The movement of particles from an area of highconcentration to an area of lowconcentration until they're evenly spread out, (for particles move randomly and spreads out).
Diffusion occurs in both liquids and gases because particles in these states have the FREEDOM TO MOVE randomly.
Here are some examples of Diffusion in CELLS:
oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves.
urea diffuses from cells into the blood plasma for excretion by the kidney.
digested food molecules from the small intestine diffuse into the blood.
You can increase the rate of diffusion by:
Increasing the difference in concentration between the two areas.
Increasing the TEMPERATURE, as particles have more energy to move faster.
Increasing the SURFACE AREA of the membrane where diffusion is occurring
The efficiency of exchange surfaces by diffusion is determined by the SURFACE AREA to VOLUME RATIO (SA:V).
LARGER organisms have a SMALLER SA:V ratio than smaller organisms.
Therefore the bigger cube has a lower surface area to volume ratio.
A) 1m
B) 6m
C) 6:1
D) 8m
E) 24m
F) 3:1
Gas Exchange in the Lungs
In the lungs, it has tiny air sacs called alveoli which are surrounds by a capillary network.
oxygen diffuses from the alveoli into the blood, while carbondioxide moves from the blood into the alveoli to be exhaled.
Gas Exchange in the Lungs
Adaptations of Alveoli for Gas Exchange
Has a HUGE SURFACE AREA to increase efficiency of gasexchange.
Has a MOISTLINING for dissolving gases, which aids in the diffusionprocess.
Their WALLS are THIN to minimize the distance gases must diffuse.
Surrounded by a crowded CAPILLARYNETWORK, for a rich bloodsupply and rapid gasexchange.
Gas Exchange in Plant Leaves
Structure of Leaves
CARBON DIOXIDE diffuses into AIR SPACES within the leaf for photosynthesis.
Leaves have an EXCHANGE SURFACES underneath, with small openings called STOMATA.
OXYGEN and WATER VAPOUR exit the leaf through these stomata.
The shape of the leaf and the arrangement of cells optimize the internal surface area for gas exchange.
Gas Exchange in Plant Leaves
Adaptations for Gas Exchange
Stomata are beside by GUARD CELLS that controls their opening, so gasexchange only occurs when necessary.
The FLATTENEDSHAPE of the leaf increases the surfacearea for gas exchange.
Internal cellwalls also contribute to a largerexchangesurface, with air spaces to assist DIFFUSION.
Nutrient Absorption in the Small Intestine
Villi Increase Surface Area
The SMALLINTESTINE boosts absorptionefficiency through tiny projections (a thing that extends outwards from something else) called VILLI that expand the surfacearea for nutrient absorption into the blood.
villi consists of a SINGLELAYEROFSURFACECELLS and a rich supply of BLOODCAPILLARIES for quickabsorption of digested nutrients.
nogaps between cells.
Has many microvilli to increase surface area.
wall of villus only onecell thin and capillaries are close to surface, so short pathway.
good bloodsupply to transport food molecules to the body and maintain a diffusiongradient.
cells have many mitochondria, where respiration takes place as activetransport requires energy to absorb food.
redbloodcells is the part of blood that carries the most oxygen.
Alveoli provides a large surface area of gas exchange.
give other ways the lungs are adapted of efficient GAS EXCHANGE.
wall of alveolus are one cell thick.
wall of capillary are one cell thick.
cells of capillarywall are thin
goodbloodsupply
wellventilated
shortdistance between alveolus and blood
SA:V of X: 2.4x10^-7 : 8x10^-12
SA:V of Y: 726 : 1331
so diffusion distance is longer in multicellular organism, so diffusion rate per unit volume is slower in a multicellular organism.
ACTIVE TRANSPORT
the net movement of particles from an area of LOWconcentration to an area of HIGHconcentration using energy from RESPIRATION.
CONCENTRATION GRADIENT
difference in concentration between the two areas.
Active transport involves particles movingAGAINST a concentration gradient and it is NOT a PASSIVE process like diffusion.
Examples of active transport:
Humans absorbing GLUCOSE from the gut.
Root cells to take in MINERALS
Root cells using active transport to take in MINERALS:
Minerals are usually at a higher concentration in root hair cells than in the surrounding soil.
Since diffusion can't occur against the concentration gradient, root hair cells use ACTIVE TRANSPORT to absorb minerals from the surrounding soil.
This allows plants to absorb nutrients from a low concentration in the soil.
CONCENTRATION GRADIENT
Difference in concentration between the two areas.
Humans using active transport to absorb GLUCOSE from the gut.
In the human gut, when there's a lower concentration of nutrients compared to the blood, ACTIVETRANSPORT allows nutrients to be absorbed into the bloodstream.
This is to provide ENERGY to our cells.
Because the phloem cells has a higher concentration than the leaf cell so sugars move into the phloem cell by activetransport, which requires energy, and the companion cell contains mitochondria where respiration occurs.
explain what the results in the table above show about how nitrate ions are absorbed.
more nitrate ions are absorbed in the presence of oxygen, which they are absorbed by activetransport, which requires energy from respiration, so somenitrate ions absorbed were requiring energy from anaerobic respiration.
Plants need nitrate ions in order to make protein, but a plant is in soiled flooded with water.
Why can't the plant absorb enough nitrate ions?
ions are absorbed by activetransport, which is the movement of ions from a low to high concentration and it requires energy from respiration but respiration need oxygens and there's no oxygen in water-flooded soil.