Final review 2 Flashcards
Actin filament/microtubule structure
twisted two stranded 8-9nm diameter
Microtubule structure?
Hollow tubes 24nm diameter
Intermediate filament structure?
rope-like structure, 10nm diameter
What is G-actin?
globular, monomeric actin
What is F actin?
filamentous actin polymer
What is a thin flexible filament that is highly dynamic?
F - actin
What end is the ATP binding site?
Minus end
What are sequestering proteins responsible for?
Important to maintain a high concentration of monomeric actin in the cell
What are the three responsibilities of actin networks?
Shape cells, move cells, and divide cells
What are myosin motors?
Force-generating ATPases that walk along actin cables
What is a tubulin subunit made of?
a and b tubulin
What tubulin binds tightly to GTP and does not hydrolyze the nucleotide?
A tubulin
What tubulin hydrolysis and exchanges the bound nucleotide?
B tubulin
A tubulin is bound to what and what is B tubulin?
a tubulin is bound to GTP whereas b tubulin is GDP-bound
What direction does kinesis go in while transporting cargo on microtubule tracks?
to positive end
What microtubule tracks goes to negative end?
Dynein
What initiates transcription?
promoter (TATA box)
what is the role of the TATA box?
Recruits general transcription factors
What does the general transcription factor recruit?
RNA polymerase
What direction does transcription run?
5’ to 3’ of coding strand
What is polyadenylation?
(poly A tail) the process where Adenines added to the 3’ end of the mRNA
What are the three steps mRNA needs to go through before it is able to be transported out of the nucleus?
Capped, polyadenylated, spliced
What is the role of nuclear lamina?
Structural support (intermediate filament)
What are the most abundant and largest protein complexes in the cell?
Ribosome
What is the role of tRNA synthase?
links proper amino acid to the corresponding tRNA
What is the start codon?
ATG
What happens at each site of the ribosome?
A site - first binding site of aminoacyl-tRNA
P site - tRNA linked to the polypeptide
E site - Exit site for the tRNA
What is the chaperone Hsp 70 responsible for?
binds to hydrophobic regions and prevents aggregation of unfolded protein (gives the protein enough time to find the proper fold)
What is the chaperon Hsp60 responsible for?
forms a large cavity that separated the unfolded protein from the cytosol and thus prevents aggregation
What is the function of the ER?
Protein translocation, protein folding, protein glycosylation, protein quality control, calcium ion storage
Where are transmembrane proteins and soluble lumenal proteins translated?
At the ER
What terminus is luminal and which one is in the cytosol?
The N-terminus is lumenal, the C-terminus is in the cytosol
What occurs in the N-linked glycosylation?
modification of the amino group
What occurs during O-linked glycosylation?
modification of a OH group
What happens to most proteins that are translated and translocated at the ER?
Become glycosylated
What can glycosylation help with?
can increase stability of secreted proteins
Why is glycosylation of surface proteins important?
for recognition of self versus foreign (immune system)
In hydropathy, what does a positive number indicate?
hydrophobic
What are Rab proteins?
small GTPases that act as regulators/switches
Explain vesicle fusion with the golgi
the ER derived vesicles uncoat, tether with the Golgi, dock and fuse with the Golgi membrane
What does small GTPases require to hydrolyze GTP and exchange GDp with GTP?
Require GAPs and GEFs
What is the role of the golgi apparatus?
Protein sorting
What side of the golgi aparatus receives vesicles?
cis side
what side of the golgi forms transport vesicles that traffic to the endosome or the cell surface?
trans side
What occurs in constitutive secretion?
delivery of plasma membrane proteins
What is regulated secretion?
mainly used for secretion of regulatory proteins (insulin), fusion of vesicle with plasma membrane is regulated
What is phagocytosis?
engulfing of large particles and performed by macrophages
What is pinocytosis?
uptake of fluid-filled vesicles that are formed by clathrin
What is the lysosome/vacuoles?
Acidic compartment with a large number of enzymes that degrade macromolecules
What is a proteasome?
large protein complex that degrades poly-ubiquitinated proteins
What is autophagy induced by?
starvation
What is responsible for the degradation of soluble proteins in both the cytoplasm and the nucleus?
the proteasome
What is autophagy?
is a degradation pathway for organelles and other large structures
What does starvation cause?
the degradation of cytoplasmic proteins by autophagy which releases amino acids important to survive the starvation conditions
What occurs during M phase of the cell?
cell divides
What happens during G1 and S phase of the cell cylcle?
the cell grows in g1 and DNA replicate in S
What phase is interphase?
G1, S, G2
What is the cell cycle controlled by?
Cyclin-dependent kinases (CDKs)
What chemical reaction do CDks assist with?
Phosphorylation of proteins that are responsible for the cell cycle
Cyclins are ubiquinated and degraded by what?
proteasome
