Electric Fields and Protein Electrophoresis
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Questions and Answers

What determines the distance traveled by particles of the same size over a given time in an electric field?

  • The mass of the particles
  • The shape of the particles
  • The temperature of the environment
  • The electric charge of the particles (correct)

    • Which statement is true about electric dipoles?

  • The magnitude of the dipole moment is independent of the distance between charges.
  • The dipole moment is directed from the negative to the positive charge. (correct)
  • Dipoles do not generate any electric fields.
  • They consist of two charges of the same sign.

    • What is the unit of electric current?

  • Coulomb
  • Ohm
  • Ampere (correct)
  • Volt

    • What defines direct current (DC)?

    <p>The flow of charges is constant and in a single direction.</p> Signup and view all the answers

    How can electric fields and potentials of an electric dipole be determined?

    <p>By superposing the point charge potentials of its two charges.</p> Signup and view all the answers

    What is the formula for current across an area?

    <p>I = \Delta q / \Delta t</p> Signup and view all the answers

    Which of the following is NOT true about pulse current?

    <p>It flows continuously in one direction.</p> Signup and view all the answers

    Which molecules can exhibit an electric dipole moment?

    <p>Molecules such as water and sodium chloride</p> Signup and view all the answers

    What current level is generally considered the threshold for sensation in humans?

    <p>1 mA</p> Signup and view all the answers

    Which of the following describes the physiological effects of a current between 10 mA and 20 mA?

    <p>Onset of sustained muscular contraction</p> Signup and view all the answers

    At what current is ventricular fibrillation possible and often fatal?

    <p>100-300 mA</p> Signup and view all the answers

    What is the calculated current through a dry body when a voltage of 120 V is applied?

    <p>80 mA</p> Signup and view all the answers

    What current level can lead to respiratory paralysis and sustained ventricular contraction?

    <p>6000 mA</p> Signup and view all the answers

    How does the resistance of the human body change when it is wet compared to when it is dry?

    <p>Resistance decreases significantly</p> Signup and view all the answers

    At what current level is ventricular fibrillation likely to occur?

    <p>100 mA</p> Signup and view all the answers

    Which of the following factors does not directly influence the severity of an electric shock?

    <p>Voltage</p> Signup and view all the answers

    Which frequency range is the human body most sensitive to electrical shocks?

    <p>50-60 Hz</p> Signup and view all the answers

    What phenomenon is created when gas becomes conductive due to high temperatures or strong electric fields?

    <p>Plasma formation</p> Signup and view all the answers

    What is the leading cause of death from electrical shock?

    <p>Ventricular fibrillation</p> Signup and view all the answers

    What type of ion is known to have positive contributions to well-being by destroying harmful bacteria?

    <p>Negative ions</p> Signup and view all the answers

    How does the frequency of alternating current (AC) affect physiological effects during an electric shock?

    <p>It influences the onset of pain and muscle contractions</p> Signup and view all the answers

    Which factors can increase the ionization of gas, making it conductive to electric current?

    <p>Sunshine beams and cosmic radiation</p> Signup and view all the answers

    What health disturbances are commonly associated with exposure to positive ions?

    <p>Headaches and irritability</p> Signup and view all the answers

    What is the procedure called that uses artificially generated aeroions for treatment?

    <p>Aeroionotherapy</p> Signup and view all the answers

    What is the relationship between electric field (E) and potential difference (∆ϕ) as described?

    <p>E = -Δϕ/Δr</p> Signup and view all the answers

    What does electrophoresis primarily enable in biological applications?

    <p>Transport of charged macromolecules under voltage</p> Signup and view all the answers

    What is the net charge range of a protein that can undergo electrophoresis?

    <p>-100 to +100 elementary charges</p> Signup and view all the answers

    What force, denoted as Fe, acts on a charged protein in the electric field?

    <p>Fe = qE</p> Signup and view all the answers

    Which of the following equations correctly represents the drag force (Fd) on a migrating protein?

    <p>Fd = -6πηav</p> Signup and view all the answers

    What is the equation that signifies the equilibrium between electric force and drag force on a protein?

    <p>Fe = Fd</p> Signup and view all the answers

    What is the primary purpose of using electrophoresis in clinical diagnostics?

    <p>Separating components in blood plasma</p> Signup and view all the answers

    How does the pH of the solution affect a protein's net charge during electrophoresis?

    <p>pH variations influence the charge of the protein</p> Signup and view all the answers

    What happens to charged particles of different charges when subjected to the same electric field?

