Chapter 5 questions

Approximately what proportion of human genes are thought to encode protein kinases?

2%

Which of the following factors would tend to increase membrane fluidity?

A greater proportion of unsaturated phospholipids

An integral membrane protein would have to be..

Amphipathic, with at least on hydrophobic region

Which of the following would diffuse through the lipid bilayer of a plasma membrane most slowly, if at all?

An amino acid

Which of the following statements correctly describes the normal tonicity relationships between typical plant and animal cells and their respective environments?

Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

By increasing the percentage of unsaturated phospholipids in the membrane

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each kind of membrane

combination of forces acting on an ion

Electrochemical gradiant

At puberty, an adolescent female body changed 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 has different responses to its binding

water and hydrophilic solutions cross the membrane with the help of transport proteins

Facilitated diffusion

Following activation of a receptor, which sequence below represents the correct order in which components will be involved in a signaling pathway that utilizes the second messenger cAMP?

G protein- adenyl cyclase- cAMP- protein kinase

carbohydrates bonded to lipids

Glycolipids

carbohydrates bonded to proteins

Glycoproteins

Which of the following is the greatest advantage of having multiple steps in a transduction pathway?

Having multiple steps provides for greater possible amplification of a signal

Cystic fibrosis is a genetic disorder in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins?

Hydrophilic channels

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 about diffusion is correct?

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

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

It would not be able to activate G proteins in the cytoplasmic side of the plasma membrane

a molecule that specifically binds to another molecule

Ligand

The sodium potassium pump generates the following concentration gradients across the plasma membrane:

Low Na+ and high K+ inside he cell and high Na+ and low K+ outside

Which of the following would diffuse through the lipid bilayer of a plasma membrane most rapidly?

O2

the control of solute concentrations and water balance

Osmoregulation

not embedded in the lipid bilayer, they are loosely bound to the surface of the membrane

Peripheral proteins

Proton pumps are used in various ways by members of every domain of organisms: bacteria, arches, and eukarya. What does this most probably mean?

Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life

What kinds of molecules pass through a cell membrane most easily?

Small hydrophobic

How do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid rains that prevent adjacent lipids from packing tightly together

Which of the following is true for the evolution of cell membranes?

The evolution of cell membranes is driven by the evolution of all membrane components as a result of natural selection

A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water- equal to the volume of blood lost- is transferred directly into one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells

Which of the following is true of steroid receptors?

The receptor molecules may be soluble proteins in the cytoplasm

Which of the following provides the most likely explanation for why cell membranes are asymmetrical?

The two sides of a cell membrane face different environments and carry out different functions

Which of the following is true of integral membrane proteins?

They are usually transmembrane proteins

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 of the following is most likely fate of animal cells that lack receptors for local paracrine signal molecules?

They would be unable to grow and divide in response to growth factors from nearby cells

ability of a surrounding solution to cause a cell to gain or lose water

Tonicity

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

The cel membranes of Antarctic ice fish might have which of the following adaptations?

a high percentage of unsaturated fatty acids

Which of the following would increase the electrochemical gradient across a membrane?

a proton pump

A protein that spans the phospholipid bilayer one or more times is...

a transmembrane protein

The primary function of kinases in signal transduction is to...

activate protein kinases or other relay molecules in a series

Immediately following binding of a growth factor, an activated receptor would most likely stimulate...

activation of a protein kinase

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

alteration of protein kinases in cell cycle regulation in order to slow cancer growth

has both a hydrophilic region and a hydrophobic region

amphipathic

A major group of G protein- coupled receptors contains seven transmembrane ax (weird a) helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others. The coupled G protein most likely interacts with this receptor...

at the loop between helices 5 and 6

The mechanism by which testosterone alters cell function is by..

