Eukaryotic Cells facts
- A eukaryotic cell is larger and more complex than a prokaryotic cell and found in animals, plants, algae, fungi, and protozoa.
- When we look at a eukaryotic cell with a microscope we’ll notice a highly organized structure of organelles that are bound by a membrane.
- Each organelle performs a specialized function for the cell’s metabolism.
- Eukaryotic cells also contain a membrane bound nucleus where the cell’s DNA is organized into chromosomes.
- Depending on the organism, a eukaryotic cell may contain external projections called flagella and cilia.
- These projections are used for moving substances along the cell’s surface or for moving the entire cell.
- Flagella move the cell in a wave like motion within its environment. Cilia move substances along the cell’s surface and also aid in movement of the cell.
- Flagella and cilia are comprised of axoneme microtubules. An axoneme microtubule is a long, hollow tube made of protein called a tubulin.
- Eukaryotic cells of other organisms (such as animals) that lack a cell wall have an outer plasma membrane that serves as an outside cover for the cell.
- Many eukaryotic cells have a cell wall.
- The composition of the cell wall differs with each organism. For example, the cell walls of many fungi are composed of chitin cellulose.
- Chitin is a polysaccharide, which is a polymer of N-acetylglucosamine (NAG) units.
- The cell wall of other fungi is made of cellulose, which is also a polysaccharide.
- Cellulose is also found in the cell wall of plants and many algae.
- Yeast has a cell wall composed of glucan and mannan, which are two polysaccharides.
- In contrast, protozoa have no cell wall and instead have a pellicle. A pellicle is a flexible, proteinaceous covering.
- The outer plasma membrane has a sticky carbohydrate called glycocalyx on its surface.
- Glycocalyx is made up of covalently bonded lipids and proteins in order to form glycolipid and glycoprotein in the plasma membrane.
- A eukaryotic cell lacks peptidoglycan, which is critical in fighting bacteria with antibiotics.
- The plasma membrane is a selectively permeable membrane enclosing the cytoplasm of a cell.
- This is the outer layer in animal cells.
- The plasma membrane surrounds a eukaryotic cell and serves as a barrier between the inner cell and its environment.
- In a eukaryotic microorganism, the cytoskeleton provides support and shape for cells and helps transport substances through the cell.
- The plasma membrane of a eukaryotic cell functions like the plasma membrane of a prokaryotic cell.
- Eukaryotic cells extend parts or sections of plasma membrane.
- The extensions of the plasma membrane are called pseudopods.
- The word pseudopod means “false foot,” and these “feet” enable the cell to have amoeboid motion.
CYTOPLASM AND NUCLEUS
- The cytoplasm of a eukaryotic cell contains cytosol, organelles, and inclusions, which is similar to the cytoplasm of the prokaryotic cell.
- Eukaryotic cytoplasm also contains a cytoskeleton that gives structure and shape to the cell and assists in transporting substances throughout the cell.
- The nucleus of a eukarytoic cell contains DNA (hereditary information) and is contained within a nuclear envelope.
- In the nucleus, the cell’s DNA is combined to form several proteins called histones.
- The endoplasmic reticulum contributes to the mechanical support and distribution of the cytoplasm and is the pathway for transporting lipids and proteins throughout the cell.
- The ER also provides the surface area for the chemical reaction that synthesizes lipids, it stores lipids and proteins until the cell needs them.
- It consists of cisterns, which are a network of flattened membranous sacs.
- The end of these cisterns can be pinched off to become membrane-enclosed sacs called secretory vesicles.
- Vesicles transport synthesized material in the cell.
There are two kinds of endoplasmic reticula:
Rough endoplasmic reticulum: Covered by ribosomes, which are the sites for synthesizing protein.
Smooth endoplasmic reticulum: Not covered by ribosomes, this is the site for synthesizing lipids.
- The Golgi complex is considered the “Fedex System” of the cell because it packages and delivers proteins, lipids, and enzymes throughout the cell and to the environment.
- The Golgi complex contains cisterns stacked on top of each other.
- A cistern is a sac or vessel and is filled with proteins or lipids (packaged), detached from the Golgi complex, and transported to another part of the cell.
- A lysosome is a sphere in animal cells that, it contains enzymes used to digest molecules that have entered the cell.
- Think of lysosomes as the digestive system of the cell. For example, lysosomes in a white blood cell digest bacteria that is ingested by the cell during phagocytosis.
- The mitochondrion is an organelle that is comprised of a series of folds called cristae that is responsible for the cell’s energy production and cellular respiration.
- Chemical reactions occur within the center of the mitrochondrion, called the matrix, it is filled with semifluid in which adenosine triphosphate (ATP) is produced.
- ATP is the energy molecule in the cell.
- The mitochondrion is the powerhouse of the cell.
- Eukaryotic cells of green plants and algae contain chloroplast.
- Chloroplasts are organelles that contain pigments of chlorophyll and carotenoids used for gathering light and enzymes necessary for photosynthesis.
- Photosynthesis is the process that converts light energy into chemical energy.
- The pigment is stored in membranous sacs called thylakoids that are arranged in stacks called grana.
- A centriole is a pair of cylindrical structures near the nucleus that is comprised of microtubules and aids in the formation of flagella and cilia.
- The centriole also has a part in eukaryotic cell division.