transport in cells Flashcards
What is diffusion
Net movement of particles from an area of high concentration to n area of low concentration down the concentration gradient
Adaptations in the lungs for diffusion
Alveoli: oxygen diffuses across thin layer(one cell thick) into the blood, CO2 diffuses in the opposite direction
Steep concentration gradient: breathing refreshes the air in the alveoli and blood constantly removes oxygen and brings CO2
Large surface area: many alveoli
why does diffusion happen
Bc molecules move as they have their own kinetic energy
What are factors affecting diffusion
distance molecules have to travel
-cell membranes are thin
Surface area
-some cells have cell membranes that are folded to give a large surface area to allow molecules to cross by diffusion
Concentration gradient
-cells keep a low concentration inside the cytoplasm so cells can keep diffusing bc the cell is maintaining a steep concentration gradient
Temperature.
-faster at warmer temps as the molecules have higher kinetic energy so the particles move faster and collide more often w\ each other
Where does diffusion happen in plants
Gas exchange occurs inside the leaf
- spongy mesophyll cells provide a large surface area for the exchange of gases
- airspace b/w the cells exchanges gases w/ the air
- efficient s diffusion thru air is 15x300k faster than through water
Why is water considered the universal solvent
75% of cytoplasm is water an is the main component of transport fluids like blood, xylem sap and phloem sap
Everything transported in plants and animals has to dissolve in water and most of. The chemical reactions that occur in cells happen in water
What is osmosis
Diffusion of water molecules from a dilute solution into a more concentrated solution through a partially permeable membrane
Why does osmosis happen thru a partially permeable membrane
Bc it allows small molecules such as water to pass throug, but not large solute molecules
What’s water potential
A way of thinking about the ability of water to move by osmosis
- dilute solutions have a higher water potential (contain a lot of. H20 molecules).
- concentrated solutions have a low water potential
How do you represent a cell wall and cytoplasm in a practical
Cw; visking tube
Cytoplasm: a sugar solution
Define turgid
If you place a plant cell in water, H20 will move into the cell by osmosis and the cell will expand
The cell wall prevents the plant cell. From bursting, instead the cell becomes swollen
Define flaccid.
Plant cell in a concentrated solution, water moves out of the cell by osmosis
This causes the cell to shrink
Define plasmolysed
If you have a flaccid cell and more water continues to flow out of the cell the cytoplasm moves inwards away from the cell membrane.
The cell decreases in volume
What happens in animal cells when water passes into the cell by osmosis.
As animal cells don’t have a cell wall, they end up bursting as they cannot resist the increase in size
This is haemolysis
What happens in animal cells when water passes out of cells by osmosis
They shrink
