane - just like in plant cells, this structure allows for molecule movement through the cell itself and protects the internal structures of the cell, that is, other organelles.
Mitochondria - generates the energy necessary to sustain cell life by breaking down nutrients and transforming them into "food" molecules for the cell.
Cytokinesis - responsible for the division of cytoplasm while the cell is dividing. In animal cells, this division happens via the formation of cleavage furrow that grips the membrane and divides it in half.
Centrioles - cylindrically shaped objects within the cells are active during the process of cell division. Their function is to arrange the formation of microtubules - structural polymers of the cell.
Cilia - microtubules that assist in locomotion of the cell.
Main Differences Between Plant and Animal Cells
Both types of cells are identical in so much that they need to somehow produce energy to support themselves and to allow for growth. Both cell types also contain internal structures that are employed in specific processes that permit optimal functioning on a cellular level.
As was visible throughout the article, there are certain types of cells that are found in animal cells that cannot be found in plant cells, and vice versa.
The most obvious ones are cell chloroplast, wall, and vacuoles. These cells can only be found in plants. Although both animal and plant kingdom falls under the eukaryotes (multi-celled, as opposed to prokaryotic, which is single-celled), animal cells have much more complex structure.
Some organelles that are found in animal cells but not in plant cells are as follows: centrioles, cilia, desmosomes and lysosomes.
Size and Structure
Animal cells look very different to plant cells. They are typically smaller than plant cells, with a roundish shape which is fairly irregular. Plant cells have a rectangular shape and are larger.
The Cell Wall
Animal cells do not contain cell walls as one of the organelles, but they do have a plasma membrane which is the same as in plants.
Both types of cells do have a nucleus, which is expected. However, in plants, it is located to the side of the cell, whereas in animal cells have their nucleus in the middle.
Number of Vacuoles
Animal cells contain a multitude of small vacuoles, while plant cells can only accommodate one, which is quite large.
Animal cells are not equipped to carry out the synthesis of nutrients, while plants have no issues with synthesising various acids, vitamins and similar.
Lack of Communication Signals
Pores called plasmodesmata are in charge of communication signals, but also the passing of molecules between two cells. These pores are not identified in animal cells.