Biophysics Flashcards
Which of the following describes the process of diffusion?
a) Movement of molecules from a region of high concentration to low concentration
b) Movement of molecules from a region of low concentration to high concentration
c) Movement of molecules from a region of equal concentration to another region of equal concentration
d) Movement of molecules from a region of low concentration to another region of low concentration
Movement of molecules from a region of high concentration to low concentration
The resting membrane potential inside the cell is?
-70mV
________ has high concentration outside.
Na+
Diffusion of a Solute is defined by _________ Equation?
Fick’s Equation
Flux is a _________ quantity
a. Scaler
b. Vector
c. Positive
d. Negative
Vector
The net flux of a particle is dependent on the
diffusion coefficient of the medium for the particle, and the difference in concentration of the particle. True or false?
True
Permeability does NOT depend on:
a. Type of ion
b. Thickness of the membrane,
c. Temperature
d. Area
Area
Name Small uncharged Polar Molecules?
H2O
urea
glycerol
C02
O2,
alcohol
Name Large Uncharged Polar Molecules?
Glucose
Sucrose
Which of the following is an example of active transport?
a) Osmosis
b) Diffusion
c) Facilitated diffusion
Osmosis
Which of the following is a factor that affects the rate of osmosis?
a) Size of the molecules
b) Charge of the molecules
c) Temperature
d) All of the above
All of the above
Which of the following statements about diffusion is true?
a) It requires the input of energy
b) It occurs from areas of low concentration to high concentration
c) It occurs from areas of high concentration to low concentration
d) It is a highly selective process
It occurs from areas of high concentration to low concentration
Which of the following is NOT a characteristic of osmosis?
a) It is a passive process
b) It only occurs in living organisms
c) It involves the movement of water
d) It occurs across a semi-permeable membrane
It only occurs in living organisms
Which of the following factors affect the rate of diffusion?
a) Temperature
b) Concentration gradient
c) Membrane permeability
d) All of the above
All of the above
Which of the following is an example of osmosis in living organisms?
a) Movement of water from soil to plant roots
b) Movement of water from blood to cells
c) Movement of water from the bladder to urine
d) Movement of water from the stomach to small intestine
Movement of water from blood to cells
The Nernst equation is used to calculate:
a. The electrical potential across a cell membrane
b. The concentration of ions inside and outside a cell
c. The rate of ion diffusion across a cell membrane
d. The electrical conductivity of a cell membrane
The electrical potential across a cell membrane
The Nernst equation is applicable for which type of ions?
a. Only positively charged ions
b. Only negatively charged ions
c. Both positively and negatively charged ions
d. None of the above
Both positively and negatively charged ions
In the Nernst equation, what does the variable “R” represent?
The gas constant
The Nernst equation can be used to calculate the equilibrium potential for _______ ion?
Potassium (K+)
The equilibrium potential for an ion is dependent on:
a. The concentration gradient of the ion across the cell membrane
b. The electrical gradient of the ion across the cell membrane
c. The temperature of the cell
d. Both a and b
d. Both the concentration gradient of the ion across the cell membrane and the electrical gradient of the ion across the cell membrane
Which ion has a higher equilibrium potential in neurons, potassium or sodium?
Potassium
Which of the following factors can affect the resting membrane potential of a neuron?
a. Changes in the extracellular concentration of ions
b. Changes in the intracellular concentration of ions
c. Changes in the permeability of the cell membrane to ions
d. All of the above
All of the above
If the concentration of potassium inside a neuron is 100 mM and the concentration of potassium outside the neuron is 10 mM, what is the equilibrium potential for potassium (in mV) according to the Nernst equation?
a. -60 mV
b. -70 mV
c. -80 mV
d. -90 mV
-90 mV
If the concentration of sodium inside a neuron is 10 mM and the concentration of sodium outside the neuron is 100 mM, what is the equilibrium potential for sodium (in mV) according to the Nernst equation?
+60 mV
What is the relationship between the equilibrium potential and the resting membrane potential of a neuron?
They are the same
How many ions are needed to move across the cell membrane to change the electrical potential by 60 mV according to the Nernst equation?
