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Q5(a):
Differentiate between the following:
(a) Diffusion and Osmosis
Solution :
Definition and Theoretical Foundation
The transport of water and solutes across biological membranes is governed by the principles of thermodynamics and kinetic molecular theory. Diffusion and Osmosis represent two distinct modes of passive transport, defined by the nature of the medium and the movement of solutes versus solvents.
| Feature | Diffusion | Osmosis |
|---|---|---|
| Definition | Movement of particles from a region of higher concentration to lower concentration. [Per Fick’s Law of Diffusion]. | Movement of solvent molecules across a semi-permeable membrane from low solute potential to high solute potential. |
| Requirement | Does not require a membrane. | Requires a semi-permeable membrane. |
| Substance Moved | Solutes, ions, or gases. | Specifically solvent (water) molecules. |
Step 1: Mechanism of Diffusion
Diffusion is a passive movement driven by the kinetic energy of molecules. The net flux $J$ is defined by the equation $J = -D \frac{dC}{dx}$, where $D$ is the diffusion coefficient and $\frac{dC}{dx}$ is the concentration gradient. It continues until the system reaches dynamic equilibrium.
Step 2: Mechanism of Osmosis
Osmosis is a specialized case of diffusion restricted by a semi-permeable membrane. The driving force is the Water Potential Gradient ($\Delta \psi_w$). Water moves from a region of higher water potential ($\psi_w$) to a region of lower water potential. The equation governing this is $\psi_w = \psi_s + \psi_p$, where $\psi_s$ is solute potential and $\psi_p$ is pressure potential.
Step 3: Visual Representation of Transport
Conclusion and Summary
The primary distinction lies in the selectivity of the barrier and the specificity of the substance transported. While diffusion is a general physical phenomenon of random thermal motion, osmosis is a biological necessity for maintaining cellular turgidity and water balance in plant cells. [As defined by the principles of Plant Physiology, NCERT].
Final Solution: Diffusion is the movement of any molecule along its concentration gradient without a membrane, whereas osmosis is the specific movement of solvent molecules across a semi-permeable membrane down a water potential gradient.
More Questions from Class 11 Biology Transport in Plants EXERCISES
- Q1: What are the factors affecting the rate of diffusion?
- Q2: What are porins? What role do they play in diffusion?
- Q3: Describe the role played by protein pumps during active transport in plants.
- Q4: Explain why pure water has the maximum water potential.
- Q5(b): Differentiate between the following: (b) Transpiration and Evaporation
- Q5(c): Differentiate between the following: (c) Osmotic Pressure and Osmotic Potential
- Q5(d): Differentiate between the following: (d) Imbibition and Diffusion
- Q5(e): Differentiate between the following: (e) Apoplast and Symplast pathways of movement of water in plants.
- Q5(f): Differentiate between the following: (f) Guttation and Transpiration.
- Q6: Briefly describe water potential. What are the factors affecting it?
- Q7: What happens when a pressure greater than the atmospheric pressure is applied to pure water or a solution?
- Q8(a): (a) With the help of well-labelled diagrams, describe the process of plasmolysis in plants, giving appropriate examples.
- Q8(b): (b) Explain what will happen to a plant cell if it is kept in a solution having higher water potential.
- Q9: How is the mycorrhizal association helpful in absorption of water and minerals in plants?
- Q10: What role does root pressure play in water movement in plants?
- Q11: Describe transpiration pull model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?
- Q12: Discuss the factors responsible for ascent of xylem sap in plants.
- Q13: What essential role does the root endodermis play during mineral absorption in plants?
- Q14: Explain why xylem transport is unidirectional and phloem transport bi-directional.
- Q15: Explain pressure flow hypothesis of translocation of sugars in plants.
- Q16: What causes the opening and closing of guard cells of stomata during transpiration?
CBSE Solutions for Class 11 Biology Transport in Plants
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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