Diffusion, Osmosis and Active Transport

2nd Biology topic y9

Name 3 ways for substance to move in and out of cells

Diffusion, Osmosis and Active transport

name 2 substances that move into cells

Oxygen and Glucose

name two substances that move out of cells

co2 and urea

define diffusion

movement of gas/dissolved molecule from high to low concentration

how to molecules diffuse

down a concentration gradient

If the gas being diffused is more dense then what is needed

more energy

what can diffuse

liquids and gases

what process is diffusion

passive

what energy is needed for diffusion

none

where does diffusion mostly occur

cell membrane

what is special about cell membrane

not solid have pores and gaps

what does the rate of diffusion depend on

steepness of concentration gradient, temperature, total surface area

why does the steepness of the concentration gradient effect diffusion

the difference in concentration

why does temperature effect rate of diffusion

higher temp = more kinetic energy = particles move faster

why does surface area effect rate of diffusion

bigger surface area = more particles can diffuse

what happens when there is a large difference in concentration

faster rate of diffusion

why does diffusion across the surface area of small organisms work effectively

large surface area to volume ratio

what is the ratio for large multicellular organisms

small surface are to volume ratio

what do large organisms have to help with diffusion

specialized exchange surfaces

where does lots of diffusion occur in the human body (3 examples)

oxygen to lungs across alveoli to blood to cells, glucose and amino acids (from food) to blood, urea diffuses from liver to blood plasma to kidneys

why does lots of capillaries and good blood supply help with diffusion

maintain steep concentration gradient so molecules move faster down the gradient

why does thin exchange surfaces help with diffusion

short diffusion distance

what makes the small intestines good at diffusion

villi in small intestine (have extra microvilli to increase surface area). walls are one cell thick, good blood supply (maintain steep concentration gradient)

what does the small intestines diffuse

glucose, amino acids, vitamins and minerals diffuse

what makes the lungs good at diffusion

have alveoli these have: large surface area, one cell thick lining, good blood supply (maintain steep concentration gradient), ventilation (air in alveoli is constantly being replaced (breathing in and out)

what does the alveoli diffuse

o2 and co2

what makes the fish gills good at diffusion

lots of layers (increase surface area), large surface

what does fish gills diffuse

o2 and co2

what makes roots good at diffusion

have root hair cells that: large surface area and lots of root hair cells

what does root hair cells diffuse

o2 and h2o

what makes leaves good at diffusion

large surface area, thin and flat, specialized guard cells

what does root hair cells diffuse

o2, co2 and h2o

what is Osmosis (simple/literal)

special type of diffusion that only involves the movement of water molecules

where does osmosis occur

only across a partially permeable membrane

define osmosis (long answer)

diffusion of water from a concentrated solution to a more dilute solution across a partially permeable membrane

how does osmosis and the cell membrane work together

cell membrane is partially permeable and so only some molecules are let across ie wate molecules

what must the cell membrane be for osmosis to occur

intact and not damaged

what does the direction of osmosis depend on

concentration of the solution surrounding the outside of the cell

define hypotonic solution

for example the cell is in a hypotonic solution - means the cell is in a lower concentrated solution (inside the cell is more concentrated than outside)

define hypertonic solution

for example the cell is in a hypertonic solution - means the cell is in a higher concentrated solution (inside the cell is less concentrated than outside)

define isotonic

for example the cell is in a isotonic solution - means the cell is in the same concentration of solution (inside the cell has the same concentration as outside)

in osmosis which way will water move

from an area of high concentration to an area of low concentration

what do animal cells not have

cell wall

if animals cells dont have a cell wall what is the limitation of water entering the cell

amount of water entering the cell is not limited

what happens if an animal cell swells with water

it burts and becomes haemolysed

what happens if water leaves the cell via osmosis

cell will shrink and shrivel up becomes crenated

what energy is need in osmosis

no energy

is osmosis passive

yes

is energy needed in active transport

yes

define active transport

movement of substances in and out of cells by diffusion molecules move down the concentration gradient from low to high concentration

how do molecules move against the concentration gradient (active transport)

special carrier proteins in the cell membrane transport the molecules/ions from one side to the other (cell membrane)