2
If the extracellular concentration of potassium increases, what would happen to the resting membrane potential?
The resting membrane potential would become more positive
Which of the following statements is true about a cell membrane at rest?
a. The cell membrane is permeable to both sodium and potassium ions
b. The cell membrane is impermeable to both sodium and potassium ions
c. The cell membrane is permeable to sodium ions but impermeable to potassium ions
d. The cell membrane is permeable to potassium ions but impermeable to sodium ions
The cell membrane is permeable to both sodium and potassium ions
What does the Gibbs-Donnan equation describe?
a. The relationship between osmotic pressure and solute concentration
b. The distribution of ions between two compartments separated by a semipermeable membrane
c. The relationship between the equilibrium constant and reaction rate
d. The relationship between pH and the dissociation constant of a weak acid
The distribution of ions between two compartments separated by a semipermeable membrane.
__________ and ________ ions are most affected by the Gibbs-Donnan effect in biological systems
Potassium and chloride.
What is the significance of the Gibbs-Donnan effect in determining the distribution of ions across a cell membrane?
It ensures that the concentration of ions is higher outside the cell than inside the cell.
What is the main factor that affects the magnitude of the Gibbs-Donnan effect?
a. The size of the ions
b. The charge of the ions
c. The concentration of the ions
d. The permeability of the membrane
The charge of the ions
What is the equilibrium potential of an ion?
The potential at which the net flow of the ion across the membrane is zero.
What is the equation used to calculate the equilibrium potential of an ion?
a. Ohm’s Law
b. The Nernst equation
c. The Goldman equation
d. The Poisson equation
The Nernst equation.
What is the relationship between the equilibrium potential of an ion and the membrane potential of a cell?
The relationship depends on the concentrations of the ion inside and outside the cell.
How does a change in the concentration gradient of an ion affect its equilibrium potential?
a. It does not affect the equilibrium potential.
b. It increases the magnitude of the equilibrium potential.
c. It decreases the magnitude of the equilibrium potential.
d. It changes the sign of the equilibrium potential.
It decreases the magnitude of the equilibrium potential.
Which of the following factors does NOT affect the equilibrium potential of an ion?
a. Temperature
b. Ionic charge
c. Membrane permeability
d. Ionic concentration gradient
Temperature
Which of the following ions has the most positive equilibrium potential in most cells?
a. Sodium (Na+)
b. Potassium (K+)
c. Chloride (Cl-)
d. Calcium (Ca2+)
Sodium (Na+)
Calculate the equilibrium potential of sodium (Na) when the concentrations across a cell membrane are [Na+] I =27 mM, [Na+] o=193 mM. What is the driving force acting on sodium ions if the membrane potential is –65 mV?
E Na = +51 mV
Resting cells are not at their equilibrium but they are _____________
at steady state.
What is necessary to maintain a constant
composition of the ions across the cell membrane?
An active pump
At the steady state, the sum of passive and active current for a specific ion must be ______.
ZERO
Electroneutral Pump does not carry net charge across the membrane. True or false?
True
Define Equilibrium?
Equilibrium is defined as the state in which the net force on a particle equals 0.
What is steady-state?
Steady-state is defined as the situation in which the net current carried by ions equal to 0.
What is the process by which a cell creates a membrane potential?
A. Cellular respiration
B. Membrane diffusion
C. Ion transport
D. Osmosis
Ion transport
The resting membrane potential of a typical mammalian cell is around:
A. -70 mV
B. 0 mV
C. +30 mV
D. -30 mV
-70 mV
Which ions contribute to the resting membrane potential of a cell?
Potassium and chloride
The Na+/K+ ATPase pump plays a crucial role in the maintenance of the membrane potential by:
A. Transporting K+ ions into the cell and Na+ ions out of the cell
B. Transporting Na+ ions into the cell and K+ ions out of the cell
C. Transporting both Na+ and K+ ions into the cell
D. Transporting both Na+ and K+ ions out of the cell
Transporting K+ ions into the cell and Na+ ions out of the cell
The Goldman equation is used to calculate?
