Physiology Chapter 4 CELL MEMBRANE TRANSPORT

If a cells Na+/ K+ pump worked in reverse and had more leak channels for Na+ than for K+, what would the ion concentrations of the cell look like?

Although the body tries to maintain an extracellular concentration of Na+ at 145mM, the intracellular concentration of Na+ would still be higher.

Why do lipophilic hormones require carrier proteins while being transported in the blood?

Because lipophilic hormones don't dissolve well in blood plasma.

Which of the following statements is TRUE of carriers found in the plasma membrane?

Carriers are membrane-bound proteins that transport molecules across a membrane

what is the process whereby a signal from the outside of the cell is brought into the cell, resulting in some kind of cellular response?

Signal transduction

What is true of passive transport of solutes across the plasma membrane?

The direction of movement is determined by concentration gradient.

Which of the following statements is true of passive transport of solutes across the plasma membrane?

The direction of movement is determined by concentration gradient.

Which ion(s) have a net electrical force acting to move the ion(s) into the cell? (Assume a resting membrane potential (Vm) of -70mV.)

X+, whose [ECF] is120 mM and [ICF] is 30 mM

Which of the following enzymes catalyzes synthesis of cAMP?

adenylate cyclase

The enzyme that catalyzes synthesis of cAMP is called ________ and is activated by ________.

adenylate cyclase : a Gs protein

The function of a second messenger system is to

amplify response of the first messenger

Adenylate cyclase is __________.

an enzymme

Neurohormones __________

are exocytosed by neurons

What part of a neuron releases neurotransmitter by exocytosis?

axon terminal

Which ion(s) have a net chemical force acting to move the ion(s) into the cell? (assume a resting membrane potential (Vm) of -70mV)

both X+ and B- ions

The chemical force for which of the following ions is directed into the cell?

both sodium and calcium

Which of the following is the most common second messenger in the human body?

cAMP

________ are proteins attached to intermediate filaments in regions where cells are exposed to mechanical stresses.

cahderins

All of the following solutes are found in higher concentration inside of the cell EXCEPT

calcium

what are needed to adequately dissolve lipid-based molecules (like steroid hormones) in blood plasma?

carrier proteins

Based solely upon its electrical charge, the inside of a typical cell will tend to attract extracellular ________ to move inward.

cations

A carrier is a transmembrane protein that moves molecules across the membrane through

conformational changes in its protein shape.

________ are proteins that form channels between cells, allowing ions and small molecules to diffuse directly from one cell to the other

connexins

As an ion moves passively across a membrane into the cell, the progressive increase in concentration within the cell will

decrease the net flux across the membrane

The junctions created by intermediate filaments which penetrate the membranes between two cells at the site of protein plaques, thereby forming strong linkage between the two cells, are also known as

desmosomes

If a molecule crosses a membrane and is quickly removed from the area by the blood stream or some biological pathway, what effect does this have on its rate of diffusion?

diffusion rate will increase

Most water molecules that cross the plasma membrane do so by

diffusion through aquaporins.

Molecules with a relatively high lipid solubility are capable of crossing the membrane

directly through the lipid bilayer

Which of the following molecules is LEAST likely to diffuse through the phospholipid bilayer of the plasma membrane?

disaccharide

Molecules tend to move spontaneously ________ their chemical gradient.

down

the driving force for simple diffusion is moving __________ its electrochemical gradient

down

In facilitated diffusion, a molecule is moved

down its concentration gradient with the assistance of a protein carrier molecule, and no energy is required.

Of the gradients listed below, which is the MOST accurate description of the force that ultimately determines the movement of ions across the membrane?

electrochemical gradient

When molecules are passively transported across a membrane, the direction of their movement is dictated by the molecule's tendency to move

from higher to lower energy

Direct communication between cells in contact with one another is accomplished through

gap junctions

In some cases, signals originating within one cell can diffuse directly to a neighboring cell through

gap junctions

Inflammation is characterized in part by redness and swelling. In inflammation, __________ increases blood flow to affected tissues (producing redness) and causes fluid to leak out of the blood vessels and into the tissue (producing swelling).

histamine

What chemical messenger is released from endocrine glands into the bloodstream?

hormone

Which type of chemical messenger is released into the bloodstream by an endocrine gland where it can affect target cells throughout the body?

hormone

The process of diffusion involves the random movement of

individual molecules due to thermal motion.

