1.2- S4: Exchange surfaces and breathing

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What is an exchange surface?
a specialised area adapted to make it easier for molecules to cross from one side of the surface to the other.
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Why do organisms need to exchange substances?
To take in oxygen for aerobic respiration and nutrients. To remove waste products like carbon dioxide and urea.
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Smaller animals have ? surface area: volume ratios
larger- bigger surface area relative to its volume
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Why do multicellular organisms need exchange organs?
single-celled: direct diffusion across cell surface membrane, quick enough-small diffusion distance. Multicellular: some cells too deep within the body, large diffusion distance. Low surface area to volume ratio-small outer surface to diffuse through
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What is the structure of the lungs?
Trachea> Bronchi> Bronchioles> alveoli
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Describe gas exchange in an alveolus
oxygen diffuses out of the alveolus, across the alveolar epithelium and capillary endothelium to blood blood cells. Carbon dioxide diffuses into the alveolus from the blood across the capillary endothelium and alveolar epithelium.
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What is gaseous exchange?
the movement of gases by diffusion between an organism and its environment across a barrier.
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How are most gaseous exchange surfaces adapted?
Larger surface area, increases ROD. More space for molecules to pass through. Thin barrier- reduce diffusion distance, increase ROD. Maintains steep concentration gradient, increase ROD.
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How are the lungs adapted for efficient gaseous exchange?
They have a large surface area for diffusion to occur across. Alveolar and capillary epithelium are only one cell thick- short diffusion distance. Concentration gradient maintained by good blood supply and breathing in and out.
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What do goblet cells do?
Trachea, bronchi and bronchioles. They secrete mucus which traps micro-organisms and dust particles in inhaled air, stopping them reaching alveoli, to prevent risk of infection.
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What is the function of the ciliated endothelium?
Trachea, bronchi and bronchioles. Cilia beat mucus away by moving in a synchronised pattern. This moves trapped micro-organisms up and away from alveoli, up to the throat.
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What is the function of elastic fibres?
Trachea, bronchi, bronchioles and alveoli. Inspiration- lungs inflate and elastic fibres are stretched. When the smooth muscle relaxes, the elastic fibres recoil to dilate the airway and help push air out.
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What is the function of smooth muscle?
Trachea, bronchi, bronchioles. When smooth muscle contracts, it constricts the airway, making the lumen narrow. When it relaxes, lumen becomes bigger, so there's less resistance to airflow.
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What do rings of cartilage do?
Trachea and bronchi. Provide support, stopping the trachea and bronchi collapsing during inspiration and the pressure decreases. Trachea has C- shaped cartilage allowing flexibility.
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Describe the process of inspiration
external intercostal muscles contract, lifting the ribcage upwards and outwards, causing the diaphragm to flatten, increasing the volume of the thorax and chest cavity. Pressure of air in lungs decreases, so air flows into lungs.
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Describe the process of expiration
The external intercostal muscles and diaphragm relax. The ribcage moves down and inwards and the diaphragm becomes curved. The thorax and chest cavity volume decreases, increasing the pressure above atmospheric pressure. Air is forced out of lungs.
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What is tidal volume?
the volume of air in each breath when at rest
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What is vital capacity?
the maximum volume of air that can be breathed in or out in one breath.
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What is residual volume?
The volume of air that always remains in the lungs
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What is dead space?
The air in the trachea, bronchi and bronchioles where there is no exchange.
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What is inspiratory reserve volume?
How much more air can be breathed in above the normal tidal volume.
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What is expiratory reserve volume?
How much more air can be breathed out above the normal tidal volume.
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Explain how a spirometer works
an oxygen filled chamber with a movable lid, floating on water. The person breathes through a tube connected to the oxygen chamber. As the person breathes in and out, the lid moves up and down. Movements are recorded with a pen and dataloger
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How is soda lime used?
CO2 exhaled is absorbed by soda lime so there's only O2 from the chamber the person inhales from. Some of the volume of air breathed out is absorbed and the overall volume decreases.Volume of CO2 breathed out (volume decrease)= O2 breathed in.
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Card 2

Front

Why do organisms need to exchange substances?

Back

To take in oxygen for aerobic respiration and nutrients. To remove waste products like carbon dioxide and urea.

Card 3

Front

Smaller animals have ? surface area: volume ratios

Back

Preview of the front of card 3

Card 4

Front

Why do multicellular organisms need exchange organs?

Back

Preview of the front of card 4

Card 5

Front

What is the structure of the lungs?

Back

Preview of the front of card 5
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