BIOS 1610 EXAM 3, homework assignment quizzes

Nicotine from cigarette smoke acts as a ligand and associates with the acetylcholine receptor on specific cells in the nervous system. Nicotine eventually produces feelings of pleasure and well-being. The listed statements are descriptions of the events that happen in the cellular response to nicotine. Place the events in the correct order to describe the steps in the signaling pathway. A) The acetylcholine receptor is an ion channel, and when a ligand binds, the ion channel opens. B) An influx of ions carries the signal to the reward areas of the brain. C) Nicotine binds to the transmembrane protein that normally binds the neurotransmitter acetylcholine. D) The signal causes release of dopamine in the brain, which causes good feelings. E) Nicotine is quickly eliminated from the body (causing cravings for more cigarettes to produce good feelings).

C; A; B; D; E

what is a key difference between cell signaling by a cell-surface receptor and cell signaling by an intracellular receptor?

Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules.

which of the answer choices is responsible for amplifying the signal in a cell responding to adrenaline? Select all that apply.

One molecule of adenylyl cyclase can activate many molecules of protein kinase A (PKA). One molecule of protein kinase A (PKA) can phosphorylate and activate many target proteins.One activated receptor can activate many G proteins.

Mutations in the Pax6 gene cause developmental defects in the eyes of flies, mice, and humans. This suggests that:

Pax6 may be a master regulator of eye development.Pax6 activates multiple genes.Pax6 has been evolutionarily conserved.

Of the answer choices, what is the most likely reason that paracrine signaling does not activate the cell that is producing the signaling molecule?

The cell does not have the proper receptor.

How does the extracellular matrix affect a cell that it surrounds? Select all that apply.

The cell's shape depends in part on the structure and composition of the extracellular matrix.The genes that the cell expresses depend in part on the types of proteins in the extracellular matrix.

What is the consequence of inactivating the Notch receptor in the type 2 progenitor cell in C. elegans?

The progenitor cell will not complete its differentiation into a type 2 cell.

You strip off all proteins on the cell surface by using a protease (an enzyme that destroys proteins). Now, when you add a specific signaling molecule, the cell still responds. What is the most reasonable explanation of this?

The receptor for this signal is inside the cell, and the signaling molecule is nonpolar and can diffuse into the cell.

How would signaling be affected if a mutation caused a G protein to replace GDP with GTP on its own without needing to be activated by the G protein-coupled receptor?

The signaling pathway would be activated even when no ligand was present.

Suppose there is a mutation in a laminin-binding integrin gene that causes a loss of function in the cytoplasmic domains of the integrin. Which one of the outcomes would you expect to observe as a result of this mutation?

The strength of tissues would decrease because the integrin could no longer associate with microfilaments.

A patient in a physician's office has a deep cut, and as it is being stitched up, a sample of tissue is taken for testing. Analysis of the tissue reveals it has few cells, surrounded by a large amount of extracellular matrix proteins with some blood vessels, sweat glands, and nerve cells. What kind of tissue is this?

The tissue is most likely dermis, and should also have some fibroblasts, but few keratinocytes and melanocytes.

Vascular endothelial growth factor (abbreviated VEGF and pronounced "Veg-F") is a peptide signaling molecule related to platelet-derived growth factor. VEGF is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. Tumors also produce and secrete VEGF, causing nearby blood vessels to branch and grow to form new blood vessels that supply these tumors. Given what you know about the different kinds of cell signaling and VEGF, which statement is true?

VEGF is a paracrine signaling molecule because it binds to receptors on nearby cells, at the site where new blood vessels are needed.

What would you expect to happen if you added activity B to whorl 1 in an Arabidopsis floral meristem? Refer to the figure shown:

You would get a flower with extra petals but no sepals.

Epidermolysis bullosa is a set of rare genetic disorders that is caused by:

a keratin gene that disrupts intermediate filaments, weakening connections between epidermal cell layers.

A number of mutations have been described in the G protein Ras that have profound effects on its activity. For example, some mutations greatly increase the affinity of the G protein for GDP, making it very difficult for GDP to be exchanged for GTP. Other mutations prevent the GTPase activity of Ras, preventing it from causing the hydrolysis of GTP to GDP:

a mutation that blocks the GTPase activity of Ras

Which one of the choices matches a type of cell junction with its proper cytoskeletal element and cell adhesion molecule?

adherens junction, microfilament, cadherin

A decrease in cell-cell adhesion was caused by the introduction of an experimental substance that compromised the structural integrity of the tissue. Which type of cell junction would most likely be affected by this treatment given that the treatment caused a decrease in the strength of cell-cell adhesion?

adherens junctions

If one isolated cells at random from an organism at different times in its development and measured developmental potential as the average number of distinct cell types that the cells could differentiate into, which of the curves shown here would most likely result?

curve K

Kohler and Lipton first discovered platelet-derived growth factor (PDGF) by observing that fibroblasts:

grew better in cell culture containing blood serum containing proteins released by platelets during clotting.

Shown are four ligands (M, H, K, and L) and their corresponding receptors along with four genes (S, T, U, and V), whose activity the receptor controls through signal transduction. The arrows indicate gene activation, the T-bars indicate gene repression.

ligand L

Epithelial tissue is found:

lining the lungs.on the outer surface of the body.lining blood vessels.lining the gastrointestinal tract.

Which of the choices enable(s) the movement of cells?

microtubules and microfilaments

Which of the choices correctly lists the sequence in which the plant cell wall is synthesized?

middle lamella → primary cell wall → secondary cell wall

In John Gurdon's nuclear-transfer experiments, he used nuclei from tadpole intestinal cells. Do you think he would have had more success or less success if he had taken cells from a blastula? From an adult frog?

more; less

A cis-regulatory element may _____ transcription:

not affect, activate, repress

Evidence that cytoskeletal elements have ancient origins comes from the:

presence of cytoskeletal elements in both eukaryotes and prokaryotes.sequence similarities of cytoskeletal elements when comparing distantly related organisms.observation that both prokaryotes and eukaryotes use cytoskeletal elements to assist cell division.ability to form functional hybrid microfilaments from actin monomers taken from distantly related organisms.

phosphate groups play a key role in receptor kinase activation by:

providing binding sites to recruit and activate signal-transduction proteins.

In the ABC model of floral development, flower development in Arabidopsis is regulated by _____ activities controlled by _____ genes:

three; four

The mRNA for caudal and hunchback are distributed evenly throughout the Drosophila embryo, yet the Caudal protein is found only in the posterior portion of the embryo, and the Hunchback protein is present in greater amounts anteriorly. This distribution is due to:

translational regulation of the hunchback and caudal mRNAs in the zygote.