3. Movement In & Out of Cells Flashcards
Diffusion definition
Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration
What do molecules move down during diffusion and why?
Molecules move down a concentration gradient, as a result of their random movement
How does a cell membrane affect diffusion?
can restrict the free movement of the molecules
The cell membrane is a partially permeable membrane – this means it allows some molecules to cross easily, but others with difficulty or not at all
How does the cell membrane filter the molecule? (what is it based on)
The simplest sort of selection is based on the size of the molecules
What does diffusion help living organisms do
Diffusion helps living organisms to:
obtain many of their requirements
get rid of many of their waste products
carry out gas exchange for respiration
What molecules move through the small intestine?
digested food products:
glucose
amino acids
fatty acids
glycerol
From where to where do substances in the small intestine move from and to?
FROM lumen of small intestine
TO blood / lymph in villi found covering small intestine walls
What molecules move through the leaf?
oxygen
carbon dioxide
water vapour
From where to where do substances in the leaf move from and to?
O2
- FROM air spaces between mesophyll cells
- TO mitochondria in all cells
CO2
- FROM air spaces between mesophyll cells
- TO chloroplasts in mesophyll cells
WATER VAPOUR
- FROM stomatal pores
- TO air outside stomata
What molecules move through the lungs?
oxygen
carbon dioxide
From where to where do substances in the lungs move from and to?
O2
- FROM alveolar air space
- TO blood in capillaries around alveoli
CO2
- FROM blood in capillaries around alveoli
- TO alveolar air space
What is the Brownian Motion?
Theory that particles move around randomly
Where does the energy for diffusion come from?
The energy for diffusion comes from the kinetic energy of this random movement of molecules and ions
What factors influence diffusion?
distance
temperature
concentration gradient
How does a cells size affect the surface area to volume ratio? What does this affect?
The bigger a cell or structure is, the smaller its surface area to volume ratio is, slowing down the rate at which substances can move across its surface
In what ways are cells adapted for diffusion
Many cells which are adapted for diffusion have increased surface area in some way – eg root hair cells in plants (which absorb water and mineral ions) and cells lining the ileum in animals (which absorb the products of digestion)
How does distance affect the rate of diffusion?
The smaller the distance molecules have to travel the faster transport will occur
Examples of cells being adapted for diffusion (distance factor)
This is why blood capillaries and alveoli have walls which are only one cell thick, ensure the rate of diffusion across them is as fast as possible
How does temperature affect the rate of diffusion?
The higher the temperature, the faster molecules move as they have more energy
This results in more collisions against the cell membrane and therefore a faster rate of movement across them
How does the concentration gradient affect the rate of diffusion?
The greater the difference in concentration either side of the membrane, the faster movement across it will occur
This is because on the side with the higher concentration, more random collisions against the membrane will occur
Osmosis definition
Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
What property does a cell membrane have which aids in diffusion? How does it help?
The cell membrane is partially permeable which means it allows small molecules (like water) through but not larger molecules (like solute molecules)
What are plant cells that are full of water called?
Plant cells that are turgid are full of water and contain a high turgor pressure (the pressure of the cytoplasm pushing against the cell wall)
Why is turgor pressure useful in plant cells?
This pressure prevents any more water entering the cell by osmosis, even if it is in a solution that has a higher water potential than inside the cytoplasm of the cells
This prevents the plant cells from taking in too much water and bursting
How can water move into plant cells from soil?
Plant roots are surrounded by soil water and the cytoplasm of root cells has a lower water potential than the soil water
This means water will move across the cell membrane of root hair cells into the root by osmosis
How is a concentration gradient formed in plants?
The water moves across the root from cell to cell by osmosis until it reaches the xylem
Once they enter the xylem they are transported away from the root by the transpiration stream, helping to maintain a concentration gradient between the root cells and the xylem vessels
Why are the results of osmosis more severe in animal cells?
As animal cells do not have a supporting cell wall, the results on the cell are more severe
What will happen if an animal cell is placed into a strong sugar solution?
If an animal cell is placed into a strong sugar solution (with a lower water potential than the cell), it will lose water by osmosis and become crenated (shrivelled up)
What will happen if an animal cell is placed into distilled water?
