NBL 355 Module 5

The rate of chemical ____ of an atom/molecule depends on its mass, the solvent/medium, its concentration gradient, as well as the temperature and pressure.

Diffraction

Diffusion

Solubility

Refraction

Permeability

Diffusion

The lipid bilayer ______.

Prevents diffusion of most hydrophilic molecules across it

Is very thin, only about 4-5 nm in diameter

Is a component of the plasma membrane and intracellular membranes

All of these answers

Allows small hydrophobic molecules like oxygen and steroids to diffuse across it

All of these answers

Membranes contain _____ proteins that allow selective movement of ______ molecules across the membrane

Transport, hydrophobic

Channel, all

Cytoplasmic, soluble

All of these answers

Transmembrane, hydrophilic

transmembrane, hydrophilic

Which of the following best describes passive transport?

Channels or carriers are required to facilitate transport of polar uncharged and polar charged molecules

It is essential for establishing the overall ion gradients inside and outside of neurons

There is one type called simple diffusion

Atoms/molecules can move either up/against or down/along their concentration gradient

Only hydrophobic molecules can move by passive transport

channels or carriers are required to facilitate transport of polar uncharged and polar charged molecules

_________ move from the extracellular fluid rapidly across the plasma membrane to the cytoplasm by the process of simple diffusion.

Ions such as Na+ and Cl-

Polar molecules such as water and urea

Sugars such as glucose and sucrose

Gases such as oxygen and carbon dioxide

Peptides and proteins

Gases such as oxygen and carbon dioxide

Active transporters ________.

Are involved in the transport of different types of molecules including ions, sugars, amino acids, and vitamins

Can function in both directions to move molecules into or out of the cell

Are expressed in all cells

All of these answers

Can be expressed/localized to both the plasma membrane and intracellular membranes

All of these answers

Which of the following BEST DESCRIBES the Na+/K+ ATPase/pump?

It is the main mechanism that establishes and maintains the Na+ and K+ gradients in cells

It is a type of secondary active transporter

It pumps ATP out of the cell

It becomes phosphorylated by phospholipids as an intermediate

It is non-electrogenic because it pumps 3 K+ in for every 3 Na+ out

It is the main mechanism that establishes and maintains the Na+ and K+ gradients in cells

All of the following are types of primary active transporters EXCEPT ______.

H+ (proton) ATPase/pump

Na+/K+ ATPase/pump

Ca2+ ATPase/pump

electron transport chain

Mg2+/ATPase/pump

Mg2+/ATPase/pump

The primary active transporters that uses redox energy from NADH/FADH2 to move ions across the membrane are the ______.

Na+/K+ ATPases at the plasma membrane

Nuclear pore complexes in the nucleus

Enzymes involved in glycolysis in the cytoplasm

Electron transport chains in mitochondria

All of these answers

electron transport chains in mitochondria

Secondary active transporters _______.

All of these answers

Use the energy stored in an ion gradient to move another atom/molecule across the membrane

Are involved in the transport of many types of molecules including ions, sugars and lipids up/against their concentration gradients

Can be co-transporters/symporters or antiporters/exchangers

Involve movement of at least two types of atoms or molecules

All of these answers

It is has been proposed that one important function for the _____ gradient(s) in ALL cells is so it/they can be used to co-transport essential nutrient molecules like glucose, amino acids and vitamins into the cell.

All of these answers

Na+ and K+

Electron

ATP

Proton

Na+ and K+

The main similarity between active transport and facilitated passive transport is that _____.

Both can involve conformational changes in the protein responsible for movement of the atom/molecule

Both contribute to the selective permeability of the plasma membrane

Both involve the movement of hydrophilic molecules across the membrane

Both involve transmembrane proteins with multiple transmembrane spanning domains

All of these answers

All of these answers

The main difference between active transport and facilitated passive transport is that ____.

Active transport requires energy while facilitated passive transport does not

All of these answers

Active transport functions all the time while facilitated passive transport involves proteins that can be gated or ungated

Active transport is involved in moving many different types of ions and nutrients while facilitated passive transport is involved in the movement of primarily water and ions

Active transport can move atoms/molecules up/against their concentration gradient while facilitated passive transport allows molecules to move only down/along their concentration gradient

All of these answers

Because ions are BOTH charged particles and chemicals, ion gradients have ____.

