Movement Of Substances In And Out Of Cells Flashcards
What do we call the cell membrane when it only lets small molecules through
Semi permeable or partially permeable
Why is the cell membrane important
It controls what passes in and out of each cell. It allows small molecules to pass through but not large molecules
What are plant cell walls made out of
Cellulose
Why are large molecules able to pass through the cell wall
Cellulose forms fibres with spaces in between
What do we call the cell wall when it lets all molecules pass through
Fully permeable
In a plant what controls what enters and exits the cell
Cell membrane
What do the two methods of moving substances rely on?
Concentration of substances
What are the two methods of moving substances in and out
Diffusion
Active transport
What is diffusion
This is the movement of molecules and particles of a substance from an area of high concentration to and area of low concentration until an equilibrium is reached and the substance is equally spread out. This occurs in gases and liquid ( in cellls) and is a passive process and requires no energy to take place. The continuous movement of air/water molecules that moves the substance
What is active transport
Active transport is the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration. In active transport, particles move against the concentration gradient - and therefore require an input of energy from the cell.
What factors affect the rate of diffusion
Surface area
Difference in concentration
Distance
Temperature
Explain how surface area affects the rate of diffusion
The larger the surface area, the faster the rate of diffusion
What is an example of surface area affecting the rate of diffusion
The villi greatly increase the surface area as they are highly folded which let food molecules diffuse into the bloodstream quicker
Explain how the difference in concentration affects the rate of diffusion
The larger the difference in concentration the faster the rate of diffusion will be. If there is a difference in concentration, we call this a concentration gradient. The steeper the gradient the greater the difference in concentration. The gradient is maintained by breathing in and out and by blood constantly flowing throught the blood vessels
Give an example of how concentration affects rate of diffusion
Potassium permanganate crystals were placed in water abd the purple colour slowly spread through the water because there was a high concentration of potassium permanganate at the bottom and a low concentration at the top.
