Module 3- exchange surfaces Flashcards
Definition of surface area
total surface over which substances and heat can be exchanged
What does volume determine?
the number of substances that need to be taken in and transported out. As the volume increases, more materials are needed more materials are needed for the metabolism because there are more cells
How does SA:V ratio change for organism size?
-decreases with increasing organism size because the increase in the number of cells means there is less SA for the exchange of materials because many of the cells are in contact with one another
Describe prokaryotic organisms SA:V ratio
-they have a large ratio allowing them to meet the cells energy requirements through diffusion occurring across the plasma membrane only
Describe eukaryotic organisms SA:V ratio
smaller ratio so they need mitochondria which have an increased membrane SA in which enough proteins can be embedded for respiration to meet the larger cells needs
How do transport systems increase the rate of transport?
-allow for a steeper concentration gradient to be maintained
-allows substances to move closer to the cells
Describe single celled organisms exchange of substances?
-exchange directly with their external environment e.g oxygen for respiration and CO2 removal to avoid harming the cell
-can be adapted to increased SA:V ratio e.g making themselves wide, flat or folded
-diffusion rate is fast as they only have to move across one cell surface membrane
Describe an insects exchange system
-use a gas exchange system called tracheal system which consists of a network of small tubes called tracheoles that carry oxygen around the body
-tracheoles branch into cells and contain tracheal fluid which gases can dissolve into
-when the insect is more active, the tracheal fluid moves further into the tissue meaning gas exchange happens closer to respiring cells
-diffusion alone does not supply oxygen to the cells quickly enough so thoracic and abdominal movements can move gases
-insects bodies have openings along the thorax and abdomen called spiracles
-gases such as oxygen and carbon dioxide diffuse through the spiracles and into the tracheoles
What gas exchange system is the most efficient in active animals?
tracheal system
Describe the structure of a fishes exchange system
-use an exchange surface that is specialised for obtaining oxygen from the water
-gills are filaments of thin tissue that are highly branched and folded creating a large SA for gas exchange
-folded structures are called lamellae
-gills in bony fish are covered by an operculum (gill cover)
Describe the diffusion of oxygen in a fishes gas exchange system
-When the mouth opens water enters the buccal cavity because of its increased volume. The opercula remains closed
-when mouth closes the internal volume decreases and the operculum opens, forcing water across the gills
-when water flows through the gills, oxygen in water diffuses quickly into the bloodstream due to the counter current system
-in the counter current system blood flows through the lamellae in the opposite direction of the flow of water through the gills
-the counter current system ensures there is always a steep concentration gradient between the water and blood
Describe mammalian gas exchange
-takes place in the lungs which are specialised for the quick exchange of O2 and CO2 in the blood stream
–when breathe in air flows through the trachea
-ridges of cartilage surround the front of the trachea to provide protection and structure (there is none at the back so the oesophagus isn’t restricted)
-air flows along a bronchus to a lung
-the bronchioles branch throughout the lungs into small air sacs called alveoli
-alveoli fill with air when you breathe in, O2 diffuses into the bloodstream and CO2 diffuses into the alveoli
What is ventilation controlled by
ribcage, intercostal muscles and diaphragm
Describe the structure of the alveoli
-each alveolus is surrounded by a network of capillaries which provide a large SA for gas exchange between the alveoli and the bloodstream
-epithelium is made up of a single layer of epithelial cells that line the walls of the capillaries which maximises the rate of gas exchange
What happens during inspiration in mammals? (muscles)
-the external intercostal muscles contract and move the ribcage up and out
-diaphragm contracts and moves downwards
-energy is required to power the muscle contraction
-the volume of thoracic cavity increases causing pressure in lungs to decrease
-air flows inside the lungs, down the pressure gradient, down trachea, inside alveoli
