Bio344-Exam#3 (Q's & A's) Flashcards
What does the protein cohesin do?
It keeps identical chromosomes attached to each other
What are the components of a proteoglycan?
protein, a tetrasacharide linker and glycosaminoglycans
Which cyclin becomes abundant in a cell when the cell moves from the G2 phase into mitosis?
M cyclin
Which factor below would directly impact filament growth rates?
subunit concentration
What does the protein Myc do?
It is a DNA binding protein that increases transcription of the cyclin D gene which codes for the G1 cyclin.
How does Ca2+ cause muscle contraction?
it binds troponin which shifts tropomyosin on the actin filaments
What happens to microtubules when they lose their GTP cap?
they will likely shrink
What is a function of the basal lamina?
filters toxins from blood in the formation of urine
What is a function of hemidesmosomes?
anchor cells to the extracellular matrix
What would happen in a cell if p27 proteins are degraded?
A p27 protein can bind to a cyclin Cdk complex thus in the absence of p27 many CdK would remain active.
What is the structure of collagen?
Three alpha-helices wrapped around each other
What does the E2F protein do?
It is a DNA binding protein that initiates S-phase gene transcription
What extracellular signal causes a cell to divide?
mitogens
What kind of proteins are gap junctions made out of?
connexins
What happens if the DNA of a dividing cell is damaged?
The enzyme p53 is activated
What could activate the enzyme p53?
DNA damage
What enzyme is responsible for moving a cell between the different phases of the cell cycle?
cyclin dependent kinase
What protein is present in desmosomes?
cadherin
What protein reduces M-CdK levels during the M phase?
APC
How can an active cyclin dependent kinase complex be inactivated?
through inhibitory phosphorylation
Why does proteolysis of the extracellular matrix impact the severity of cancer?
degradation of the extracellular matrix allows cancerous cells to spread through the body
What is a function of tight junctions?
prevent movement of small molecules between cells
The cytoskeleton in animal cells…
is dynamic and changes all the time
Which cells excrete large amounts of extracellular components?
fibroblasts
Where in most cells would you expect to find actin bundles?
right below the plasma membrane
Which protein below, if hyperactive, could lead to cancer?
Myc
What are the three parts of the myosin protein?
motor head, hinge region and tail
What protein is present in the nucleation complex of microtubules?
gamma-tubulin
What filament is mostly responsible for mechanical strength?
intermediate filaments
What is the motif present in the amino acid chains that make up collagen?
glycine amino acid X amino acid Y
What do survival factors do?
they inhibit apoptosis
Which of the following is true of gap junctions?
they may be opened or closed
How does a high level of Ca2+ effect cell to cell binding?
it causes the cadherins to become rigid and promotes homolytic binding between cells
How do your muscles move?
myofibrils are contracted when myosin pulls on actin filaments
which protein is common in the extracellular matrix?
collagen
In which phase does cytokinesis occur?
the M phase
Which group of proteins are motor proteins that interact with actin filaments?
myosin
What enzymes initiate the apoptosis cascade?
caspases
What type of polysaccharide is present in the extracellular matrix?
glycosaminoglycans
What are the 4 phases in the cell division cycle?
G1, S, G2, and M
What is apoptosis?
programmed cell death
What protein below binds to the basal lamina?
integrin
What does gelsolin do?
it breaks actin filaments
What filament is involved with movement of vesicles around the cell?
microtubules
What do actin subunits need to bind to be incorporated into a filament?
ATP
What happens to actin filaments immediately after a blood platelet is activated?
Actin filaments are first severed producing many actin filament fragments
Which of the following often occurs during apoptosis?
cytochrome C is released from the mitochondria.
Where is the microtubule organizing center in the cell?
centrosome
Which of the following proteins could decrease the rate of filament growth inside a cell?
stathmin
What does the Rb protein do?
It functions as a brake of the cell cycle by binding the E2F protein.