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

Proteins that allow the diffusion of ions across membranes in the direction of their concentration gradients are most likely....

channel proteins

The fluid mosaic model of the membrane proposed that membranes

consist of protein molecules embedded in a fluid bilayer of phospholipids

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

contributes to the membrane potential

The phosphate transport system in bacteria importas phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. phosphate import depends on a pH gradient across the membrane- more acidic outside the cell than inside the cell. Phosphate transport is an example of

cotransport

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?

decreased affinity of growth factor receptors for their respective ligands

The movement of the hydrophobic gas nitrous oxide into a cell is an example of...

diffusion through the lipid bilayer

Transport of potassium ions into an animal cell by he sodium potassium pump requires...

energy from ATP

A primary function of cholesterol in the plasma membrane of some animals is to...

facilitate cell-cell interactions by binding to receptors on neighboring cells

Glucose diffusion slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose- rich food into their glucose - poor cytoplasm. Based on this information, which transport mechanism is most likely responsible for glucose transport in the intestinal cells?

facilitated diffusion

The primary function of phosphates in signal transduction is to..

inactivate protein kinases to turn off signal transduction

Sutherland discovered that the signaling molecule epinephrine...

increase concentrations of cyclic AMP in the cytoplasm

penetrate the hydrophobic interior of the lipid bilayer

integral proteins

Lipid-soluble signaling molecules, such as an aldosterone, cross the membranes of all cells but affect only target cells because....

intracellular receptors are present only in target cells

Water passes quickly through cell membranes because..

it moves through aquaporin channel proteins

Which of the following enzymes adds a phosphate group to target proteins?

kinase

Submerging a red blood cell in distilled water will result in...

lysis of the cell

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in..

lysosomes

A primary function of polysaccharides attached to glycoproteins and glycolipids of animal cell membranes is to..

mediate cell to cell recognition

What is the voltage across a membrane called?

membrane potential

What of the following membrane activities requires energy from ATP hydrolysis?

movement of sodium ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

Familial hypercholesterolemia is characterized by extremely high levels of cholesterol in the blood, which results from...

nonfunctional or missing LDL receptors on cell membranes

In receptor-mediated endocytosis, receptor molecules are initially localized on the outer surface of the plasma membrane. Where do the receptors end up following endocytosis?

on the inside surface of a vesicle

The secretion of a signal molecule by a cell into the local environment, followed by a response by a number of cells in the immediate vicinity, is an example of..

paracrine signaling

Which of the following processes includes all the others?

passive transport

Which of the following tend to lack hydrophobic regions on their surface?

peripheral proteins

Which of the following are localized on the exterior of a phospholipid bilayer?

phosphate groups

Which of the following correctly describes the relationship between an enzyme and its function?

phosphate: removal of a phosphate group

The primary structural components of the cell membrane are..

phospholipids and proteins

The difference between pinocytosis and receptor-mediated endocytosis is that..

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis is highly selective

Which of the following characteristics is unique to plan hormones?

plant hormones may be delivered to target cells through the air

an enzyme that transfers phosphate groups from ATP to protein

protein kinase

In general, a signal transmitted via a phosphorylation cascade..

results in a conformational change in each phosphorylated protein

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

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 selectively enters the target cells?

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

Submerging a plant cell in distilled water will result in...

the cell becoming turgid

Submerging a red blood cell in a hypertonic solution will result in...

the cell wall shriveling

Celery stalks that are immersed in fresh water for several hours become turgid (stiff). Celery stalks left in 0.15 M salt solution become flaccid (limp). From this we can deduce that...

the fresh water is hypotonic and the salt solution is hypertonic tot he cells of the celery stalks

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that...

the hydrophobic interactions between the fatty acid tails of the two phospholipid monolayers are the weakest interactions in the membrane

Which of the following is the first event that occurs following the binding of a ligand by a membrane receptor protein?

the membrane receptor protein undergoes a conformational change

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

they amplify the original signal manyfold

The primary function of transcription factors is...

to regulate gene expression

The primary function of G proteins in signal transduction is...

transfusing the signal from an activated receptor to the next protein in the pathway

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

water will leave the cells, causing them to shrivel and collapse

Why are lipids and proteins free to move laterally in membranes?

weak hydrophobic interactions in the interior of the membrane are easily disrupted