Skip to content
Login Register

#concentration gradient

6 public questions tagged with this topic.

p-n Junction, Depletion Region and Diode Characteristics

The diffusion current in a p-n junction is due to:

**Depletion region** also called space-charge region, thickness typically 0.5 μm, contains no mobile carriers, only fixed ions, negative on p-side, positive on n-side, diffusion current due to concentration gradient, drift current due to field, equilibrium when J_drift + J_diff =0, voltage drop mainly across depletion region. Diffusion current arises from the movement of carriers (holes from p-side to n-side, electrons from n-side to p-side) due to concentration gradients across the junction during its formation. Substituting values gives Concentration gradient, which matches expected behaviou

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details
Membrane Transportation

In a U-tube experiment, if Side A has 4M NaCl and Side B has 10M NaCl, what will be the movement of water?

Demonstration using U-tube separated by membrane permeable only to water nicely illustrates colligative water movement. Osmotic pressure approximated by van't Hoff law pi equals i times C times R times T proportional to total particle concentration. Solution A holding 4 molar NaCl dissociates into sodium and chloride giving factor near two, so effective osmolarity roughly 8 osmoles, solution B 10 molar near 20 osmoles, markedly higher. Chemical potential of water mu equals mu naught plus RT ln a water minus V bar P, and a water declines with solute. Therefore water potential higher in dilute a

Ref: Nelson & Cox, Lehninger Principles of Biochemistry, Chapter 11: Osmosis and Water Movement Between Compartments.

View Details
Membrane Transportation

Which of the following conditions describes osmotic pressure?

Osmotic pressure is a colligative property describing tendency of water to move across semipermeable membranes that allow solvent but restrict solute permeation. When compartment containing dilute solution is separated from concentrated solution, water chemical potential is higher where solute activity is lower. Spontaneous diffusion drives water toward higher solute until chemical potentials equalize, causing volume increase and hydrostatic pressure rise on concentrated side. The additional hydrostatic pressure required to stop net influx and hold volumes constant at equilibrium defines osmot

Ref: Alberts et al., Molecular Biology of the Cell, Chapter 11: Osmotic Pressure Definition and van't Hoff Equation.

View Details
Membrane Transportation

Which of the following best defines Fick’s law of diffusion?

Fick's laws provide quantitative framework for diffusion in solutions and across biological membranes integrating concentration, distance and membrane properties. First law states net diffusive flux J, amount per area per time, is proportional to concentration difference divided by distance, expressed mathematically as J equals minus D diffusion coefficient times dC/dx concentration gradient, where negative sign denotes direction from high to low. D depends on temperature increasing Brownian motion, solute Stokes radius inversely via Stokes-Einstein relation, viscosity of medium and partition

Ref: Berg et al., Biochemistry, 9th ed., Chapter 11: Fick's Law of Diffusion and Concentration Gradient.

View Details
BASICS of PLANT+PYQS

According to Fick’s law, diffusion flux is directly proportional to:

Answer: C) Concentration gradient. For BASICS of PLANT, remember the key idea and you’ll land on this option; the distractors usually swap cause and effect or confuse similar terms. Avoid: A) Distance travelled; B) Temperature only; D) Molecular weight. Name the process first, then pick the option that describes it — don’t reverse cause and effect.

Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.

View Details