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AQA A level Biology- Gas exchange all Questions & answers solved accurately with Complete Solution Graded A+ latest version CA$19.27
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AQA A level Biology- Gas exchange all Questions & answers solved accurately with Complete Solution Graded A+ latest version
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AQA A level Biology- Gas exchange all Questions & answers solved accurately with Complete Solution Graded A+ latest version

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  • July 6, 2024
  • 5
  • 2023/2024
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AQA A level Biology- Gas exchange
What is ventilation?-✔✔ movement of air in and out of the lungs

What are gas exchange systems in humans?-✔✔ Mouth
Trachea
Bronchi
Bronchioles
Alveoli

How is the trachea supported?-✔✔ A series of cartilaginous rings, or
C-shaped rings are what support and prevents the airway from collapsing
during pressure changes

What happens during human inspiration?-✔✔ The diaphragm contracts
and becomes flat
The external Intercoastal muscle contracts and pulls the ribs up and out
The volume of the thorax and lungs increases and the elastic walled alveoli
stretches
The pressure in the alveoli decreases below atmospheric
air flows in down a pressure gradient

What happens during human expiration?-✔✔ The diaphragm relaxes and
becomes domed shaped
The internal Intercoastal muscle contracts and pulls the ribs down and in
The volume of the thorax and lungs decreases and the elastic walled
alveoli shrinks by elastic recoil
The pressure in the alveoli increases above atmospheric
air flows out down a pressure gradient

Why do the lungs require a thorax?-✔✔ They are not muscular and so
need another system to change their volume

How is carbon dioxide transported out of the body?-✔✔ Carbon dioxide
flows in blood and flows next to the alveoli.

, Carbon dioxide diffuses into the alveoli down a concentration gradient
This increases the carbon dioxide concentration in the alveoli
When exhaling carbon dioxide flows out
The carbon dioxide level is now decreases in the alveoli

How are alveoli adapted for gas exchange?-✔✔ • large surface area so
faster absorption of oxygen
Many small rounded alveoli
Many branching capillaries
• good blood supply
Ventilation and circulation of blood ensues a concentration gradient
• thin - short diffusion pathway
Single layer of flattened epithelial cells
• moist - dissolve gases
• small capillary diameter
Red blood cells have a large diameter and so must squeeze through the
capillaries and so this slows the flow of blood and increases the time of gas
exchange

How are gills adapted for gas exchange?-✔✔ Made up of thin plates
called gill filaments which maximise the surface area, these are covered in
lamellae which increase the surface area further and the lamellae have lots
of blood capillaries to speed up diffusion, they also have a thin layer of cells

How do fish breathe?-✔✔ The fish breathe in water through the mouth as
it flows over the gills
Deoxygenated blood flows across the lamellae through capillaries
Oxygen diffuses from water into blood at at the lamellae
Oxygenated blood flows along hill filaments to body cells
Carbon dioxide diffuses from blood to water

What is the counter current mechanism in fish?-✔✔ Blood and water flow
in opposite directions
Water always has a higher oxygen concentration than blood
Oxygen from water diffuses into blood down a concentration gradient

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