Gas Exhange Flashcards
Why does single-celled organisms such as amoeba not need a specialised gas exchange system but a mammal/fish/insect do?
- Smaller organisms have a large SA: volume. This makes exchange across their surface by diffusion faster - smaller diffusion distance.
- Larger organisms have a small SA: volume ratio, this makes exchange across their surface by diffusion relatively slow - larger diffusion distance. They also have more cells that require O2.
- Single-celled organism have a much lower metabolic rate, are less active. They have a lower demands for 02 and produce less CO2 to get rid of.
In multicellular organisms, diffusion across the outer membrane is too slow, why?
- Some cells are deep within the body - there’s a big between them and the outside environment.
- Large animals have a small surface area:volume ratio - it’s difficult to exchange enough substances to supply a large volume of animal through a small outer surface. short diffusion distance.
- Multicellular organisms have a higher metabolic rate than single-celled organism, so they use up oxygen and glucose faster.
What is the formula for surface area and volume of sphere?
- Surface area - 4 pi R^2
- Volume - 4/3 pi r^3
What are the 4 factors that create an effective exchange surface?
- Big surface area
- Thin
- Big concentration gradient
- Permeable to gases.
explain how a large surface area increases effectiveness of exchange surfaces
large SA:vol = short diffusion distance of gases
How does a mammal provide a large surface area?
- lots of alveoli collectively give a big SA.
- intestine cells have microvilli for absorption of digested food.
- in plants, root hair cells increase SA to absorb water/ mineral ions.
What would create a short diffusion distance in the alveoli?
alveoli has very thin walls - due to squamous epithelium, it is one cell- thick
In mammals how is a big concentration gradient achieved?
- Achieved by the exchange surface having a good blood supply. This ensures that O2 is constantly moved away from the alveoli to the cells and CO2 is returned to the alveoli to maintain the diffusion gradient.
- It is also achieved by ventilation. Breathing air in/ out delivers oxygen and removes CO2 to/from alveoli in mammals.
Why is it necessary for the exchange surface to be permeable to gases?
necessary if oxygen and CO2 has to move in/out
Mammals are relatively large organisms, so generally have a small SA/volume ratio. They also have a metabolic rate. What does this mean?
High cell respiration rate, to produce ATP fast enough to supply the cells with enough energy to carry out active process.
What are the important features of the nasal cavity?
- A large surface area with a good blood supply, which warms the air to body temperature.
- A hairy lining, which secrets mucus to trap dust and bacteria, protesting delicate lung tissue from irritation and infection.
- Moist surfaces, which increase the humidity of the incoming air, reducing evaporation from the exchange surfaces.
What are goblet cells?
Secretes mucus. The mucus traps microorganisms and dust particles, stopping them from reaching the alveoli.
What is cilia?
- Cilia are hair-like structures on the surface of epithelial cells lining the airways.
- They beat the mucus secreted by the goblet cells - this moves the mucus upwards from the alveoli towards the throat, where it’s swallowed. This helps prevent lung infections.
What does smooth muscle do?
During exercise the smooth muscle relaxes, making the tubes wider. This means there’s less resistance to airflow and air can move in and out of the lungs more easily.
Where is cartilage found and what does it do?
- 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.