The membrane potential of a cell
The Nernst equation is used to calculate:
A. The membrane potential of a cell
B. The concentration of ions in a cell
C. The rate of ion transport across a cell membrane
D. The diffusion coefficient of ions in a cell
The membrane potential of a cell
________ type of ion channels open in response to changes in the membrane potential?
A. Ligand-gated channels
B. Voltage-gated channels
C. Mechanically-gated channels
D. All of the above
Voltage-gated channels
The depolarization of a cell membrane occurs when:
A. Positive ions enter the cell
B. Positive ions leave the cell
C. Negative ions enter the cell
D. Negative ions leave the cell
Positive ions enter the cell
Action potentials are generated in response to:
A. A small depolarization of the membrane potential
B. A large depolarization of the membrane potential
C. A small hyperpolarization of the membrane potential
D. A large hyperpolarization of the membrane potential
A large depolarization of the membrane potential
The threshold potential is the:
A. Point at which an action potential is generated
B. Resting potential of a cell
C. Potential at which ion channels begin to open
D. Potential at which ion channels begin to close
Potential at which ion channels begin to open
Which of the following is true regarding the myelin sheath?
A. It increases the rate of ion transport across the cell membrane
B. It decreases the rate of ion transport across the cell membrane
C. It increases the capacitance of the cell membrane
D. It decreases the capacitance of the cell membrane
It decreases the rate of ion transport across the cell membrane
Which of the following is responsible for generating the initial depolarization of the membrane potential during an action potential?
A. Sodium influx
B. Potassium influx
C. Chloride efflux
D. Calcium influx
Sodium influx
Which type of ion channel is responsible for the repolarization phase of the action potential?
A. Voltage-gated sodium channels
B. Voltage-gated potassium channels
C. Ligand-gated sodium channels
D. Ligand-gated potassium channels
Voltage-gated potassium channels
Which of the following is true regarding the all-or-none principle of action potentials?
A. Action potentials can be of varying amplitudes
B. Action potentials can be generated with only partial depolarization
C. Action potentials are generated with a fixed amplitude
D. Action potentials are generated with a variable amplitude
Action potentials are generated with a fixed amplitude
Which of the following factors can affect the membrane potential of a cell?
A. Changes in extracellular ion concentration
B. Changes in intracellular ion concentration
C. Hormonal signaling
D. All of the above
All of the above
What is membrane capacitance?
A. The ability of the membrane to store electrical charge
B. The ability of the membrane to transmit electrical charge
C. The ability of the membrane to generate electrical charge
D. The ability of the membrane to resist electrical charge
The ability of the membrane to store electrical charge
What is the role of membrane capacitance in generating the action potential?
It contributes to the rapid depolarization phase of the action potential
Which of the following factors can affect the membrane capacitance of a cell?
A. The size of the cell
B. The thickness of the cell membrane
C. The presence of ion channels in the cell membrane
D. All of the above
The thickness of the cell membrane
How does the membrane capacitance change during the action potential?
It increases during depolarization and decreases during repolarization
What is the relationship between membrane capacitance and the speed of nerve conduction?
A. Higher membrane capacitance results in faster nerve conduction
B. Lower membrane capacitance results in faster nerve conduction
C. Membrane capacitance has no effect on nerve conduction speed
D. The relationship between membrane capacitance and nerve conduction speed is unclear
Lower membrane capacitance results in faster nerve conduction
What is the Goldman equation used for?
To calculate the resting membrane potential of a cell
Which of the following ions is not included in the Goldman equation?
A. Sodium
B. Potassium
C. Chloride
D. Calcium
Calcium
What is the importance of the Goldman equation in physiological processes?
A. It helps to determine the concentration gradients of ions across the cell membrane
B. It helps to determine the selectivity of ion channels in the cell membrane
C. It helps to determine the permeability of ions across the cell membrane
D. It helps to determine the thickness of the cell membrane
It helps to determine the concentration gradients of ions across the cell membrane
Which of the following factors can affect the accuracy of the Goldman equation?
A. Changes in ion concentration gradients
B. Changes in membrane potential
C. Changes in membrane capacitance
D. All of the above
All of the above
Which of the following is an assumption of the Goldman equation?
