Diffusion


Transport of Food And Minerals In Plants - I - Concepts
Class - 8th ICSE Subjects
 
 
Concept Explanation
 

Diffusion

Transport of substances by diffusion

One of the process of transport of substances within and across the cell by the process of diffusion. Transport of substances in cell can occur in two different ways: Passive and Active transport.

Passive transport :  Passive transport is the movement of a solute from a region of high concentration to a region of low concentration. This type of transport occur without the expenditure of energy.

Active transport : Active transport is the type of transport in which there occur movement of substances from region of low concentration to high concentration against the concentration gradient. In this type of movement there occur expenditure of energy.

The difference between passive transport and active transport is that the active transport requires energy, and moves substances against their respective concentration gradient, whereas passive transport requires no cellular energy and moves substances in the direction of their respective concentration gradient.

Example :

When gases like carbon dioxide and oxygen accumulate inside the cell, their concentration is greater inside compared to the external environment. Due to this difference in concentrations, their net movement is to the outside by diffuse, i.e., from their region of higher concentration to lower concentration.

Similarly, when the concentration is greater outside, O_2 and CO_2  move inside the cell from the external environment following the principle of diffusion. In unicellular organisms, transport of gases by diffusion occurs all over the cell membrane, e.g., Chlamydomonas, Paramecium, Amoeba, etc.

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Sample Questions
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Question : 1

Which of the following are correct :

(a) Passive transport is the movement of a solute from a region of high concentration to a region of low concentration.

(b)  Active transport is the movement of a solute from a region of high concentration to a region of low concentration.

(c) Active transport is the type of transport in which there occur movement of substances from region of low concentration to high concentration against the concentration gradient.

Right Option : C
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Question : 2

Choose the best definition of 'Diffusion'

Right Option : A
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Question : 3

Which of the following organism perform exchange of gases through it body surface by the process of diffusion ?

Right Option : A
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