Topic 3 - Gas Exchange Flashcards
How to single-celled organisms exchange substances?
Diffusion across the cell membrane directly into or out of the cell
Give two reasons why in multicellular organisms diffusion across out of membranes would be too slow
The diffusion distance is too large due to internal organs as well as a low surface area: volume ratio
What two things do you gas exchange surfaces have that increase the rate of diffusion?
Small diffusion distance and a large surface area
What is the priciple called that fish use for gas exchange?
Countercurrent principle
What is each gill made up of giving it a large surface area?
Gill filaments
What are gill filaments covered in increasing its surface area?
Lamellae
Explain the countercurrent system in fish
Water and blood flowing opposite directions this maintains a constant diffusion gradient due to water having a high oxygen concentration and blood having a low oxygen concentration
What is the pathway of exchange in fish?
Oxygenated water enters through the mouth, water passes over the gills then deoxygenated water leaves
What is the specialised gas exchange organ in a fish?
Gills
How is a concentration gradient maintained in the fish?
Thhe blood flows towards the front of the fish in the gill lamellae while the water flows towards the back. This means that there is always a higher concentration of O2 in the water than in the blood, so oxygen continues to diffuse into the blood along the whole length of the lamellae.
What four adaptations do fish have for efficient gas exchange?
1) Each gill hass four gill arches which have thousands of filament attached.
2) Filaments are covered in feathery lamallae each only a few cells thick.
3) Structure gives large SA and short diffusion distance.
4) Water flows over the filaments and lamellae and oxygen can diffuse down its concentration gradient in a countercurrent system.
What is the main gas exchange surface in plants?
Mesophyll
Where do gases move in and out in the leaf?
Through the stomata in the lower epidermis
What controls the opening and closing of stomata?
Guard cells
What are the 4 mechanisms for gas exchange in plants?
1) When the guard cells are turgid (full of water) the stoma remains open allowing air to enter the leaf.
2) The air spaces within the spongy mesophyll layer allows CO2 to rapidly diffuse into cells.
3) The CO2 is used up in photosynthesis by cells containing chloroplasts, maintaining the concentration gradient.
4) No active ventilation is required as the thinness of the plant tissues and the presence of stomata helps to create a short diffusion pathway.
Explain how plants control water loss
Water enters guard cells making them turgid which open the stomatal pore and if the plant loses water the guard cells lose water and the pores close
What are xerophytes?
Plants that live in extremely dry or windy environments where water loss is an issue
Give five examples of adaptations that xerophytes have to control water loss
Sunken stomata, wax layer, curled leaves and layers of hairs to trap water vapour
What are the microscopic air filled pipes in insects called?
Tracheae
What are the pores on the surface of an insect called?
Spiracles
What has a tendency to make an organism lose water?
Exchanging gases
What do insects do/have to control water loss?
Spiracles that close, waterproof wax cuticle, and tiny hairs
How is concentration gradient maintained in insects?
A concentration gradient is maintained as gases diffuse in and out of the trachea along their concentration gradient. Muscles can contract to squeeze the trachea when the insect moves. This can move air in and out.
What are 2 limitations of insect gas exchange?
1) System is effective but relies only on diffusion for gases to reach the tissues.
2) Requires short distance and limits the size of insects.
Why do insects have a waterproof exoskeleton?
For protection and to prevent the insect from drying out
What are tracheae and tracheoles held open by?
Rings of chitin
Why do insects need to respire quickly?
They are relatively small
Which three things work together to move air in and out of the lungs?
Diaphragm, intercostal muscles and rib cage
What do external intercostal and diaphragm do during inspiration?
Contract
What type of process is inspiration?
Active
What happens to the external intercostals and diaphragm during expiration?
Relax
What type of process is normal expiration?
Passive
What happens to the external and internal intercostals during forced expiration?
They contract
What are alveoli?
Small air sacs in the lungs where gas exchange takes place
What are the alveoli wall made from?
Alveolar epithelium
What are the walls of the capillary made from?
Capillary endothelium
What protein do the walls of the alveoli contain?
Elastin
What is the role of elastin in the walls of alveoli?
Helps alveoli return to normal shape after inhaling and exhaling air
What 3 features does alveoli have that increases the rate of diffusion?
Short diffusion distance, large surface area, steep concentration gradient.
What is the tidal volume?
The maximum amount of air inhaled in one breath.
How do you calculate stroke volume?
Tidal volume X HR
What is asthma?
A condition caused by inflammation of the bronchioles
What is COPD?
Chronic Obstructive Pulmonary Diseases
How are epithelial cells adapted for gas exchange?
Epithelial cells support a rich network of blood capillaries. As oxygenated blood flows away, it is replaced with deoxygenated blood which maintains a steep concentration gradient so that oxygen can continue to diffuse in.
How are alveoli adapted for gas exchange?
Alveolar walls are very thin and the cells of the wall are flattened, short diffusion pathway. Alveolar walls are permeable allowing oxygen to pass into cells and lets water out, so the gas exchange surface is always moist.
What happens when we breathe in (inspiration)?
1) External intercostal muscles contract, raising the ribcage and increasing the volume inside the thorax.
2) The diaphragm muscles contract, lowering the diaphragm.
3) Air flows into the lungs down a pressure gradient.
What happense when we breather out (expiration)?
1) External intercostal muscles relax, allowing the ribcage to move back to its original position, which decreases the volume inside the thorax.
2) The diaphragm muscles relax, allowing the diaphragm to move back to its original position and decreasing the volume of the thorax.
3) Air flows out of the lungs down a pressure gradient.