A. The membrane is impermeable to all ions
B. The ion channels are voltage-gated
C. The ion channels are selective for only one type of ion
D. The membrane is permeable to all ions
The membrane is permeable to all ions
What would be the approximate membrane
potential of a neuron if the ratio of sodium to potassium conductance of membrane (gNa/gK) is 1/20 and ENa=+60mV, EK=-85mV? (assume that chloride ions do not contribute to the membrane potential)
-78mV
Following is NOT the electrical parameters of neuron based on its construction and functions:
* Voltage source
* Current source
* Electromotive force
* Capacitance
Electromotive force
Conductance of an ion is directly proportional to the resistances. True or false?
False, conductance of an ion is inversely proportional to the resistances
The study of the electrical properties of biological cells and tissues is called?
Electrophysiology
____________ technique in electrophysiology allows the study of single or multiple ion channels in cells.
Patch clamp technique
What is an action potential?
A change in the membrane potential of a cell
Which ion is primarily responsible for the depolarization phase of the action potential?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
Sodium
What is the threshold potential?
A. The potential at which ion channels begin to open
B. The potential at which ion channels begin to close
C. The potential at which no ion channels are open
D. The potential at which the cell is at rest
The potential at which ion channels begin to open
Which of the following is a characteristic of the action potential?
A. It is graded
B. It is always the same amplitude
C. It can be initiated at any point on the membrane
D. It lasts for a very long time
It is always the same amplitude
Which of the following is an example of an excitable cell?
A. Muscle cell
B. Fat cell
C. Connective tissue cell
D. Bone cell
Muscle cell
What is the role of voltage-gated ion channels in the action potential?
They open and close in response to changes in membrane potential
The period of time during which the cell cannot generate another action potential?
Refractory period
What are types of refractory period?
Absolute Refractory Period
Relative Refractory Period
Which ion is primarily responsible for the repolarization phase of the action potential?
A. Potassium
B. Sodium
C. Calcium
D. Chloride
Potassium
What is the all-or-none law of the action potential?
A. The amplitude of the action potential is always the same
B. The action potential can be initiated at any point on the membrane
C. The action potential is graded
D. The action potential either occurs or it doesn’t occur at all
The action potential either occurs or it doesn’t occur at all
__________________ helps to maintain the resting membrane potential
Sodium-potassium pump
Which of the following is a characteristic of the absolute refractory period?
A. It is the period of time during which the cell cannot generate another action potential
B. It is the period of time during which the cell is depolarized
C. It is the period of time during which the cell is hyperpolarized
D. It is the period of time during which the cell is at rest
It is the period of time during which the cell cannot generate another action potential
Voltage-gated calcium channels open and close in response to changes in membrane potential. True or false?
True.
What is the role of the myelin sheath in the action potential?
A. It helps to generate the action potential
B. It helps to maintain the resting membrane potential
C. It increases the speed of conduction of the action potential
D. It decreases the speed of conduction of the action potential
It increases the speed of conduction of the action potential
Which of the following is a characteristic of the relative refractory period?
A. It is the period of time during which the cell cannot generate another action potential
B. It is the period of time during which the cell is depolarized
C. It is the period of time during which the cell is hyperpolarized
D. It is the period of time during which the cell is at rest
It is the period of time during which the cell cannot generate another action potential, but with a strong enough stimulus, it can generate another action potential.
What is the role of the sodium inactivation gate in the action potential?
It is responsible for the repolarization phase of the action potential
Which of the following is NOT a factor that affects the speed of conduction of the action potential?
A. Diameter of the axon
B. Presence of myelin sheath
C. Presence of voltage-gated ion channels
D. Strength of the stimulus
Strength of the stimulus
What is the role of the potassium channels in the action potential?
A. They are responsible for the depolarization phase of the action potential
B. They open and close in response to changes in membrane potential
C. They are always open
D. They are responsible for the repolarization phase of the action potential
They are responsible for the repolarization phase of the action potential
Which of the following is a characteristic of the all-or-nothing principle of the action potential?