Electrochemical potential

Energy stored in the gradient

Electrical potential

Chemical potential

All of these answers

all of these answers

The Nernst/equilibrium potential _______.

Depends on the chemical/concentration gradient of an ion and valence/charge of an ion

Calculates the electrochemical potential stored in the ionic concentration gradient and is expressed in mV

Is Ex and equals +60 mV/z x log [out]/[in], where z is the valence, [out] is the ion concentration outside and [in] is the ion concentration inside the cell

Is the membrane potential at which there would be no net movement of that ion across the membrane

All of these answers

all of these answers

Given a concentration of Na+ outside the neuron of 150 mM and inside of 15 mM, the Nernst potential for Na+ is ____.

-120 mV

-60 mV

+60 mV

0 mV

+120 mV

+60 mV

Given a concentration for K+ of 4 mM outside and 100 mM inside, the Nernst potential for K+ would be ___. (note the log 1/25 = -1.4)

+84 mV

0 mV

+61.4 mV

-84 mV

-61.4 mV

-84 mV

In diabetes, which leads to hyperglycemia, the concentration of glucose is about 10 times higher in the extracellular fluid than it is in the intracellular cytoplasm. What would the Nernst potential for glucose be?

+120 mV

-60 mV

0 mV

+60 mV

-120 mV

0 mV

Although there are individual ionic gradients, the overall (bulk) extracellular fluid and intracellular cytosol/cytoplasm in a neuron are ______.

At equilibrium

Identical in composition

Hypotonic and hypo-osmotic

Isotonic and iso-osmotic

Hypertonic and hyper-osmotic

isotonic and iso-osmotic

When healthy neurons are at rest, they are in a situation ______.

Called steady state

Where the Gibbs free energy = 0

All of these answers

Where energy output is greater than energy input

Called equilibrium

Called steady state

Electric ____ is the physical property of matter that causes it to experience a force when placed in an electromagnetic field, with two types-called positive and negative.

Energy

Field

Charge

Potential

Charge

An electric charge produces or induces a(n) ______; expressed another way, a(n) ________ surrounds an electric charge.

Coulomb force

Electric potential energy

Electrical potential

Electric field

Electric field

The ______ force is the electrostatic force that acts between two electric charges.

Electric potential

Electric charge

Electric field

Coulomb

Coulomb

The ______ is defined as the amount of work needed to move a unit of charge from a reference point to a specific point inside an electric field. The unit of this is volts (joules per coulomb).

Electric field

Electric potential

Electric charge

Coulomb force

Electric potential

Biological membranes are ideal for establishing and maintaining the membrane potential because they are _________.

Selectively permeable to ions and very thin

Composed of phospholipids which have charged head groups that bind ions tightly

Highly permeable to small polar molecules such as water and glucose at rest

Composed of lipids and constantly undergo endocytosis

Permeable to oxygen and small hydrophobic molecules

Selectively permeable to ions and very thin

Which of the following BEST DESCRIBES the membrane potential? The membrane potential _____.

Involves the separation of electrons across the plasma membrane

Is the difference in electric potential between the inside and outside of the plasma membrane

Exists in only neurons and muscles cells

Remains constant in a neuron

Is the difference in electric charge between the total/bulk intracellular cytoplasm and extracellular fluid

Is the difference in electric potential between the inside and outside of the plasma membrane

The membrane potential involves a separation and movement of _____ across the membrane.

Oxygen and protons

Cations and anions

All of these answers

Free electrons

Lipids and water

Cations and anions

The Na+/K+ATPase is called electrogenic since it pumps 3 Na+ ions out for each 2 K+ ions in. This electrogenic feature of the Na+/K+ATPase ________.

Does not contribute to the resting membrane potential

Contributes a small amount (between -7 mV to -10 mV) to the resting membrane potential

Prevents Na+ and K+ from moving across the membrane through leak channels

Is responsible for the majority of the resting membrane potential

Provides the energy for the activation of leak channels

Contributes a small amount (between -7 mV to -10 mV) to the resting membrane potential

The resting membrane potential is determined predominantly by the _____.

