Overview
This lecture explains how molecules move in and out of cells, focusing on diffusion, osmosis, and active transport, including their definitions and examples.
Movement of Molecules in and out of Cells
- Molecules move via diffusion, osmosis, and active transport.
- Movement can involve nutrients and waste products crossing cell membranes.
Diffusion
- Diffusion is the net movement of solute molecules from high to low concentration, down a concentration gradient.
- This process does not require energy input.
- Cell membranes control which substances can diffuse in or out.
Osmosis
- Osmosis is the movement of a solvent (mainly water) from high to low concentration through a partially permeable membrane.
- The cell surface membrane acts as the barrier in osmosis.
- Cell walls made of cellulose are permeable and allow most substances through.
- Osmosis is used in food preservation, such as pickling, by drawing water out of food with salt or sugar.
Active Transport
- Active transport moves substances against the concentration gradient, from low to high concentration.
- This process requires cellular energy in the form of ATP (adenosine triphosphate).
- Examples include absorption of mineral salts by root hair cells and uptake of glucose and amino acids in the human small intestine.
Key Terms & Definitions
- Diffusion — Movement of solute molecules from an area of high to low concentration, without energy input.
- Osmosis — Movement of water from high to low concentration through a partially permeable membrane.
- Active Transport — Movement of molecules against a concentration gradient, requiring energy (ATP).
- ATP (Adenosine Triphosphate) — The energy molecule used by cells for active transport.
Action Items / Next Steps
- Review the video on diffusion and active transport for further understanding.
- Study examples of osmosis in food preservation and biological systems.