Differences between Plant and Animal Cells
Written by tutor Kathie Z.
Plant cells have cell walls for support outside their cell membrane and are usually rectangular in appearance when viewed under the microscope. They are rectangular prisms in 3-dimensions. Most plants are autotrophs and have chloroplasts (plastid organelles filled with chlorophyll) which provide a distinctive green color. These two organelles are key in identifying a plant cell: if they are present it has to be a plant cell.
In contrast, an animal cell is recognized by not having plant structures. Animal cells tend to be spherical in 3-dimensions (rounded when viewed under the microscope). They may be simple or complex eukaryotic cells but all are heterotrophs.
Originally, there were thought to be two kingdoms of living organisms on Earth: Plants and Animals. Over time as technology improved our methods of observation we have added the prokayrotic domains of Archaea and Bacteria, and we are still arguing where and how to classify the few groups of organisms which are mixotrophs.
In the multicelluar organisms it is usually easy to determine whether the cell of organism is a member of the Kingdom Animalia or Plantae. Both are eukaryotic. All cells have membranes which separate the cell interior from the outside environment. All cells have cytoplasm which keeps the membrane from collapsing together. It is the single cell organisms which are confusing.
Animal cells lack cell walls and plastids. They are heterotrophs which ingest their food and nutrients. They have a complex cell structure with differentiated jobs but don’t create energy.
Plant cells are autotrophs which acquire nutrients and create energy from sunlight transforming light into glucose in their chloroplasts (speciallized plastids). Plants also have cell walls outside their membranes which provide a rigid frame for the cell.
Fungi cells have cell walls but no plastids for photosynthesis because most live underground and secret digestive enzymes. Some are parasitic.
Monera cells are prokaryotic and lack cell walls and plastids. However, some can carry out photosynthesis.
Protista cells are also prokaryotic and have no cell walls, but some have plastids and perform photosynthesis. This group of organisms is sometimes subdivided into “animal-like” and “plant-like” based on the way they generate energy. Some consider this a dumping ground for organisms which do not fit into one of the other groups.
autotrophs are cells which are capable of producing food from raw materials and generate their own energy usually by photosynthesis. Although in no-light environments, autotrophs carry out chemosynthesis.
heterotrophs are cells which gain their energy by absorbing it from other cells.
mixotrophs organisms which are capable of photosynthesis in sunlight, yet switch to predation in no-light environments.
prokaryotes are cells without a nucleus. These cells tend to be smaller.
eukaryotes are cells with a nucleus. These cells tend to be larger and more complex due to the variety of membrane bound organelles they contain.
The Wyzant Biology help section on Cell Structure and Function is an excellent source on organelle definitions and diagrams. Also your textbook will have diagrams and definitions of the various organelles.