    <p>They travel different distances based on their charge.</p> Signup and view all the answers

    Which statement accurately describes an electric dipole?

    <p>It consists of two equal and opposite charges separated by a distance.</p> Signup and view all the answers

    Which of the following best describes direct current (DC)?

    <p>Current that flows continuously in one direction.</p> Signup and view all the answers

    How is electric current defined mathematically?

    <p>I = ∆q / ∆t</p> Signup and view all the answers

    Which type of current alternates in direction at regular intervals?

    <p>Alternating current (AC)</p> Signup and view all the answers

    What is the significance of the dipole moment in electric fields?

    <p>It describes the separation of positive and negative charges.</p> Signup and view all the answers

    Which of the following statements about pulse current is true?

    <p>It changes in strength during the time interval.</p> Signup and view all the answers

    What is the unit of measurement for current?

    <p>Ampere (A)</p> Signup and view all the answers

    What is the primary factor that determines the net charge of a protein during electrophoresis?

    <p>The pH value of the solution</p> Signup and view all the answers

    Which equation represents the velocity of a migrating protein in an electric field?

    <p>v = -qE/6πηa</p> Signup and view all the answers

    In the context of electrophoresis, what is the primary role of the drag force acting on a protein?

    <p>To balance the electric force acting on the protein</p> Signup and view all the answers

    How does the equation E = -Δϕ/Δr relate electric field to potential difference?

    <p>E is equal to the potential difference divided by distance</p> Signup and view all the answers

    What forces must be balanced for a charged protein to move through an electrolyte in electrophoresis?

    <p>Electric force and drag force</p> Signup and view all the answers

    What is the significance of a protein's folding pattern in biological functions?

    <p>It influences the protein's functional properties</p> Signup and view all the answers

    Which application does electrophoresis NOT typically serve?

    <p>Measuring electrical conductivity of gases</p> Signup and view all the answers

    What does the negative sign in the relationship E = -Δϕ/Δr indicate?

    <p>Electric field points in the direction of decreasing potential</p> Signup and view all the answers

    What is the formula for current density in terms of current and surface area?

    <p>$j = \frac{dI}{dS}$</p> Signup and view all the answers

    Which equation represents the relationship between electric field and electrolytic current?

    <p>$E = I \cdot R$</p> Signup and view all the answers

    What does the symbol $ u$ represent in the expression for current density involving multiple charged particles?

    <p>The velocity of charged particles</p> Signup and view all the answers

    How is the resistance R defined when considering two parallel plates in an electrolyte?

    <p>$R = \frac{\rho l}{S}$</p> Signup and view all the answers

    What is the primary factor that affects the electrophoretic mobility of ions?

    <p>The viscosity of the solution</p> Signup and view all the answers

    What does the term resistivity ($\rho$) refer to in the context of electrolytes?

    <p>The capacity of an electrolyte to resist electric flow</p> Signup and view all the answers

    What is the value of typical resistivity for body fluids?

    <p>$1 \Omega m$</p> Signup and view all the answers

    What is the significance of the term $\mu$ in the context of ion movement in an electric field?

    <p>It defines the electrophoretic mobility of ions</p> Signup and view all the answers

    What is the relationship between conductance and resistivity?

    <p>Conductance is the inverse of resistivity.</p> Signup and view all the answers

    Which tissue type has the highest resistivity value?

    <p>Bone</p> Signup and view all the answers

    What is meant by the term 'impedance' in electric current in tissues?

    <p>The total resistance to the current, including capacitance effects.</p> Signup and view all the answers

    What diagnostic method uses impedance measurements to evaluate tissue condition?

    <p>Rheography</p> Signup and view all the answers

    Which of the following statements is true regarding the severity of electric shock?

    <p>The severity is dependent on the duration of exposure to electric current.</p> Signup and view all the answers

    What current level is generally considered to produce noticeable resistance changes due to nerve damage?

    <p>Between 10 mA and 20 mA</p> Signup and view all the answers

    Which factor does NOT influence the tissue impedance value?

    <p>Temperature of the surrounding environment.</p> Signup and view all the answers

    What is the typical frequency range of the alternating current used in rheography?

    <p>20-30 kHz</p> Signup and view all the answers

    What is the smallest possible charge that can exist, as defined in the fundamentals of electricity?

    <p>1.6 × 10^-19 C</p> Signup and view all the answers

    What happens when two like charges are placed close to each other?

    <p>They repel each other.</p> Signup and view all the answers

    Which of the following represents the correct formula for the electrostatic force between two charged particles in a medium?

