Exchange surfaces Flashcards
What is the relationship between surface area and volume ratios in smaller organisms compared to larger animals?
Smaller organisms have a bigger surface area to volume ratio than larger animals
For example, a mouse compared to a hippo.
How is the surface area to volume ratio calculated?
Ratio = Surface area / Volume
Why is the rate of diffusion quicker in single-celled organisms?
Because of the short distance substances have to travel and their high surface area to volume ratio
What are three reasons diffusion across the cell surface membrane is more difficult in multicellular organisms?
- Some cells are deep within the body
- Larger animals have a low surface area to volume ratio
- Multicellular organisms have a higher metabolic rate
What is a characteristic of exchange surfaces that improves their efficiency?
•A large surface area
An example is root hair cells on plant roots increase plant root surface area
•They’re thin
An example is alveoli is made from a single layer of thin flat cells called alveolar epithelium. Because it is thin, It decreases the distance by which O2 diffuses out of alveolar space into the blood and CO2 diffuse into the alveolar space from the blood
• A good blood supply and or ventilation
An example
Alveoli is surrounded by a large capillary network giving good blood supply
Lungs are also ventilated (you breath in and out) so air in each alveolus is constantly replaced
Fill in the blank: A root hair cell has ______ that stick out into the soil.
long hairs
True or False: Single-celled organisms have a higher surface area to volume ratio than multicellular organisms.
True
How does altitude (less oxygen) affect gas exchange in the alveoli?
The concentration gradient for oxygen between the alveoli and the capillaries will be lower than normal, so rate of diffusion and therefore gas exchange, will be lower
One of the effects of severe obesity is that the sufferer cannot fully inhale. Suggest the effect this would have on rate of diffusion of oxygen.
Less air, and so less oxygen, will be inhaled in each breath. This means the concentration gradient of oxygen between the alveoli and the capillaries will be less steep, slowing the rate of diffusion
What is the main difference between the alveoli in a healthy lung tissue and diseased lung tissue in someone with emphysema?
Healthy lung tissue has intact alveoli, while diseased lung tissue shows enlarged and damaged alveoli
In emphysema, the walls between alveoli break down, leading to fewer but larger alveolar spaces.
Why do patients with emphysema damaged/ enlarged alveoli)have lower levels of oxygen in their blood?
Having enlarged alveoli means there’s a smaller surface area for gas exchange, slowing rate of diffusion of oxygen into the blood.
The SA:Vol of the alveoli will be smaller in a person with enlarged alveoli
Q1 a) Name two substances an animal needs to take in from the environment
Oxygen
Glucose
b) Name two substances an animal needs to release into its environment
Carbon dioxide and urea
Q2 Explain three reasons why diffusion is too slow in multicellular organisms for them to absorb and excrete substances in this way.
Some cells are deep within the body -
so the distance between them and the outside environment is too great for diffusion to take place quickly.
Larger animals have a low
area: volume ratio -
This means they don’t have a large enough area exposed to the environment to be able to exchange all the substances they need quickly enough using diffusion.
Multicellular organisms have a higher metabolic rate than single-celled organisms, so they use up oxygen and glucose faster than diffusion could provide them.
Q3 a) Describe an example where a large surface area increases the efficiency of an exchange system.
a) Plant roots are covered in root hair cells, which vastly increase the surface area of the root, so the rate of absorption of water and mineral ions from the soil is increased.
