Cell Bio Final

the binding of an extracellular chemical signal to a GPCR leads to _____ of a _____.

activation, heterotrimeric G-protein

IS GPCR’s multi-pass or single-pass proteins?

multi-pass

When a heterotrimeric G-protein binds GTP, what happens to its subuinits?

the alpha subunit dissociates for the beta gamma complex

How is the alpha and beta gamma subunits bound to the membrane?

via hydrophobic domains

The beta subunit of a heterotrimeric G-protein is directly connected to the cell membrane. True/False

False. they’re tethered to the cell membrane via hydrophobic domains

When acetylcholine binds to a GPCR on a heart cell membrane, ____ channels ____.

potassium, open

The heterotrimeric G-protein-gated potassium channel in the cell membrane of a heart pacemaker muscle cell are activated by the alpha subunit of a heterotrimeric G-protein in response to the binding of the acetylcholine to GPCR. True/False

False- the potassium channels are activated by the beta gamma complex of the heterotrimeric G-protein

Where can receptors accepting extracellular signals be ?

• embedded in the membrane

• located in the cytosol or nucleus

The two most common cell membrane-bound enzyme targets of heterotrimeric G-proteins are adenylyl cyclase and phospholipase C. True/false

True

AC and PLC are activated by the same type of heterotrimeric G-proteins. True/False

False- itd done by different types of heterotrimeric G-proteins

When active, adenylyl cyclase produces what?

cAMP

In GPCR-mediated signal transduction pathway that involves adenylyl cyclase (AC), when does the signal first begin to diffuse throughout the entire volume of the cytosol?

after the activation of AC

Phospholipase C is a cell membrane-bound enzyme. True/False

True

PLC cleaves ___ into ___ and ___.

PIP₂, IP₃, DAG

When your blood glucose is low, what is released by the pancreas?

glucagon

What does the glucagon bind to on the liver? What is the process that follows?

GPCR

• it activates the heterotrimeric G-protein

• ot then actives AC, which converts ATP to cAMP

  • cAMP then activates PKA

What is the function of PKA?

• turns off the synthesis of glycogen from glucose

• break down glycogen into glucose

• upregulates genes in glucose production

The binding of extracellular chemical signal to one or both RTK monomers result in ____ of the exracellular domains.

dimerization

Regardless of the type of RTK, each RTK monomer binds one extracellular chemical signal. True/False

False- they each have their own kind of chemical signal

The activation loop blocks what?

the ATP binding site

During trans-autophosphorylation, each monomer phosphorylates itself. True/False

False- they phosphorylate each other

What does dimerization do?

bring both kinase domains together

once RTK dimer is fully active and phosphorylated, the signal transduction pathway diverge into two. True/false

true

SH2 and PTB domain- containing proteins bind to phosphorylated ___ residues within the ___ of activated RTKs.

tyrosine, C-terminal tail

What is the function of adaptor proteins?

to connect RTKs to other proteins

What is the function of Docking Proteins?

to expand the number of proteins that can be recruited

In epidermal growth factor-mediated signal transduction, the phosphorylated RTK C-terminal tails directly recruit what?

Grb2

MAPKK phosphorylates what?

MAPK

What i the major calcium binding protein in virtually all eukaryotic cells?

CaM

It is common for the signal transduction events of a GPCR-mediated pathway to interact with events of an RTK-mediated pathway. True/False

True

During DNA replication, both ssDNA strands are replicated at the same time. True/False

True

DNA replication occurs in a ____ manner.

semi-conservative

DNA replication begins at what?

origins of replication (ORI)

During DNA replication initiation, the dsDNA is easily pulled apart because it is rich in _____ base pairs.

A-T

prokaryotic chromosomes possess _____ ORI (s)

one

DNA replication is mechanistically more complex in eukaryotes than in prokaryotes. True/False

True

During DNA replication, DNA helicase uses the energy released from ATP hydrolysis to unwind dsDNA into ssDNA. True/False

True

The leading strand runs through the central helicase channel. True/False

False

The clamp protein clamps DNA polymerase III onto the ssDNA template. True/False

True

How many clamp DNA polymerase III complexes are present at each replication fork?

