B4 Flashcards
when does diffusion happen
when there are unequal concentrations of molecules
how does diffusion happen
particles move about and hit eachother
how is diffusion important for plants
co2 enters plant leaf
and o2 leaves plant leaf
because there is more CO2 outside of plant and there is more O2 inside leaf
how does co2 enter plants
through stomata
finds it’s way to photosynthesising cells where it’s used up
what is an adaptation of a lung
lots of alveoli for increased surface area
what is active transport
to go against concentration gradient
needs energy
from low concentration to high concentration
energy comes from respiration
example of active transport
transport of mineral ions from soil into root hair cells
what happens when air is breathed in
oxygen in air moves into capillaries
blood is deoxygenated to start with
so oxygen in lungs is at higher concentration
this means that the oxygen moves from lungs into the blood
now the blood is blood is oxygenated
what happens when blood is received back into the lungs
when blood first reaches lungs it has a high level of co2 in the plasm
because co2 concentration is higher in blood it moves into lungs down it’s concentration gradient
how much oxygen is absorbed by blood when respiring
about 4-5%
why does mouth to mouth resuscitation work
you breath out more o2 than co2
how does ventilation work
mechanical process
air at high pressure in one place moves to place with low pressure
space opens up in lungs - which reduces pressure - because:
rib cage moves upward and outward through muscle contractions
and diaphragm contracts and moves downwards
what do living cells need for chemical reactions to take place
glucose oxygen water
what is a partially permeable membrane
let’s smaller molecules pass through and not higher ones
all cell membranes are partially permeable
what do root hair cells do
increase surface area
maximise water uptake
why is it important for water to be moved from root as and into the rest of the plant
during osmosis movement stops when the concentration of water on either side of the cell membrane is the same
otherwise the plant could not gain anymore water
what is the potato experiment
pieces of potatoes are weighed and left in a salt solution
left for a while
weighed again so change in mass can be recorded
this is because of osmosis
why does the mass of a potato increase when left in water
because the water concentration is higher in the water in the beaker
than in the cytoplasm of the potato cells
even though water moves both waves across the membrane
- the net movement is into the potato cells so the mass goes up
why does the mass of a potato decrease when in a very salty solution
because the very salty water has a lower water concentration than the cytoplasm inside the cells
the net movement of water is out the potato cells and into the solution in beaker
the cells shrink and the mass goes down
how can a potatoes mass not change if it’s put in a salt solution
if the salt solution in the beaker has the same exact concentration of water molecules than inside the potatoes
no net movement
what have a high surface to volume ratio
one cell because it only has one cell membrane to cross and it’s very efficient
what had a low surface area to volume ratio
multi cellular animals
nutrients need to get into the cytoplasm of every single cell
and dispose of the waste products
very challenging because it’s a complex organism
how do fish take up oxygen
through the gills
gills have many filaments and each has its own blood supply
this structure gives the gills a high surface area to volume ratio and ensures maximum effectiveness
how do filaments work
oxygen diffuses from water into the bloodstream
carbon dioxide diffuses out of the blood and into the water
how do animals get nutrients
in humans food is digested into small soluble molecules
that cross into the blood stream
across the wall of the small intestine
how is the surface area of the small intestine increased
by villi (small projections of its surface)
villi have an extensive network of capillaries to absorb food molecules by diffusion and active transport
why are water lily’s shaped the way they are
they need co2 to reach chloroplasts for photosynthesis
it’s leaves are large to maximise the surface area available for diffusion of carbon dioxide
it’s thin so the gas doesn’t have far to go to reach all the leafs cells
the have a high surface area to volume ratio
this ensures maximum efficiency
why are organ systems specialised with the exchange of various materials
the effectiveness of a exchange surface is increased by having a large surface area and by being thin
this provides a short diffusion path
a large surface area to volume ratio maximises the efficiency of an exchange surface
