3.3 Organisms exchange substances with their environments Flashcards
what is mass transport used for
maintains final diffusion gradients that bring substances to + from cell membranes of individual cells
maintains relatively stable environment that is tissue fluid
small organism SA;V
higher SA;V
describe the relationship between SA;V and metabolic rate
- rate of heat loss per unit body mass increases as SA increases
- so higher metabolic rate/ faster respiration
- to generate enough heat to maintain constant body temp
why do larger organisms need a specialised surface for gaseous exchanged
- small SA;V ratio
- high demand for 02 + to remove co2
state the adaptations of a gas exchange surface
thin flat shape
-large sf area
-short diffusion pathway
for rapid diffusion
gas exchange in an insect
- air moves through spiracles on surface of insect
- air moves through tracheae
- gas exchange directly to/from cells via conc gradient
adaptations of an insect for gas exchange
lots of thin, branching tracheoles–>short diffusion pathway + SA–>rapid diffusion
rhythmic abdominal movements–>creates pressure gradient–>greater exchange of gases
gas exchange in fish
counter current flow
- blood flows through lamellae, water over lamellae in opp directions
- conc gradient of o2 between water + blood maintained along whole length of lamellae
- maximising diffusion of o2
adaptations of a fish for gas exchange
- each gill made of lots of gill filaments-covered in many lamellae-large sf area
- vast network of capillaries on lamellae-remove o2 to maintain conc gradient
- thin/flattened epithelium - shorter diffusion pathway between water + blood
gas exchange in plants
- co2/02 diffuse via stomata
- stomata opened by guard ells
- c02/02 diffuse into mesophyll layer into air spaces
- co2/o2 diffuse down conc gradient
adaptations of plants for gas exchange
lots of stomata close together -large sf area for exchange interconnecting air spaces -gases come into contact with mesophyll cells thin -short diffusion pathway
adaptatopns of xerophytic plants to reduce water loss
Thick cuticle/ wax layer = waterproof/impermeable to water
Sunken stomata = trap humidity to reduce diffusion gradient
Hairy = trap humidity to reduce diffusion gradient
Small leaves/reduced to spines,needles = reduce S.A. for water loss
Leaves roll up in dry weather= less S.A. for water loss/stomata covered/traps humidity
Reduced no. of stomata = reduced S.A. for water loss
gross structure of human gas exchange system
trachea
splits into two bronchi
into bronchioles
end in air sacs-> alveoli
gas exhange in alveoli
- o2 diffuses from alveoli
- down conc gradient
- across alveolar epithelium
- across capillary endothelium
- into blood
why is ventilation needed
maintains a conc gradient
- brings in air with higher o2 conc
- removes air with lower o2 conc
adaptations of alveoli for gas exchange
epithelium one cell thick
-short diffusion distance -> faster diffusion
large SA;V
-fast diffusion
permeable
good blood supply from network of capillaries
-maintains conc gradient
elastic tissues allows to recoil after expansion
surfactant
adaptations of the lung for efficient/rapid gas exchange
many alveoli/capillaries -large SA->fast diffusion thin walls -short diffusion distance ventilation/circulation -maintains conc gradient
describe inspiration
- external intercoastal muscles contract, internal relax
- ribcage moves up + outwards
- diaphragm contracts
- increase volume in thoracic cavity
- decreases pressure in thoracic cavity
- atmospheric pressure greater than in cavity
- air moves down pressure gradient into lungs
describe expiration
- external intercoastal muscles relax, internalcontract
- ribcage moved down + inwards
- diaphragm relaxes
- decreases vol in thoracic cavity
- increases pressure
- pressure in cavity greater than in atmosphere
- air moves down pressure gradient out of lungs
describe fibrosis
formation of scar tissue in lungs increases diffusion distance ->decreases rate of diffusion faster ventilation rate lungs expand + recoil less reduced tidal volume reduced forced vital capacity
describe asthma
inflamed bronchi
smooth muscle lining bronchi contracts
constriction of airway->reduced airflow->reduced FEV->less o2 enters blood -> reduced rate of respiration->less energy released->fatigue weakeness
how to improve reliabilty
- large sample
- randomly chosen
- healthy
- equal no. of test subjects
- repeat
what happens during digestion
large biological molecules are hydrolysed
to smaller molecules
that can be absorbed across cell membranes
how is starch digested
by amylase starch-->maltose membrane bound maltase maltose-->glucose hydrolysis of glycosidic bond
