B3 - Exchange Of Materials Flashcards
What is osmosis?
The diffusion of water.
Explain osmosis.
Water moves from a dilute to a more concentrated solution through a partially permeable membrane that allows water to pass through.
What is a partially permeable membrane?
A membrane which only lets some types of particles through.
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How does osmosis restore water balance in the cells?
- If a cell uses water for a chemical reaction, the cytoplasm becomes more concentrated so water moves in by osmosis.
- If water is made from a chemical reaction, the cytoplasm becomes too dilute so the water moves out.
How can osmosis damage cells?
- If the solution outside a cell is more dilute than the cell contents, the water moves into the cell which can cause the cell to swell and burst.
- If the solution outside the cell has a high concentration, the water moves out of the cell causing the cell to shrivel so it can no longer survive.
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How does osmosis support plant structure?
Water moves into the cell causing the vacuole to swell and push the cytoplasm against the cell wall making the cell hard and rigid.
What is active transport?
Moving substances against a concentration gradient.
Why is active transport necessary?
To allow cells to absorb ions from dilute solutions and move them through cells.
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What is needed for active transport?
Energy from respiration.
What types of cells carry out a lot of active transport?
Root hair cells and cells in the gut, both of which have lots of mitochondria.
Give two examples of how active transport is important.
- Mineral ions in soil are usually in dilute solutions. Plants are only able to to absorb the ions by active transport.
- Sugar such as glucose is actively absorbed out of the gut.
What do sports drinks contain and why?
- Sugars to replace sugars used in energy release.
- Water and mineral ions to replace those lost during sweating.
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What causes dehydration?
- Exercise causes the loss of water and mineral ions.
- Body fluids become more concentrated.
- Water leaves the cells by osmosis.
What happens if water and mineral ions aren’t replaced?
Cells don’t work as efficiently.
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Give four adaptations that make an organ efficient at gas or solute exchange.
- Large surface area
- Being thin
- Efficient blood flow
- Ventilated for gaseous exchange
Why is does being thin make an organ more efficient for diffusion?
There is a shorter diffusion path.
Why does having an efficient blood supply make an organ more efficient for diffusion?
The diffusing substances are moved away, maintaining the concentration gradient.
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What is the purpose of alveoli?
They give the lungs a greater surface area.
What distinct adaptations do the lungs have?
- Alveoli
- Rich supplies of capillaries
- Ventilation
What separates the lungs from the abdomen?
The diaphragm.
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What is the process for breathing in?
- As the ribs move up and out, the diaphragm flattens increasing the volume of the chest.
- The increased volume lowers the pressure in the lungs.
- Atmospheric pressure is higher meaning air is drawn into the lungs.
Describe the process for breathing out.
- The ribs fall and the diaphragm moves up decreasing the volume of the chest.
- The decreased volume increases pressure in the chest.
- The pressure in the chest is higher than outside forcing air out of the lungs.
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What does breathing in do?
Supplies oxygen rich air into the lungs, maintaining a steep concentration gradient.
What does breathing out do?
Removes carbon dioxide from the lungs maintaining a steep concentration gradient.
Which muscles move when breathing in?
Intercostal muscles
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How do intercostal muscles move when breathing in?
They contract.
Give three reasons why people may struggle to breathe.
- The tubes to their lungs may be very narrow.
- The structure of the alveoli may break down.
- Some people are paralysed.
What method of pressure does the “iron lung” use?
Negative pressure.
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How does the “iron lung” work?
- The patient lays in a metal cylinder with a tight seal around their neck.
- Air is pumped out creating a vacuum.
- The lower pressure causes the chest to rise and air to be drawn into the lungs.
- The vacuum then turns off and air is forced out of the lungs.
How does a positive pressure ventilator work?
- A measured volume of air is forced into the lungs.
- The lungs then deflate as the ribs move down.
Which two ways can a ventilator be used?
- As a face mask.
- A tube that inserted into the trachea.
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Give three advantages of positive pressure ventilation.
- There is no need to place the patient inside a machine.
- The patient can use it at home and about.
- Patients can have control over the system.
What are villi?
Finger like projections in the small intestine.
Why do food molecules move into the blood from the small intestine?
There is a higher concentration in the small intestine than in the blood so the molecules diffuse.
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What is the purpose of villi?
To increase the surface area of the small intestine allowing for greater net diffusion.
What are villi covered in?
Microvilli
How is glucose moved into the blood?
Active transport
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Why is some food moved by active transport?
Sometimes the concentration gradient isn’t right but glucose cannot be wasted.
How does carbon dioxide enter the leaf of a plant?
Through the stomata by diffusion.
How are leaves adapted for gaseous exchange?
They have a flat, thin shape and internal air spaces.
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Why can’t gases flow freely through a leaf?
-Too much water vapour would be lost by evaporation.
What are stomata?
Small openings in a leaf to allow for gas exchange.
What controls the opening and closing of stomata?
Guard cells.
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How are root hair cells adapted?
- They have projections which can push between the soil particles.
- They have a partially permeable membrane which allows water to diffuse in.
- There is then only a short distance to the xylem.
- They can carry out active transport and have many mitochondria to carry out the process.
What is transpiration?
The loss of water vapour from the surface of plant leaves.
When is transpiration fastest?
Hot, dry, windy or bright conditions.
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What is the transpiration stream?
The constant movement of water from the roots to the leaves.
Why do some conditions increase the rate of transpiration?
- These conditions also increase the rate of photosynthesis which means stomata need to be open to let in carbon dioxide.
- Hot conditions increases the rate of evaporation.
Why are the stomata on the bottom of the leaf?
They are protected from direct sunlight.
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What is wilting?
A protection mechanism to prevent water loss.
How does wilting prevent water loss?
It reduces the surface area for water loss by evaporation.
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