Electrogenic nature of the Na+/K+ ATPase/pump

Secondary active transporters and gated ion channels

Diffusion of Na+ and K+ up their chemical gradients

Difference between incoming potentials and outgoing potentials

Na+/K+ ATPase/pump and leak ion channels

Na+/K+ ATPase/pump and leak ion channels

The typical resting membrane potential in neurons is about -67 mV, and is determined by the expression of about 20-40 times more plasma membrane ____ at rest.

Gated ion channels

Leak and gated Na+, K+ and Cl- channels

Leak K+ channels

Leak Na+ and leak Cl- channels

Na+/K+ ATPase transporters

Leak K+ channels

In neurons, the reason that the resting membrane potential (RMP) is close to, but not as negative as the Nernst potential for K+ is because _____.

Secondary active transporters are activated at the RMP

All of these answers

The Na+/K+ ATPase pumps K+ back into the cell at the RMP

Leak Na+ and leak Cl- channels contribute to the RMP

Some leak K+ channels are closed at the RMP

Leak Na+ and leak Cl- channels contribute to the RMP

What can determine the number and type of specific ion channel proteins that are present at the plasma membrane?

The endosomal pathway

All of these answers

The biosynthetic/secretory pathway

Gene expression

Membrane trafficking

All of these answers

Since there is about 10 times less Cl- in the intracellular cytosol-cytoplasm compared with the extracellular fluid, what are the anions inside the cell that ensures it is electrically neutral?

Acetate and bicarbonate

All of these answers

Chloride, fluoride and iodide

Proteins with negatively charged amino acids on their surface

Phosphate and sulphate

All of these answers

The GHK equation calculates the_______.

Membrane potential

Chemical potential

Electrochemical potential

Electric force

Nernst potential

Membrane potential

The membrane is said to be "selectively permeable." What is the basis of this? 

Selective permeability means that the membrane allows only certain molecules to move across from the outside to inside or inside to outside. The membrane is selectively permeable to hydrophobic molecules because of the lipid bilayer. Hydrophobic molecules like oxygen and steroids can diffuse directly across the lipid bilayer but hydrophilic (polar uncharged and polar charged) molecules can't diffuse across the lipid bilayer. However, the membrane also contains transmembrane proteins and it is selectively permeable to some hydrophilic molecules because of the presence of transporters and channels that allow specific molecules to move across the membrane by active or passive transport.

The rate of chemical diffusion of an atom or molecule depends on _____.

Its diffusion coefficient

All of these answers

The concentration gradient

The Temperature, Pressure, and solvent/medium

Its Mass

All of these answers

Which of the following is NOT TRUE about selective permeability of biological membranes?

It requires the lipid bilayer

It allows the movement of all small hydrophobic molecules

It requires channels, transporters, and/or carriers

It prevents the movement of all hydrophilic molecules

It requires transmembrane proteins

It prevents the movement of all hydrophilic molecules

Which of the following is NOT TRUE about passive membrane transport?

Small gases such as Oxygen and Carbon Dioxide can move easily across the membrane by the process of simple diffusion

It is essential for nutrients such as glucose and fatty acids to be taken up into the cell

It does not require energy directly

Atoms/molecules move down/along their concentration gradient (or down their electrochemical gradient of the atom/molecule is charged)

For facilitated diffusion, channels or carriers are required to facilitate transport of polar uncharged and polar charged molecules

It is essential for nutrients such as glucose and fatty acids to be taken up into the cell

Which of the following is NOT TRUE about the Na+/K+/ATPase/ Pump?

It is called an ATPase because it is used to produce ATP

It is called a pump since it pumps Na+ out of the cell (against its concentration gradient) and pumps K+ into the cell (against its concentration gradient)

It is electrogenic since it transports 3 Na+ out for every 2 K+ in

It is a type of primary active transporter

It establishes the overall Na+ and K+ gradients

It is called an ATPase because it is used to produce ATP

Active transporters (including primary and secondary) are _________.

