(3) exchanging substances Flashcards
what are examples of things that organisms need to exchange with the environment?
(what processes are required)
- respiratory gases (O2, CO2)
- nutrients (glucose, fatty acids, amino acids, vitamins, minerals)
- excretory products (urea, CO2)
- heat
except heat, these take place by active transport, diffusion or osmosis
as organisms become larger what happens to the diffusion rate?
their volume increases faster than their surface area therefore diffusion slows and becomes inefficient
what are the features of specialised exchange surfaces?
- large SA which increases the rate of exchange
- very thin membrane, diffusion distance is shorter and materials can cross the exchange surface rapidly
- selectively permeable to allow selected material to cross
- movement of exchange medium e.g blood to maintain a concentration gradient
what adaptations do insects have to prevent water loss in their bodies?
- small SA:V to minimise the area over which water is lost
- have a waterproof covering (rigid exoskeleton [made of chitin] with a cuticle to prevent water loss through evaporation)
- spiracles (small holes on sides of insect’s body) to allow efficient gas exchange
how does the spiracle mechanism work in insects?
the spiracles are opened and closed by a valve
when open, water vapour can evaporate from the insects so they are mainly closed to prevent water loss
periodically they open to allow gas exchange
how do respiratory gases move in and out of an insects tracheal system along a diffusion gradient?
when cells are respiring, oxygen is used up and so its concentration towards the ends of the tracheoles falls, creating a diffusion gradient
-> causes gaseous oxygen to diffuse from atmosphere along tracheae and tracheoles to cells
CO2 is produced by cells by respiration: creating a diffusion gradient is the opposite direction
-> causes gaseous CO2 to diffusion along tracheoles and tracheae from cells to atmosphere
how do respiratory gases move in and out of an insects tracheal system by mass transport?
the contraction of muscles can squeeze the trachea enabling mass movements of air in and out which further speeds up the exchange of respiratory gases
how do respiratory gases move in and out of an insects tracheal system because of the ends of the tracheoles are filled with water?
muscles cells around tracheoles respire and carry out anaerobic respiration, producing lactate (soluble and lowers ψ of the muscle cells)
-> water moves into the cells from the tracheoles by osmosis and the water in the ends of the tracheoles decrease in volume and also draws more air into them.
meaning the final diffusion in the pathway is a gas instead of a liquid so it is more rapid (but also increases water evaporation)
what is the structure of the gills in fish and where are they located?
what is the structure of the lamellae?
located behind the head of the fish and alos possess several gills between their mouth cavity and the operculum (chamber at sides of mouth)
ecah gill made of GILL FILAMENTS which are stacked in a pile
each filament is covered in lamellae (containing blood capillaries and have thin flattened cells to shorten the diffusion pathway between water and blood
how does a countercurrent flow system enable a fish to gain as much a oxygen as possible from water?
the blood and water flow over the gill lamellae in opposite directions which means
the oxygenated blood meets water w its maximum concentration of oxygen so diffusion
the deoxygenated blood meets water with very little O2 so diffusion of oxygen from water to blood takes place
SO THE DIFFUSION GRADIENT FOR OXYGEN UPTAKE IS MAINTAINED ACROSS THE ENTIRE WIDTH OF THE GILL LAMELLAE
what would happen is the water and blood flowed in the same direction across the gill lamellae?
diffusion gradient would only be maintained across part of the gill lamellae and less gas exchange would take place
it would reach equillibrium and diffusion would not take place
what is the function of the leaves?
- trap energy for photosynthesis
- exchange of gases required for photosynthesis and respiration
- producing glucose from photosynthesis
how does the volumes and types of gas being exchanged by a plant leaf change depending on the rates of photosynthesis and respiration?
- when photosynthesis takes place, most CO2 is obtained from external air (although some comes from the respiration of cells)
and in the same way some oxygen from photosynthesis is used in respiration but most diffuses out of the plant
-when photosynthesis is not occurring, oxygen diffuses into the leaf because it is being used by cells during respiration
in the same way CO2 produced during respiration diffuses out
how is gas exchange in plants similar to that of insects?
- no living cell is far from external air, therefore there is a source of O2 and CO2
- diffusion takes place in the gas phase which makes it more rapid than if it were in water
what are the adaptations of leaves that enable rapid diffusion?
- large surface area of mesophyll cells for rapid diffusion
- numerous interconnecting air spaces that occur throughout the mesophyll so gases can readily come into contact with mesophyll cells
- many small pores (stomata) and no cell is far from a stoma so the diffusion pathway is short
what are the adaptations of the leaves for photosynthesis?
wide: helps catch more light energy
thin: helps get CO2 from bottom to tip f leaf for photosynthesis
stomata:opened and closed by guard cells
when open, allows gas exchange (Co2 in O2 out) and transpiration (H2O out of leaf)
what are xerophytes?
plants that have adapted to living where there is a short water supply
how does having a thick cuticle help a xerophyte survive?
the waxy cuticle forms a waterproof barrier and the thicker the cuticle the less water can escape
how does the rolling up of leaves help a xerophyte survive?
it protects the lower epidermis and helps trap a region of still air within the rolled leave which becomes saturated with water vapour and has a high ψ
(no ψ gradient between the inside and outside of the leaf therefore no water loss)
how does having hairy leaves help a xerophyte survive?
a thick layer of hairs traps still moist air next to the leaf surface
the ψ gradient between the outside and inside of the leaves is reduced so less water is lost by evaporation
how does having stomata in pits or grooves help a xerophyte?
these trap still, moist next to the leaf and reduce the ψ gradient
why is the volume of O2 to be absorbed and CO2 removed is large in mammals?
