PCB 3023 - Exam 4

Which of the following types of cell signaling is long range and uses hormones as signals?

endocrine

What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute?

one that involves a change in gene expression

The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is

binding of the signal molecule to a receptor

Which of the following describes negative feedback regulation?

A component late in the pathway inhibits an enzyme early in the pathway

Enzymes that add a phosphate group to switch protein are called

kinase

One of the two types of GTP-binding proteins, often called G-proteins, are membrane bound. These are the

trimeric GTP-binding proteins

The active form of a monomeric GTP-binding protein is the

GTP-bound form

Which type of cell-surface receptor(s), when activated, caralyze(s) a reaction inside the cell?

enzyme-coupled receptors

When activated, a G-protein has a structure that

is bound to GTP

Which of the following would produce the fastest response to G-protein activation?

ion channel activation

Which of the following correctly matches. a G-protein-activated enzyme with the second messenger molecule it produces?

phospholipase C --> diacylglycerol

Which cAMP-mediated signaling pathway would take on the order of minutes to hours for a response to develop (as opposed to seconds)?

a response where cAMO leads to the activation of transcriptional regulator

Calcium ion release triggers all of the following biological processes EXCEPT

action potential transmission along an axon

Which of the following depicts the correct order of steps involved in nitric oxide (NO) signaling to trigger smooth muscle relaxation?

acetylcholine receptor activation --> activation of NO synthetase --> NO diffusion into neighboring cells --> activation of guanylyl cyclase --> cGMP production

How does the binding of a signal molecule activate an RTK for downstream signaling?

the RTK forms a dimer and cross-phosphorylates itself

Which of the following is NOT an intracellular signaling protein activated by an RTK?

G-protein

If Ras contains a mutation that leads to a defect in GTP hydrolysis, this could fuel uncontrolled proliferation in cancer because

Ras is able to signal to downstream pathways inappropriately

Steroid hormones trigger transcription of target genes by

binding to nuclear receptors that act as transcription factors for specific genes

Which signal(s) would lead to activation of both kinase 1 and kinase 2?

signals A and D

Which is the toughest and most durable of the different types of cytoskeletal filaments?

intermediate filaments

Intermediate filaments are found in what structure?

nuclear lamina

Which term best describes the structure of intermediate filament monomers?

ropelike

Which of the following types of intermediate filaments are found in all animal cells?

nuclear lamins

GTP hydrolysis and whether GTP or GDP is bound to tubulin is an important mechanism to control the dynamic instability of microtubules. Certain aspects of dynamic instability can be viewed using GFP-EB1. Which process(es) is it useful for visualizing and why?

How would the animation of microtubule dynamics change after adding a non-hydrolyzable analog of GTP to the cells expressing GFP tubulin?

growing microtubules, because EB1 binds to the GTP-tubulin cap on microtubules

Microtubules would grow longer.

Which of the following cytoskeletal structures are the most common for providing tracks for guiding intracellular transport?

microtubules

What do microtubules resemble?

hollow tubes

Dynamic instability in microtubules stems from the intrinsic capacity of tubulin molecules to hydrolyze what?

GTP

Which of the following describes the structure of an actin filament?

It is a twisted chain of actin molecules.

What is the name of the thin, sheetlike structures that a fibroblast regularly extends during cell crawling?

lamellipodia

Which actin-binding proteins would be most involved in the assembly of the contractile ring?

formins

An actin filament undergoing treadmilling at the leading edge of a lamellipodium can do what?

remain the same size

Which of the following correctly matches the phrase of the eukaryotic cell cycle with an event that takes place in that phase?

M phase - cytokinesis

Which is NOT a transition point where the cell cycle control system regulates progression through the cell cycle?

S/G2 transition

The expression levels of different _________________ fluctuate throughout the cell cycle.

cyclins

What accounts for the difference in the curve shapes depicting concentration of M-cyclin versus M-Cdk activity during the cell cycle?

the M-Cdk complex is not activated until M-cyclin is bound and M-Cdk is dephosphorylated

At the end of M phase, cells shut down Cdk activity through which of the following mechanisms?

deployment of Cdk inhibitors

Rb is an important protein for controlling cell proliferation by blocking entry into S phase. How does it exert its effect?

in its unphosphorylated state, Rb is active and blacks transcriptional regulators

In response to DNA damage, the ____________ protein is phosphorylated and activates the transcription of a Cdk inhibitor to halt cell cycle progression.

p53

How does S-Cdk prevent re-replication?

phosphorylation of ORC and Cdc6

M-Cdk is suddenly activated at the end of G2 by

dephosphorylation by Cdc25

What is the function of condensins?

to coil sister chromatids into a compact form

The contractile ring is composed of

actin and myosin

What is the difference between a malignant tumor and a metastasis?

A metastasis is a tumor in different distant tissue

An oncogene is different from a tumor suppressor gene in that

mutation of the gene can contribute to cancer

Cancer cells often lack normal DNA damage response and cell-cycle control mechanisms. Why does this make them more susceptible to DNA-damaging chemotherapies?

cancer cells might ignore the normal mechanisms that halt the cell cycle in response to damage, and subsequent division with damage leads to death

Some cancer cells are missing a key protein needed to repair double-strand DNA breaks. They survive by relying on alternative DNA repair mechanisms. To treat these cancers, researchers have developed drugs that do which of the following?

inhibit alternative DNA mechanisms