b2.1.1-b1.1.3 (diffusion, osmosis, active transport) Flashcards
diffusion
net movement of particles from an area of high concentration to an area of low concentration down their concentration gradient
what process is diffusion
passive process as energy is not transferred
when does diffusion stop
when conc of particles is the same everywhere
where does diffusion occur in the body
your blood transports substances around your body, glucose and oxygen diffuse into cells that need them.
carbon dioxide diffuses out of respiring cells
how does distance affect diffusion
shorter distance - less time to travel
e.g, blood capillaries are only one cell thick - increases rate of diffusion of gases into and out of the blood stream
how does concentration gradient affect diffusion
steeper concentration gradient - greater net movement of particles
e.g, as plant cells use co2 for photosynthesis, the co2 concentration inside the plant cells drop which increases the diffusion rate of co2 into the cells
how does SA affect diffusion
increased SA - more space for diffusion - more particles can move in a period of time
e.g, small intestine wall is highly folded, increasing SA that is in contact with blood steam - increases rate if diffusion with molecules produced during digestion
osmosis
net movement of water molecules from a high water potential to a low water potential down their concentration gradient across a semi-permeable membrane
water potential
concentration of free water molecules
more concentrated solution - lower water potential
how does difference in water potential affect osmosis
greater difference in water potential - greater rate of osmosis
plant cells
cells placed in solution more dilute than its contents
lower conc outside of cell
water diffused into cell via osmosis
pressure in cell increases - turgid pressure
cell becomes firm or turgid
enlarged / swollen with water
plant cells
cell placed into solution with same conc as its contents
no net movement of water
cell remains the same
plant cells
cell places into more conc solution than contents
high conc outside of cell
loses water via osmosis
turgor pressure falls - cell becomes flaccid (soft)
eventually crop contents collapse away from the cell wall
this is called a plasmolysed cell
cell shrinks
animal cells
cell placed into solution more dilute than its contents
lysis
cell takes up water, swells and may burst
animal cells
cell placed in solution with same water potential as its contents
no net movement of water
cell remains the same
animal cells
cell placed in more conc solution than contents
cell loses water via osmosis
cell becomes crenated (crinkles)
active transport
movement of molecules from an area of low concentration to an area of high concentration against their concentration gradient using energy
three key features of active transport
particles are transported against a concentration gradient
ATP is required (comes from respiration)
process makes use of carrier proteins in the cell membrane
what does rate of active transport occurs depend on
depends on the rate of respiration as it produces the required ATP
cells that carry out a lot of active transport contain many mitochondria - meaning they can respire rapidly to produce large quantities of ATP
carrier proteins
help move substances across the membrane
the molecule attaches to the carrier protein at its binding site
carrier protein changes shape with the help of ATP so it can change shape or rotate
carrier protein transports molecule into the cell
examples of active transport
digestion - in small intestine, carbohydrates are broken down into glucose - glucose actively transported into bloodstream through the villi
plants - plants use it to take in minerals from the soil - plants need nitrate ions to make proteins for growth- normal lower concentrations of nitrate ions in soil water surrounding roots - plant root hair cells use active transport to move ions across cell mebrane and into root cell
