Cell signaling test

which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?

protein kincase

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 lack receptors for local regulators?

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

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

signal reception, signal transduction, and cellular response

The process of transduction usually begins

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

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

A, B, and C are true.

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

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?

It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

G proteins and G-protein-linked receptors

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

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

epinephrine

Testosterone functions inside a cell by

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

Chemical signal pathways

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

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

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.

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.

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

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

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.

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.

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

which of the following poses the best evidence that cell signaling pathways evolved early in the history of life

signal transduction molecules identified in distantly related organisms are similar

a protein receptor binds a hormone outside the cell membrane and activates a kincase inside the cell. Is the receptor a peripheral or integral membrane protein

integral

which of the following is not a typical event associated with cell signaling?

release of calcium ions from cell membranes

a cell secretes the following growth factors that have a slow diffusion rate and interacting only with other cells in the immediate area is an example of ______ signaling

paracrine

Estrogen and testosterone are steroid hormones and are most likely to bind to

cytoplasmic receptors

in a fight or flight response, ….

all of the above

Direct cellular connections such as gap junctions in animal cells and plasmodesmata in plant cells permit

second messengers produced in one cell to rapidly diffuse into and stimulate events in another

Some receptors for growth factors activate a protein kinase cascade, with the participation of multiple enzymes to effect a change in gene expression. Which of the following statements about a protein kinasae cascade are true

all of the above are true

many signal transduction pathways use second messengers to

relay the message from the inside of the membrane throughout the cytoplasm

which of the following is a major cause of the size limits for certain types of cells

the need for a surface area of sufficient area to allow the cell's function

plasmodesmata in plant cells is most similar in function to which of the following strucutres in animal cells

gap junctions

ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through

gap junctions

which of the following types of molecules are the major structutral components of the cell membrane

phospholipids and proteins

the presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops

according to the fluid mosaic model of cell membranes which of the following is a true statement about membrane phospholipids?

they can move laterally along the plane of the membrane

which is the most important function of glycoproteins and glycolipids of animal cell membranes

they provide cells' ability to distinguish one type of neighboring cell from another

which of the following spans the phospholipids bilayer, usually a number of times

transmembrane proteins

a transmembrane protein would have which type of amino acids on the extracellular and cytoplasmic ends?

polar hydrophillic

which of these often serve as receptors or cell recognition molecules on cell surfaces?

glycoproteins

what kinds of molecules pass through a cell membrane most easily

small and hydrophobic

which of the following is a characteristic feature of a carrier protein in a plasma membrane

it exhibits a specificity for a particular type of molecule

which of the following statements is correct about diffusion

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

 Water passes quickly through cell membranes because

it moves through aquaporins in the membrane.

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to fresh water but hypotonic to the salt solution.

A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?

isotonic

A cell with a solute potential of -7.30 is placed in a solution with a solute potential of -4.65. which of the following best describes the water potential of the cell and flow of water

the cell has a lower water potential, water will flow into the cell

 You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell?

similarity of the drug molecule to other molecules transported by the target cells

differences in the electrical potential between the interior and exterior of a cell is called

membrane potential

The sodium-potassium pump is called an electrogenic pump because it

contributes to the membrane potential.

calcium ions diffuse across membranes through carrier proteins down their concentration gradients. this is an example of

facilliated transport

 What mechanisms do plants use to load sucrose produced by photosynthesis into specialized cells in the veins of leaves?

B and C

in an experiment to examine how different hydrogen ion concentration affects the flow of sucrose in plant cells, scientists were able to decrease the flow into plant cells by placing them un

basic solutions which increased ph

when molecules bind to membrane receptor proteins, causing inward budding of the plasma membrane 

(invagination) forming vesicles

receptor mediated endocytosis

the difference between pinocytosis and receptor mediated endocytosis is that

pinocytosis is nonselective in the molecules it brings into the cellwhereas the receptor mediated endocytosis more selective

in what way do the membranes of eukaryotic cells vary

certain proteins are unique to each membrane

which of the following factors would tend to increase membrane fluidity

a greater proportion of unsaturated phospholipids

if a potato is allowed to dehydrate sitting in the open air, describe the changing water potential of the potato cells

water potential would decrease as water is leaving the cells

water potential decreases when

solute potential decreases and pressure decreases

choose the pair of terms that correctly completes this sentence: catabolism is to anabolism as _____ is to _____

exergonic; endergonic

most cells cannot harness heat to preform work because

temperature is usually uniform throughout a cell

which of the following metabolic processes can occur without net influx of energy from some other process

C6H12O6+6O2 → 6CO2+^H2O

if an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

add more of the enzyme

some bacteria are metabolically active in hot springs because

their enzymes have high optimal tempatures

if an enzyme is added to a solution where it’s substrate and product are in equillibrium what will occur

Nothing, the reaction will stay at equillibrium

which would reaction would prevail if both Q and S were present in the cell in high concentrations

Cl → N