Given the signaling pathway below, which of the following mutant proteins would NOT be rescued by constitutively active Ras?
Active RTK → protein W → protein X → Ras → Protein Y → Protein Z → cell signal
Group of answer choices
An inactive mutant protein Y
An inactive mutant protein X
An inactive mutant protein W
An RTK that cannot bind ligand

In which of the following types of cell signaling does the signal molecule travel the largest distance?
Group of answer choices
Contact-dependent signaling
Endocrine signaling
Neuronal signaling
Paracrine signaling

Intermediate filaments are made from elongated fibrous proteins that are assembled into a ropelike structure. You are interested in how intermediate filaments are formed, and you create a keratin subunit whose α-helical region is of normal length, but the globular heads at the N-terminus and C-terminus of the subunit are changed to those found in a neurofilament subunit. If you were to assemble intermediate filaments using this hybrid subunit, which of the following predictions describes the most likely outcome?
Group of answer choices
The filaments assembled will form dimers that are twice as long as dimers assembled from normal keratin filaments.
Dimers of the hybrid subunit will form by interactions of the N-terminal globular heads with the C-terminal globular tails.
Sixteen tetramers assembled from the hybrid subunits will be needed for a ropelike structure to form.
The filaments assembled will interact with different cytoskeletal components than keratin does.

Each type of extracellular signal molecule induces a similar response in different target cells.
Group of answer choices
False
True

Which of the following statements is most likely to be true?
Group of answer choices
Cells carrying a Cdc42 mutation that makes Cdc42 act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells.
Cells carrying a Cdc42 mutation that makes Cdc42 unable to exchange GDP for GTP will polymerize more branched actin filaments than normal cells.
Cells carrying a Cdc42 mutation that makes Cdc42 act as if it is always bound to GTP will polymerize more unbranched actin filaments than normal cells.
Cells carrying a Cdc42 mutation that makes Cdc42 unable to exchange GDP for GTP will polymerize more unbranched actin filaments than normal cells.

Intermediate filaments help protect animal cells from mechanical stress because ____________.
Group of answer choices
filaments remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components.
filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells.
filaments make up the desmosome junctions that connect cells; these junctions are more important than the internal network of filaments for protecting cells against mechanical stress.
filaments directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next, helping to distribute locally applied forces.

A target cell will respond slowly to an extracellular signal if:
Group of answer choices
the signal molecule binds to a transmembrane receptor.
the response depends on G proteins.
the response depends on phosphorylation.
the response depends on second messengers.
the response requires changes in gene expression.

Myosin-I has a globular head which binds __________ and a single tail that binds __________. Myosin-I hydrolyzes __________ to move toward the __________ end of an actin filament.
Group of answer choices
an actin filament; cargo; GTP; plus
cargo; an actin filament; ATP; minus
an actin filament; cargo; ATP; plus
cargo; an actin filament; GTP; minus

All hormones signal by interacting with a transmembrane receptor.
Group of answer choices
True
False

Intermediate filaments are found in what structure?
Group of answer choices
Nuclear lamina
The mitotic spindle
Centrosomes
Cilia

Cell crawling depends on:
Group of answer choices
intermediate filaments.
hydrolysis of ADP by motor proteins.
microtubule assembly.
actin polymerization.

Which of the following events normally activates a GTP-binding protein?
Group of answer choices
Activation of a GTPase-activating protein (GAP)
Pi release after GTP hydrolysis
Activation of a guanine nucleotide exchange factor (GEF)
Phosphorylation of a bound GDP molecule by an upstream kinase
GTP hydrolysis by the protein

Which of the following statements about the structure of microtubules is NOT true?
Group of answer choices
Within a microtubule, each protofilament is in the opposite orientation to the protofilament on either side of it, giving the microtubule structural polarity.
The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end.
Microtubules are built from thirteen protofilaments that come together to make a hollow structure.
α-Tubulin and β-tubulin are non-covalently bound to make the tubulin dimer that then assembles into protofilaments.

In general, a signal transmitted via phosphorylation of a series of proteins:
Group of answer choices
brings a conformational change to each protein.
requires GTPase activity.
allows target cells to change their shape and therefore their activity.
requires binding of a hormone to a cytosolic receptor.

Which of the following statements is true?
Group of answer choices
Each extracellular signal molecule interacts with a single class of cell-surface receptor.
G-protein–coupled receptors are GTP-binding proteins.
Ion-channel-coupled receptors can rapidly alter the membrane potential in response to ion binding.
Not all enzyme-coupled receptors have an intrinsic catalytic domain on the cytosolic side of the plasma membrane.

In response to binding extracellular signaling molecules,
ion-channel-coupled receptors open and cause a change in the permeability of the plasma membrane to selected ions.
Group of answer choices
False
True

In eukaryotic cells, the cell cortex is made of a network of:
Group of answer choices
keratin.
lamins.
intermediate filaments.
actin filaments.
microtubules.

Activated trimeric G-proteins:
Group of answer choices
phosphorylate tyrosine amino acids on specific target proteins.
activate other proteins that produce secondary messenger molecules.
must continuously hydrolyze GTP to GDP to remain active.
are released into the cytoplasm to activate gene regulatory proteins.

Which of the following statements about the function of the centrosome is NOT true?
Group of answer choices
Basal bodies are the major microtubule-organizing centers in cilia and flagella.
Microtubules emanating from the centrosome exhibit a polarity such that all of them have their plus ends attached to the centrosome.
Centrosomes contain γ-tubulin ring complexes important for microtubule nucleation.
Centrosomes typically contain a pair of centrioles, each made up of a cylindrical array of short microtubules.

What is the correct order of steps in a common G-Protein coupled receptor (GPCR) signal transduction? The answer does not include all steps.
I. Formation of ligand-receptor complex
II. Release of neurotransmitter into synapse
III. Alpha subunit regulates target protein
IV. G protein acquires GTP
V. Dissociation of G protein subunits
VI. Cross-phosphorylation of G proteins
VII. Hormone binds to GPCR
Group of answer choices
I, IV, V, III
II, I, IV, VI, III
I, IV, III, V
VII, I, IV, VI, III

Given the signaling pathway below, which of the following mutant pr...