Biology Chapter 3: Cell Movement

Study Notes

Chapter 3: Movement into and out of Cells

Diffusion: The net movement of molecules or ions from a high concentration to a low concentration, due to random movement and kinetic energy.
Diffusion importance: Critical for gas exchange (O2 and CO2) in plants and animals, and nutrient absorption (in the ileum).
Factors affecting diffusion rate:
- Temperature: Higher temperatures increase kinetic energy, increasing the rate.
- Concentration gradient: A larger difference in concentration speeds up diffusion.
- Surface area: A higher surface area increases the rate of diffusion.
- Distance: Shorter distances lead to faster diffusion.
Osmosis: A special type of diffusion, specifically the movement of water molecules across a partially permeable membrane from a high water potential to a low water potential.
Water potential: A measure of the tendency of water molecules to move from one region to another; Higher water potential means more freedom for the water molecules to move (more water).
Importance of osmosis in plants:
- Water absorption by root hair cells.
- Maintaining turgor pressure in plant cells (keeps them rigid).
- Preventing the plant cell from bursting.
Importance of osmosis in animals:
- Maintaining water balance in cells.
- Preventing cell damage or bursting.
Active transport: Movement of molecules across a cell membrane against a concentration gradient, using energy from respiration.
How active transport works: Special carrier proteins within the cell membrane change shape, moving substances across the membrane against their concentration gradient to maintain homeostasis.
Active transport importance in plants and animals:
- Absorbing nutrients from the soil.
- Taking in glucose in the ileum.
- Reabsorbing glucose in the kidneys.
Dialysis tubing: Used as an example of a partially permeable membrane to study osmosis.