IGCSE: Movement in and out of cells

Diffusion

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.

Mechanism of Diffusion

Molecules like glucose and proteins enter cells through the cell membrane, while waste products such as carbon dioxide exit the cell.

Nutrient Movement

Nutrients move into the cell when there are more nutrients outside than inside, balancing the concentration.

Surface Area

Larger surface areas increase the rate of diffusion as more molecules can diffuse simultaneously.

Temperature

Higher temperatures increase molecular movement, thus increasing the rate of diffusion.

Concentration Gradient

A steeper gradient (greater difference in concentration) leads to a faster rate of diffusion.

Distance

Shorter distances allow for quicker diffusion.

Osmosis

The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.

Importance of Water

Water is vital for transporting dissolved substances, aiding digestion, and excreting waste.

Partially Permeable Membrane

A membrane that allows only certain molecules (like water) to pass through.

Water Potential

Refers to the potential of water to move; a dilute solution has high water potential, while a concentrated solution has low water potential.

Dialysis Tubing Experiment

Demonstrates osmosis where water moves from a dilute solution into a concentrated sucrose solution within the tubing.

Effects on Plant Cells in Pure Water

Cells become turgid (swollen) as water enters.

Effects on Plant Cells in Concentrated Solution

Cells lose water, become flaccid, and may undergo plasmolysis (cytoplasm shrinks away from the cell wall).

Active Transport

The movement of particles against a concentration gradient using energy from respiration.

Protein Carriers

Embedded proteins in the cell membrane that capture molecules and change shape to transport them across the membrane.

Energy Requirement in Active Transport

Active transport requires energy to move molecules against the gradient.

Comparison of Processes

A table comparing diffusion, osmosis, and active transport based on movement, energy requirement, and direction of movement.

Conclusion

Understanding these processes is essential for grasping how cells interact with their environment and maintain cellular functions.

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