Cell Bio Exam 3

Which of the following conditions is likely to decrease the likelihood of skeletal muscle contraction?

Addition of a drug that blocks Ca2+ binding to troponin.

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport?

Glucose transporter uniport

Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed below. Which of the following statements is FALSE?

In the absence of a survival signal, Bad is phosphorylated.

How does S-Cdk help guarantee that replication occurs only once during each cell cycle?

It phosphorylates the Cdc6 protein, marking it for destruction.

Which family of GTPases control the organization of the actin cytoskeleton?

Rho

When does DNA replication occur?

S phase

The following happens when a G-protein-coupled receptor activates a G protein.

The α subunit exchanges its bound GDP for GTP.

K+ leak channels are found in the plasma membrane. These channels open and close in a random fashion. What do they accomplish in a resting cell?

They keep the resting membrane potential at slightly below zero.

The figure below shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active (always ON) Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line?

addition of a drug that blocks protein Y from interacting with its target

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?

an aquaporin

Apoptosis differs from necrosis in that necrosis _____.

causes cells to swell and burst, whereas apoptotic cells shrink and condense.

You observe cells under a microscope undergoing mitosis. The sister chromatids have condsensed, but they are not paired up. The cell is in Prometaphase. This is likely due to a defect in which protein?

cohesion

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling.

contact dependent

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ______?

hormone

Where does most new membrane synthesis take place in a eukaryotic cell?

in the endoplasmic reticulum

A protein kinase can act as an integrating device in signaling if it

is activated by two or more proteins in different signaling pathways.

Irradiated mammalian cells usually stop dividing and arrest at a G1 DNA damage checkpoint. Which of the following would occur first?

p53 phosphorylated

Which of the following structures shorten during muscle contraction?

sacromere

Transporters, in contrast to channels, work by ____________.

specific binding to solutes

Membrane lipids are capable of many different types of movement. Which of these rarely occurs spontaneously in biological membranes?

switching or flip flopping between lipid layers

During which stage of mitosis does the nuclear envelope reform?

telophase

DNA damage is present during the G1 stage of interphase. All of the following are possible outcomes EXCEPT.

the cell immediately enters S phase

Scramblase catalyzes the transfer of random phospholipids from one side of the membrane to the other.

true

Which of the following is required for the secretion of neurotransmitters in response to an action potential?

voltage gated Ca2+ channels

After an action potential, which channel opens to return the membrane potential back to resting?

voltage gated K+ channels

An action potential is triggered by depolarization of the plasma membrane. This causes ___________ to flicker open, rapidly furthering depolarization of the membrane.

voltage gated Na+ channels