B3- Exchange of Materials Flashcards
How does air travel through the lungs?
- Air passes into the nasal cavity, where dust and bacteria are filtered out by sticky mucus.
- The air is drawn down the trachea, which is kept open by rings of cartilage.
- At the bottom of the trachea it divides into two bronchi.
- Each bronchus subdivides again into a mass of fine branches known as bronchioles.
- These end in tiny hollow bags with bulb-like pockets called alveoli in which gases are exchanged.
- Blood flowing through capillaries absorbs oxygen and releases carbon dioxide which diffuses back into the alveoli.
Define osmosis.
Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane.
Amoeba live in fresh water. How does an amoeba stop too much fresh water diffusing into it by osmosis?
They have contractile vacuoles inside their bodies.
These fill with water, then open to the outside to let any excess water out.
What do Xylem tubes do?
Transport water and minerals to leaves.
How are villi adapted to be efficient exchange surfaces?
- Finger-like with large surface area➡️more surface area for exchange to occur.
- Thin walls, only one cell thick➡️shorter diffusion distance.
- Contain blood capillaries to carry away absorbed food molecules.
What do Phloem tubes do?
Transport sugars from the leaves to growing regions and storage organs.
What gases diffuse in and out of leaves and how?
- Oxygen: needed for respiration and a waste product of photosynthesis.
- Carbon dioxide: needed for photosynthesis and a waste product of respiration.
What do most sports drinks contain?
- Water➡️To replace water lost when sweating.
- Sugar➡️To replace sugar used for energy release in exercise.
- Mineral ions➡️To replace those lost in sweating.
What is meant by the transpiration stream?
Movement of water from roots via xylem to the leaves.
Plant roots absorb water mainly by osmosis.
Plant roots absorb ions mainly by active transport.
Explain why roots need to use the two different methods to absorb water and ions (4marks).
The solution in the soil is more dilute (1) so water moves from a dilute to a more concentrated region (1).
The concentration of the ions in soil is less that in roots (1) so energy is needed to move ions (1).
How is water lost in plants?
Transpiration➡️Water evaporates from the leaves through the stomata.
Why are isotonic sports drinks marketed as ideal for endurance sports?
Because an isotonic drink is taken up by the body as quickly as water, due to the drink concentration matching the body fluids.
What happens when we breathe out?
- The muscles relax.
- The ribcage moves down and in and the diaphragm becomes domed.
- The volume decreases.
- The pressure increases and air is forced out.
What is an exchange surface and what features make them efficient?
Large, complex organisms have exchange surfaces to obtain all the food and oxygen they need.
Efficient exchange surfaces have a large surface area, thin walls/short diffusion path and an efficient transport system (i.e: the blood supply in animals).
Define active transport.
Active transport is the movement of particles against the concentration gradient (i.e: from a low to a high concentration).