Exchange and Transport Flashcards
Smaller animals have a … SA:V ratio
Higher
Larger animals have a …. SA:V ratio
Lower
How to calculate SA:V ratio
Divide the SA by the volume
In single celled organisms how do substances move into cells and at what speed
Diffusion directly into the cell across cell surface membrane, this occurs quickly due to the small distances the substances have to travel
Why are multicellular organisms unable to use diffusion
- Some cells are too deep in the body
- Larger animals have a lower SA:V so is difficult to exchange enough substances to supply an organism
- They have a higher metabolic rate than single-celled organisms so use up oxygen and glucose faster
How do multicellular organisms exchange substances
Using specialised exchange surfaces such as the alveoli in the lungs.
How are root hair cells specialised to improve their efficiency
- They grow into long hairs which stick out giving a large SA
- And increased rate of absorption of water and mineral ions from the soil
How are the alveoli specialised to improve their efficiency
- Thin walls
- Short diffusion distance
- Good blood supply = capillary network
- Moist lining
- Good ventilation so air in alveolus is constantly replaced
How are fish gills specialised to improve their efficiency
- Large network of capillary’s
- Well ventilated as fresh water is constantly passing over them
What is the passage of air in the body
1) As you breathe in air enters the trachea
2) The trachea splits into two bronchi - one bronchus leading to each lung
3) Each bronchus then branches off ino bronchioles
4) The bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged
5) The ribcage, intercostal muscles and diaphragm all work together to move air in and out
Function of goblet cells
Lines the airways and secretes mucus trapping microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli
Function of cilia
On the surface of cells lining he airways and beats the mucus moving it upward away from the alveoli towards the throat, where it is swallowed preventing lung infections.
Function of elastic fibres
Found in walls of trachea, bronchi, bronchioles and alveoli and help with process of breathing out. When breathing in, the lungs inflate and the elastic fibres are stretched. Then the fibres recoil to help push air out when exchanging
Function of smooth muscle
In the walls of the trachea, bronchi, bronchioles allows their diameter to be controlled. During exercise the smooth muscle relaxes, making the tubes wider, so less resistance to airflow and air can move in and out of the lungs more easily.
Function of rings of cartilage
In the walls of the trachea and bronchi provide support. It’s strong but flexible it stops the trachea and bronchi collapsing when you breathe in and the pressure drops.
What happens during inspiration
1) External intercostal and diaphragm muscles contract
2) Causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax
3) As the volume of the thorax increases the lung pressure decreases
4) This causes air to flow into the lungs
What happens during expiration
1) The external intercostal and diaphragm muscles relax
2) The ribcage moves downwards and inwards and the diaphragm becomes curved again
3) The thorax volume decreases causing air pressure to increase
4) Air is forced out of the lungs
Define tidal volume
The volume of air in each breath
Define vital capacity
The maximum volume of air that can be breather in or out
Define breathing rate
How many breaths are taken usually in a minute
Define oxygen consumption or oxygen uptake
The rate at which an organism uses up oxygen
How does a spirometer machine work
1) Has an oxygen-filled chamber with a movable lid
2) The person breathes through a tube connected to the oxygen chamber
3) As the person breathes in and out, the lid of the chamber moves up and down
4) These movements can be recorded by a pen attached to the lid of the chamber this writes on a rotating drum, creating a spirometer trace. Or the spirometer can be hooked up to a motion sensor using movements to produce electronic signals, picked up by a data logger
5) Soda lime in the tube the subject breathes into absorbs carbon dioxide.
Why does the total volume of gas in the chamber decrease over time
The air that’s breathed out is a mixture of oxygen ad carbon dioxide. The CO2 is absorbed by the soda lime - so there’s only oxygen in the chamber which the subject inhales from. As this oxygen gets used up by respiration, the total volume decreases.
How do fish use a counter-current system for gas exchange
1) Water, containing oxygen, enters the fish through its mouth and passes out through the gills
2) Each gill is made of lots of thin branches called gill filaments or primary lamellae, which give a large SA for exchange. The gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae, which increase the SA even more. Each gill is supported by a gill arch.
3) The gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion.
4) Blood flows through the gill plates in one direction and water flows over in the opposite direction called counter-current. It maintains a large concentration
