Gas Exchange Flashcards
(27 cards)
What does the exchange of many substances between environment and organism rely on?
Diffusion.
What ways can substances be exchanged?
- Simple diffusion.
- Facilitated diffusion.
- Osmosis.
- Active transport.
What substances do organisms exchange with their environments?
- CO2 and O2 = respiratory gases.
- Water. In sweat and urine.
- Urea = waste product in sweat and urine.
- Mineral ions - e.g. nitrogen into plaantss to produce chlorophyll.
- Nitrogen - provided by bacteria to plants for a symbiotic relationship.
- Nutrients - We eat and decompose.
What makes a good exchange surface?
- Selectively permeable.
- Thin ∴ short diffusion distance.
- Large surface areas in comparison to the organism’s volume/ large SA:Vol.
- Both mediums on either side of the surface need to have movement so the substances can move across the surface.
Which organisms have the most simple exchange methods and why?
Small organisms. The smaller the organism, the more simple the exchange method because they have a large surface are to volume ratio.
Most of the cells, if not all, are near the surface of the organism ∴ the diffusion of the substance will be fast enough to satisfy the demands of the cell as there is a short diffusion distance.
What issues does a large surface are to volume ratio arise?
- Large amount of heat lost relative to organisms mass.
- Large amount of water lost relative to organisms mass.
What issues does a small surface area to volume ratio arise?
- Overheating.
Why do large animals overheat?
They have a large volume of cells.
They all perform metabolic processes.
This releases alot of heat, mainly from cellular respiration.
How have large animals adapted to prevent overheating?
- Large, thin ears = increase in surface area for heat to be lost from.
- large feet = increase in surface area for heat to bee lost from.
What are some other ways organisms evolved to increase their surface area?
- Lots of small, spherical alveoli in the lungs.
- Many gill filaments and gill lamellae in the gills of a fish.
- Villi in the small intestine.
How have small organisms evolved to prevent heat loss?
They respire at a high rate to maintain a constant body temperature.
Respiration produces ATP which can be hydrolysed to produce energy.
What is metabolic rate?
The amount of energy expended by an organism in a given time period.
What is metabolic rate?
The amount of energy expended by an organism in a given time period.
What happens to the metabolic rate when the SA:Vol. decreases?
It USUALLY decreases.
What is the respiratory system in insects?
Tracheal system.
What is a one way system? Can you give an example?
When the gases in a respiratory system only move down it in one direction. Respiratory system of a fish, the gills.
Is the tracheal system a one way system?
No, it is a two way system.
What are the structural components of the tracheal system in insects?
Trachea, tracheoles, bands of cuticle, spiracle.
Can you describe oxygen’s pathway to the muscle cell?
Oxygen enters the trachea via a whole on the insects surface called the spiracle.
The oxygen moves through the trachea, tracheoles, and then diffuses into the muscle cells by diffusion down an O2 concentration gradient.
Can you describe carbon dioxide’s pathway from the muscle fibre to the outside of the insect?
The carbon dioxide diffuses from the muscle fibre into the tracheoles down a CO2 concentration gradient.
It moves through the tracheoles, trachea, and then leaves the insect from its surface through the spiracles.
Why are insects limited to a small size?
- The tracheal system of insects (their respiratory system) relies on diffusion to bring oxygen to respiring cells.
- If insects were large, it would take too long for oxygen to reach all the respiring cells rapidly enough to satisfy the oxygen requirements for aerobic respiration.
- This is because the diffusion distance is too long as a large animal has a smaller surface area to volume ratio so more of the cells are NOT close to the organisms surface.
- This would cause a low rate of respiration, resulting in the insect dying quickly.
How is gas diffusion enhanced in insects?
1- Muscle contractions.
2- Fluid in the tracheole ends.
In what state does diffusion happen fastest?
Gaseous state.
Can you describe gas exchange in insects?
1- Muscle contracts.
2- The muscle cells respire.
3- This produces lactate which is soluble in water.
4- The lactate dissolves in the muscle cell. This decreases the muscle cell’s water potential (ψ).
5- Water moves into the muscle cells from the fluid filled tracheole ends across a semipermeable membrane from a higher ψ to a lower ψ.
6- This decreases the water volume in the ends of the tracheoles.
7- This pulls air into them from the trachea.
8- This ensures the final diffusion pathway is a gas, not a liquid.
9- This is important as diffusion of gas is faster than the diffusion of liquid.
