Exchange and Transport Flashcards
Why do large organisms need an exchange system?
It has a small surface-area-to-volume ratio and its has more cells so needs more substance. The outer surface is not large enough to take in all of the substances that the organism needs to keep all of the cells alive.
Why does a single cell organism not need a gas exchange system?
They have a large surface-area-to-volume ratio, which allows them to exchange substances across their outer substances.
What does a good exchange system need?
- A large surface area ratio (more space for molecules to pass through)
- Thin barrier (reduces the diffusion distance)
- Fresh supply of molecules on one side (conc. gradient kept high)
- Fast removal of molecules on other side (conc. gradient kept high)
Give some examples of exchange systems in living organisms.
Alveoli in lungs (O2 received, CO2 released)
Small intestine (nutrients are absorbed)
Liver (sugar levels are adjusted)
Root hairs in plants (water and minerals absorbed)
hyphae of fungi (nutrients are absorbed)
What is the trachea?
The windpipe, which branches into two bronchi.
What are the bronchi and the bronchioles?
The trachea branches into two bronchi, and these branch into smaller bronchioles.
What are alveoli?
They are tiny, air filled sacs. the walls of the alveoli is where gaseous exchange takes place.
what is the diaphragm?
A layer of muscle beneath the lungs, helps to create breathng movements and ventilation.
How are the lungs adapted to gaseous exchange?
- Large SA
- Plasma membrane allows O2 and CO2 to pass through readily
- Thin barrier ad short distance for diffusion
- conc. gradient is maintained
Explain how the lungs are adapted by having a thin barrier to reduce diffusion distance.
- Alveoli and capillary walls are 1 cell thick
- Both walls has squamous (squashed) cells
- capillary an alveoli are quite close together
- capillaries are narrow, squeezing blood cells against the wall, making them closer to the alveoli
- The barrier of diffusion is only 1 um thick
Explain how the diffusion gradient is maintain in the lungs.
good blood supply brings CO2 to the lungs readily so the conc. is high. it carries O2 away so that O2 conc. in capillaries is kept low. Breathing movements ventilate the lungs, replacing the air, keeping a high conc. of O2 and low conc. of CO2. all of this maintains a high conc. gradient.
What happens when we inhale?
During inspirations:
- the diaphragm contracts and becomes flatter
- external intercostal muscles contract and raise ribs
- volume of chest cavity increases
- pressure in chest less that atmospheric pressure
- air moves into lungs
What happens During Expiration
When we exhale:
- Diaphragm relaxes and pushed up by organ underneath
- External intercostal muscles relax and ribs fall
- Volume in chest cavity decreases
- Pressure in lungs drops below atmospheric pressure
- Air moves out of lungs
