B1 DOAT
Diffusion
The net movements of particles in a solution from an area of higher concentration to an area of lower concentration along a concentration gradient
Occurs in gas exchange in the alveoli-oxygen and CO2 as well as across the cell membrane in animal cells
Capillaries are 1 cell thick to accommodate diffusion
Osmosis
The net movement of water from a dilute solution to a solute solution across a partially permeable membrane
cells in a hypertonic solution have a higher concentration than the surrounding area, this makes cells flaccid and can even make plant cells plasmolysed
Isotonic cells have the same concentration within and outside the cell, this is perfect for animal cells but results in flaccid plant cells
Cells in a hypotonic solution have a lower concentration of water than the surrounding area and swell, in animal cells such as a red blood cell they can burst whereas in a plant cell this makes the cell turgid and strong
Example includes movement of water into plant and animal cells
Active Transport
The net movement of particles from an area of low concentration to an area of high concentration through a partially permeable membrane against the concentration gradient using a transport protein
Examples include root hair cells in plants which absorb mineral ions from soil and absorption of sugars into villi in the small intestine in animals.
Diffusion will occur quicker the larger the difference in concentration between two solutions
Diffusion occurs quicker the higher the temperature
Many things have a large SA to accommodate diffusion
High water pressure makes plant cells turgid(ideal) as the vacuole swells
Requires a lot of energy, therefore active transport using cells will have many mitochondria
Exchanging Materials
SA to volume ratio is important as it makes a big difference to the way animals can exchange substances with the environment. A high ratio means a shorter diffusion distance
Long diffusion distances cause gases and food molecules to not be able to reach cells and metabolic waste to stay in cells long enough to poison them
Adaptations include having a large SA
Having a thin membrane to provide short diffusion path
Efficient blood supply maintains steep concentration gradient
Ventilation makes gas exchange more Efficient as it ensures a steep concentration gradient