2.3 Flashcards
all cells have
similar biological membranes
two categories of organisms
prokaryotes - NO membrane enclosed organelles
eukaryotes - membrane enclosed organelles
nucleoid
prokaryote’s chromosomes are located in a region of the cytoplasm called the nucleoid
chromosomes
supercoiled, circular DNA, RNA, and proteins
plasmid
small circular DNA that some prokaryotic cells have
cell wall
made of peptidoglycans (+ an outer membrane)
protection and shape
capsule
slimy polysaccharide layer (due to -OH groups)
hydration of cell
flagellum
made of protein flagellin
cell movement
animal cells vs. plant cells
animal cells have centrioles and lysosomes
plant cells have vacuoles and chloroplasts
nucleus
contains most of the cellular DNA and is the site of replication and transcription
nucleolus
RNA is synthesized, ribosome subunits assembled (synthesis)
nucleoplasm
chromatin, the DNA-protein complex is assembled
nuclear envelope
a lipid double membrane containing thousands of nuclear pores
surrounds the nucleus
separates chromatin from cytoplasm
nuclear pore
large complex of multi-subunit proteins and regulates the transport of macromolecules
FG Nups layer
made up of phenyalanine and glycine
macromolecules need the assistance of special proteins to pass here
site of protein synthesis
always begins on free ribosomes in the cytosol
ribosomes
site of protein synthesis
similar structure in prokaryotes and eukaryotes
lack membranes
consist of two subunits made up of rRNA and numerous proteins
signal sequence
added to the polypeptide chain during translation indicating where it in cell it belongs
added to the N-terminus of newly synthesized proteins
binds to receptor proteins on the surface of an organelle
removed by proteases after translation
post-translational translocation
proteins are synthesized by free ribosomes in the cytosol and then sorted to a specific organelle via signal sequences
leads to peroxisomes, plastids, mitochondria, or the nucleus
nuclear localization signal (NLS)
directs a protein to the nucleus
consists of one or more clusters of positively charged lysine or arginine
binds to a special protein (nuclear transport protein) for import
co-translational translocation
ER signal sequence causes translation to pause and directions ribosomes to the rough ER
a signal recognition particle in the cytoplasm binds to the ER signal sequence and bring the polypeptide-ribosome complex to the RER
endomembrane system
group of membranes and organelles that works together to process and transport proteins and lipids
vesicles
shuttle between parts of the endomembrane system
endoplasmic reticulum
network of membranes in the cytoplasm
continuous with the nuclear envelope
2 regions - smooth and rough ER
rough endoplasmic reticulum
formed when ribosomes attach to the ER membrane
- in the ribosome attached to the outside of the RER
–protein synthesis occurs
- in the lumen of RER
– protein folding
– protein modification (glycosylation, proteolysis of signal peptide)
–protein translocation to other locations in vesicle
smooth endoplasmic reticulum
lacks ribosomes
chemical modification of small toxic molecules taken in by the cell
glycogen degradation in animal cells
synthesis of lipids (phospholipids, steroids)
storage of calcium ions
golgi apparatus
flattened membranous sacs (cisternae) and small membrane enclosed vesicles
cis face - receives proteins from RER (closest to RER)
medial face - in between
trans face - ships content to the cell membrane, etc. via vesicles (closest to membrane)
golgi apparatus function
modifies, processes, packages, and sorts proteins in its lumen before they are sent to their destination
-protein modification (glycosylation, -modification of carbohydrates)
-proteolysis of precursor proteins into smaller, functional fragments
-synthesis of polysaccharides for the cell wall
-protein targeting to their destination