The only mechanisms that establish the ion gradients and uptake of nutrients in cells

The only mechanisms that allow the movement of ions in or out of the cells

Expressed only in excitable cells

Localized to only the plasma membrane and mitochondrial membrane

Functioning in only one direction to move molecules inside cells

The only mechanisms that establish the ion gradients and uptake of nutrients in cells

The ER membrane and synaptic vesicle membrane contain __________, which allows them to uptake H+, Ca2+, or neurotransmitters inside the organelle.

Active transporters

Transport vesicles

Specialized lipid bilayers

All of these answers

Ion Channels

Active transporters

Which of the following is NOT a type of active transporter?

H+ ATPase

Ca2+ ATPase

Electron Transport Chain

Na+/K+ ATPase

Cl- ATPase

Cl- ATPase

The main difference(s) between active and passive transport is that active transport _______.

Involves transporter proteins while passive transport involves channels and carriers

Requires energy while passive transport does not

Moves at least one atom/molecule against/up its concentration gradient while passive transport allows the movement of atoms/molecules down its concentration gradient

Is always active while passive transport can involve leak channels that are always open and gated channels that require activation to be open

All of these answers

All of these answers

The reason that an ion has electric potential energy when placed in an electric field is because it ________.

Is small and contains electrons

Contains an atom

Is hydrophilic

All of these answers

Has an electric charge

Has an electric charge

The electric _______ is defined as the amount of work needed to move a unit of charge from a reference point to a specific point inside an electric field, and its unit is the volt (joules per coulomb).

Field

Energy

Charge

Potential

Force

Potential

An electric charge will produce or induce an electric __________. Described another way, an electric ____________ surrounds an electric charge.

Force

Energy

Field

Potential

Energy

Field

Because ions are both charged particles and chemicals, in a cell, an ion gradient has all of the following EXCEPT __________.

Energy stored in the gradient that has the ability to do work

Electrical potential

The ability to transfer electrons

Electrochemical potential

Chemical potential

The ability to transfer electrons

Which of the following is NOT TRUE about the Nernst/Equilibrium potential. It _________.

Is the membrane potential at which there would be no net movement of an ion across the membrane (for a specific ion gradient)

Transforms the electrical potential of an ion into a chemical gradient of the ion

Depends on the valence/charge of an ion

Depends on the chemical/concentration gradient of an ion

Converts the ionic concentration gradient into an electrical term (mV)

Transforms the electrical potential of an ion into a chemical gradient of the ion

The Nernst equation calculates the _________ potential stored in the concentration gradient of the ion.

All of these answers

Electrochemical

Electrode

Membrane

Steady-state and equilibrium

Electrochemical

Which of the following best describes the Nernst equation, where z is the valence of the ion, [out] is the concentration outside and [in] is the concentration inside.

Ex= -60 mV * ln [in]/[out]

Ex= +60 mV/z * log [out]/[in]

Ex= -60 mV * log [out]/[in]

Ex= +60 V/z * log [in]/[out]

Ex= z * +60 V/z * log [out]/[in]

Ex= +60 mV/z * log [out]/[in]

Given a concentration of K+ outside the neuron of 4 mM and inside of 100 mM, the Nernst potential for K+ would be ____________. Note the log [4/100] = log [.04] = -1.4 and the charge/valence of K+ is +1

+84 mV

0 mV

-61.4 mV

+61.4 mV

-84 mV

-84 mV

Given a concentration of Cl- outside the neuron of 100 mM and inside of 10 mM, the Nernst potential for Cl- would be ________. Note the log [100/10] = log [10] = +1 and the charge/valence of Cl- is -1.

-1 mV

+1 mV

0 mV

-60 mV

+60 mV

-60 mV

Which of the following is NOT TRUE about the membrane potential? It __________.

Is the difference in electric charge between the total/bulk intracellular cytoplasm and extracellular fluid

Can be measured by a recording electrode and is expressed in millivolts

Involves the separation of negative and positive ions across the plasma membrane

Is the electric potential difference between the inside and outside of the plasma membrane

Is present in all cells, which have a resting membrane potential

Is the difference in electric charge between the total/bulk intracellular cytoplasm and extracellular fluid

The membrane potential involves a separation and movement of ________ across the membrane.

