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movement of substances in and out of cells - Coggle Diagram
movement of substances in and out of cells
diffusion
the movement of particles from a region of higher concentration to an area of lower concentration
molecules move down a concentration gradient
examples
small intestine
digested food products such as glucose, amino acids, fatty acids and glycerol etc.
leaf
oxygen, carbon dioxide and water vapour
lungs
oxygen and carbon dioxide
factors affecting diffusion
surface area to volume ratio
bigger the cell is, the smaller the SA to volume ratio, slowing down the rate of diffusion
many cells which are adapted for diffusion have increased surface area in some way e.g villii cells
diffusion distance
smaller the distance molecules have to travel, the fastr the rate of diffusion
temperature
the higher the temperature, the faster the rate of diffusion as they have more energy, resulting in more collisions against the cell ,membrane.
concentration gradient
the greater the difference in concentration on either side of the membrane, the greater the rate of diffusion, due to more random collisions against the membrane
osmosis
the net movement of water from a high water potential to a low water potential, across a partially permeable membrane
water moves down a concentration gradient
animal cells lose and gain water as a result of osmosis.
animal cells don't have a cell wall so if the cell is placed in a strong sugar solution, it will lose water by osmosis and become crenated
if an animal cell is placed in distilled water, it will gain water by osmosis as it has no cell wall to create turgor pressure. therefore if it stretches too far, it will burst (lysis)
the human body is adapted to maintain the optimum osmatic balance using sweating/ increasing or decreasing urine concentration etc. this is called osmoregulation
plant cells
have a cell wall which protects it from lysis.
if a plant is placed in a strong sugar solution, it will lose water, meaning the vacuole gets smaller and the cell membrane comes away from the cell wall (turgid)
if a plant is placed in distilled water, it will gain water by osmosis meaning the vacuole gets bigger, pusing the cell membrane against the cell wall (turgid)
solutions
hypertonic
cells have higher water potential than solution so water moves out.
isotonic
when the water potentials are equal so there is no net movement of water
hypotonic
cells have lower water potential so water moves in
active transport
the net movement of particles from a region of lower concentration to a region of higher concentration with energy, through a partially permeable membrane
energy needed because particles are being moved against a concentration gradient, the opposite direction to normal
animals
active transport allows molecules such as glucose to be transported into the bloodstream when the concentration of sugar in the blood is higher.
the also happens in kidney tubules to allow for reabsorption of glucose back into the blood so none is lost in the urine
plants
root hair cells need to move minerals such as Mg ions up a concentration gradient, which are needed to make chlorophyll as well as nitrate ions being needed for amino acids for protein synthesis
diffusion practical
investigate how temperature affects diffusion using beetroot
CORMS analysis
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
M1 – We will observe the colour change of the liquid
M2 – …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
osmosis practical
We can investigate osmosis using cylinders of potato and placing them into distilled water and sucrose solutions of increasing concentration
CORMS
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
M1 – We will measure the change in mass of the potato cylinders
M2 – …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