If an animal cell is placed into distilled water (with a higher water potential than the cell), it will gain water by osmosis and, as it has no cell wall to create turgor pressure, will continue to do so until the cell membrane is stretched too far and it bursts
Active transport definition?
Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
What is specifically needed for only active transport?
Energy is needed because particles are being moved against a concentration gradient, in the opposite direction from which they would naturally move (by diffusion)
What are examples of active transport?
uptake of glucose by epithelial cells in the villi of the small intestine and by kidney tubules in the nephron
uptake of ions from soil water by root hair cells in plants
How does active transport work?
Active transport works by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient:
Process in steps for active transport
Substance combines with carrier protein molecule in the cell membrane
Carrier transports substances across membrane using energy from respiration to give them the kinetic energy needed to change shape and move the substance through the cell membrane
Substance released into cell
Define diffusion.
Diffusion is the net movement of molecules from a region of its higher concentration to a region of its lower concentration down a concentration gradient as a result of their random movement.
Where does the energy for diffusion come from?
The energy for diffusion comes from the kinetic energy of the random movement of molecules and ions.
Four factors that affect the rate of diffusion and therefore the movement of molecules through membranes:
Distance.
Temperature.
Surface area.
Concentration gradients.
How does surface area affect the rate of diffusion?
As the surface increases, the rate of diffusion increases. This is because there is more space available for the substances to diffuse through.
How does distance affect diffusion?
A greater diffusion distance slows the rate of diffusion as molecules must travel further.
How does temperature affect diffusion?
As temperature increases, the rate of diffusion increases. This is because the molecules gain kinetic energy and thus move faster.
How does the concentration gradient affect the rate of diffusion?
As the concentration gradient increases, rate of diffusion increases.
Describe the importance of diffusion of gases and solutes in living organisms.
obtain many of their requirements.
get rid of many of their waste products.
carry out gas exchange for respiration.
SUMMARY - Basically metabolic reactions.
For how long will diffusing particles spread?
The particles spread out until they are evenly spread and have reached an equilibrium.
State that some substances move into and out of cells by diffusion through the cell membrane. What is the cell membrane?
The cell membrane is a partially permeable membrane therefore it controls the movement of substances in and out of a cell.
How does digested food product diffuse in the small intestine?
Digested food product molecules move from lumen of small intestine to blood/lymph in villi found covering small intestine walls.
How does oxygen diffuse into the leaf?
Oxygen molecules move from air spaces between mesophyll cells to mitochondria in all cells.
How does carbon dioxide diffuse into the leaf?
Carbon dioxide molecules move from air spaces between mesophyll cells to chloroplast in mesophyll cells.
How does water vapor move diffuse into the leaf?
Water vapor moves from stomatal pores to air outside stomata.
How does oxygen diffuse around the body?
Oxygen molecules move from alveolar air space to blood in capillaries around alveoli.
How does carbon dioxide diffuse out of the body?
Carbon dioxide molecules move from blood in capillaries around alveoli to alveolar air space.
Explain surface area to volume ratio.
The bigger a cell or structure is, the smaller its surface area to volume ratio is, slowing down the rate at which substances can move across its surface.
What type of molecules do the cell membrane partially permeable membrane allow through?
The cell membrane is partially permeable which means it allows small molecules (like water) through but not larger molecules (like solute molecules).
Define osmosis.
Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane, down the water potential gradient.
What happens if you place a plant cell into a solution that has a higher water potential than the water potential of the cell e.g. distilled water?
When the cell is more concentrated than the surrounding cells, water molecules diffuse into the cell via osmosis, making it turgid.
What happens if you place a plant cell into a solution that has a lower water potential than the water potential of the cell e.g. strong sugar solution?
When it is less concentrated than the surrounding cells, water molecules will leave the cell, making it flaccid leading to plasmolysis (the cell membrane peels away from the cell wall).
What happens if you put a cell into a solution that has the same water potential as the water potential of the cell?
There is no net movement of water in or out of the cell.
What causes a plant to wilt?
If plants do not receive enough water the cells cannot remain rigid and firm (turgid) and the plant wilts.
