2- movement of substances in and out of cells and nutrition in plants and humans Flashcards
diffusion
the movement of molecules from a region of its higher concentration to a region of its lower concentration
molecules move down a concentration gradient as a result of
their random movement
diffusion helps living organisms-
obtain many of their requirements, get rid of waste products, carry out gas exchange for respiration
diffusion in small intestine
digested food products from limen of small intestine to blood/lymph in villi found covering small intestine walls
diffusion in a leaf- oxygen
oxygen moving from air space between mesophyll cells to mitochondria in all cells
diffusion in leaf- carbon dioxide
carbon dioxide moving from air spaces between mesophyll cells to chloroplasts in mesophyll cells
diffusion in leaf- water vapour
water vapour moves from stomatal pores to air outside stomata
diffusion in lungs- oxygen
oxygen moves from alveolar air space to blood in capillaries around alveoli
diffusion in lungs- carbon dioxide
carbon dioxide moves from blood in capillaries around alveoli to alveolar air space
difference in concentration gradient affect on diffusion
the greater the difference in concentration between two regions the faster the overall rate of diffusion because the higher concentration the more random collisions against the membrane will occur
temperature affect on diffusion
the higher the temperature the more kinetic energy the particles of that substance will have so they move and spread faster compared to when at a lower temp and they have less kinetic energy
surface area affect on diffusion
a membrane with a greater surface area will have a greater rate of diffusion
rate of diffusion is influenced by
temperature, surface area, concentration gradient, diffusion distance
how can you investigate the temperature affect on diffusion
by using beetroot as it contains a dark purple-red pigment and heating above 45°c can damage the membrane meaning that the pigment can leak out so the speed at which this pigment leaks out of the cell tells us about the rate of diffusion
apparatus needed to investigate the effect of temperature on diffusion
beetroot, knife, cutting board, ruler, test tube, water bath, stopwatch
method to investigate the effect of temperature on diffusion
1) using a knife cut 2 equally sized cubes of beetroot, they have to be the same dimensions so they all have equal surface area/volume as these factors could affect the rate at which the pigment leaks out
2) rinse the beetroot to remove any pigments that is released during cutting
3) put 5cm3 of water into 2 test tubes labled A and B
4) keep test tube A at room temperature and then transfer test tube B a hot water bath at 90 degrees c
5) leave the test tubes fir 2 minutes then add a piece of beetroot into each tube
6) after 10 minutes observe the colour of the liquid in both test tubes
results and analysis of investigating temperature affect on diffusion
you should notice that the higher temperature more of the pigment has leaked out because the cell membrane of the beetroot cells has become damaged so more pigment can leak out. at a higher temperature particles have more kinetic energy so this results in faster movement of particles compared to when they have less energy
limitations of investigating temperature affect on diffusion
the beetroot pieces may not be identical in size and shape meaning one test tube could have slightly more beetroot tissue than the other - the solution to this is cut the beetroot as accurately as possible using a knife and ruler and repeat each investigation several times to find a mean
some parts of the beetroot tissue could have more pigment in their cells than others- solution is conduct several repeats using different parts of the beetroot and find a mean
our results would be more reliable if we tested a range of temperatures rather than just two- solution is to set up 5 test tubes in water baths at different temperatures ( etc 10-50 going up in 10s)
observing colour can be very subjective which means it is difficult to compare the differences in diffusion between test tubes- solution use a colorimeter to measure how much light is absorbed as it passes through each of the five samples of coloured liquid
corms investigation for investigating temperature affect on diffusion
c- we are changing the temperature of the environment
o- the beetroot cubes will all be taken from the same beetroot or beetroot of the same age
r- we will repeat the investigation several times to ensure our results are reliable
m- we will observe the colour change of the liquid after 10 minutes
s- we will control the volume of water used, the dimensions of the beetroot cubes and each cube must be blotted before it is weighed each time
water can move in and out of cells by
osmosis
all cells are surrounded by
a partially permeable cell membrane
osmosis
the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
osmosis is water moving down a
concentration gradient
the cell is partially permeable which means it allows
small molecules (like water) through but not the larger molecules (like solute molecules)
animal cells lose and gain water as a result of
osmosis
if an animal cell is placed in a solution with a lower water potential than the cell
it will lose water by osmosis and become crenated (shrivelled up)
if an animal cell is placed into distilled water with a higher water potential than the cell
it will gain water by osmosis as it has no cell wall to create turgor pressure
plant cells lose and gain water as a result of
osmosis
as plants have a cell wall they are protected from
cell lysis
if a plant cell is placed in a strong sugar solution (with a water potential lower than the cell)
it will lose water by osmosis and the vacuole gets smaller and the cell membrane shrivels away from the cell wall and it becomes flaccid or plasmolysed
if a plant cell is put in distilled water (higher water potential than the cell)
it will gain water by osmosis and the vacuole gets bigger, pushing the cell membrane against the cells wall and the cell becomes turgid due to the high turgor pressure caused by the cytoplasm pushing against the cell wall
water entering a cell by osmosis makes the cell
rigid and firm
why is it important for the cell to become rigid and firm after water has entered the cell by osmosis