A. The amplitude of the action potential is proportional to the strength of the stimulus
B. The amplitude of the action potential is inversely proportional to the strength of the stimulus
C. The amplitude of the action potential is always the same regardless of the strength of the stimulus
D. The amplitude of the action potential is always changing depending on the strength of the stimulus
The amplitude of the action potential is always the same regardless of the strength of the stimulus.
The minimal current amplitude of indefinite duration (few hundred milliseconds) that results in the depolarization threshold of the cell membranes being reached (i.e. an action potential or the contraction of a muscle) is called?
Rheobase
_____________ is the shortest duration of an electrical stimulus.
Chronaxy
At ________, the threshold amplitude is twice the rheobase
Chronaxy
What is the primary mechanism by which the action potential is propagated along an axon?
A. Diffusion of ions
B. Electrostatic repulsion
C. Conformational changes in voltage-gated ion channels
D. Enzymatic reactions
Conformational changes in voltage-gated ion channels
Which of the following is a characteristic of saltatory conduction?
A. It occurs in unmyelinated axons
B. It is slower than continuous conduction
C. It requires less energy than continuous conduction
D. It occurs in myelinated axons
It occurs in myelinated axons
What is the role of the nodes of Ranvier in the propagation of the action potential?
They help to regenerate the action potential along the axon
Which of the following is a characteristic of continuous conduction?
A. It occurs in myelinated axons
B. It is faster than saltatory conduction
C. It requires more energy than saltatory conduction
D. It occurs in unmyelinated axons
It occurs in unmyelinated axons
What is the role of the refractory period in the propagation of the action potential?
A. It allows the cell to generate another action potential immediately
B. It prevents the cell from generating another action potential immediately
C. It helps to generate the action potential
D. It helps to maintain the resting membrane potential
It prevents the cell from generating another action potential immediately
What is the role of the myelin sheath in the propagation of the action potential?
It increases the speed of conduction of the action potential
Which of the following is a characteristic of depolarization in the propagation of the action potential?
A. It causes the membrane potential to become more negative
B. It causes the membrane potential to become more positive
C. It has no effect on the membrane potential
D. It causes the membrane potential to become more neutral
It causes the membrane potential to become more positive
____________ is the site where the action potential is regenerated
Axon hillock
___________ period lasts for a fixed period of time
refractory period
What is electrotonic conduction?
A. The passive spread of electrical signals along a neuron’s dendrites and cell body
B. The active propagation of action potentials along an axon
C. The process of converting electrical signals into chemical signals
D. The process of converting chemical signals into electrical signals
The passive spread of electrical signals along a neuron’s dendrites and cell body
Which of the following factors affect the extent of electrotonic conduction?
A. The diameter of the axon
B. The myelination of the axon
C. The distance between the synapses
D. The frequency of action potentials
The diameter of the axon
What is the role of the dendritic tree in electrotonic conduction?
A. It helps to generate the action potential
B. It helps to maintain the resting membrane potential
C. It amplifies the incoming signals
D. It attenuates the incoming signals
It amplifies the incoming signals
Which of the following is a characteristic of electrotonic conduction?
A. It is faster than action potential conduction
B. It is slower than action potential conduction
C. It does not require energy
D. It requires more energy than action potential conduction
It is slower than action potential conduction
What is the main advantage of electrotonic conduction over action potential conduction?
It allows for longer distances of communication between neurons
In which type of neuron is electrotonic conduction the predominant mode of signal transmission?
INTERNEURONS
What is the maximum distance that electrotonic signals can travel before they become too weak to be detected?
A. 1 cm
B. 10 cm
C. 100 cm
D. There is no maximum distance
There is no maximum distance
What is local circuit theory?
A theory that explains how electrotonic signals are propagated through neuronal tissue
According to local circuit theory, what is the main mechanism responsible for the spread of electrotonic signals?
A. Action potentials
B. Synaptic transmission
C. Ionic currents
D. Membrane capacitance
Ionic currents
The sliding filament theory was explained by ____________ and __________
A.F.Huxley and Hugh Huxley
What is the Sliding Filament Theory?
a) A theory that explains how muscles produce force and movement
b) A theory that explains how bones move in the human body
c) A theory that explains how neurons transmit signals
A theory that explains how muscles produce force and movement
Which of the following is not a component of the Sliding Filament Theory?
a) Actin filaments
b) Myosin filaments
c) Calcium ions
d) Z-discs
Z-discs
During muscle contraction, which of the following occurs?
a) Actin filaments slide towards each other
b) Myosin filaments slide towards each other
c) Actin and myosin filaments remain stationary
d) Calcium ions bind to the myosin filaments
Myosin filaments slide towards each other
What is the role of calcium ions in muscle contraction?