    <p>$F = \frac{1}{4\pi\epsilon_0 \epsilon_r} \cdot \frac{q_1 q_2}{r^2}$</p> Signup and view all the answers

    What is the SI unit of electric charge?

    <p>Coulomb</p> Signup and view all the answers

    How does electrical charge behave according to the principle of conservation?

    <p>Charge is neither created nor destroyed.</p> Signup and view all the answers

    What is the primary driving force for the movement of electrons when materials are rubbed together?

    <p>Electrical force</p> Signup and view all the answers

    What does the electric field E define in a given space?

    <p>The electric force on a positive unit charge</p> Signup and view all the answers

    In Coulomb's law, what do the constants $ ext{k}$ and $ ext{E}$ represent?

    <p>Electrostatic constant and permittivity of the medium</p> Signup and view all the answers

    What is the total resistance to the current in living tissues referred to as?

    <p>Impedance</p> Signup and view all the answers

    Which type of tissue is characterized by the highest resistivity?

    <p>Dry skin</p> Signup and view all the answers

    Which of the following factors does NOT influence the severity of an electric shock?

    <p>Duration of exposure</p> Signup and view all the answers

    What method uses small alternating currents for diagnostic purposes related to tissue impedance?

    <p>Rheography</p> Signup and view all the answers

    Based on the provided information, which tissue has a resistivity of 2 $, ext{Ωm}$?

    <p>Muscle tissue</p> Signup and view all the answers

    Which ions are typically involved in defining the current density ('j') in living tissues?

    <p>Positive and negative ions</p> Signup and view all the answers

    How is conductance ($ackslashsigma$) of tissue related to resistivity ($ackslashrho$)?

    <p>Conductance is the reciprocal of resistivity.</p> Signup and view all the answers

    What factors are considered when assessing the impedance (Z) of living tissues?

    <p>Capacitance and ohmic resistance</p> Signup and view all the answers

    Study Notes

    Electric Field and Voltage

    • Electric field (E) is the negative potential gradient: E = -dφ/dr.
    • An approximate relationship is E = -Δφ/Δr, where Δφ is the potential difference and Δr is the distance between two points.

    Electrophoresis of Proteins

    • Electrophoresis separates charged macromolecules (proteins or DNA) using an applied voltage.
    • Protein net charge (from -100 to +100 elementary charges) depends on the solution's pH.
    • Electric force on a protein: Fe = qE (q = charge, E = electric field).
    • Drag force on a protein: Fd = -6πηav (η = viscosity, v = velocity, a = radius).
    • At equilibrium, Fe = Fd, leading to v = -qE/(6πηa). Velocity is proportional to charge (v ∝ q), enabling separation based on charge.

    Electric Dipole

    • An electric dipole consists of two equal and opposite charges separated by a distance.
    • Dipole moment (p) = qd (q = charge magnitude, d = distance, direction towards positive charge).
    • Dipoles are useful models for biological systems (e.g., cell membranes, cardiograms).

    Electric Current

    • Electric current (I) is the net charge transferred per unit time: I = Δq/Δt (Amperes).
    • Direct current (DC) flows continuously in one direction.
    • Alternating current (AC) changes direction periodically.
    • Current density (j) in an electrolyte: j = qn+v+ + qn-v- (n = ion concentration, v = velocity). j can also be expressed using ion mobility: j = qnE(μ+ + μ-).

    Electric Current in Living Tissues

    • Tissue conductance (σ) = 1/ρ (ρ = resistivity).
    • Resistivities vary greatly across tissues: spinal fluid (0.55 Ωm), blood (1.66 Ωm), muscle (2 Ωm), brain (14.3 Ωm), dry skin (105 Ωm), bone (107 Ωm).
    • Living tissues have high electrical resistance due to capacitance and ohmic resistance.
    • Impedance (Z) considers both resistance (R) and capacitance (C): 1/Z² = 1/R² + (ωC)².
    • Rheography uses AC current (20-30 kHz) to measure tissue impedance for diagnostic purposes.

    Physiological Effects of Electric Current

    • Severity of electric shock depends on current, path, duration, and AC/DC type.
    • (50Hz AC) 1 mA: sensation, 5 mA: maximum harmless current.
    • (50Hz AC) 10-20 mA: muscle contraction, breathing difficulty.
    • (50Hz AC) 50 mA: pain, 100-300+ mA: ventricular fibrillation (often fatal).
    • 6000 mA: ventricular contraction, respiratory paralysis (temporary).
    • Values for females are 60-80% of male values.
    • Human body resistance: ~1500 Ω (dry), ~500 Ω (wet).
    • Body is most sensitive to shocks around 50-60 Hz.
    • High-frequency currents mainly cause thermal effects.

