Exchange- Gas Exchange Flashcards
Why do Fish have Specialised Gas Exchange Systems?
multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand
& body surface impermeable
therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas
exchange system called Gills
Structure of Gills in Fish?
many gill filaments and gill lamellae = large surface area
gill lamellae have a thin wall (short diffusion distance) and are permeable
ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated
blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent
flow), which maintains concentration gradient all the way along the gill lamellae
Why do Insects have Specialised Gas Exchange Systems?
multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand
& body surface made of exoskeleton (impermeable barrier to reduce water loss)
therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas
exchange system called Tracheal System
Structure of Tracheal System in Insects?
starts with openings on body surface called Spiracles
spiracles contain valves, open = gas exchange, closed = prevent water loss
spiracles connect to Trachea
trachea connect to Tracheoles
tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)
How does Gas Exchange occur in Tracheal System of Insects?
at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by
simple diffusion
when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
Function of Lungs?
site of gas exchange in mammals (oxygen
into blood – used in cells for respiration,
carbon dioxide out of the blood – toxic waste product of respiration)
What is Lungs made up of?
Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)
Function of trachea, bronchi, bronchioles?
transport of air and filter air, (bronchioles also
controls amount of air reaching alveoli)
Adaptation of alveoli?
millions of tiny alveoli that are folded (large surface area)
thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to
push the air out)
ventilation maintains concentration gradient (high oxygen, low carbon dioxide)
Adaptation of capillaries?
millions of tiny capillaries (large surface area)
thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
narrow lumen (increases diffusion time, decreases diffusion distance)
circulation maintains concentration gradient (low oxygen, high carbon dioxide)
How O2 moves from the alveoli to the capillaries?
by simple diffusion
How CO2 moves from capillaries to the alveoli?
by simple diffusion
Describe the process of Inhalation?
Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm
contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in
Describe the process of exhalation?
Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm
relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed
out (aided by elastic recoil in the alveoli)
Formula for Pulmonary Ventilation?
PV = tidal volume x ventilation rate
tidal volume = volume of air breathed in/out in one breath
ventilation rate = number of breaths per minute
Pulmonary Ventilation = volume of air breathed in/out per minute
Why do Humans/Mammals require a Specialised Transport System?
multicellular organisms therefore have large diffusion distances and high demand
need a transport system to deliver nutrients and remove waste from all cells
transport system in humans/mammals called Circulatory System
Circulatory System made of heart, blood vessels, blood
(heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)
Structure of Leaves?
upper layer called Upper Epidermis
waxy cuticle on upper epidermis (barrier to reduce water loss)
beneath the upper epidermis are Palisade Cells
palisade cells are were photosynthesis takes places
beneath palisade cells are Spongy Mesophyll Cells
are loosely packed leaving air spaces to allow ease of gas exchange
lower layer called Lower Epidermis
Adaptation of palisade cells for photosynthesis?
located near top of leaf, closer to light
large size, large surface area for light
thin cell wall, short diffusion distance for carbon dioxide
contains many chloroplasts, site of photosynthesis
large vacuole, pushes chloroplast to the edge of the cell closer to light
How does Exchange occur in Leaves?
lower epidermis of leaf contains pairs of cells called Guard Cells
when turgid, guard cells form an opening called Stomata
gas exchange occurs via the stomata
In Day, plant photosynthesises and respires, CO2 moves in for photosysnthesis and O2 moves out (some is used in respiration)
At Night, plant only respires, O2 moves in for respiration and CO2 moves out
What is Transpiration?
loss of water vapour from the leaf via the stomata
How does Transpiration occur?
moist lining of spongy mesophyll cells evaporate forming water vapour
water vapour builds up in air spaces
if water vapour concentration is high enough & stomata is open, water vapour diffuses out
Factors that increase rate of transpiration?
light = more light, more stomata open, increase surface area for transpiration
temperature = more temperature, more evaporation (increase water vapour concentration) &
more kinetic energy
wind = more wind, maintains concentration gradient
humidity = less humidity, less water vapour in the surrounding air, increase in water vapour concentration gradient
What is a Xerophyte?
a plant adapted to reduce water loss (reduce transpiration)
Adaptations of Xerophyte?
spiky, needle like leaves = reduced surface area
thick waxy cuticle = waterproof, impermeable barrier
densely packed spongy mesophyll = less air spaces, less water vapour build up
sunken stomata/hairy leaves/rolled up leaves = traps moist layer of air, reduces concentration gradient
Function of Phloem?
transport organic material (e.g. Sucrose) up and down a plant
Structure of phloem?
made of 2 parts (Sieve Tube with Companion Cells alongside)
How does phloem transport organic material like sucrose?
by principle of Mass Flow (mass flow of water carries the sucrose)
Sucrose loaded into Phloem at Source
Hydrogen Ions (H+) actively transported from companion cells into source
therefore, H+ diffuses back into companion cells from source
as they do, they pull in sucrose with them by co-transport
sucrose then diffuses into sieve tube
this lowers the water potential of sieve tube so water follows by osmosis
this water will carry the sucrose by hydrostatic pressure (mass flow)
Sucrose unloaded from Phloem at Sink
sucrose moves out of phloem/sieve tube into sink by diffusion
water follows by osmosis
