Internal Organization of Cells and Nuclear Import and Export Flashcards
all cells have…
a plasma membrane and contain genetic material
prokaryotes
lack a nucleus
include bacteria and archaeons
eukaryotes
have a nucleus
include animals, plants, fungi, and protists
in mammals…
cholesterol is present in cell membranes
choleserol belongs to a group of chemical compounds known as sterols → molecules containing hydroxyl group attached to a gour-ringed structure
from an evolutionary perspective…
archaeons and ukaryotes are more closely related to each other than either is to bacteria
nucleoid
prokaryotes
a discrete region of cell interior where DNA is concentrated; contains multiple loops formed from supercoils of DNA
prokaryotes
plasmids
prokaryotes → bacteria
additional, small, circular moelcules of DNA carrying a small number of genes
prokaryotes → bacteria
pili
prokaryotes → bacteria
a hollow, threadlike structure that connects bacteria allowing the transfer of plasmids via conjugation
prokaryotes → bacteria
nucleus
eukaryotes
the compartment of the cell that houses DNA in chromosomes
eukaryotes
nuclear membrane
eukaryotes
allos for more complex regulation of gene expression than is possible in prokaryotes
eukaryotes
organelles
eukaryotes
compartements that divide the cell contents into smaller spaces with specialized functions; defined by their membranes
eukaryotes
mitochondria
typical features of an animal cell
produces most of the ATP that serves as the energy currency of the cell
typical features of an animal cell
plasma membrane
typical features of an animal cell
composed of phospholipids and proteins; regulates the passage of material into and out of the cell
typical features of an animal cell
cytoskeleton
typical features of an animal cell
a network of protein fillaments and other associated proteins that provide the cell with an interal structural framework
typical features of an animal cell
endoplasmic reticulum
typical features of an animal cell
involved in both protein and lipid synthesis
typical features of an animal cell
lysomes
typical features of an animal cell
contain enzymes that break down macromolecules such as proteins, nucleic acids, lipids, and carbohydrates
typical features of an animal cell
golgi apparatus
typical features of an animal cell
modifies and sorts proteins and lipids as they move to their final destinations in or out of the cell
typical features of an animal cell
peroxisomes
typical features of an animal cell
break down speciifc organic molecules, such as fatty acids, and synthesize other organic molecules, such as cholesterol and some types of phospholipids
typical features of an animal cell
cell wall
typical features of a plant cell
rigid barrier composed of polusaccharides
typical features of a plant cell
chloroplasts
typical features of a plant cell
enable plant cells to harness the enrgy of sunlight to synthesize sugars
typical features of a plant cell
plasmodesmata
typical features of a plant cell
connect neighboring plant cells
typical features of a plant cell
vacuoles
typical features of a plant cell
contribute to the structural rigidity of plants by absorbing water and contributing to turgor pressure
typical features of a plant cell
cytoplasm
the entire contents of a cell other than the nucleus
cytosol
jelly-like internal environment of the cell that surrounds the organelles inside the plasma membrane
nuclear envelope
encloses nuclear DNA and defines the nuclear compartment; separates nucleus and cytoplasm; formed from the inner and outer nuclear membrane (the outer membrane is continuous with the membrane of the ER)
inner nuclear membrane
contains some small proteins; acts as binding sites for chomosomes; provides anchorage for the nuclear lamina
nuclear lamina
finely woven meshwork of protein filaments that lines the inner face of the membrane and provides structural support for the nuclear envalope
nuclear pore
figure C
perforates the nuclear envalope in all eukaryotic cells; forms the gates through which molecules enter or leave the nucleus
figure C
nuclear localization signal (NLS)
the signal sequence that directs a protein from the cytosol into the nucleus; ususally consists of one or two short sequences containing several positively charged lysines or arginines
nuclear import receptors
cytosolic proteins which recognize NLS; help direct newly synthesized proteins to a nuclear pore by interacting with fibrils that extend from the rim of the nuclear pore into the cytosol
import/export of nuclear proteins
figure D
rewuires energy provided by the hydrolysis of GTP
figure D
thylakoid membrane
third membrane found in chloroplasts
nuclear pore complex
the only place where small polar molecules, ions, and macromolecules (proteins and RNAs) can travel between the nucleus and the cytoplasm
Ran-GTP (importins)
molecule which carries a molecule of GTP and binds to inportin → changing its conformation and forcing it to release its cargo protein into the nucleus → the importin-Ran complex is then re-exported out through the nuclear pore
Ran GAP (GTPase-activating protein)
stimulates ran to hydrolize its GTP to GDP → this causes Ran to release the importin back into the cytoplasm
NTF2
GDP-Ran protein receptor which binds to GDP-Ran and transports it back through the nuclear pore into the nucleus
Ran GEF (guanine nucleotide exchange factor)
stimulates Ran-GDP in the nucleus to release its GDP and pick up new GTP
nuclear export signals (NES)
proteins targeted for export from the nucleus by specific amino acid sequences
exportins
receptors within the nucleus who recognize NES and direct protein transport through the nuclear pore complex to the cytoplasm
Ran-GTP (exportins)
promotes the formation of stable complexes between exportins and their cargo proteins; does the opposite for importins that their cargo; once in the cytoplasm GTP hydrolysis and relese of Ran-GDP leads to dissociation of the cargo protein which is released into the cytoplasm
Ran-GDP (exportin)
recycles exportins through the nuclear pore complex to the nucleus for reuse
