Intracellular Compartments and Transport Flashcards
Advantages of organelles
“House” chemical reactions: sequester damaging molecules, keep reactions together
Membrane: create gradient for H+ motive force, regulation
Organelle anchorage
Held in place by cytoskeleton
Cytosol
Contains many metabolic pathways
Protein synthesis
Nucleus
Main genome
DNA and RNA synthesis and maintenance
Nucleolus
Storage of ribosomal RNA and euchromatin
Endoplasmic reticulum
Synthesis of most lipids (smooth)
Synthesis of proteins for distribution to many organelles and to the plasma membrane (rough)
Golgi apparatus
Modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle
Lysosomes
Intracellular degradation
Endosomes
Sorting of endocytosed material
Mitochondria
ATP synthesis by oxidative phosphorylation
Chloroplasts
ATP synthesis and carbon fixation by photosynthesis
Peroxisomes
Oxidation of toxic molecules
Cajal
Area of nucleus where RNA is processed
P bodies
RNA turnover
Endomembrane system
Nucleus, plasma membrane, ER, golgi, endosomes, lysosomes/vacuoles, vesicles
Originally formed from invaginations of plasma membrane
Protein sorting
Transport through nuclear pores (nucleus proteins)
Transport across membranes
Transport by vesicles
Signal sequences
Targeting motif
Directions to where the protein is supposed to go
How to determine where protein goes
Look at signal sequence
Label w/ fluorescent antibody and see where it goes (stain organelles or proteins in organelles)
Mutate sequence and see what happens (determine correct sequence as signaling)
Nuclear envelope
Outer membrane: contiguous with ER
Inner membrane: nuclear lamina
Nuclear localization signal (NLS)
Allows nuclear protein to be transported through pores into nucleus
Nuclear pores
Openings into nucleus: selective gates
Protein with NLS is attached to transport protein
Protein swings from tangle to tangle until it reaches nucleus
Mitochondrial and chloroplast protein import
Signal sequence is recognized by receptor
Receptor diffuses- forms contact site
Unfolded protein snakes through
Protein is folded in matrix
ER Transport
Proteins destined for golgi, lysosome, plasma membrane, endosomes, or secretion enter the ER first
2 types of proteins: water-soluble (lumen or secreted) or transmembrane
Proteins are imported as they are translated
Polypeptide being synthesized directs its ribosome to ER by its signal sequence
Directing an ER polypeptide to the ER
- Signal recognition particle (SRP) binds to ER signal sequence
- SRP binds to SRP receptor in ER membrane
- Translocation channel opens
- Polypeptide snakes through channel