Cell Biology Fundamentals And Biophysical Methods Practice Tests

Question 1

A cell membrane has a surface area of $5 	imes 10^{-9} m^2$ and a thickness of 7.5 nm. If the membrane is composed of phospholipids with a density of 920 kg/m³, what is the mass of the phospholipids in the membrane?

Accepted Answer

A. 3.45 	imes 10^{-14} kg

Answer

B. 4.20 	imes 10^{-12} kg

Answer

C. 1.50 	imes 10^{-16} kg

Answer

D. 6.80 	imes 10^{-10} kg

Question 2

A spherical cell has a radius of 10 μm. If the concentration of a particular protein inside the cell is 2.5 μM, how many molecules of that protein are present in the cell? (Assume Avogadro's number is $6.022 	imes 10^{23}$ molecules/mol)

Accepted Answer

B. 6.3 	imes 10^{7} molecules

Answer

A. 2.5 	imes 10^{6} molecules

Answer

C. 1.0 	imes 10^{9} molecules

Answer

D. 4.2 	imes 10^{5} molecules

Question 3

The diffusion coefficient of a protein in the cytoplasm is $1 	imes 10^{-12} m^2/s$. How long will it take for the protein to diffuse an average distance of 5 μm?

Accepted Answer

C. 12.5 s

Answer

A. 2.5 s

Answer

B. 5.0 s

Answer

D. 25.0 s

Question 4

The nuclear envelope contains pores that allow molecules to pass through. If the pore has a radius of 25 nm, what is the approximate area available for transport through a single pore, assuming it's circular?

Accepted Answer

D. 1.96 	imes 10^{-15} m^2

Answer

A. 7.85 	imes 10^{-14} m^2

Answer

B. 3.14 	imes 10^{-16} m^2

Answer

C. 6.25 	imes 10^{-17} m^2

Question 5

A cell imports glucose via facilitated diffusion. The rate of glucose transport is given by $V = V_{max} \frac{[glucose]_{out}}{K_m + [glucose]_{out}}$, where $V_{max} = 10 \mu mol/min$ and $K_m = 5 mM$. Calculate the transport rate when the external glucose concentration is 10 mM.

Accepted Answer

6.67 μmol/min

Question 6

The rate of passive diffusion across a cell membrane is directly proportional to the square root of the concentration gradient. True or False?

Accepted Answer

False

Answer

True

Question 7

Which of the following components contribute to the structure and function of the cytoskeleton?

Answer

A. Actin filaments

Answer

B. Microtubules

Answer

C. Intermediate filaments

Answer

D. Glycogen inclusions

Question 8

If the surface area of a cell membrane is doubled while the concentration gradient of a substance remains constant, by what factor will the rate of passive diffusion change, assuming Fick's Law applies?

Accepted Answer

B. The rate will double

Answer

A. The rate will remain the same

Answer

C. The rate will be halved

Answer

D. The rate will quadruple

Question 9

A spherical cell with a radius of 10 $\mu m$ is subjected to a force of 5 $pN$ using optical tweezers. If the cell's displacement is 0.5 $\mu m$, calculate the effective spring constant $k$ of the cell using Hooke's Law, $F = kx$, where $F$ is the force and $x$ is the displacement. Provide your answer in $pN/\mu m$.

Accepted Answer

10 pN/\mu m

Question 10

In Magnetic Twisting Cytometry (MTC), a twisting force is applied to magnetic beads attached to a cell. If the applied torque $\tau$ is 20 $pN \cdot \mu m$ and the bead's radius $r$ is 1 $\mu m$, what is the force $F$ exerted on the cell, assuming $\tau = F \cdot r$?

Accepted Answer

A. 20 pN

Answer

B. 10 pN

Answer

C. 40 pN

Answer

D. 5 pN

Question 11

In cytoindentation, a stiffer cell will exhibit a smaller indentation depth for a given applied force compared to a less stiff cell.

Accepted Answer

True

Answer

False

Question 12

During a shear flow experiment, cells are subjected to a shear stress of 15 $dyn/cm^2$. If the area of a cell exposed to the flow is 200 $\mu m^2$, what is the force experienced by the cell in piconewtons (pN)? Note: 1 $dyn/cm^2 = 0.1 \, N/m^2$ and 1 $N = 10^{12} \, pN$.