    Electricity in Gases

    • Gases are usually non-conductive.
    • Plasma (ionized gas) conducts electricity, forming sparks, arcs, or lightning.
    • Ionization can occur through high temperatures, strong electric fields, or radiation (e.g., sunlight, X-rays, cosmic rays).
    • Aeroions (gaseous ions) exist in the air, with negative ions generally having positive effects and positive ions inducing negative health effects.
    • Aeroionotherapy uses artificially generated aeroions for treatment.

    Fundamentals of Electricity

    • Electricity is a force stemming from a net electrical charge between objects.
    • Electric charge, a fundamental property of particles, is quantized (exists in multiples of the elementary charge, e = 1.6 x 10^-19 C).
    • Like charges repel; opposite charges attract. A neutral atom has no net charge.
    • Charge is conserved (neither created nor destroyed). Transfer of electrons creates electrical force.
    • Coulomb's Law describes the electrostatic force (F) between two charges (q1, q2) separated by distance (r): F = k(q1q2/r^2), where k = 9 x 10^9 Nm²/C². The permittivity constant (ε₀ = 8.85 x 10^-12 F/m) modifies this for media other than a vacuum.
    • Electric field (E) is the force exerted on a unit positive charge; E = -dΦ/dr (negative potential gradient). Approximated as E = -ΔΦ/Δr.

    Electrophoresis of Proteins

    • Electrophoresis separates charged macromolecules (proteins, DNA) in an electrolyte using an applied voltage.
    • Protein net charge (from -100 to +100 elementary charges) depends on solution pH.
    • The electric force (Fe = qE) on a protein is balanced by drag force (Fd = -6πηav), where η is viscosity, v is velocity, and a is protein radius.
    • Electrophoretic separation relies on the relationship v = -qE/6πηa; velocity is proportional to charge (v ~ q), allowing separation of proteins with different charges.

    Electric Dipole

    • An electric dipole consists of two equal, opposite point charges separated by a small distance.
    • Dipole moment (p) is defined as p = qd (charge magnitude x distance).
    • The electric field and potential are found by superposing the point charge potentials of the two charges.
    • Dipoles model many molecules (water, NaCl) and are useful for describing electric fields generated by cells or organs (e.g., cardiogram generation).

    Electric Current: Basics

    • Electric current (I) is the net charge transferred per unit time (I = Δq/Δt); measured in amperes (A).
    • Direct current (DC) flows continuously in one direction.
    • Alternating current (AC) changes direction periodically.
    • Pulse current varies in strength over time.
    • Current density (j) is current per unit cross-sectional area (j = dI/dS) or j = qnv (charge x particle density x velocity). For multiple particle types: j = Σᵢ qᵢnᵢvᵢ.
    • In conductors (metals), electrons carry charge; in liquids/gases, ions carry charge.

    Electric Current in Electrolytes

    • Human body fluids are electrolytes.
    • The relationship between electric field (E) and electrolytic current (I) is E = IR, where R is resistance.
    • Resistance (R = ρl/S) depends on resistivity (ρ), length (l), and cross-sectional area (S) of the electrolyte. Body fluid resistivity is ~1 Ωm (much higher than copper).
    • Ion velocity (v = μE) relates to electrophoretic mobility (μ = q/6πηr), dependent on charge, size, and viscosity.
    • Current density in electrolytes: j = qnE(μ+ + μ-) (for positive and negative ions of the same salt).

    Electric Current in Living Tissues

    • Tissues have varying conductance (σ = 1/ρ).
    • High conductance: body fluids (blood, spinal fluid, urine).
    • Medium conductance: internal organs, muscle.
    • Low conductance: bone, dry skin.
    • Resistivity examples: spinal fluid (0.55 Ωm), blood (1.66 Ωm), muscle (2 Ωm), dry skin (10⁵ Ωm), bone (10⁷ Ωm).
    • Living tissue resistance is high due to capacitance and ohmic resistance; total resistance is impedance (Z).
    • Rheography uses small AC current (20-30 kHz) to measure impedance changes for diagnosis. Increased resistance can indicate nerve damage or tumors.

    Physiological Effects of Current, Electric Shock

    • Electric shock severity depends on current magnitude and other factors.

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    Description

    Explore the concepts of electric fields, voltage, and electrophoresis in this quiz. Understand the principles of electric dipoles and how proteins are separated based on their charge using an applied voltage. Test your knowledge on the relationships between electric force, drag force, and velocity.

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