Gas exchange Flashcards
Adaptions for gas exchange surfaces?
-Large surface area to volume ratio
-(one layer of epithelial cells)- provides a short diffusion pathway across the gas exchange surfaces
-Maintained a concentration gradient
How do single celled organisms exchange gases?
-Absorb and release gases by diffusion through their outer surface
-Have a large surface area, thin surface and a short diffusion pathway so theres no need fore a gas exchange system
Describe the fish gas exchange system
1)Water, containing O2, enters the fish through its mouth and passes out through the gills
2)Gills are made up of lots of thin plates called gill filaments, give a big surface area for exchange gases
3)Gill filaments are covered in lamellae, increases the surface area more
4)Lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion.
5)Blood flows through the lamellae in one direction and water flows over in the opposite direction- called counter current system, maintains a large conc gradient between the water and the blood, conc of oxygen is higher in water than in the blood, so oxygen diffuses from the water into the blood.-Ensures the equilibrium is not reached
What do fish use for gas exchange
Counter-current system
What do insects use to exchange gases
Tracheae
How do gas exchange work in insects?
1)Air moves into the tracheae through pores on the surface called spiracles
2)Oxygen travels down the conc gradient towards the cells
3)Tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells- oxygen diffuses directly into the respiring cells
4)Carbon monoxide from the cells moves down its own conc gradient towards the spiracles to be released into atmosphere.
5)Use rhythmic abdominal movements to move air in and out of the spiracles.
Insect adaptations to prevent water loss
-Small surface area to volume ratio
-Waterproof exoskeleton
-Spiracles ,where gases enter and water can evaporate from, can open or close to prevent the water loss
Where do gas exchange occurs in dicotyledonous plants
-at the surface of the mesophyll cells
Describe the gas exchange of dicotyledonous plants
-plants need CO2 for photosynthesis which produces O2 as a waste gas. They need O2 for respiration, which produces CO2 gas
-Main gas exchange surface is the surface of the mesophyll cells in the leaf- have a large surface area
-Gases move in and out through special pores in the epidermis called stomata
-Stomata can open to allow gas exchange and close if the plant is losing too much water
-Guard cells control the opening and closing of stomata
How do plants prevent water loss
-Stomata usually kept open during the day to allow gaseous exchange, water enters the guards cells making them turgid which opens the stomatal pore. If the plant starts to get dehydrated, guard cells lose water and become flaccid which closes the pore.
What are the xerophytic adaptations
-Stomata sunk in pits that trap moist air, reducing the conc gradient of water between the leaf and the air. Reduces the amount of water diffusing out of the leaf and evaporating away
-A layer of hairs on the epidermis to trap the moist air around the stomata
-Reduced number of stomata so there are fewer places for water to escape
-Waxy, waterproof cuticles on leaves and stems to reduce evaporation
-Curled leaves with stomata inside, protecting them from wind
Gas exchange system in humans
-air enters the trachea
-Trachea splits into two bronchi- one bronchus leading to each lung
-Each bronchus then branches off into smaller tubes called bronchioles
-Bronchioles end in small air sacs called alveoli
-Ribcage, diaphragm and intercostal muscles work together to move in air and out
Describe inspiration- (beathing in)
-External intercostal and diaphragm muscles contract
-causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity
-As the volume of thoracic cavity increases, lung pressure decreases
-Air flow from an area of high pressure to an area of low pressure so air flows down the trachea and into the lungs
-active process requires energy
Describe expiration
-External intercostal and diaphragm relax
-Ribcage moves downwards and inwards and diaphragm becomes curved again
-Volume of the thoracic cavity decreases causing the air pressure to increase
-Air is forced down the pressure gradient and out of the lungs
-Normal expiration is a passive process-doesnt require energy
How the gas exchange happens in the alveoli?
-Alveoli made from a single layer of thin, flat cells called alveolar epithelium
-1)Huge number of alveoli in the lungs, means there is a large surface area for exchanging oxygen and carbon dioxide
2)Alveoli are surrounded by a network of capillaries
3)O2 diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium (type of epithelium that forms the capillary walls) and into haemoglobin in the blood happens down a diffusion gradient.
4)CO2 diffuses into the alveoli from the blood and is breathed out
-Steep conc gradient of O2 and CO2 between the alveoli and the capillaries which increases the rate of diffusion- maintained by the flow of blood and ventilation