What prevents the plant cells from taking in too much water and bursting?
Plant cells that are turgid are full of water and contain a high turgor pressure. The pressure created by the cell wall stops too much water from entering and prevents the cell from bursting.
How are plant cells supported by the pressure of water?
When water moves into a plant cell, the vacuole gets bigger, pushing the cell membrane against the cell wall.
Why is it important for plant cells to be firm?
This is important for plants as the effect of all the cells in a plant being firm is to provide support and strength for the plant.
Define turgid.
Cells are described as turgid when they are swollen due to high water content.
Define turgor pressure.
The pressure on the cell wall from the cell membrane pushing upon it. This is a result of the cell becoming turgid as water moves into the cell via osmosis.
Define flaccid.
Occurs when water moves out of the cell via osmosis. The cell shrinks but the cell membrane does not peel away from the cell wall.
Define plasmolysis.
The process by which the cytoplasm pulls away from the cell wall as a result of water loss from the cell.
What happens when an animal cell is placed into a solution that has a higher water potential than the water potential of the cell?
There is a net movement of water into the cell which causes the animal cell to burst.
What happens if you place an animal cell into a solution that has a lower water potential than the water potential of the cell?
There is a net movement of water out of the cell which causes the animal cell to shrink (crenate).
Define active transport.
Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.
Examples of active transport include:
uptake of glucose by epithelial cells in the villi of the small intestine and by kidney tubules.
uptake of ions from soil water by root hair cells in plants.
Explain how active transport involves proteins.
Carrier proteins move substances from one side of the membrane to the other using energy.
Active transport by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient:
1) Substance combines with carrier protein molecule in the cell membrane.
2) Carrier transports substances across the membrane using energy from respiration to give them the kinetic energy needed to change shape and move the substance through the cell membrane.
3) Substance released into cell.
Diffusion
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration
The greater the difference in concentration, the faster the rate
No energy needed
No membrane needed (but commonly has a membrane)
All particles have a natural desire to move (brownian motion) which allows for passive transport
Eg. smells moving around (perfume)
hypertonic to hypotonic solution
Factors affecting diffusion
Temperature
Size of molecules
Concentration of the solute
Osmosis
Net movement of water molecules from a region of higher water concentration (dilute) to a region of lower water concentration (concentrated)
No energy needed (passive movement)
Aquaporin in membrane allows for water to pass through
Type of passive movement
Passive transport
No energy (ATP) needed
High concentration to low concentration
Diffusion, Facilitated diffusion, osmosis
Facilitated Diffusion
High concentration to low concentration
Has a channel protein that molecules pass through
Some molecules such as glucose and sodium ions are unable to pass through the layer of cell membranes but with the aid of a channel protein, they are able to be transported
Solute
Substance dissolved in another substance (commonly liquid)
Solvent
Liquid that dissolves a solute
Hypertonic Solution
Greater concentration or number of solute particles outside a membrane than there are inside it.
Isotonic Solution
concentration or number of solute particles outside a membrane is the same as inside it. There will be no net movement of water
Hypotonic Solution
Lower concentration or number of solute particles outside a membrane than there are inside it.
Cells in a hypertonic solution
Animal cell - water will move out of the cell so the cell will become shrivelled and eventually die due to dehydration and the lack of water
Plant cell - water will move out of the cell so the plant cell will be plasmolysed and go through plasmolysis which is when the cell membrane moves away from the cell wall leading the plant to wilt and eventually die. The cells become damaged
Cells in a isotonic Solution
Animal Cell - there will be no net movement of water. Animal cells want to be in an isotonic solution (no effect on cell - natural occurance)
Plant cell - there will be no net movement of water. Plant cells will become flaccid. Due to the lack of turgor pressure the plant will start to wilt but if you spray water at it it can stand up again
Cells in a hypotonic solution
Animal cell - water will move into the cell so the animal cell will explode due to the lack of cell wall and the increase in water
Plant cell - water will move into the cell so the plant cell will become turgid which will allow it to stand up. This is where the plant wants to be and the natural occurrence of a plant
Transport in root hair cells
Osmosis - water and minerals from the soil into the cell
Transport in capillaries
one-cell thick wells which allows exchange of substances between capillaries and tissue cells to occur rapidly through diffusion
oxygen and dissolved food substances diffuse from capillaries into tissue fluids and cells
Metabolic waste products diffuse from the cells into tissue fluids and then into blood capillaries
Transport in unicellular organisms
oxygen and nutrients can diffuse through cell surface membrane and easily reach all parts of the cell. Metabolic waste can also diffuse out and be removed from the cell
Transport in red blood cells
Oxygen diffuses from the lungs into the RBCs, where it binds to haemoglobin.
