Gas Exchange Flashcards
(26 cards)
Why does the volume affect the rate of gas production or use?
Bigger volume means more/bigger cells and therefore increase use of oxygen and production of carbon dioxide in more respiration.
Explain why larger organisms such as fish and mammals need specialised gas exchange systems.
- Larger organisms have a small surface area to volume ratio, so not enough surface area to supply their needs by diffusion as it is too slow.
- Therefore, a larger surface area to volume ratio is provided by lungs and gills.
- Length of diffusion pathway is too long.
What is meant by metabolic rate?
Rate at which chemical reactions occur in the body.
What is Fick’s law?
Diffusion rate is directly proportional to surface area X difference in concentration divided by thickness of exchange surface.
What are the features of an exchange surface?
- Provide a large surface area.
- Maintain a high concentration gradient.
- Ensure that the exchange surface is as thin as possible (short diffusion pathway).
How are single-celled organisms adapted for gas exchange?
- Have a large surface area to volume ratio and a short diffusion pathway due to small size.
- Continuous aerobic respiration will maintain concentration gradients for oxygen and carbon dioxide.
How are fish adapted for gas exchange?
- A large surface area: each gill consists of many filaments each covered in many lamellae.
- A short diffusion pathway: many capillaries, with a single layer of thin endothelium, close to the thin-walled lamellae.
- A concentration gradient: continuous flow of blood through capillaries ensures that freshly oxygenated blood is quickly removed from the gills and replaced with deoxygenated blood.
- Counter current flow:
• Water flows over the gill plages in the opposite direction to the flow of blood in the capillaries.
• Blood always meets water with a higher concentration of oxygen.
• The concentration gradient is maintained so diffusion occurs across the entire surface of the gill/lamellae.
How are insects adapted for gas exchange?
- The tracheal system consists of many tracheae that open to the outside through small holes in the exoskeleton called spiracles.
- These finer tubs tracheoles are the sites of gas exchange.
- The large number of small, highly branched tracheoles give a large surface area for diffusion, while their thin walls, extensive branching snd close proximity to the cells provide a short diffusion pathway.
How are insects adapted to minimise water loss?
- Waterpoof waxy cuticle all over their body.
- Spiracles may be guarded by valves which can close spiracles.
- Spiracles surrounded by hairs which trap a layer of moist air around the spiracles to minimise water loss as it reduces the water potential gradient.
- All these prevent evaporation of water.
How does concentration gradient adaptation differ in small/inactive insects and active insects?
Inactive:
- Have a shorter diffusion pathway.
- So they can rely purely on diffusion down a concentration gradient that is maintained in the tracheal system due to cellular respiration.
Active:
- Flight requires more ATP for increased muscle contraction.
- Ventilation by contraction of the muscles of the abdomen can force air in and out of the spiracles and tracheae to maintain a greater air flow and maintain steeper concentration gradients for fast diffusion.
- The insects can also remove the fluid fromm the ends of their tracheoles to increase diffusion rates as gases diffuse quicker in air than in a liquid.
How are plants adapted for gas exchange?
- Cells of the spongy mesophyll layer are loosely packed, creating a large surface area for gas exchange.
- A short diffusion pathway: the spongy cells having thin cell walls and in direct contact with the air.
- Large concentration gradient - via photosynthesis during the day.
How does the leaf minimise water loss while still maintaining effective diffusion?
- Stomata mainly on underside only.
- Thicker waxy cuticle on upper epidermis.
- Action of guard cells can close stomata.
- All these refuse evaporation of water.
What is the role of cilia and mucus in the body?
Mucus - traps micro-organisms and debris, helping to keep airway clean.
Cilia - beat regularly to move microorganisms and dust particles along with the mucus.
What is the gross structure of the human gas exchange system.
- Trachea.
- Branches into bronchi, bronchioles and alveoli.
How are mammals adapted for gas exchange?
- A large surface area due to millions of alveoli. There is also a large surface area of blood capillaries.
- Short diffusion pathway as alveoli and capillary walls are each only one cell thick.
- Large concentration gradient via circulation and ventilation.
What is inspiration and expiration?
Inspiration - taking air into the thorax.
Expiration - moving air out of the thorax.
Why is air forces out of the lungs in terms of pressure?
- Pressure in the thorax is greater than pressure in the atmosphere.
- Air moves down a pressure gradient.
- Pressure is inversely proportional to volume.
What are antagonistic muscles?
A pair of muscles which, on contraction, produce opposite effects to each other.
What is the process of inspiration?
- External intercostal muscles contract and ribcage moves up and out.
- Diaphragm muscles contract and diaphragm flattens.
- Elastic tissue stretches.
- Volume increases in thorax.
- Pressure decreases below that of the atmosphere.
- Air enters down a pressure gradient.
What is the process of expiration at rest?
- External intercostal muscles relax and intercostal muscles relax.
- Ribcage moves down and in.
- Diaphragm muscles relax and diaphragm returns to dome shape.
- Elastic tissue recoils.
- Volume of thorax/lungs decreases.
- Pressure increases above atmospheric.
- Air is forced out down a pressure gradient.
What is different about forced expiration?
External intercostal muscles relax and the intercostal muscles contract, pulling the ribcage further down and in.
What is tidal volume?
The volume of air breathed in or out of the lungs in a normal resting breath.
What is ventilation rate?
The number of breaths in and out per minute.
