While both plant and animal cells are eukaryotic and share many similarities, they also differ in several ways. Learn about the key differences between these two cell types in this lesson.
Animals vs. Plants
Are you slouching in your chair while reading this lesson? Try to sit up straight. Reach your arms to the sky and stretch.... Feels good, right? Like it or not, you are an animal. Your cells are squishy blobs of cytoplasm, yet you are able to use your muscles and bones to stand upright and move about. As a heterotroph like all animals, you have to obtain nutrition from other sources. If you were feeling hungry or thirsty, you would just stand up and walk over to the refrigerator.
Now think about plants. Picture a tall oak tree or even a tiny blade of grass. They stand upright without having muscles or bones, but they don't have the luxury of walking somewhere to obtain food and drink. Plants, being autotrophs, make their own food using the sun's energy.
Many of the key differences between plants and animals come down to structural differences at the cellular level. Plant cells have some parts that animal cells don't, and vice versa. Let's take a quick look at what animal and plant cells have in common and then explore what makes them different.
Both plant and animal cells are eukaryotic, so they have a lot of similarities. They have a membrane-bound nucleus that contains their genetic material (DNA). A semi-permeable plasma membrane surrounds both types of cells. Their cytoplasm contains many of the same parts and organelles, including ribosomes, Golgi complexes, endoplasmic reticulum, mitochondria and peroxisomes among others.
Structures common to both plant and animal cells
As eukaryotic cells, they are also similar in size, being about 10-100 times larger than prokaryotes, like bacteria which do not have a nucleus. Now let's examine the unique features of each cell type.
Features Unique to Plant Cells
How are plants able to stand upright? Credit for that ability goes to the cell wall, which surrounds the membrane of all plant cells. The cell wall provides support and rigidity to plant cells and often gives them a rectangular or even hexagonal appearance when observed in a microscope.
Plant cells have a rigid, regular shape and can contain many chloroplasts.
Plant cell walls can be several micrometers thick. Their composition varies among groups of plants, but they are usually made of fibers of the carbohydrate cellulose embedded in a matrix of proteins and other carbohydrates. Cell walls help plant cells maintain turgor pressure from the uptake of water, which helps contribute to their stiffness and plants' capacity for vertical growth. Channels through the cell wall called plasmodesmata allow neighboring cells to exchange cytoplasm and certain materials.
Plants are not able to move from place to place, so they need a way to make their own food. An organelle called the chloroplast is responsible for photosynthesis. Plant cells can contain multiple chloroplasts, sometimes hundreds of them. Chloroplasts are surrounded by a double membrane and contain stacks of membrane-bound thylakoid discs suspended in a fluid interior known as the stroma. Pigments in the thylakoid discs absorb sunlight, and this energy is used to power the production of the plant's food via photosynthesis. No running to the kitchen for these guys...
Plant cell and organelles; note the cell wall, chloroplast and central vacuole
One of the most prominent structures found in plant cells is the large central vacuole. The vacuole occupies a large portion of the cell volume and is enclosed by a membrane called the tonoplast. It stores water as well as ions like potassium and chloride. As the cell grows, the vacuole absorbs water and helps the cell elongate.
Features Unique to Animal Cells
Unlike plant cells, animal cells lack a cell wall. They don't really have a defined shape, looking like soft and squishy blobs when viewed with a microscope. Certain cell types (muscle and bone, in our case) can organize into tissue and organs that give the bodies of animals their shape and the ability to move.
Human cheek cells lack a cell wall and have an irregular shape.
The centrosome is a structure found in animal cells but not in plant cells. It is usually located close to the nucleus and acts as microtubule organizing center during cell division. The centrosome contains a pair of centrioles at right angles to each other. Centrioles are composed of special proteins called microtubules. These microtubules replicate prior to cell division; during division they move to opposite ends of the cell and the mitotic spindle stretches between them.
Animal cell and organelles, including the centrosome with centrioles
Plant and animal cells, while sharing many of the same basic structures, do have some important differences. The cell walls that surround plant cells provide rigidity and support, allowing plants to stand upright. The large central vacuole stores water and other compounds and also helps maintain the shape of plant cells. Plants are anchored in place and must make their own food, so plant cells do this with the help of chloroplasts. In contrast, animal cells do not have the regular, rigid structure of plant cells. They don't have chloroplasts, so animals have to find ways to take in food. Animal cells contain centrosomes with centrioles that function during cell division, and these are not present in plant cells.