Diffusion, osmosis and active transport.
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- Created by: Kristenvermaak
- Created on: 25-03-23 10:29
What is diffusion?
Diffusion is the movement of molecules from an area of higher concentration to lower concentration.
Molecules move down a concentration gradient, as a result of their random movement.
Molecules move down a concentration gradient, as a result of their random movement.
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What does the cell membrane do?
The cell membrane can restrict the free movement of the molecules down a concentration gradient.
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What does a partially permeable membrane mean?
This means it allows some molecules to cross easily but others with difficulty or not at all.
Selection is based on the size of molecules.
Selection is based on the size of molecules.
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With what does diffusion help organisms?
-Obtain many of their requirements.
-Get rid of waste products.
-Carry out gas exchange for respiration.
-Get rid of waste products.
-Carry out gas exchange for respiration.
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What are examples of diffusion?
-Digested food products moving from the lumen of small intestine to the blood/lymph in villi found covering small intestine wall.
-Oxygen in the leaf moving from air spaces between mesophyll cells to mitochondria.
-Carbon dioxide in the leaf moving from a
-Oxygen in the leaf moving from air spaces between mesophyll cells to mitochondria.
-Carbon dioxide in the leaf moving from a
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Where does the energy for diffusion come from?
Energy for diffusion comes of this random movement of molecules and ions.
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Complete the sentence.
The bigger a cell or structure is..
The bigger a cell or structure is..
the smaller it's surface area to volume ratio is, slowing down the rate at which substances can move across it's surface.
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How are cells adapted for more efficient diffusion?
Cells have an increased surface area in some way.
E.g.- root hair cells and cells lining the ileum.
E.g.- root hair cells and cells lining the ileum.
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What are the factors that affect the rate of diffusion?
Temperature.
Distance
Concentration gradient
Distance
Concentration gradient
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How does distance affect the rate of diffusion?
The shorter the distance molecules have to travel, the faster the rates of diffusion.
This why a lot of cells that carry out diffusion have walls that are one cell thick.
This why a lot of cells that carry out diffusion have walls that are one cell thick.
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How does temperature affect the rates 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.
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How does the concentration gradient affect the rate of diffusion?
The greater the difference in concentration on either side of the membrane, the faster the movement across them.
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Why is water incredibly useful and essential for all life?
Many substances are able to dissolve in it (use water as a solvent.)
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What are some uses of water in an organism?
-Dissolved substances can be transported throughout the organism.
-Digested food molecules in the alimentary canal need to be transported to cells throughout the body.
-Toxic substances as urea and substances in excess of requirements such as salts can be
-Digested food molecules in the alimentary canal need to be transported to cells throughout the body.
-Toxic substances as urea and substances in excess of requirements such as salts can be
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What is osmosis?
Osmosis is the net movement of water molecules from a high-water potential (dilute solution) to an are of low water potential (concentrated solution) through a partially permeable membrane down a concentration gradient.
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What happens when water moves into a plant cell by osmosis?
The vacuole gets bigger, pushing the cell membrane against the cell wall- increasing the turgor pressure.
The cell becomes turgid.
The pressure created by the cell wall prevents too much water entering and prevents the cell from bursting.
The cell becomes turgid.
The pressure created by the cell wall prevents too much water entering and prevents the cell from bursting.
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What happens when plant cells get placed in a concentrated solution?
Water molecules will move out of the plant cells by osmosis, making them flaccid.
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What happens when plant cells are placed in a dilute solution?
The water moves into the plant cell via osmosis.
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Why is it important for plant cells to be turgid?
It is important because this supports and gives structure and strength to the plant cell.
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What happens to plants if they do not get enough water?
The cells are no longer turgid and firm- the plant wilts.
The plant cell might be plasmolysed.
The plant cell might be plasmolysed.
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What is meant by a cell might be plasmolysed?
The cell membrane has pulled away from the cell wall.
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What will happen to an animal cell if it is placed into a strong sugar solution (hypertonic solution)?
It will lose water by osmosis and become crenated (shrivelled up).
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What will happen to an animal cell if it is placed in distilled water (hypertonic solution)?
It will gain water by osmosis and as it has no cell wall to create turgor pressure will continue to gain water until it bursts.
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What is active transport?
Active transport is the movement of particles through a membrane from a low concentration to a high concentration using energy from respiration.
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Why is energy needed for active transport?
Because particles are moving up a concentration gradient; the opposite way of how they would naturally move.
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Why is active transport a vital process?
It is the vital process for the movement of molecules and ions across membranes.
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What are examples of active transport?
Absorbing nutrients and ions from the soil through root hair cells.
Uptake of glucose by epithelial cells in the villi of the small intestine.
Uptake of glucose by epithelial cells in the villi of the small intestine.
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With what does active transport work by?
It works with protein carriers embedded in the cell membrane to pick up specific molecules and take them through the cell membrane up the concentration gradient.
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Write down how the molecules move through the membrane?
1. Substance combines with carrier protein molecule in the membrane.
2. Carrier transports substance across membrane using energy from respiration.
3. Substance released in cell.
2. Carrier transports substance across membrane using energy from respiration.
3. Substance released in cell.
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Other cards in this set
Card 2
Front
What does the cell membrane do?
Back
The cell membrane can restrict the free movement of the molecules down a concentration gradient.
Card 3
Front
What does a partially permeable membrane mean?
Back
Card 4
Front
With what does diffusion help organisms?
Back
Card 5
Front
What are examples of diffusion?
Back
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