Calcium ions activate the myosin-actin binding process, allowing myosin to pull on actin
What is the function of the cross-bridge in muscle contraction?
The cross-bridge connects the actin and myosin filaments
What is the first step in a single cross bridge cycle?
a) Calcium ions bind to troponin
b) ATP binds to myosin
c) Myosin binds to actin
d) ADP and phosphate are released from myosin
ATP binds to myosin
What happens after ATP binds to myosin in a single cross bridge cycle?
Myosin releases ADP and phosphate
Calcium ions cause myosin to bind to actin in a single cross bridge cycle. True or false?
True
What is the final step in a single cross bridge cycle?
a) Myosin releases ADP and phosphate
b) The cross bridge disconnects
c) Calcium ions bind to troponin
d) ATP binds to myosin
The cross bridge disconnects
What is the first step in multiple cross bridge cycling?
Calcium ions bind to troponin
What happens after calcium ions bind to troponin in multiple cross bridge cycling?
a) Myosin releases ADP and phosphate
b) Myosin binds to actin
c) The cross bridge disconnects
d) Calcium ions cause the tropomyosin to move away from the binding site on the actin filament
Calcium ions cause the tropomyosin to move away from the binding site on the actin filament
What is the role of tropomyosin in multiple cross bridge cycling?
a) Tropomyosin binds to calcium ions
b) Tropomyosin prevents myosin from binding to actin
c) Tropomyosin allows myosin to bind to actin
d) Tropomyosin provides energy for muscle contraction
Tropomyosin prevents myosin from binding to actin
What happens after tropomyosin moves away from the binding site on actin in multiple cross bridge cycling?
Myosin binds to actin
Which of the following is the main component of thin filaments in skeletal muscle fibers?
a) Actin
b) Myosin
c) Tropomyosin
d) Troponin
Actin
__________________ proteins blocks the myosin binding site on actin in the absence of calcium ions
Tropomyosin
Which of the following statements is true about the sliding filament theory?
a) The theory states that muscles contract by increasing the length of the sarcomere
b) The theory states that myosin filaments slide past actin filaments during muscle contraction
c) The theory states that ATP is the primary source of energy for muscle contraction
d) The theory states that calcium ions directly cause muscle fibers to contract
The theory states that myosin filaments slide past actin filaments during muscle contraction
Which of the following molecules provides the energy required for myosin heads to move along actin filaments?
a) Calcium ions
b) ADP
c) ATP
d) Troponin
ATP
What is the role of troponin in muscle contraction?
Troponin binds to calcium ions, which causes tropomyosin to move away from the myosin binding site on actin
In case of ATP depletion, _________ phenomena is observed.
Rigor Mortis
Which of the following best describes an isometric contraction?
a) The muscle shortens during contraction
b) The muscle lengthens during contraction
c) The muscle generates tension without changing length
d) The muscle contracts without generating tension
The muscle generates tension without changing length
Which of the following best describes an isotonic contraction?
a) The muscle shortens during contraction
b) The muscle lengthens during contraction
c) The muscle generates tension without changing length
d) The muscle contracts without generating tension
The muscle shortens during contraction
Which type of contraction is typically associated with holding a heavy object without moving it?
a) Isometric contraction
b) Isotonic contraction
c) Eccentric contraction
d) Concentric contraction
Isometric contraction
Which type of contraction is typically associated with lifting a heavy object?
a) Isometric contraction
b) Isotonic contraction
c) Eccentric contraction
d) Concentric contraction
Isotonic contraction
Which of the following types of contraction is typically associated with lowering a heavy object?
a) Isometric contraction
b) Isotonic contraction
c) Eccentric contraction
d) Concentric contraction
Eccentric contraction
