Gas Exchange Flashcards
How does gas exchange take place in small organisms?
Oxygen diffuses directly into the cell from the environment due to small diffusion distances and having a large surface to area ratio
Metabolic demands are low
What factors affect the rate of diffusion?
Surface area
Concentration gradient
Diffusion distance
What are the features of an effective gas exchange system?
Large surface area
Thin layers to minimise diffusion distance
Rich blood supply to respiratory surfaces
Moist surfaces
Permeable
What is the epiglottis?
A flap of tissue that closes over the when food is swallowed to prevent it from going into the lungs
What is the trachea?
The major airway into the bronchi
Lined with mucas-secreting cells and cilia
Why are the incomplete rings of cartilage in the trachea and bronchi important?
They enable food to be swalloed but still prevent it from collapsing
What are bronchioles?
Small tubes that spread through the lungs and end with the alveoli, transporting air
What are the alvioli?
The main site of gas exchange in the lungs
How thick is the cell wall of the alveoli?
1 cell thick
How does has exchange occur at the alveoli?
Blood has a low oxygen concentration while the alveoli is high. Oxygen diffuses across the membrane and into the blood stream
As blood is constantly moving, the gradient is maintained
How does breathing take place?
The diaphram lowers which reduces the pressure in the chest cavity. As it’s lower than the atmosphere, air rushes into the lungs and they expand.
When we exhale, muscles surrounding the diaphram relax and the diaphram moves up which forces air out.
How are the lungs protected against infection?
The trachea and broncolies are lined with mucas-sectreting cells which catch pathogens and are moved up into the throat by cilia
What are the parts of gas exchange in insects?
Spiracles
Tracheae
Tracheoles
What are spiracles?
Found along the thorax and abdoman of most insects. Small holes where gases can enter and exit
Kept closed as much as possible to reduce water loss
What are tracheae?
Tubes from the spiracles to the tissues in insects that carry gas
They are supported by spirals of chitin for support and branch off to form tracheoles
How does gas exchange in insects work?
Air enters the system through spiracles and moves along the tracheae and tracheoles by diffusion into the tissues
How is the rate of gas exchange controlled in insects?
Opening and closing of the spiracles
What adaptations do very active insects have to meet their higher need for oxygen?
Air is actively pumped into the tracheae
Collapsable tracheae increase the volume of air moved through the system
How does gas exchange occur in fish?
Air travels through the mouth and over the gills and out through the operculum. The oxygen is absorbed by the gill filaments through diffusion and goes into the blood stream.
Blood and water flow in opposite directions to maximise gas exchange
Why can’t fish breathe out of water?
The gill filaments stick together and surface area is too small
What adaptations help fish to breathe?
Countercurrent exchange system to keep steep concentration gradient
Overlapping gill filaments to increase waer resistance and slow the flow enough for diffusion to take place
How does air enter the plant during gas exchange?
Air enters through the stomata
What is the purpose of gas exchange in plants?
Get carbon dioxide for photosynthesis and release the oxygen produced in respiration
How is the rate of gas exchange in plants controlled?
The stomata open and close
How do the stomata close?
Turgor in the gard cells decrease and the pores close as the cell wall becomes thicker
How do the stomata open?
Potassium ions are moved into the gard cells by active transport and turgor increases
