Gas exchange Flashcards
Surface area to volume ratio
surface area divided by volume
larger the organism the smaller the ratio
factors affecting gas exchange
diffusion distance
surface area
concentration gradient
temperature
ventilation
inhaling and exhaling in humans
controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
inspiration
external intercostal muscles contract and internal relax
pushing ribs up and out
diaphragm contracts and flattens
air pressure in lungs drops below atmospheric pressure as lung volume increases
air moves in down pressure gradient
passage of gas exchange
mouth/nose > trachea > bronchi > bronchioles > alveoli
crosses alveolar epithelium into capillary endothelium
expiration
external intercostal muscles relax and internal contract
pulling ribs down and in
diaphragm relaxes and domes
air pressure increases above atmospheric pressure as long volume decreases
air forced out down pressure gradient
alveoli structure
tiny air sacs
highly abundant in each lung
surrounded by the capillary network
epithelium 1 cell thick
why do large organisms need specialised exchange surface
they have a small surface area to volume ratio
higher metabolic rate - demands efficient gas exchange
specialised organs
fish gill anatomy
fish gills are stacks of gill filaments
each filament is covered with gill lamellae at right angles
how fish gas exchange surface provides large surface area
many gill filaments covered in many gill lamellae are positioned at right angles
creates a large surface area for efficient diffusion
countercurrent flow
when water flows over gills in opposite direction to flow of blood in capillaries
equilibrium not reached
diffusion gradient maintained across entire length of gill lamellae
name 3 structures in tracheal system
involves trachea, tracheoles, spiracles
how tracheal system provides large surface area
highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles moves into tissues during exercise
Fluid-filled tracheole ends
adaptation to increase movement of gases
when insect flies and muscles respire anaerobically - lactate produced
water potential of cells lowered, so water moves from tracholes to cells by osmosis
gases diffuse faster in air
how do insects limit water loss
small surface area to volume ratio
waterproof exoskeleton
spiracles can open and close to reduce water loss
thick waxy cuticle increases diffusion distance so less evaporation
gas exchange in plants
palisade mesophyll is site of photosynthesis
oxygen produced and CO2 used created a conc gradient
oxygen diffuses through air spaces in spongy mesophyll and diffuses out stomata
role of guard cells
swell - open stomata
shrink - close stomata
at night they shrink, reducing water loss by evaporation
xerophytic plants
plants adapted to survive in dry environments with limited water
structural features for efficient gas exchange but limiting water loss
adaptations of xerophyte
adaptations to trap moisture to increase humidity - lowers water potential inside plant so less water lost via osmosis
sunken stomata
curled leaves
hair
thick cuticles reduce water loss by evaporation
longer root network
digestion
process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
so they can be absorbed across cell membranes
locations of carbohydrate digestion
mouth
duodenum
ileum
location of protein digestion
stomach
duodenum
ileum
endopeptidases
break peptide bonds between amino acids in the middle of the chain
creates more ends for exopeptidases for efficient hydrolysis
exopeptidases
break peptide bonds between amino acids at the ends of polymer chain
membrane-bound dipeptidases
break peptide bond between 2 amino acids
digestion of lipids
digestion by lipase
emulsified by bile salts
lipases produced in liver and stored in the gall bladder
lipase
produced in pancreas
breaks ester bonds in triglycerides to form
monoglycerides
glycerol
fatty acids
role of bile salts
emulsify lipids to form tiny droplets and micelles
increases surface area for lipase action - faster hydrolysis
micelles
water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts
lipid absorption
micelles deliver fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
cross via simple diffusion as lipid-soluble and non-polar
lipid modification
Smooth ER reforms monoglycerides/fatty acids into triglycerides
golgi apparatus combines triglycerides with proteins to form vesicles called chylomicrons
how do lipids enter blood after modification
chylomicrons move out of cell via exocytosis and enter lacteal
lymphatic vessels carry chylomicrons and deposit them in bloodstream
how are glucose and amino acids absorbed
via co-transport in the ileum
