Cell structures

• Eukaryotic cells


  Cells characterized by having multiple compartments with different functions, each separated by a membrane
• Their ability to have multiple environments inside of a single cell lets eukaryotes carry out complex metabolic reactions that prokaryotes cannot, which is part of why they grow to be much bigger
• Unlike prokaryotes, Eukaryotes have:

  • A nucleus
  • Organelles
  • Linear chromosomes, instead of one circular one
• Endomembrane system


  Group of organelles and membranes in eukaryotic cells that work together to transport, modify, and package lipids and proteins
• Endoplasmic reticulum


  Plays a key role in the modification of proteins and the synthesis of lipids, consisting of a network of membranous tubules and flattened sacs
• Lumen


  The hollow space inside the discs tubules and membranes in a cell
• Rough ER


  Named after the bumpy ribosomes on the cytoplasmic surface that feed in strands of proteins into the lumen to be modified
• The Endoplasmic reticulum folds and modifies proteins, like adding extra carbohydrate side chains
• Proteins modified in the ER are either incorporated into the cell's membranes or secreted from the cell
• Some protein chains transfer fully into the ER and float freely inside, while others remain anchored to the membrane
• Vesicles


  Small spheres of membrane that are used for transport within a cell
• Cells whose jobs are to secrete lots of proteins or enzymes, like liver cells, will have lots of rough ER
• Smooth ER


  Continuous with rough ER but has few or no ribosomes on its cytoplasmic surface
• Functions of the smooth endoplasmic reticulum:

  • Synthesis of carbohydrates, lipids, and steroid hormones
  • Detoxification of medications and poisons
  • Storage of calcium ions
• Sacroplasmic reticulum


  Specialized type of smooth ER made for storing the calcium ions necessary to triggering coordinated contractions in muscle cells
• Transitional ER


  Smooth sections of ER within the rough ER that serve as exit sites for vesicles
• Golgi apparatus


  Organelle made up of flat discs of membrane that sort, package, and tag proteins and lipids in transport vesicles before they can be shipped off to their final destination
• The receiving side of the Golgi apparatus is called the cis face, and the opposite side is called the trans face
• While going through the Golgi apparatus, proteins and lipids undergo further modification:

  • Short strings of sugar molecules are added or removed
  • Phosphate groups may be attached as tags
• There are many Golgi sacs in cells that secrete lots of proteins, like salivary glands or immune cells
• In plant cells, the Golgi apparatus also makes polysaccharides, some of which are incorporated into the cell wall
• Lysosome


  Organelle containing digestive enzymes to break down old and unnecessary structures so their molecules can be reused, and digest foreign particles from the outside
• Some of the vesicles from the Golgi apparatus are bound for lysosomes, where they are broken down
• The lysosomes are a part of the endomembrane system
• Macrophage


  Type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells
• Phagocytosis


  When a macrophage's pseudopods fold inward to engulf a pathogen, which then pinches off to form a membrane around the pathogen, called a phagosome, which then fuses with a lysosome so the pathogen can be digested
• Phagosome


  Pinched off section of the plasma membrane holding an enveloped pathogen that will eventually be attached to a lysosome to digest it
• Vacuole


  Lysosome-like organelle unique to plant cells that stores water, isolates waste, and has enzymes that can break down macromolecules and cellular components
• Vacuole


  Plant organelle that works to maintain a water balance and can store toxins and pigments
• Peroxisome


  Organelle that houses enzymes capable of triggering oxidization reactions, which produce hydrogen peroxide as a by-product. They break down amino and fatty acids, and help detoxify some substances that enter the body
• Peroxisome


  Lysosome-like organelle that is not a part of the endomembrane system because it does not get shipments from the Golgi apparatus
• Chloroplast


  Disc-shaped organelle found exclusively in plant and photosynthetic algae cells, carries out photosynthesis
• Photosynthesis


  The process of turning light and carbon dioxide into sugars
• Cellular respiration


  When the mitochondria harvests energy from sugars
• Thylakoids


  Membrane discs found inside of chloroplasts
• Grana


  Interconnected stacks of thylakoids inside of a chloroplast
• Stroma


  Clear fluid surrounding grana inside of a chloroplast
• Chlorophyll


  A green pigment, present in all green plants and in cyanobacteria, which is responsible for the absorption of light to provide energy for photosynthesis
• Mitochondria


  The powerhouse of the cell
• ATP

  Adenosine triphosphate