How do substances like CO 2 and water move in and out of the cell? Discuss.

The molecules, in general, tend to move from a place of their higher concentration to a lower concentration. This process is known as diffusion. The diffusion of water across a semi-permeable membrane is called osmosis. It can be observed between the cytoplasm of cells and extracellular fluid. The molecules such as CO 2 and water move across a cell with respect to their concentration gradient. If the concentration of CO 2 and water molecules is high within the cytoplasm of a cell as compared to extracellular fluid, they move outside the cell and vice versa.

Movement by diffusion is passive, and may be from one part of the cell to the other, or from cell to cell, or over short distances, say, from the intercellular spaces of the leaf to the outside. No energy expenditure takes place. In diffusion, molecules move in a random fashion, the net result being substances moving from regions of higher concentration to regions of lower concentration. Diffusion is a slow process and is not dependent on a ‘living system’. Diffusion is obvious in gases and liquids, but diffusion in solids is more likely rather than of solids. Diffusion is very important to plants since it is the only means for gaseous movement within the plant body.

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Why do the doctors administer saline (salt solution) only, not the distilled water?

Important Questions on Plasma Membrane

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Science>Biology>Plasma Membrane>Transport Across the Membrane

A few dried raisins are put in water for some time and then placed inside the concentrated salt solution. What we observe is, raisins:

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Science>Biology>Plasma Membrane>Transport Across the Membrane

The movement of molecules during diffusion can be described through all of the following except -

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Science>Biology>Plasma Membrane>Transport Across the Membrane

Explain the following terms:
Diffusion

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Science>Biology>Plasma Membrane>Transport Across the Membrane

In simple organisms, exchange of gases and excretion occurs through –

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Science>Biology>Plasma Membrane>Transport Across the Membrane

Which one of the following will have maximum diffusion pressure?

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Science>Biology>Plasma Membrane>Transport Across the Membrane

The plasma membrane (pm) forms the boundary of lung cells. Which of the following statements is true for the pm?
A. Plasma membrane is a semipermeable membrane
B. Water moves across the pm by osmosis.
C. O₂ and CO₂ can cross the pm by diffusion.
D. Na⁺ and K⁺ ions can pass the pm by diffusion.

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Science>Biology>Plasma Membrane>Transport Across the Membrane

In ____ permease assists a molecule to diffuse through the membrane that it cannot penetrate alone.

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Science>Biology>Plasma Membrane>Transport Across the Membrane

Write a note on endocytosis.

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Science>Biology>Plasma Membrane>Transport Across the Membrane

Movement of a substance from the area of low concentration to an area of high concentration is called diffusion.

MEDIUM

Science>Biology>Plasma Membrane>Transport Across the Membrane

How does carbon dioxide move in and out of cells?