2

During DNA replication, the 3’ phosphate group of the incoming nucleotide is joined to the 5"‘ hydroxyl group of the previous nucleotide. True/False

False- its backwards.

The proofreading capability of DNA polymerase III is only possible because the energy required for polymerization comes from the incoming nucleotides. True/False

True

DNA polymerization on the leading strand is what?

continuous

DNA polymerization on the lagging strand is what?

discontinuous

DNA replication is considered to be what?

semi-discontinuous

RNA nucleotides are released with DNA nucleotides by what?

DNA polymerase I

Ligase forms a covalent bond between one ___ nucleotide and one ___ nucleotide.

DNA; DNA

Telomerase polymerizes ___ nucleotides using a ___ template.

DNA; RNA

In cells that divide a lot, telomerase is fully active. True/False

True

DNA damage occurs regularly in cells. True/False

True

What can lead to exogenous DNA damage?

UV radiation

Because of base pair complementarity, if one DNA strand is damaged, the other strand can serve as a template for the repair. True/False

True

The first step in DNA repair involves the enzyme ligase. True/False

False

errors resulting in DNA replication are called what?

mismatches

99% of mismatches’ are repaired by DNA polymerases. True/False

False- done by mismatch repair proteins

dsDNA breaks can rely on base pair complementarity for fixing. True/False

False

non-homologous end joining can be considered a quick and messy way to fix dsDNA breaks.

true

Cell division occues during which phase?

M phase

What is not apart of interphase?

cytokinesis

If cells did not double their size and contents before dividing, they would become smaller and smaller with each round of division.True/False

True

Cells spend vast majority of their time in M phase. Tru/False

False- its interphase

In both animal and plant cells, cytokinesis occurs via a contractile ring. True/False

False- contractile ring for plants and cell wall is produced between the two daughter cells for animal cells

During prophase, the chromosomes are tightly condensed, in part, because of proteins called cohesions. True/ False.

False- its done by condensins

Sister chromatids are held together by proteins called condensins. True/False

False- cohesions do

Which of the following events does not occur during the prophase?

DNA replication

Spindle fibers from opposite poles can interact with each other through what?

kinesin

The beginning of prometaphase is marked by what?

the breakdown of the nuclear envelope

a kinetochore is formed by the recruitment of many different scaffolding proteins to the centromere. True/False

True

What describes the situation when the kinetochore of one sister chromatid is attached to a spindle fiber from one pole and the kinetochore of the other sister chromatid is attached to a spindle fiber from the opposite pole?

bi-orientation

Checkpoint proteins within the kinetochore are carried away by what?

dynein

When will sister chromatids be separated?

when securin is degraded

kinetochore microtubules are interpolar microtubules work together to segregate the sister chromatids. True/False

True

cytokinesis only begins after telophase is complete. True/False

False- it begins before it is complete

In animal cells, the parent cells is split into two daughter cells by interactions of what?

actin and myosin filaments

Only once all of the checkpoint conditions have been met can a cell transition to the next cell cycle phase. True/False

True

Cells that pass through a checkpoint can sometimes revert back to the previous phase, but only if the conditions are right to do so. True/False

False- they have to always move in the forward direction.

At which checkpoint is it most important for the extracellular environment to be favorable and for the cell to have enough nutrients and resources?

restriction point

Which of the following is NOT a condition required to pass through the G₂/M checkpoint?

A. the completion of DNA replication

B. the absence of any DNA damage

C. the availability of nutrients

D. the completion of centrosome duplication

the availability of nutrients.

Once a cell enters G₀ it can never return to the cell cycle. True/False

False

Cells in G₀ are usually not very active.True/ False

False

Which of the following proteins undergoes cycles of high and low intracellular concentrations throughout the cell cycle?

A. M-CDK

B. serine/threonine kinases

C. cyclins

D. CDKs

c. Cyclins

CDK activity is dependent on cyclin binding. False/True

True

Which of the following is NOT a factor in the activation of CDKs?

A. cyclin binding

B. the phosphorylation status of CDK

C. CDK concentration

D. the binding of a CDK inhibitor

C. CDK concentration

Full CDK activation requires the displacement of the activation loop.False/True

True