- relatively large organisms with a large volume of living cells
- they maintain a high body temperature meaning they have high metabolic and respiratory rates
as a result mammals evolve specialised surfaces called lungs
why are the lungs located inside the body?
- air is not dense enough to support the delicate structures
- the body would lose a great deal of water and dry out
what are the main parts in the human gas exchange system?
lungs
trachea
bronchi
bronchioles
alveoli
what are the lungs?
pair of lobed structures made of bronchioles and end in alveoli
what is the trachea?
and what are its adaptations?
flexible airway that is supported by rings of cartilage (prevents trachea from collapsing as the air pressure falls when breathing in)
the tracheal walls are made up of muscle lined with ciliated epithelium and goblet cells (produces mucus + protects and lubricates the surface)
what are the bronchi and what are its adaptations?
two divisions of the trachea (each leading to one lung)
have goblet cells to produce mucus and cilia to move dirt-laden mucus towards the throat
larger bronchi supported by cartilage
what are the bronchioles and what are their adaptations?
series of branching subdivisions of the bronchi
walls made of muscle lined with epithelial cells
muscle allows them to constrict so they can control the flow of air in n out of alveoli
what are the alveoli and what are their adaptations?
epithelium lined minute air-sacs at the end of the bronchioles
collagen and elastic fibres between the alveoli
elastic fibres allow alveoli to stretch as they fill with air when breathing in
spring back during breathing out of expel the CO@ rich air
alveolar membrane = gas exchange surface
what is ventilation?
(breathing) when the air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium
what is inspiration?
(inhalation)
when the air pressure of the atmosphere is greater than air pressure in the lungs, air is forced into the lungs
what is expiration?
(exhalation)
when the air pressure of the lungs is greater than air pressure in the atmosphere, air is forced out of the lungs
what 3 muscles bring about the pressure changes within the lungs?
diaphragm (sheet of muscle that separates the thorax from the abdomen)
internal intercostal muscles (contraction leads to expiration)
external intercostal muscles (contraction leads to inspiration)
what happens during inspiration?
active process (uses energy)
- external intercostal muscles contract, while the internal IM relax
- ribs are pulled upwards and outwards, increasing the volume of the thorax
- diaphragm muscles contract, causing it to flatten (also increases volume of the thorax)
-increased volume of thorax results in reduction of pressure in the lungs
-atmospheric pressure is now greater than pulmonary pressure and air is forced into the lungs
what happens during expiration?
passive process (doesn’t require energy)
- internal intercostal muscles contact while external IM relax
- ribs move downwards and inwards, decreasing the volume of the thorax
- diaphragm muscles relax and is pushed up (volume of thorax is further decreased)
- decreased volume of thorax increases the pressure in the lungs
- pulmonary pressure is now greater than that of the atmosphere so air is forced out of the lungs
how does gas exchange take place in the alveoli?
Oxygen in the alveoli diffuses into the bloodstream and carbon dioxide in the bloodstream diffuses into the alveoli
what are the adaptations of the alveoli to ensure rapid diffusion?
- red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
- distance between the alveolar air and red blood cells is reduced (red blood cells are flattened against capillary walls)
- walls of alveoli n capillaries = v thing, short diffusion distance
- blood flow through pulmonary capillaries maintain a concentration gradient
- breathing movements ventilate lungs and heart circulates blood around alveoli maintains steep concentration gradient
what factors can affect the lungs having unobstructed airways, a large surface area and short diffusion pathways?
pathogens
smoking
pollution
asthma
how does tuberculosis affect breathing?
caused by mycobacterium tuberculoses bacteria, causing infection in the lungs
- bacteria damages epithelium (surface tissues) of alveoli
- lesion forms, reducing SA of alveoli
- scar tissue form, reducing flexibility of bronchioles and alveoli
- passed on though coughing, sneezing which sreads to blood and into lungs
how does smoking affect breathing?
cigarette contains dangerous chemicals:
- tar coats inside of alveoli n prevents efficient gas exchange
-> in response, the epithelial mucus-secreting cells proliferate and membrane thickens, lungs become filled w mucus preventing gas exchange
- cilia in trachea stops moving (lungs filled w mucus)
how does asthma affect breathing?
- airways narrow and swell and produce extra mucus which causes infection in lungs
- inflammation may further reduce the diameter of airways
- triggered by air-born pollutants or allergens
- smooth muscle cells in bronchi and bronchioles contract to reduce the cross-sectioned area of airways
what is tidal volume?
vol of air breathed in/out during quiet breathing at rest