Movement Of Substances Flashcards
What is diffusion?
The spreading out of particles from an area of high concentration to an area of lower concentration
(Down a concentration gradient)
What can diffusion only occur in?
Liquids and gases
What materials can diffuse take place in?
Cell membranes
—> ‘partially permeable’ - only some molecules can diffuse through
What kind of process is diffusion?
A passive process
—> doesn’t require any energy from the cell
Which substances can move into and out of cells via diffusion?
Oxygen
Water (osmosis)
Glucose
Amino acids
What are the 3 factors that affect the rate of diffusion?
Concentration gradient
Temperature
Surface area to volume ratio
- also diffusion distance
What is the concentration gradient?
The difference in concentration between 2 places
Temperature (affecting rate of diffusion)
Higher temperatures give the particles more energy
—> particles more around faster
—> diffuse more quickly
Higher temperature —> higher rate of diffusion
Surface area (affecting rate of diffusion)
Larger surface area —> higher rate of diffusion
What is osmosis?
The diffusion of water from an area of higher concentration of water (concentration) to an area of lower concentration of water (dilute) through a partially permeable membrane
What is water concentration?
The amount of water, as compared to other molecules (like sugars or salts) that are dissolved in the water
What would happen if red blood cells were placed in pure water?
They would gain water, swell and possibly burst
What is active transport?
The movement of molecules across a cell membrane, from a region of lower concentration to a region of higher concentration and requires energy from cellular respiration
(Moving against their concentration gradient)
What kind of process is active transport?
An active process - requires energy from the cell
—> always takes place across a membrane
—> requires special proteins that sit in the membrane and transfer the molecule from one side to the other
Where does the energy for active transport come from?
Cellular respiration
What is cellular respiration?
Process that happens mainly in the mitochondria when they break down glucose to release energy
- stores the energy in ATP - these molecules act as batteries taking the energy from the mitochondria to the different parts of the cell that need it
4 steps of carrier proteins
1) the molecule enters the carrier protein and binds to the specific binding site
2) energy is required to carry the molecule across the membrane
3) the carrier protein opens on the other side of the eod the cell membrane, releasing the molecule on the other side
4) after, the protein carrier returns to its original position, ready to transport another molecule
Example of where active transport is used
Plants: need to absorb lots of water and minerals to survive (from the soil)
Around the outside of the roots are special cells called root hair cells
—> they absorb water and minerals
Minerals they need are at a higher concentration inside the cell than they are outside in the soil
—> have to use energy to absorb them by active transport against their concentration gradient
—> energy comes from cellular respiration (happens in mitochondria)
Adaptations of root hair cells: lots of mitochondria
Which ion is needed for plant growth?
Nitrate ions
Which ion is needed to make chlorophyll?
Magnesium ions
