Exchange Of Materials Flashcards
(43 cards)
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
What is osmosis a type of?
Diffusion.
Why does the concentration in the cells need to remain the same?
So that they can work properly.
What is the concentration of tissue fluid used for?
It is usually different to the concentration inside a cell so water will move into or out of the cell.
How does the cytoplasm regulate?
If it uses up water in chemical reactions the cytoplasm becomes more concentrated and water moves in by osmosis. On the other hand if the cytoplasm becomes too dilute, water leaves the cell by osmosis.
What are the problems with osmosis?
If the solution outside the cell is more dilute than the cell contents, water will move into the cell by osmosis. The cell may swell and burst. If the concentration outside the cell is more concentrated the cell will shrivel up.
Why do plants need osmosis?
They rely on it to support their stems and leaves.
What happens when water moves into the cell of a plant?
The vacuole swells and presses the cytoplasm against the cell walls. he pressure builds up until no more water can enter. This makes the cell hard and rigid.
What is active transport?
When substances are moved through a partially permeable membrane against the concentration gradient.
What does active transport enable to happen?
Cells can absorb ions from very dilute substances. Substances such as sugars and ions can also be moved.
Where does the energy for active transport come from?
Cellular respiration.
How are root hair cells adapted for absorbing water and minerals?
They have a big surface area. They also have long hairs which stick out into the soil.
How do root hair cells take in minerals?
Using active transport.
When is active transport used in humans?
When taking glucose from the gut and from the kidney tubules.
How can the effectiveness of exchanging materials be increased?
Having a large surface area, being thin to provide a short diffusion path, having an efficient blood supply, this moves the diffusing substances away and maintains the concentration gradient, being ventilated, to maintain the gaseous exchange and steep concentration gradient.
How do stomata help with gas exchange?
They let carbon dioxide diffuse through, and let oxygen and water diffuse out of the stomata.
How do the guard cells help with water loss?
Thy close the stomata if the plant is losing water faster than it is being replaced by the roots. Without them the plant will soon wilt.
How does the flattened shape help the plant?
Increases the surface area.
How do the air spaces help the plant?
Increases the amount of CO2 which can get into the cell.
In the body where does gas exchange take place?
In the lungs there are millions of air sacs called alveoli.
How are the alveoli adapted to maintain the concentration gradient.
They have an enormous surface area, a moist lining for dissolving gases, very thin walls, a good supply of blood.
How is the thorax separated from the digestive organs?
The diaphragm.
What is the diaphragm?
A strong sheet of muscle.
How does air get into the blood?
The air which is breathed in goes through the trachea. This splits into two tubes called bronchi, one going to each lung. The bronchi split into progressively smaller tubes called bronchioles. The bronchioles then end up at the alveoli, where gas exchange takes place.