Both hydrophilic and hydrophobic molecules

Only free electrons

Only ions and free electrons

All Hydrophilic molecules

Only ions

Only ions

Biological membranes are ideal for establishing and maintaining the membrane potential because they are ____________.

Composed of lipids and constantly undergo endocytosis

Composed of phospholipids which have charged head groups that bind ions tightly

Selectively permeable to ions and very thin

Permeable to oxygen and small hydrophobic molecules

Highly permeable to small polar molecules such as water and glucose at rest

Selectively permeable to ions and very thin

The resting membrane potential is about -67 mV and is established and maintained predominantly by the ______.

Electrogenic nature of the Na+/K+ ATPase/pump

Diffusion of Na+ and K+ up their electrochemical gradients

Difference between incoming potentials and outgoing potentials

Active transporters and leak channels

Transporters and gated ion channels

Active transporters and leak channels

The number and type of transporters and channels that are present in a neuron’s plasma membrane is determined by _________.

All of these answers

The ion concentration gradients

The relative ratio of active and passive transport

Gene expression and membrane trafficking

The Nernst potentials

Gene expression and membrane trafficking

The reason(s) that the resting membrane potential is negative on the inside (about -67 mV) is because at rest, ______.

All of these answers

Leak channels are always open at rest

The membrane is more permeable to K+ than to Na+ or Cl-

The Na+/K+ ATPase establishes the gradients with high Na+ outside and high K+ inside

There are between 20-30 times more leak K+ channels than leak Na+ or leak Cl- channels

All of these answers

The reason(s) the resting membrane potential is not as negative as the Nernst potential for K+ is because _____.

Neurons activated gated Na+ and Cl- channels at rest to adjust the resting membrane potential

The leak K+ channels are endocytosed after they allow K+ to flow through

Neurons change their Na+ and K+ gradients to adjust the resting membrane potential

All of these answers

There are also leak Na+ and Cl- channels open at rest

There are also leak Na+ and Cl- channels open at rest

The reason that all cells express the Na+/K+ ATPase and have a resting membrane potential is because _____.

All cells use electrical signaling to communicate

They use the Na+ and K+ gradients to produce ATP

All of these answers

They use the Na+ and K+ gradients to transport essential nutrients

If they didn’t they would become hypo-osmotic and shrink

They use the Na+ and K+ gradients to transport essential nutrients

The GHK equation is used to calculate the _______.

Nernst potential

Equilibrium potential

Electrode potential

Membrane potential

All of these answers

Membrane potential

In the GHK equation for a neuron under normal healthy conditions at constant temperature and pressure, the variable(s) that can change during signaling is/are the ______ of the ions.

All of these answers

Relative permeabilities

Faraday and gas constants

Valences/charges

Concentration gradients

Relative permeabilities

If ATP was rapidly deleted from the cell, the concentrations of Na+ and K+ would be the same inside and outside the cell (all gradients would be lost), and the resting membrane potential would be close to _____.

-84 mV

-60 mV

+60 mV

-10 mV

0 mV

0 mV

In an individual with acute hyponatremia, the Na+ concentration outside the cell is lowered to 37.5 mM while the inside concentration is normal at 12.5 mM. In this condition, the Nernst potential for Na+ would be ______ and the resting membrane potential would be ______ than normal. Note the log [37.5/12.5] = log [3] = 0.5 and the charge/valence of Na+ is +1

+30 mV; more negative/less positive

+60 mV; greater

0 mV; depolarized

+30 mV; more positive/less negative

+60 mV; identical

+30 mV; more negative/less positive

Assuming normal ion gradients and Nernst potentials, and a resting membrane potential of about -67 mV, what effect would the following have on the RMP?

10 times more leak K+ channels

10 times more leak Na+ channels

10 times more leak Cl- channels

10 times more Na+/K+ ATPases

RMP would be more negative/less positive

RMP would be more positive/less negative

RMP would be about the same

RMP would be about the same