Removing a(n) ______ protein from a cell membrane would irreversibly disrupt the membrane.

integral

Of the three major fluid compartments in the body, what is the fluid that surrounds the cells called?

interstitial fluid

What molecules are hydrophobic and can easily cross the plasma membrane?

lipophilic

The location of the receptor depends on whether the messenger is

lipophilic or lipophobic

Based on your knowledge of signal amplification, which type of chemical messenger can have relatively small concentrations within the bloodstream and still get a large response?

lipophobic

Which of the following is a reflection of the unequal distribution of positive and negative ions across the plasma membrane?

membrane potential

If the solutions on either side of the membrane have an unequal distribution of charged ions, with the inside having an excess of anions, then the inside of the cell would have to be

more negative, relative to the outside of the cell.

Which of the following transport mechanisms is passive?

movement of sodium through ion channels

Comparing intracellular to extracellular fluid, the intracellular fluid has a ________ charge relative to the outside of a cell due to the presence of more ________ in that solution.

negative:anions

Vasopressin (antidiuretic hormone), which is released from the posterior pituitary, is an example of what type of chemical messenger?

neurohormone

what are synthesized and released by neurons, but put into the blood supply to act as hormones?

neurohormones

The target cells of the nervous system are

neurons, muscles, or glands.

What chemical messenger is released by a presynaptic cell?

neurotransmitter

the chemical messenger of the nervous system is __________ and chemical messenger of the endocrine system is __________.

neurotransmitter:hormone

The genetic material of a cell is stored in the cell's __________.

nucleus

A first messenger is an extracellular messenger that binds to its receptor on the _________ of the cell and therefore activates a second messenger system.

outside

If a positively charged ion is more concentrated outside the cell, the electrical forces required to balance the chemical gradient would be directed ________. Thus, the equilibrium potential for this ion would be ________ charged.

outward:positively

What chemical messenger diffuses to neighboring cells to exert an effect?

paracrine

Growth factors are _________

paracrines

In what transport do solutes move across the plasma membrane along their concentration gradient--from the side of higher concentration to the side of lower concentration?

passive

Most of the plasma membrane is composed of __________.

phospholipids

Receptors for lipophobic messengers are typically located where in the cell?

plasma membrane

Most chemical messengers are __________

polypeptides

Which of the following is found in greater concentration inside the cell than outside?

potassium

What enzyme is activated by cAMP?

protein kinase A

All of the following solutes are found in higher concentration outside of the cell EXCEPT

proteins

What experimental protocols would you use to determine if two cells were joined together by desmosomes?

pull the two cells in opposite directions

A target cell will respond to a chemical messenger once that molecule has bound to a(n)

receptor

In chemical communication between cells, a ________ cell secretes a chemical messenger that binds to ________ on the ________ cell.

secretory:receptor:target

The unequal distribution of charge in solutions on either side of a membrane will lead to a ________ of charge across the membrane and a ________ of counter ions in a region close to the membrane.

separation:clustering

The binding of chemical messengers to receptors produces a response inside the target cell through a variety of mechanisms referred to as __________

signal transduction

If a person sprays air freshener into a room, the fragrance will eventually reach your nose, even in the absence of air currents. Which of the following best describes this process?

simple diffusion

A ______can have receptors for different messengers.

single cell

Which of the following pairs of characteristics is more likely to make a substance diffuse through the cell membrane?

small,non-polar molecule

Which of the following is the major extracellular cation?

sodium

When more than one ion species (i.e., Na+ and K+) is present on both sides of the membrane, the chemical driving force acting on Na+ will include

sodium only

All the messengers in what class are derived from cholesterol?

steroids

The nervous system communicates via the _________ and the endocrine system communicates via the ___________.

synapse:bloodstream

The ___________ of a neurotransmitter is the postsynaptic cell.

target cell

what could you hypothesize if two cells were joined together by desmosomes?

that they would not separate when you pulled them in opposite directions.

What is responsible for the unequal distribution of ions across a membrane, thereby causing a charge?

the concentration of impermeable charged molecules

The number of bound receptors on a target cell depends on what two things?

the concentration of the messenger and the concentration of receptors on the target cell

In general, the molecules that move through specific carrier proteins are determined by which of the following?

the unique fit to binding sites on the channel or carrier protein

In the digestive tract, absorption is controlled by mechanisms on the cells apical membrane surface. What type of physical barriers would be in place to keep these mechanisms from being circumnavigated?

tight junctions

The type of cell junction that forms an impermeable barrier, not allowing movement between cells, would be a __________.

tight junctions

What junctions are found in epithelial tissue where they prevent paracellular movement of molecules?

tight junctions

target cells are all _____

transmembrane proteins

Which of the following enzymes catalyzes phosphorylation of a protein?

tyrosine kinase

Which of the following chemical messengers communicate with neighboring cells?

vascular endothelial growth factor

in facilitated diffusion, carrier proteins will more likely bind with solute molecules __________.

when they are in greater concentration, regardless of on which side of the membrane the concentration is higher