gas exchange Flashcards
what is the relationship between size and surface area to volume ratio
as size increases ratio decreases
how does gas exchange occur in small organisms and why
simple diffusion due to a large surface area to volume ratio, short diffusion pathways and concentration gradient maintained by constant aerobic respiration
what are three features of gas exchange surfaces
thin/one cell thick - short diffusion pathway
large surface area to volume ratio
maintained high concentration gradients
how does the tracheal system in insects have a short diffusion pathway
air enters through spiracles
tracheoles in direct contact with cells
how does the tracheal system in insects have a large surface area to volume ratio
branched trachea branch into tracheoles
how does the tracheal system in insects maintain concentration gradient
constant respiration
abdominal pumping for ventilation in active insects
how do insects regulate water loss
closing spiracles
hairs around spiracles trap water vapour to decrease water potential gradient
waterproof waxy cuticle
describe the steps of a dissection practical
external examination -> observe external features
internal examination:
- use scalpel to make an incision
- identify key structures
observations noting structures and function
what are safety considerations of a dissection
handle scalpels with care to avoid injury
wear gloves and goggles to prevent contamination and protect eyes
dispose of biological waste properly
describe how the structure of the gills increases surface area for gas exchange
each gill is made up of several gill filaments and each filament is covered in many lamellae
what feature of the gas exchange system in fish means it has a short diffusion pathway
lamellae have thin walls and a network of capillaries
what is the counter current mechanism
blood and water flow in opposite directions so blood always meets water with a higher oxygen concentration
this maintains the concentration gradient across the entire lamellae
how do leaves have a large surface area
cells in the spongy mesophyll are loosely packed with lots of air spaces
how do plants have a short diffusion pathway
thin leaf tissue
lots of stomata
how is the concentration gradient maintained in plant cells
air spaces in the spongy mesophyll circulate air and photosynthesis occurs during the day
what do guard cells do
control the opening and closing of stomata via their turgidity
how do xerophytes regulate water loss
sunken stomata / hairs around stomata / curled leaves → trap water vapour to reduce water potential gradient
thick waxy cuticle → large diffusion pathway
describe the structure of the respiratory system in humans
trachea
bronchi
bronchioles
alveoli (site of gas exchange)
what gives the human gas exchange system a large surface area
millions of alveoli and network of capillaries
how does the human gas exchange system have a short diffusion pathway
alveolar and capillary walls are one cell thick
how is the concentration gradient maintained in human gas exchange
circulation of blood through capillaries and ventilation
describe the mechanism of inspiration (breathing in) (in chronological order)
- external intercostal muscles contract; ribcage move up and out
- diaphragm muscles contract; diaphragm flattens
- elastic tissue stretches
- volume of thorax increases; pressure decreases below that of atmospheric
- air rushes in down a pressure gradient
describe the mechanism of expiration (breathing out) (chronologically)
- external intercostal muscles relax; ribcage move down and in
- diaphragm muscles relax; diaphragm assumes dome shape
- elastic tissue recoils
- volume of thorax decreases; pressure increases above that of atmospheric
- air forced out down a pressure gradient
what is the formula for pulmonary ventilation rate and what do each of the component of the equation mean
pulmonary ventilation rate → tidal volume x breathing rate
pulmonary ventilation: volume of air breathed per minute
tidal volume: volume of air inhaled per breath
breathing rate: number of breaths per minute
