Introduction to Biology: Cell Membrane Movement

Introduction to Biology

• Biology covers various topics, including classification, cells, and movement across cell membranes.

Cell Membrane Movement

• Passive Transport: Movement of molecules with the concentration gradient, no energy needed.

  • Diffusion: Net movement of molecules from higher to lower concentration.
  • Facilitated Diffusion: Diffusion aided by transport proteins.
  • Osmosis: Diffusion of water across a selectively permeable membrane.

• Active Transport: Movement of molecules against the concentration gradient, requiring energy (ATP).

  • Used when cells need substances in small quantities.

• Examples of active transport processes:

  • Absorption of nutrients in the small intestine.
  • Uptake of ions by root hairs in plants.

Types of Movement Across the Membrane

• Active transport requires special pump proteins.

• Passive Transport has three types: - diffusion - osmosis - facilitated diffusion

Osmosis

• Movement of water molecules from a dilute solution to a concentrated solution across a selectively permeable membrane.
• A solution with a higher solute concentration is called hypertonic; a solution with a lower solute concentration is called hypotonic; a solution with an equal solute concentration is called isotonic.

Consequences of Osmosis in Animal Cells

• In dilute solutions, animal cells take up water, swell, and may burst.
• In concentrated solutions, animal cells lose water and shrink.

Consequences of Osmosis in Plant Cells

• In dilute solutions, plant cells take up water, swell, and become turgid (firm). The cell wall prevents bursting.
• In concentrated solutions, plant cells lose water, the vacuole shrinks, and the cell membrane pulls away from the cell wall (plasmolysis). The cell becomes flaccid.

Diffusion in Animals

• Oxygen from the air enters the blood in the lungs.
• Carbon dioxide leaves the blood and enters the air in the lungs.
• Absorption of nutrients from the digestive system in the small intestine.

Diffusion in Plants

• Carbon dioxide from the air enters the leaves.
• Oxygen leaves the leaves.

Solution

• A solution is a liquid mixture of two or more substances.
• Solvent: The substance that dissolves other substances.
• Solute: The substance that dissolves in the solvent forming a solution.
• Aqueous solution: A solution where water is the solvent.

This quiz focuses on the fundamental concepts of cell membrane movements, including passive and active transport mechanisms. You'll explore processes such as diffusion, osmosis, and the roles of transport proteins. Test your understanding of how substances move across cell membranes in biological systems.