Plant and animals cells have many of the same organelles, such as the nucleus, mitochondrion, Golgi apparatus, ribosomes and endoplasmic reticulum. In addition, the contents of these cells are held together by cell membranes.
Cell Membrane The cell membrane, also called plasma membrane, is the outermost limiting membrane of the cell that encompasses all the cell contents. This membrane is made of proteins and lipids and acts as an interface between the cell organelles suspended in the cytoplasm and the external extracellular fluids on the cell‰Ûªs exterior. The cell membrane is semi-permeable and allows the passage of selective substances through it. Plant and animal cells have well-defined cell membranes. However, plant cells also possess cell walls, which are responsible for their rigid structure.
Cytoplasm The cytoplasm is a semi-transparent fluid present between the nucleus and the plasma membrane. Cell organelles are suspended in the cytoplasm. In addition, the cytoplasm is the medium for various biochemical reactions that promote cell growth and development.
Cell Nucleus Plants and animals cells possess a true nucleus hence are eukaryotic. The nucleus is a spherical body containing the nucleolus, several organelles and chromosomes that contain DNA. The components of the nucleus are held together by a nucleus membrane, which prevents them from dissipating into the cytoplasm. Cell nucleus contains genetic materials and controls various functions and structures of the cell.
Mitochondria Mitochondria are organelles enclosed by a membrane and scattered in the cytoplasm. These organelles are responsible for energy synthesis in the form of ATP. The number of mitochondria largely vary depending on the function of the plant or animal cell.
Ribosomes Ribosomes are spherical nonmembranous organelles made of ribonucleic acid (RNA). These organelles are often scattered in the cytoplasm and may adhere to the outer surface of the endoplasmic reticulum. In plant and animal cells, ribosomes are responsible for the synthesis of proteins and act as assembly points for proteins in accordance with the genetic instructions. In this regard, cells with high protein synthesis rate have a large number of ribosomes.
Endoplasmic Reticulum The endoplasmic reticulum is the extensive membranous labyrinth, which consists of a network of sacs and tubules known as cisternae. Plants and animal cells have two types of endoplasmic reticulum: smooth endoplasmic reticulum and rough endoplasmic reticulum.
The surface of rough endoplasmic reticulum has bumpy appearance due to attached ribosomes while smooth endoplasmic reticulum have no attached ribosomes. Rough endoplasmic reticulum is responsible for protein synthesis. On the other hand, the smooth endoplasmic reticulum synthesizes lipids and is responsible for metabolism and cell detoxification.
Golgi Apparatus Golgi apparatus, also called Golgi body, are stacks of flattened membranes that are mainly devoted to processing proteins formed in the endoplasmic reticulum. Also, these organelles modify chemical substances and transport them in and out of the cell.
Vacuoles Found in plant cells and most animal cells, vacuoles are shapeless fluid-filled sacs present in the cytoplasm. They are used for storage of gases, fluids, nutrients and wastes. Vacuoles are responsible for maintenance of pH, excretion, intercellular digestion and maintaining turgor pressure. In plant cells, the vacuoles are large, hence one single vacuole is visible. Animal cells have several small vacuoles in their cytoplasm.