IGCSE Biology: Movement into and out of Cells

Introduction

Definition: Movement of particles from high to low concentration due to random movement.
Cell Membrane Role: Controls substances entering and exiting the cell.
Examples:
- Glucose, proteins move into cells for metabolism.
- Waste products like CO2 and lactic acid move out.
Factors Affecting Diffusion:
- Surface Area: Larger area increases rate.
- Temperature: Higher temperature increases kinetic energy, speeding up diffusion.
- Concentration Gradient: Greater difference increases rate.
- Distance: Shorter distance increases rate.

Definition: Movement of water from high water potential (dilute) to low water potential (concentrated) through a partially permeable membrane.
Importance of Water:
- Solvent for transport and digestion.
- Necessary for excretion (e.g., urea in urine).
Osmosis Example:
- Dialysis tubing experiment showing movement through a non-living partially permeable membrane.
Effects on Plant Tissues:
- Pure Water: Water moves in, cells become turgid.
- Concentrated Solution: Water moves out, cells become flaccid (plasmalized in extreme conditions).
Water Potential: Key to water uptake in plants via roots.

Definition: Movement of particles against a concentration gradient using energy from respiration.
Process:
- Protein carriers in cell membranes transport molecules.
- Energy alters protein shape to transport particles.
Applications:
- Absorbing nutrients in plant and epithelial cells against gradient.

Diffusion: Particles move down concentration gradient using kinetic energy.
Osmosis: Water moves from high to low water potential across a membrane.
Active Transport: Particles move against concentration gradient requiring energy.

Understanding these processes is crucial for comprehending cell interactions with their environment.
Key processes facilitate the transport of nutrients and waste across cell membranes.

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