Transport in palisade cells
Water evaporates from the mesophyll cells into air spaces in the leaf through stomata through diffusion as the water vapour is diffusing out of the leaf.
carbon dioxide diffuses in
oxygen diffuses out
Active Transport
Requires energy
Uses a protein pump (ATP)
Low concentration to high concentration
Bulk transport
What is diffusion?
Diffusion is when particles move from an area of high concentration to an area of low concentration as a result of their random movement
Where does the energy of diffusion come from?
Kinetic energy
What is the concentration gradient?
Area of high concentration to an area of low concentration
What does passive process mean?
It does not require energy
What are three factors that affect diffusion?
Temperature
Surface area to volume ratio
Concentration gradient
List 4 ways to get a faster rate of diffusion:
Higher temperature
Larger surface area
Smaller size of particles
Higher gradient
In which medium does diffusion occur the fastest?
Gas
What is osmosis?
Osmosis is the diffusion of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane
What is a partially permeable membrane?
A partially permeable membrane has holes to allow water molecules to pass through but are too small to let larger molecules pass through
How do water particles in osmosis diffuse?
From high concentration to low concentration
What does a dilute solution mean?
Has a high concentration of molecules
What does concentrated solution mean?
Has a low concentration of molecules
What are plant and animal cells surrounded by?
Partially permeable plasma
What does a cell wall provide for a plant cell
Support
Protection
Why is water important for cells?
For chemical reactions
Support
What is active transport?
Active transport is the movement of particles from an area of low concentration to an area of high concentration using energy in the form of ATP
What happens during active transport?
Protein carriers in the cell membrane pick up particles and move them against the concentration gradient
What minerals do plants need to absorb?
Phosphorus
Nitrogen
Potassium
How is active transport used in plants
Is the soil as a low concentration of minerals then the roots can absorb it against the concentration gradient
Define diffusion
The movement of particles within a liquid or gas from a region of high concentration to a region of lower concentration (down concentration gradient)
Would diffusion take place faster or slower in hotter environments?
Faster as the molecules will have more kinetic energy
Define osmosis
The diffusion of water molecules from a region of high concentration of water molecules to a region of lowers concentration of water molecules
When does diffusion stop
When equilibrium has been reached
What separates active transport from osmosis and diffusion
Active transport requires energy where as osmosis and diffusion are passive
What process does gas exchange in the alveoli use
Diffusion
What process does the absorption of nutrients use
Diffusion
What process does water absorption in the colon use
Osmosis
What process does water uptake in plant roots use
Osmosis
What process does mineral uptake in plant roots use
Active transport
The rate of diffusion is increased when?
The distance to be diffused deceased
Surface area is increased
The difference in concentration is increased
What does flaccid mean
A plant cell that is limp
What does turgid mean
Plant cell fully inflated with water
What does crenation mean?
Shrinking of an animal cell by osmosis
What does plasmolysis mean
Bursting of an animal cell by osmosis
What factors could affect how slowly or quickly diffusion or osmosis takes place across a cell membrane?
Size of molecules
Temperature
Difference in concentration on either side
Surface area of membrane
Ph
Kinetic assistance
Moistness
Surface area to volume ration
Why is it important to have turgid cells in plants?
To keep them upright and stop them from wilting as they have no bone structure to keep the up
What is turgor pressure?
Turgor pressure is water pressure acting against an inelastic cell wall
What happens to a plant cell when placed in a solution of lower water potential?
It will become flaccid
What happens when a RBC is added to a solution of lower water potential?
It will become crenated
What will happen when RBC is added to a solution of high water potential?
