substances move in and out of
cells in three different ways...
DIFFUSION
DIFFUSION is the PASSIVE OVERALL
MOVEMENT of PARTICLES from a region
of their HIGHER CONCENTRATION to a
region of their LOWER CONCENTRATION
in easier words (for us silly peoples),
diffusion is the gradual movement of
particles from places where there are
lots of them to places where there fewer
of them - just the natural tendency for
stuff to spread out
'passive' just means that
it takes place without
needing any energy
an example of diffusion is this: when plants
photosynthesise they use up carbon dioxide from
the atmosphere and produce oxygen - these gases
pass in and out of the plant leaves by diffusion
when I said that there were three different ways that
substances move in and out of cells I was kind lying
(sozlol) - osmosis is just a specific case of diffusion
OSMOSIS is the overall MOVEMENT
OF WATER from a DILUTE to a
MORE CONCENTRATED solution
through a PARTIALLY (or semi)
PERMEABLE MEMBRANE
got that?
a 'partially permeable membrane' is just un que only
allows certain substances to diffuse through it, eg. it
may only allow pico molecules comme water to pass
through and not larger molecules comme sucrose
a DILUTE SOLUTION
has a HIGHER
CONCENTRATION of
water molecules than a
CONCENTRATED
SOLUTION...weird, huh?
as shown in the lovingly lifted diagram,
the solution on the right gets more dilute
as more water moves in - die waßer
acts as if it's trying to even up the
concentration either side of the
membrane - water, when will you learn?
plants (eg. doughnut trees) take
in water by osmosis - there's
usually a higher concentration of
water in the soil than there is
inside the plant, so the water is
drawn ino the root by osmosis
ACTIVE TRANSPORT
ACTIVE TRANSPORT is the overall MOVEMENT
OF CHEMICALS across a CELL MEMBRANE
from a region of LOWER CONCENTRATION to a
region of HIGHER CONCENTRATION using
ENERGY released by respiration
it's basically diffusion backwards
active transport is the process that incurs when chemicals
(eg. glucose) need to be moved from an area with a lower
concentration of the chemical to an area with a higher
concentration of the chemical across a cell membrane
EXAMPLE TIME!: plants take in minerals like nitrates
through their roots by active transport...the concentration of
minerals in root cells is usually plus haute que the soil
around them...active transport uses energy from respiration
to move minerals from the soil into the root cells
cells are super fusspots - the levels of certain substances
need to be exactly spot on in order for them to function properly