Accepted Answer

B. 300 pN

Answer

A. 150 pN

Answer

C. 450 pN

Answer

D. 600 pN

Question 13

An Atomic Force Microscope (AFM) cantilever has a spring constant of 0.1 N/m. If the cantilever deflects by 50 nm when interacting with a cell, calculate the force exerted on the cell in piconewtons (pN).

Accepted Answer

5000 pN

Question 14

Which of the following biophysical techniques can be used to measure the viscoelastic properties of cells?

Answer

Magnetic Twisting Cytometry (MTC)

Answer

Laser Optical Tweezers

Answer

Shear flow

Answer

Cytoindentation

Question 15

If the membrane potential of a cell is described by the Goldman-Hodgkin-Katz equation: $$V_m = \frac{RT}{F} \ln\left(\frac{P_K[K^+]_o + P_{Na}[Na^+]_o + P_{Cl}[Cl^-]_i}{P_K[K^+]_i + P_{Na}[Na^+]_i + P_{Cl}[Cl^-]_o}\right)$$, and the permeability of potassium ions ($P_K$) is significantly increased, what is the most likely effect on the membrane potential ($V_m$)?

Accepted Answer

A. The membrane potential will become more negative.

Answer

B. The membrane potential will become more positive.

Answer

C. The membrane potential will remain unchanged.

Answer

D. The membrane potential will oscillate.

Question 16

Consider a scenario where you are using fluorescence recovery after photobleaching (FRAP) to measure the diffusion coefficient (D) of a protein in a cell membrane. The recovery half-time ($t_{1/2}$) is 10 seconds, and the radius (r) of the bleached spot is 2 μm. Using the formula $$D = \frac{r^2}{4t_{1/2}}$$, calculate the diffusion coefficient.

Accepted Answer

B. 1.0 x 10^-12 m²/s

Answer

A. 0.5 x 10^-12 m²/s

Answer

C. 2.0 x 10^-12 m²/s

Answer

D. 4.0 x 10^-12 m²/s

Question 17

In X-ray crystallography, the Bragg equation, $$nλ = 2d\sinθ$$, is used to determine the spacing between atomic layers in a crystal. If X-rays with a wavelength (λ) of 0.154 nm are diffracted at an angle (θ) of 22.5° for the first order diffraction (n = 1), what is the spacing (d) between the atomic layers?

Accepted Answer

C. 0.20 nm

Answer

A. 0.10 nm

Answer

B. 0.15 nm

Answer

D. 0.25 nm

Question 18

The Hill equation, $$Y = \frac{[L]^n}{K_d + [L]^n}$$, describes the fraction of protein binding sites occupied by a ligand. If the dissociation constant ($K_d$) is 10 μM, the Hill coefficient (n) is 2, and the ligand concentration ([L]) is also 10 μM, what is the fraction of protein binding sites occupied (Y)?

Accepted Answer

B. 0.5

Answer

A. 0.25

Answer

C. 0.75

Answer

D. 1.0

Question 19

In fluorescence microscopy, the resolution is limited by the diffraction of light. According to the Abbe diffraction limit, the resolution (d) is given by $$d = \frac{λ}{2NA}$$, where λ is the wavelength of light and NA is the numerical aperture of the objective lens. If you are using a 488 nm laser and an objective lens with a numerical aperture of 1.4, what is the approximate resolution?

Accepted Answer

A. 174 nm

Answer

B. 244 nm

Answer

C. 349 nm

Answer

D. 683 nm

Question 20

The Nernst equation, $$E = \frac{RT}{zF} \ln\frac{[ion]_o}{[ion]_i}$$, describes the equilibrium potential for an ion across a membrane. At room temperature (25°C), the value of $\frac{RT}{F}$ is approximately 25 mV. If the extracellular concentration of $Na^+$ is 145 mM and the intracellular concentration is 12 mM, what is the Nernst potential for $Na^+$ (z = +1)?

Accepted Answer

C. +63 mV

Answer

A. -63 mV

Answer

B. -25 mV

Answer

D. +25 mV

Cell Biology Fundamentals And Biophysical Methods Practice Tests

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Cell Biology Fundamentals and Biophysical Methods

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