Mol Bio Ch 11 Flashcards

Flashcards from Mol Bio Ch 11 Study Guide

In the yeast signal transduction pathway, what occurs after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells?

Binding induces changes in the cells that lead to cell fusion.

Which of the following is true of the mating signal transduction pathway in yeast?

Mating type a secretes a signal called a factor.

What could happen to the target cells in an animal that lacks receptors for local regulators?

They would not be able to multiply in response to growth factors from nearby cells.

What is the primary feature of paracrine signaling?

Paracrine signaling involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.

From the perspective of the cell receiving the message, what are the three stages of cell signaling?

signal reception, signal transduction, and cellular response.

When does the process of transduction usually begin?

when the signal molecule changes the receptor protein in some way.

When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity respond, what type of signaling is this?

paracrine signaling.

Synaptic signaling between adjacent neurons is like hormone signaling in which of the following ways?

It requires binding of a signaling molecule to a receptor.

What is a small molecule that specifically binds to another molecule, usually a larger one, called?

is called a ligand.

Which of the following is (are) true of ligand-gated ion channels?

A, B, and C are true.

A receptor protein in a membrane that recognizes a chemical signal is most similar to which of the following?

the active site of an allosteric enzyme in the cytoplasm that binds to a specific substrate.

What would be true for the signaling system in an animal cell that lacks the ability to produce GTP?

Only A and C are true.

What is thought about G proteins and G-protein-linked receptors in terms of evolution?

thought to have evolved very early, because of their similar structure and function in a wide variety of modern organisms.

Membrane receptors that attach phosphates to specific animo acids in proteins are…

called receptor tyrosine-kinases.

Up to 60% of all medicines used today exert their effects by influencing what structures in the cell membrane?

G proteins

Which of the following are chemical messengers that pass through the plasma membrane of cells and have receptor molecules in the cytoplasm?

testosterone

How does testosterone function inside a cell?

binding with a receptor protein that enters the nucleus and activates specific genes.

Which is true of transcription factors?

They control which genes are expressed.

Chemical signal pathways…

often involve the binding of signal molecules to a protein on the surface of a target cell.

Where would you expect to find the carboxyl end of a G protein-linked receptor containing seven transmembrane alpha helices?

at the cytosol surface

The coupled G protein most likely interacts with this receptor…

at the loop between H5 and H6

In affinity chromatography, what do you expect will occur when an excess of the ligand (hormone) is poured through the column after the receptor binding step?

The ligand will cause the receptor to be displaced from the beads and eluted out.

This method of affinity chromatography would be expected to collect which of the following?

molecules of purified receptor

One of the major categories of receptors in the plasma membrane reacts by forming dimmers, adding phosphate groups, then activating relay proteins. Which type does this?

receptor tyrosine kinases

The receptors for a group of signaling molecules known as growth factors are often…

receptor tyrosine kinases.

In general, a signal transmitted via phosphorylation of a series of proteins…

brings a conformational change to each protein.

Sutherland discovered that epinephrine…

elevates the cytosolic concentration of cyclic AMP.

Which of the following is the best explanation for the inability of an animal cell to reduce the concentration in its cytosol compared with the extracellular fluid?

insufficient ATP levels in the cytoplasm

The general name for an enzyme that transfers phosphate groups from ATP to a protein is…

protein kinase.

Which of the following describes cell communication systems?

In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of RNA.

The toxin of Vibrio cholerae causes profuse diarrhea because it…

modifies a G protein involved in regulating salt and water secretion.

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

receptor tyrosine kinase activity

Which of the following most likely would be an immediate result of growth factor binding to its receptor?

protein kinase activity

An inhibitor of phosphodiesterase activity would have which of the following effects?

prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm

Adenylyl cyclase has the opposite effect of which of the following?

phosphodiesterase

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of…

cAMP.

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to…

design a compound that inhibits phosphorylase activity.

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to…

design a compound that increases phosphodiesterase activity.

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

phospholipase C

Which of the following statements is true?

Protein kinase A activation is one possible result of signal molecules binding to G protein-linked receptors.

Which of the following is a correct association?

GTPase activity and hydrolysis of GTP to GDP

One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. cGMP is inhibited, therefore the signal is prolonged. The original signal that is now inhibited would have…

hydrolyzed cGMP to GMP.

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?

a decrease in transcriptional activity of certain genes

Which of the substances below is a protein that can hold several other relay proteins as it binds to an activated membrane receptor?

scaffolding protein

The description above illustrates which of the following? As humans, we have receptors for two kinds of beta adrenergic compounds such as catecholamines. Cardiac muscle cells have beta 1 receptors that promote increased heart rate. Some drugs that slow heart rate are called beta blockers. Smooth muscle cells, however, have beta 2 receptors which mediate muscle relaxation. Blockers of these effects are sometimes used to treat asthma.

Just because a drug acts on one type of receptor does not mean that it will act on another type.

The use of beta 2 antagonist drugs may be useful in asthma because…

they may dilate the bronchioles by relaxing their smooth muscle.

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.

What are scaffolding proteins?

large molecules to which several relay proteins attach to facilitate cascade effects

The termination phase of cell signaling requires which of the following?

reversing the binding of signal molecule to the receptor

Why has C. elegans proven to be a useful model for understanding apoptosis?

The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.

Which of the following describes the events of apoptosis?

Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.

The main proteases involved in apoptosis are…

caspases.

Fill in the blank: can activate human caspases that lead to apoptosis.

Human caspases can be activated by irreparable DNA damage or protein misfolding.

If an adult person has a faulty version of the human-analog to ced-4 of the nematode, which of the following might more likely result?

a form of cancer in which there is insufficient apoptosis

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because…

they amplify the original signal manyfold.

Binding of a signaling molecule to which type of receptor leads directly to a change in distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

The activation of receptor tyrosine kinases is characterized by…

dimerization and phosphorylation.

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Glycogen breakdown was observed only when epinephrine was administered to intact cells.

Protein phosphorylation is commonly involved with all of the following except…

activation of G protein-coupled receptors.

Lipid-soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because…

intracellular receptors are present only in target cells.

Consider this pathway: epinephrine ® G protein-coupled receptor ® G protein ® adenylyl cyclase ® cAMP. Identify the second messenger.

cAMP

Apoptosis involves all but the following:

lysis of the cell