Active transport,diffusion,osmosis,exchanging substances Flashcards
What is diffusion?
Diffusion is the movement of particles from a region of high concentration to low concentration, i.e. along a concentration gradient.
What type of process is diffusion?
Passive process(doesn’t require energy)
What is osmosis?
Osmosis is the diffusion of water molecules from a region of high water concentration(dilute solution) to a region of lower water concentration(concentrated solution) through a partially permeable(semi permeable) membrane(cell membrane)
What type of process is osmosis?
Passive process (doesn’t require energy)
What is active transport?
This is the movement of particles from a region of low concentration to a region of high concentration(i.e. against a concentration gradient) through a cell membrane(cell membrane has carrier molecules)
What carrier molecules do cell membrane have?
The cell membrane has carrier molecules that mediate the movement of molecules that are too polar or too large to move across the membrane by diffusion. These carrier proteins bind specific molecules on one side of the membrane and allow them to pass through and be released on the other side.
Net movement?
Particles moving in - particles moving out
What are exchange surfaces?
Exchange surfaces are specialized surfaces in organisms that are adapted to maximize the efficiency of gas and solute exchange
What does the rate of diffusion depend on?
1) Concentration gradient-The higher the concentration gradient is the faster they diffuse.
2) Temperature - The higher the temperature the more kinetic energy particles gain do they move/diffuse faster
Why do single celled organisms not need an exchange surface.
Single celled organisms such as bacteria have a large surface area to volume ratio so gas particles/ solute particles can easily diffuse through the surface to all parts of the cell/organism. So they don’t need an exchange surface.
Why do multicellular organisms need an exchange surface?
Multicellular organisms tend to have a smaller surface area to volume ratio so not all the cells with get enough oxygen/glucose through diffusion across the surface meaning they will need an exchange surface eg lungs gills leaf stomata/loosely packed mesophyll layer. So that every cell in the body receives oxygen and nutrients.
What factors allow an efficient diffusion to take place?
1) Surface must be thin - shorter diffusion pathway ie cell membrane are very thin/leafs are their shorter diffusion pathway from outside to inside leaf
2) Surface area must be large - The particles tend to have a bigger area through which can pass through without coming in each others way
3) Surface must be moist/wet - Particles cant diffuse across a dry surface; they must dissolve in water before they can pass across the surface
4) A good blood supply to maintain a high concentration gradient ( diffused particles are quickly removed from the exchanged surface.
What can and cant pass through the semi permeable membrane?
Sugar molecules are too big to pass through so they cant
Water molecules are small enough to pass through so they can.
How does root hair cells absorb water from soil
Cells are concentrated so water diffuses in by osmosis.
Examples of active transport?
1) Glucose/amino acids etc pass from gut into villi
2) Kidney tubules —> reabsorb glucose back into blood
3) Root hair cells absorb mineral ions from soil
