Cell Organelles Flashcards
The nucleus
- storage and transmission of genetic information to the next generation of cells
- consists of the nuclear envelope, nuclear pores, chromatin and nucleolus
Nucleolus
- densely staining filamentous region without a membrane
- associated with specific regions of DNA that contain the genes for forming ribosomes
Ribosomes
- synthesise proteins
- consist of 2 subunits that either float free in the cytoplasm (proteins released into the cytosol) or combine during protein synthesis with rough ER (proteins secreted from the cell or distributed to other organelles)
Rough Endoplasmic reticulum
- has ribosomes bound to its cytosolic surface and it has a flattened-sac appearance
- involved in packaging proteins
Smooth Endoplasmic reticulum
- no ribosomes on its surface and has a branched tubular structure
- site of lipid synthesis
- stores and releases calcium ions
- participates in detoxification of certain hydrophobic molecules
Endoplasmic reticulum
2 types: rough and smooth
- network of membranes that enclose a space that is continuous throughout the network
Golgi Apparatus
- series of closely apposed, flattened membranous sacs that are slightly curved
- associated with membrane-enclosed vesicles
- involved in protein modifications
- sorts the modified proteins into discrete classes of transport vesicles (secretory vesicles take proteins to the plasma membrane)
Endosomes
- membrane-bound vesicular and tubular structure, lie between the plasma membrane and golgi apparatus
- involved in sorting, modifying and directing vesicular traffic in cells
Mitochondria
- site of ATP synthesis and involved in the synthesis of certain lipids
- spherical elongated, rodlike structures surrounded by an inner and outer membrane
- inner membrane is folded into sheets/tubules known as cristae, which extend into the matrix
- can fuse with other mitochondria to form a reticulum which can change in different physiological settings (as energic demands of the cell changes)
Lysosomes
- spherical or oval structures with a single membrane
- contains acidic fluid and digestive enzymes
- break down bacteria, debris from dead cells that have been engulfed by the cell, and organelles that have been damaged and no longer function properly
Perioxisomes
- moderately dense oval bodies enclosed by a single membrane
- consumes oxygen which undergoes reactions that removes hydrogen from organic molecules to produce hydrogen peroxide
- then destroys hydrogen peroxide to prevent its toxic effects
- also involved in the breakdown of fatty acids to 2-carbon fragments which can be used as a source for generating ATP
Vaults
cytoplasmic structures composed of protein and a type of untranslated RNA (vault RNA)
- barrel-shaped
- associated with nuclear pores
- hypothesis that they are important for transport of molecules between the cytosol and the nucleus
Cytoskeleton
The filamentous network within the cytoplasm of most cells
- associated with processes that maintain and change cell shape and produce cell movements
Actin filaments
composed of monomers of G-actin and assemble into a polymer of 2 twisting chains known as F-actin
- functions in determining cell shape, cell movement, cell division and muscle contraction
Intermediate filaments
- composed of twisted strands of several different proteins (keratin, desmin and lamin)
- contribute to cell shape and help anchor the nucleus
- provide strength
