transport in cells Flashcards
(38 cards)
What is diffusion
The random movement of particles from an area of high concentration to an area of low concentration
How do you calculate net movement
Particles moving in - particles moving out
What is net movement
The general movement of particles
What are the factors that determine the rate diffusion
Concentration gradient, surface area and diffusion distance
How does the concentration gradient affect the rate of diffusion
The greater the concentration gradient the quicker diffusion takes place
How does temperature affect the rate of diffusion
As the gas or solution heats up the particles gain more kinetic energy and move around faster, this increases the random movement of the particles enabling them to diffuse more rapidly
How does surface area affect the rate of diffusion
Our membranes are partially permeable, so by increasing the surface area through which the particles can move through diffusion will be faster
How does size compare to surface area to volume ratio
The larger the organism the smaller the surface area to volume ratio
List 3 adaptions for exchange
Increasing the surface area, so more particles can move at once
Have a short diffusion distance the particles have to travel
Increase the steepness of the concentration gradient to speed up the net flow of particles
How are lungs adapted for exchange
1)a large number of small alveoli creates a large surface area for rapid diffusion of gases
2) A rich capillary blood supply brings french blood to the alveoli maintaining a steep concentration gradient
Ventilation refreshes the air in the lungs to maintain a step concentration gradient
3)a thin alveolar wall gives the shortest diffusion distance for the gasses
How are the small intestines adapted for exchange
1)They have thousands of villi which in turn have numerous microvilli on their surface for large surface area
2) they have rich capillary lood supply to remove absorbed nutrients and maintain a steep concentration gradient
3)the walls are only one cell thick to keep the diffusion distance short
How are plant roots adapted for exchange
1)The tip of the roots are covered in root hair cells which increase their surface area for absorption
2) transpiration in the leaves continuously pulls water up the plant creating a steep concentration gradient
3) there is only a short distance from the edge of the root to the xylem in the middle
How are plant leaves adapted for exchange
1)There are stomata at the bottom of the leaf to allow carbon dioxide to diffuse into the leaf and oxygen out
2) the thin leaf shape minimises the diffusion distance for gasses
3) the air spaces in the spongy layer exposes a large surface area for gaseous exchange
What is osmosis
The net movement of water from a dilute solution to a strong solution across a partially permeable membrane
Osmosis model answer plan
1.Identify the hyper/hypotonic solution
2.State which way the water moves
3…..by osmosis through a partially permeable membrane
4.Describe the result eg swells up / shrivells up
What will happen to an animal cell when the solution is hypotonic to it
Water will enter the cells and can cause them to burst
What will happen to an animal cell if the solution is hypertonic to it
Water will leave the cells, causing them to shrivel up
What will happen to an animal cell when the surrounding solution is isotonic to it
(if the surrounding solution is the same concentration to the cell it is isotonic)
Under these conditions there will be no movement of water so the cells will remain the same size
What will happen to a plant cell if it is placed in a hypotonic solution
Water will enter the cell causing the vacuole to swell up and pushing the cytoplasm against the cell wall
The wall will push back preventing the cell from bursting
The cell becomes swollen and turgid
What will happen if a plant cell is placed in a hypertonic solution
Water will leave the cell via osmosis, the cell membrane will be pulled away from the cell wall in a process called plasmolysis
Tears are hypotonic to blood, a student mixes tears and blood and looks at it through a microscope what would she see
Red blood cells swelling and possibly bursting
Why does grass remain upright
Due to turgor pressure, the internal pressure exerted by the contents of plant cells due to the presence of water in the vacuole
In a drip, an infused, one uses physiologic water (=0.9% NaCl) instead of pure water. Why is that?
Because this means it would have the same concentration of solute (be isotonic) to the blood, if pure water were used it would be hypotonic compared to the blood causing them to swell and potentially burst
How does diffusion distance affect the rate of diffusion
The shorter the diffusion distance the faster the rate of diffusion will be.
