exchange Flashcards
how does the SA to volume ratio differ in different sized organisms?
larger organisms have a smaller SA to volume ratio
Why do multicellular organisms need exchange organs and mass transport systems?
small SA:V so specialised systems help overcome the large diffusion pathway
how are exchange surfaces adapted for efficient exchange?(4)
large SA
thin
selectively permeable
maintained concentration gradient
what system do insects have?
tracheal system
name 3 features of the tracheal system
spiracles
tracheae
tracheoles
what are spiracles?
small openings on the surface of the insects body. They open periodically for gas exchange as having them open also causes water loss
what is the tracheae (insects)?
internal network of tubes that are supported by strengthened rings
what are tracheoles?
smaller tubes coming off tracheae that extend into body tissue
explain how gas is exchanged in insects(3)
oxygen is used in respiration, creating concentration gradient that allows O2 to enter through spiracles
high conc of CO2 produced means it exits through spiracles
muscle contractions around tracheae help move gases
how is the tracheal system adapted for efficient gas exchange?(4)
tracheoles have thin walls-short diffusion pathway
Highly branched-large surface area
Tracheae provide tubes full of air-fast diffusion
Fluid in the end of the tracheoles that moves into tissues
during exercise- faster diffusion through the air to the gas
exchange surface
what are structures in fish gills?(2)
gill filaments
gill lamellae
how are fish gills adapted for efficient gas exchange?(2)
many gill lamellae increase surface area
surface is thin so short diffusion pathway
explain the counter current principle(3)
water and blood flow in opposite directions
this maintains a concentration gradient of oxygen as blood is always passing water with a higher conc
across the whole length of the gill filament
how is the counter current principle more efficient than the human gas exchange system?
there is a greater difference in concentration in gills so
the amount of oxygen removed from water is higher
name 9 structures of a leaf
waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
stomata
guard cells
phloem
xylem
where does gas exchange occur in a plant?
stomata
what causes CO2 to diffuse into the stomata
CO2 is being used by the cells creating a lower conc in the leaf, this means CO2 diffuses down the conc gradient
why are stomata more likely to stay closed at night?
no light for photosynthesis so no gas exchange needed
what are xerophytes?
plants that are adapted to living in areas of short water supply and/or there are high rates of water loss
what are 5 adaptations of xerophytes to limit water loss?
waxy cuticle
rolled leaves
hairy leaves
sunken stomata
needle-like leaves
how does having rolled leaves /hairy leaves /sunken stomata limit water loss?(2)
warm still air gets trapped
gets saturated with water vapour so water potential gradient is limited
how do needle-like leaves limit water loss?
limited surface area so less water lost through stomata
what are structures of the lungs?(4)
trachea
bronchi
bronchioles
alveoli
what are 2 adaptations of the trachea and bronchi?
rings of cartilage to support
contain ciliated epithelium lining with goblet cells to produce mucas and waft
what is the adaptation of bronchioles?
walls made of muscle which can contract or relax to alter diameter of airways
what are the 4 adaptations of alveoli?
one cell thick-provides short diffusion pathway
permeable walls- allows gases to diffuse
extensive blood supply and ventilation -maintains high con gradient
many alveoli-large surface area
describe the pathway of oxygen from the alveoli to the capillaries
diffuses across alveolar epithelium to endothelium of capillaries
describe inspiration(4)
external intercostal muscles contract, internal intercostal muscles relax, ribs are pushed up and out
diaphragm contracts, increases size of thorax
this increases volume inside lungs and decreases air pressure so that it is higher outside
causing air to flow in, down a pressure gradient
describe expiration(4)
external intercostal muscles relax, internal intercostal muscles contract, ribs are pushed in and down
diaphragm relaxes, decreasing size of thorax
this decreases volume and increases air pressure so that it is higher than outside
this causes air to be forced out, down the pressure gradient
what is pulmonary ventilation rate?
measure of how much air is taken in and out of the lungs in a given time.
dm3/min
what is tidal volume?
volume of air taken in at each breath when at rest
dm3
what is breathing rate?
the number of breaths taken in per min
describe the process of carbohydrate digestion(5)
- salivary amylase hydrolyses starch in food into maltose by breaking glycosidic bonds
- food enters stomach which has acidic conditions, denaturing the amylase
3.after some time, the food enters intestines where it is mixed with pancreatic amylase
4.this continues to hydrolyse remaining starch to maltose
5.maltase in cell membrane of ileum lining hydrolyses maltose into a-glucose
how is the pH maintained in the small intestine?
alkaline salts secreted by pancreas and intestinal wall maintain pH at neutral so enzyme can function
what types of enzymes hydrolyse lipids?
lipases
Describe the role of enzymes in the digestion of proteins(4)
peptidases hydrolyse the peptide bond between amino acids
Endopeptidases act in the middle of poly peptide
Exopeptidases hydrolyse bond on the terminal amino acids of polypeptides
Dipeptidases acts on dipeptides, these are membrane bound
how is the ileum adapted for efficient absorption?(4)
villi increase surface area for diffusion
epithelial cells have microvilli which further increase surface area
thin walls reduce diffusion pathway
sufficient blood supply to maintain high conc gradient for molecules
Describe the processes involved in the absorption and transport of
digested lipid molecules(6)
- monoglycerides and fatty acids are associated with bile salts, forming micelles
2.the micelles are brought to the epithelial cells lining the ileum and then broken down, releasing the monoglycerides and fatty acids
3.Fatty acids/monoglycerides absorbed by diffusion
4.these are then transported to the ER where they are reformed into triglycerides
- the triglycerides associate with cholesterol and lipoproteins, forming chylomicrons
- chylomicrons move out epithelial cells by exocytosis, entering lymphatic capillaries(lacteals)