because when a plant cell is firm it provides support and strength for the plant- making the plant stand upright with its leaves held out to catch sunlight
what happens if a plant doesn’t get enough water
the cells can’t become rigid and firm (turgid) and the plant will wilt
how can we investigate osmosis
using cylinders of potato and placing them in distilled water and sucrose solutions of increasing concentration
apparatus needed to investigate osmosis
potatoes, cork borer, knife, sucrose solution, test tube, balance, paper towels, ruler, test tube rack
method to investigate osmosis
1) prepare a range of sucrose (sugar) solutions raging from 0 mol/dm3 (distilled water) to 1 mol/dm3
2) set up 6 labelled test tubes with 10cm3 of each of the sucrose solutions
3) using the knife, cork borer and ruler, cut 6 equally sized cylinders of potato
4) blot each one with a paper towel and weigh on the balance
5) put 1 piece into each concentration of sucrose solution
6) after 4 hours remove them, blot with paper towels and reweigh them
results and analysis of investigating osmosis
the percentage change in mass can be calculated for each piece of potato by using the equation
((final mass-initial mass)/initial mass) x 100
the potato cylinder in the distilled water will of increased its mass the most because there is a greater concentration gradient in this tube between the distilled water (high water potential) and the potato cells (low water potential). this means more water molecules will move into potato cells by osmosis, pushing the cell membrane against the cell wall and so increasing the turgor pressure in the cells and making them more turgid. the potato cylinder in the strongest sucrose concentration will, have decreased its mass the most as there is a greater concentration gradient in this tube between potato cells (higher water potential) and the sucrose solution (low water potential). this means more water molecules will move out of potato cells by osmosis making them flaccid and decreasing the mass of the cylinder.
what if there is a potato cylinder that has not increased or decreased in mass
if there’s a potato cylinder which hasnt increased or decreased in mass it means there was a no overall net movement of water in or out of the potato cells. this is because the solution that the cylinder was in was the same concentration as the solution found in the cytoplasm of the potato cells so there was no concentration gradient.
limitations to investigation osmosis
slight differences in potato cylinders may mean that results aren’t reliable or comparable- solution is for each sucrose concentration , repeat the investigation with several potato cylinders making a series of repeat experiments means that any anomalous results can be identified and ignored when a mean is calculated
corms for investigating osmosis
c- we are changing the concentration of sucrose solution
o- the potato cylinders will all be taken from the same potato or potatoes of the same age
r- we will repeat the investigation several times to ensure our results are reliable
m- we will measure the change in mass of potato cylinders after 4 hours
s- we will control the volume of sucrose solution used, the dimensions of the potato cylinders and each cylinder must be blotted before it is weighed each time
active transport
the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
energy is needed in active transport because
particles are being moved against a concentration gradient in the opposite direction from which they would naturally move (by diffusion)
active transport across the cell membrane involves
protein carrier molecules embedded in the cell membrane
active transport in animals allows molecules
such as glucose to be transported into the blood stream from the lumen off the small intestine (the gut) when the concentration of sugar molecules in the blood is higher
photosynthesis- endothermic or exothermic?
endothermic because energy from sun light is transferred to the chloroplasts in green plants
photosynthesis
the process by which plants manufacture carbohydrates from raw materials using energy from light
what do plants use glucose as
a source of energy in respiration
what other things can plants use glucose for
produce starch, synthesise lipids into energy sources, to form cellulose to make cell walls, produce amino acids
photosynthesis wird equation
carbon dioxide + water -> glucose + oxygen
photosynthesis chemical equation
6CO2 + 6H2O -> C6H12O6 +6O2
limiting factor
something present in the environment in such short supply that it restricts life processes
main factors to limit the rate of photosynthesis
temperature, light intensity, carbon dioxide concentration
increasing temperature affect on photosynthesis
increasing temperature increases kinetic energy of particles, increasing the likelihood of collisions between reactants and enzymes which results in more product. however at high temperature enzymes that control the processes of photosynthesis can be denatured and this reduces the overall rate of photosynthesis
denatured
where the active site changes shape and is no longer complementary to its substrate
more light intensity on photosynthesis
the more light intensity the more photosynthesis
carbon dioxide affect on photosynthesis
more carbon dioxide the more photosynthesis
the more chloroplasts a plant has…
the more photosynthesis occurs because then more light can be absorbed
amount of chorophyll can be affected by
disease, level of nutrients, loss of leaves
wax cuticle
protective layer on top of the leaf which prevents water from evaporating
upper epidermis
thin and transparent to allow light to enter palisade mesophyll later underneath
palisade mesophyll
column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
spongy mesophyll
contains internal air spaces that increases the surface area to volume ratio for the diffusion of gases mainly carbon dioxide
lower epidermis
contains guard cells and stomata
guard cells
absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in and oxygen to diffuse out
stomata
where gas exchange takes place. opens during the day and closes during the night. evaporation of waster takes place here. in most plants its found in a much greater concentration on the underside of the leaf to reduce water loss
vascular bundle
contains xylem and phloem to transport substances to and from the leaf
xylem
transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
phloem
transports sucrose and amino acids around the plant
