Condensed Information Flashcards
prokaryotes
bacteria, archaeons, lack a nucleus
eukaryotes
store DNA in their nucleus
nucleoid
where DNA is concentrated in prokaryotes
plasmids
small molecules of DNA in prokaryotes
pili
threadlike structures which transfer plasmids between bacteria
location of mechanisms in eukaryotes
DNA is transcribed to RNA in the nucleus while translation occurs in the cytoplasm
plasmodesmata
channels (in plant cells) that allow for the passage of large molecules such as mRNA and proteins between neighboring cells
mitochondria
converts chemical energy to ATP
protein kinase
enzyme that phosphorylates another molecule (ADDS a phosphate group), activates a protein
phosphatease
enzyme that de-phosphorylates another molecule (REMOVES a phosphate group), de-activates a protein
phosphorylation
(1) protein kinase binds ATP and target protein (2) transfers a phosphate group to the target protein (3) releases phosphorylates protein and ADP
de-phosphorylation
(1) phosphatase removes a phosphate group from the target protein (2) releases de-phosphorylates protein
GTPase (GTP-binding proteins)
enzymes that bind to GTP and hydrolyze it to GDP, activated proteins are bound to GTP and inactivated proteins are bound to GDP
Ras protein
GTP bound: activates and stimulates protein phosphorylation
GAP (GTPase-activating protein)
inactivates Ras protein by hydrolyzing its bound GTP to GDP
GEF (guanine nucleotide exchange factor)
indirectly activates Ras protein by binding to GDP-Ras and causing it to release its GDP which then allows the empty Ras to pick up a new GTP molecule
GTPase switch cycle
(1) on its own GTPase slowly hydrolyzes GTP to GDP (2) GDP slowly dissociates from the GTPase (3) once GDP comes off the GTPase, GTP quickly takes its place
nuclear envelope
encloses nuclear DNA and separates the nucleus and the cytoplasm
inner nuclear membrane
contains proteins that act as the binding site for chromosomes and the nuclear lamina
nuclear lamina
finely woven meshwork of protein that provides the nuclear envelope with structural support
outer nuclear membrane
continuous with the ER
nuclear pore (complex)
gates on the nuclear envelope through which molecules can enter and exit the nucleus
NLS (nuclear localization signal)
signal sequence which marks a protein for transport from the cytosol into the nucleus
NIR (nuclear import receptors)
cytosolic proteins that recognize and transport proteins with a NLS
NES (nuclear export signals)
proteins targeted for export from the nucleus by specific amino acid sequences
exportin
receptors within the nucleus who recognize NES and direct protein transport into the cytoplasm
Ran cycle
(1) Ran-GTP binds to importin (2) moves through the nuclear pore to the nucleus (3) changes conformation and releases the cargo protein to the nucleus (3) importin-Ran is exported to the cytoplasm (4) importin-Ran is hydrolyzed by Ran-GAP to Ran-GDP (5) Ran-GDP releases the importin to the cytoplasm (6) Ran-GDP is bound to NTF2 and transported to the nucleus (7) Ran-GDP is stimulated by Ran-GEF to release its GDP (8) empty Ran picks up new GTP (9) Ran-GTP binds to exportin (10) moves through the nuclear pore to the cytoplasm (11) Ran-GTP is hydrolyzed to Ran-GDP (12) the cargo protein is released into the cytoplasm
nucleotides
DNA subunits made of a sugar, a base, and 1+ phosphate group
deoxyribose
the sugar in DNA
DNA complimentary bases
A (adenine) - T (thymine) form two H-bonds
G (guanine) - C (cytosine) form three H-bonds
phosphodiester bond
DNA bonds that form when a phosphate group is covalently joined to another sugar unit
DNA polarity
the top of a DNA strand has a 5’ phosphate group and the bottom has a 3’ hydroxyl group, because of this two strands run antiparallel to each other
replication
(1) parental DNA strands unwind (2) each individual strand serves as a template for the synthesis of a complementary daughter strand (3) the process completes with two molecules, each with one parent and one daughter strand
transcription
the synthesis of RNA from a DNA template molecule
translation
the synthesis of a polypeptide chain from a mRNA template
ribosomes
a complex structure of RNA and protein located in the cytoplasm
ribose
the sugar in RNA
RNA complimentary bases
A (adenine) - U (uracil) form two H-bonds
G (guanine) - C (cytosine) form three H-bonds
RNA polarity
the top of a RNA strand has a 3’ hydroxyl group and the bottom has a 5’ phosphate group, the RNA builds by adding to the 3’ top of the sequence
RNA polymerase
the enzyme that carries out the polymerization of the RNA transcript
stages of transcription
(1) initiation: RNA polymerase and other proteins are attracted to DNA
(2) elongation: successive nucleotides are added to the 3’ end as the RNA polymerase proceeds along the template strand
(3) termination: the RNA polymerase encounters a stop codon and releases the RNA transcript
transcription always starts at a promoter and ends at a terminator
sigma factor
a protein in bacteria which facilitates RNA polymerase binding to promoters