B2.1 Supplying the Cell - Diffusion, Osmosis, Active Transport Flashcards
Diffusion, Osmosis, Active Transport
What is diffusion?
The passive net overall movement of particles from a region of high concentration to a region of low concentration down the concentration gradient.
Particles move โฆโฆ. and โฆโฆ.. by diffusion.
Particles move constantly and randomly by diffusion
What key gases do we need to diffuse from our lungs to our blood stream?
Oxygen
What key nutrient do we need to diffuse from our blood stream to our muscle cells?
Glucose
What factors affect diffusion?
Surface area
Temperature
Concentration gradient
Distance
Name key adaptations of the body to facillitate diffusion?
Alveoli
- They are very thin - small distance to diffuse over
- They are covered by a network of fine capillaries - diffuse straight into bloodstream, maintains concentration gradient
- They are moist
- They have a large combined surface area.
Small intestines
- Villi & Microvilli - increases surface area, therefore volume that can be absorbed
- Good blood supply โ substances diffuse straight into the bloodstream, maintains concentration gradient
What role does diffusion play in nerve impulses?
- Diffusion allows a nerve impulse to travel between two neurones at a synapse
- Neurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration.
How the is placental organ is adapted to maximise diffusion?
- A large surface area between it and the uterus wall.
- Villi (finger like projections that extend into the uterus wall), which further increase the surface area of the placenta.
- A rich supply of maternal blood vessels.
What role does diffusion play in enabling photosynthesis?
- Carbon dioxide diffuses in through the stomata.
- Oxygen and water diffuse out of the stomata
- During photosynthesis, the level of CO2 is low inside the leaf, creating a big concentration gradient so CO2 diffuses into the cell
Define osmosis.
Osmosis is a special type of diffusion. The diffusion of water molecules across a partially (selectively) permeable membrane from an area of high water potential to an area of lower water potential (down a water potential gradient).
What is meant by โhypertonicโ?
A fluid has a higher osmotic pressure (lower water potential) than a particular fluid, typically a body fluid or intracellular fluid.
What is meant by the term โhypotonicโ?
A fluid has a lower osmotic pressure (higher water potential) than a particular fluid, typically a body fluid or intracellular fluid.
Why is osmosis important to plant cells in particular?
The vacuole which helps mantain the cells structure is filled by osmosis.
Explain the term โturgidโ.
When water enters the cell by osmosis and fills the vacuole. This pushes against the cell wall, making the cell turgid.
Explain the term โflaccidโ.
When water moves out of the cell by osmosis, the vacuole shrinks and the cell becomes flaccid