Difference Between Plant and Animal Cells

Plant and animal cells both are eukaryotic cells, meaning they have a defined nucleus and complex structures encased within membranes (organelles). Both cell types share common cellular machinery such as a nucleus, mitochondria, endoplasmic reticulum, ribosomes, and the Golgi apparatus. However, they also exhibit distinct structural differences that define their functions and responses to their environment. Some of these differences include the presence of cell walls and chloroplasts in plant cells, and centrioles and lysosomes in animal cells. The following article delves deep into the nuanced differences between plant and animal cells.

Why Are Plant and Animal Cells Different?

Remembering the key differences between plant and animal cells is easier when you think about the roles these cells play.

Plant cells are rigid because the stacked cells act as their skeletal system and because they store water and nutrients both for energy and to maintain their structure. Plants are photosynthetic or autotrophs, so their cells contain the necessary organelles for photosynthesis. So, plant cells have a cell wall, a large central storage vacuole, and chloroplasts.

Animals, on the other hand, are motile (can move). Movement requires flexibility, so animal cells are not rigid. While they naturally assume a round shape, but allow for changes. Because they lack a cell wall that would give the cells a fixed shape, animal cells need help making certain the chromosomes and cell contents align perfectly for mitosis and meiosis. So, they have centrioles and centrosomes. Animals are heterotrophs, meaning they get their food by eating plants or other animals. So, they lack chloroplasts. Animal cells several smaller vacuoles. Lysosomes in animal cells break down debris. Although plant cells perform this function, they do it a bit differently.

Plant vs Animal Cells: Comparing the Differences

Plant and animals cells contain somewhat different organelles, plus there are distinctions between some that they share in common:

Cell Wall

Plant cells are encased in a rigid cell wall composed mainly of cellulose. This wall not only provides structural support but also protects the cell from mechanical damage. It has a role in preventing excessive water uptake and gives shape to the cell. Animal cells lack this rigid structure; instead, they have a more flexible cell membrane which provides for diverse shapes and facilitates movement in some cells. (Plant cells also have a cell membrane.)

Intermediate Filaments

Intermediate filaments form the cytoskeleton of many animal cells. For the most part, plant cells lack intermediate filaments because the cell wall and central vacuole keep cell contents in place. In plants cells with intermediate filaments, the structure and function differs from anima cells. In a way, plant cells have an exoskeleton, while animal cells have an endoskeleton.

Chloroplasts

One of the primary distinctions between plant and animal cells is the presence of chloroplasts and other plastids in plant cells. Chloroplasts are the sites of photosynthesis, where light energy is converted into chemical energy in the form of glucose. Containing the pigment chlorophyll, these organelles enable plants to capture light energy. Animal cells do not possess chloroplasts and rely on the intake of organic compounds for energy.

Centrioles and Centrosomes

Animal cells often contain a centrosome, which includes a pair of centrioles located near the nucleus and cylinders of microtubules. These organelles play a crucial role in cell division by helping in the formation of the spindle fibers that separate chromosomes during mitosis. Although some plant cells have structures similar to centrioles, they generally lack these organelles and have alternative mechanisms for spindle formation during cell division.

Vacuoles

While both plant and animal cells contain vacuoles, the size, function, and number can differ significantly. In plant cells, a central vacuole often occupies up to 90% of the cell’s volume. This vacuole stores nutrients, waste products, and helps in maintaining turgor pressure. Animal cells may have several smaller vacuoles that mainly function in storage, excretion, and intracellular digestion.

Lysosomes

Predominantly found in animal cells, lysosomes are membrane-bound organelles containing hydrolytic enzymes. These enzymes are essential for breaking down waste materials and cellular debris. Plant cells, on the other hand, have similar structures called lytic vacuoles, which serve a similar function but are structurally different.

Ribosomes

Both plant and animal cells have ribosomes, which are the site of protein synthesis. However, the ribosomes in chloroplasts of plant cells, which are responsible for synthesizing proteins needed for photosynthesis, are more similar to those found in prokaryotic cells than the ribosomes in the cytoplasm of either plant or animal cells.

Plasmodesmata vs. Gap Junctions

Plasmodesmata are tiny channels found in plant cells that allow for communication and transport between neighboring cells. Animal cells don’t have plasmodesmata; instead, they use structures called gap junctions to facilitate intercellular communication.

Glyoxysomes

Present in plant cells, especially in the germinating seeds, glyoxysomes play a pivotal role in lipid conversion to carbohydrates. These specialized peroxisomes are absent in animal cells.

Cilia and Flagella

Cilia and flagella aid in cell motility. Mainly animal cells have these structures (but not all animal cells). So do some plant cells, too, but they are absent in higher plants.

Summary of the Difference Between Plant and Animal Cells

In conclusion, while plant and animal cells share a foundational cellular structure and machinery, the differences in their organelles and structural components are adaptations to their unique roles in nature. These differences underscore the complexity and adaptability of life at the cellular level.

References

• Alberts, B.; Johnson, A.; et al. (2015). Molecular Biology of the Cell (6th ed.). Garland Science. ISBN 978-0815344322.
• Blair, D.F.; Dutcher, S.K. (October 1992). “Flagella in prokaryotes and lower eukaryotes”. Current Opinion in Genetics & Development. 2 (5): 756–767. doi:10.1016/S0959-437X(05)80136-4
• Campbell, N.A.; Williamson, B,; Heyden, R.J. (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 978-0132508827.
• Raven, J.A. (1987). “The role of vacuoles”. New Phytologist. 106 (3): 357–422. doi:10.1111/j.1469-8137.1987.tb00149.x
• Raven, P.H.; Johnson, G.B. (2002). Biology. McGraw-Hill Education. ISBN 978-0071122610.