gas exchange and surface area Flashcards
what is the relationship between the size and structure of an organism and its surface area to volume ratio?
as size increases, the SA to VR decreases - the more thin/flat structures increase in SA to VR.
what is an advantage of calculating surface area to mass instead of to volume for for organisms?
its easier and more accurate as organisms are irregular shapes.
what is metabolic rate and how can it be measured?
the amount of energy used up by an organism in a given period of time - often measured by oxygen uptake as its used in aerobic respiration to make ATP for energy release.
explain the relationship between SA to VR and metabolic rate.
as SA to VR increases metabolic rate increases because:
- rate of heat loss per unit body mass increases
- so organisms need a higher rate of respiration to release enough heat to maintain a constant body temp i.e replace lost heat.
explain the adaptations that facilitate exchange as SA to VR reduces in larger organisms.
changes to body shape - increases SA to VR so theres a shorter diffusion pathway.
transport system e.g lungs - increases SA to VR which maintains concentration gradient for diffusion e.g by ventilation.
explain how the body surface of a single-celled organism is adapted for gas exchange.
its thin and flat with a large surface area to volume ratio which means it has a short diffusion distance for rapid diffusion.
describe the tracheal system of an insect.
spiracles - pores on the surface that can open and close to allow diffusion.
tracheae - large tubes full of air that allow diffusion.
tracheoles - smaller branches from tracheae, and are permeable to allow gas exchange with cells.
what are the adaptations of the alveoli?
large surface area
thin walls - for short diffusion distance.
moist walls - gases dissolve in the moisture, helping them to pass across the gas exchange surface.
permeable walls - allow gases to pass through.
extensive blood supply - ensuring oxygen rich blood is taken away from lungs and CO2 rich blood is taken to lungs.
large diffusion gradient - ensures O2 conc in alveoli is higher in capillaries so O2 moves from alveoli to blood.
explain how an insects tracheal system is adapted for gas exchange.
tracheoles have thin walls - so short diffusion distance to cells.
tracheae provides tubes full of air - so fast diffusion.
contraction of abdominal muscles changes pressure, causes air to move in and out - so maintains concentration gradient for diffusion.
lots of highly branched tracheoles - so short diffusion distance and larger surface area.
explain structural and functional features in insects that allow efficient gas exchange while limiting water loss.
thick waxy cuticle - increases diffusion distance so less water loss.
spiracles - can open to allow gas exchange and close to reduce water loss.
hairs around spiracles - trap moist air, reducing water potential gradient so less water loss.
explain how gills of fish are adapted for gas exchange.
gils are made of many filaments covered in lamellae - increases surface area for diffusion.
thin lamellae wall - so short diffusion distance between water and blood.
lamellae have many capillaries - so maintains concentration gradient.
explain how the leaves of dicotyledonous plants are adapted for gas exchange.
have many stomata - so large surface area for gas exchange (when open)
spongy mesophyll - contains air spaces so large surface area for gasses to diffuse through.
thin - short diffusion distance.
describe the structure of the human gas exchange system.
trachea
bronchi
bronchioles
capillary network surrounding alveoli
alveoli
describe the features of alveolar epithelium that make it adapted for gas exchange.
one cell thick - short diffusion distance.
folded - large surface area.
permeable - allows diffusion of gases.
moist - gases can dissolve for diffusion.
good blood supply from large network of capillaries - maintains concentration gradient.
describe how gas exchange occurs in lungs.
oxygen diffuses from alveolar air space into blood down concentration gradient - across alveolar epithelium and capillary endothelium.
explain the importance of ventilation?
brings in air containing higher conc. of oxygen and removes air containing lower conc. of oxygen - maintaining concentration gradients.
explain features in xerophytic plants that allow efficient gas exchange while limiting water loss.
thicker waxy cuticle - increases diffusion distance so less evaporation.
sunken stomata in rolled leaves - protect stomata from wind so reduced water potential gradient between leaf so less evaporation.
needles - reduces SA to VR.
explain how humans breathe in and out.
inspiration (breathing in)
- active process (uses energy)
- external intercostal muscles contract and internal intercostal muscles relax (antagonistic) - ribs pulls upwards and outwards.
- diaphragm muscle contracts, volume increases and pressure decreases and air is forced into lungs.
expiration (breathing out) is the opposite of the above.
ventilation equation.
pulmonary ventilation (dm3 min-1)
= tidal volume (dm3) x ventilation rate (min-1)
why is expiration normally passive at rest?
internal intercostal muscles do not need to contract.
suggest how different lung diseases reduce the rate of gas exchange.
thickened alveolar tissue - increases diffusion distance.
alveolar wall could break down - reduces surface area.
reduces lung elasticity - lungs expand which reduces concentration gradient.
suggest how different lung diseases affect ventilation.
narrow airways reduce airflow in and out of lungs - reduces maximum volume of air breathed out.
suggest why people with lung disease experience fatigue.
cells receive less oxygen so the rate of aerobic respiration is reduced and less ATP is made.
whats a xerophyte?
a plant adapted to live in very dry conditions.