It will swell up and burst
Diffusion
the net movement of molecules from their region on higher concentration to their region on lower concentration down their concentration gradient
is diffusion passive or active and why?
a diffusion is a form of passive transport as it doesn’t require any energy
diffusion takes place because
molecules contain kinetic energy which causes them to bounce around. They collide with other
particles and spread out in the fluid in this way.
The diffusion of gases and solutes is important as without it
molecules which are needed for life, for
example, glucose and oxygen for respiration, would not be able to get to the places they are needed.
Water is needed as a solvent
factors that affect diffusion
distance, concentration gradient, surface area, temperature
how does distance affect diffusion
the smaller the distance, the quicker the diffusion
how does the concentration gradient affect diffusion
The greater the concentration gradient, the quicker the diffusion
how does surface area affect diffusion
if diffusion takes place over a larger surface area, it is quicker
how does temperature affect diffusion
when hotter, particles have more KE, so Brownian motion is faster
osmosis
the net movement of water molecules from their region of higher water potential to their region of lower water potential down the water potential gradient.
plants cell wall
totally permeable
cell membrane
partially permeable
vacuole aka
tonoplast
selectively permeable membrane
muscle membrane. vacuole membrane
water to cell
endo- osmosis
cell to water
ex-osmosis
endo-osmosis and ex-osmosis are considered
plasmolysis
dried fruits are
plasmolysed
impermeable membrane
cell wall of xylem vessel
both diffusion and osmosis are passive transport as
no energy is lost
due to turgor pressure in plants
they become too full
due to turgor pressure in animals
they burst
what causes turgor pressure in plants
When a plant cell is placed in a hypotonic solution compared to inside the
cell, water from the solution moves into the cell, creating turgor pressure on
the wall. This makes the cell turgid, therefore supporting the plant, and giving
it its shape. The cell wall is inelastic, so doesn’t burst
when do plants cell wall not change
In isotonic solutions there is no concentration gradient, so the cell doesn’t
change
when do cells become flaccid
In a hypertonic solution as compared to inside the cell, water leaves the cell as
the solution inside the cell has higher water potential. The cell shrivels and
becomes flaccid
what causes plasmolysis
When too much water is lost from the cell by osmosis, the cell membrane is
pulled away from the cell wall and the cell undergoes plasmolysis .
Active transport
the net movement of molecules from their region of lower concentration to their region of higher concentration against the concentration gradient using energy from respiration with the help of carrier proteins
glucose is transported only by
active transport
active transport needs
carrier proteins
process of active transport
First, the molecule being transported combines with a carrier
protein. Energy from respiration enables the carrier protein to change its shape to carry the ion or
molecule to the inside of the membrane. After the ion or molecule is in the membrane, the carrier
protein reverts to its original shape .
why is active transport needed
when an an organism wants to optimize the number of nutrients it can take up -
ion uptake by root hairs and uptake of glucose by epithelial cells of villi.
Diffusion
the net movement of particles from their region of higher concentration to their region of lower concentration down their concentration gradient due to their random movement
The energy for diffusion comes from
the kinetic energy of random movement of
molecules and ions.
Some substances move into and out of cells by
diffusion through the cell membrane
The role of Water
solvent in organisms during digestion, excretion and transport.
Water diffuses through partially permeable membranes by
osmosis
Water moves into and out of cells by osmosis through the
cell membrane
Plants are supported by the pressure of
the water inside the cells pressing outwards on the cell wall.
Osmosis
the net movement of water molecules from their region of higher water potential to their region of lower water potential down their water potential gradient through a partially permeable membrane
a plant cell is placed in a less concentrated solution
water moves into the cell
down the water potential gradient by osmosis. pressure on the cell wall increase.
turgor pressure increase. cell wall prevents the cell from bursting.
If a plant cell is placed in a more concentrated solution
water moves out of the cell
down the water potential gradient by osmosis. Pressure on the cell wall decrease.
turgor pressure decrease. the cell membrane pulls away from the cell wall. the cell
becomes flaccid. The cell is said to be plasmolyzed.
Active transport
the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration against a concentration gradient using energy from respiration
Protein carriers move molecules
or ions across a membrane during active transport.
