OESWTE: Gas exchange Flashcards
What three features of the human lungs maximise the rate of diffusion:
- Short diffusion pathway
- Large surface area
- Steep concentration gradient of oxygen and carbon dioxide
Explain the factor of short diffusion pathway:
- The alveolar epithelium is one cell thick
- Gases have a short diffusion distance so gas exchange is quick and efficient.
Explain the factor of large surface area:
- The large number of alveoli increases the surface area available for oxygen and carbon dioxide to diffuse across.
Explain the factor of steep concentration gradient of oxygen and carbon dioxide:
- The constant ventilation and flow of blood
- Oxygenated blood is brought away from the alveoli and deoxygenated blood is brought to them.
- Maintains concentration gradient needed for gas exchange
Explain inhalation during exercise in the human lungs:
- Diaphragm contracts
- External intercostal muscles contract
- Thorax volume increases, pressure decreases
- Air is forced into the lungs
Explain exhalation during exercise in the human lungs:
- Diaphragm relaxes
- Internal intercostal muscles contract
- Thorax volume decreases, pressure increases
- Air is forced out of the lungs
What two ways are the gills in fish adapted for gas exchange?
- Steep concentration gradient of oxygen and carbon dioxide
- Large surface area
Explain the fish adaptation of steep concentration of oxygen and carbon dioxide:
- The countercurrent flow in the lamellae allows a steep concentration gradient to be maintained so oxygen moves into the the blood along the entire length of the gill
Explain the fish adaptation of large surface area:
- The gills have gill fillaments which have lamellae
Why is the countercurrent flow in fish an advantage?
- Means equilibrium is never reached
- Diffusion gradient will always be maintained along the entire length of the gill
- Constant flow of oxygen
Single celled organisms absorb and release gases by diffusion through their ___________.
Cell-surface membranes
Fish have a _________ system of blood flow.
Counter-current
What happens in the counter-current system in fish?
Blood flows through the lamellae in one direction
Water flows over the lamellae in the opposite direction.
What is the purpose of the counter-current system in fish?
Water with a high oxygen concentration always flows next to blood with a lower oxygen concentration - steep concentration gradient is maintained between water and blood.
What is the main gas exchange surface in plants?
Mesophyll cells
In plants what are the pores called which gases move in and out of?
Stomata
What cells control the opening and closing of the stomata?
Guard cells
Why do insects have an exoskeleton?
- Protection
- Prevent water loss (with lipid layer)
What do insects have instead of lungs?
Tracheal system
What are spiracles?
- Round, valve-like openings along the abdomen of an insect
What substances enter and leave via spiracles?
- Oxygen
- Carbon Dioxide
What is the trachea?
A network of internal tubes