Exchange Flashcards
Elephant surface area to volume ratio
small
mouse SA:V ratio
large
Fick’s law equation
rate of diffusion = (SA x difference in concentration)/length of diffusion path
how do single celled organisms exchange gases
across their body surface as they have a large SA:V ratio
Describe the tracheal system of insects
Trachea + tracheoles
spiracles
How does gas exchange occur in insects
- Gases enter and exit through spiracles
- gas exchange through diffusion as CO2 and O2 move down the concentration gradient
- Mass transport, contraction of abdominal muscles to move gases along
- when aerobic respiration occurs to produce lactate, lactate will lower cells water potential of cells so water moves from tracheoles to cells, so more air is drawn in due to decreases volume in tracheoles
How does gas exchange occur in fish
Structure of gills in fish
Gill filaments at right angles to increase surface area
lamellae in gill filaments, deep folds in gills which lead to an increased surface area
Gill bar in the middle of gill filaments
Adaptations of gills in fish
lamellae are folded so have a large surface area
lamellae and filaments are thin so diffusion rate increases
counter current exchange to ensure a high amount of oxygen diffuses into blood
what is counter current exange
water and blood flow in opposite directions
this ensures a favourable concentration gradient of oxygen is maintained across the whole length of the lamellae between the water and bloodstream
Adaptations of plants for gas exchange and how it happens
Gas enters and exits through stomata
guard cells control opening and closing of stomata which prevents water loss by evaporation
Small SA : V which prevents evaporation
thick waxy cuticle preventing water loss by evaporation
Hairy leaves trap water vapour, reducing water potential gradient, reducing water lost by evaporation
rolled leaves can reduce water potential gradient
Structures of the lungs
Trachea
bronchi
bronchioles
alveoli
diaphragm
How does inspiration work
External intercostal muscle contract and internal relaxes
ribs are pulled upwards and outwards
diaphragm contracts and flattens
this increases thoracic volume, so air pressure decreases, forcing air to move down the pressure gradient into the lungs
How does expiration work
Internal intercostal muscles contract and external relax
ribs are pulled downwards and inward
diaphragm relaxes and pushes back into a dome shape
this decreases thoracic volume, increases air pressure, so air is forced out of the lungs
adaptation of alveoli
very large surface area, so a higher rate of diffusion
surrounded by lots of capillaries, diffusion distance is thin
alveolar epithelium is thin
Where is amylase produced and where is it secreted
salivary glands
the pancreas secretes into small intestine
What does amylase do
hydrolyses starch into maltose
what are membrane bound disaccharidases
enzymes present in membrane of small intestine
hydrolyse disaccharides to monosaccharides
What does lipase do
hydrolyse lipids to monoglycerides and fatty acids
What do proteases do and what are the 3 types
hydrolyse proteins ( polypeptides ) into amino acids
endopeptidases
exopeptidases
membrane bound dipeptidases
What is the role of endopeptidases
hydrolyse peptide bonds in the middle region of the polypeptide chain
what is the role of exopeptidases
to hydrolyse bonds on the terminal amino acids
What is the role of membrane bound dipeptidases
Hydrolyse dipeptides into 2 amino acids
how are lipids digested into the epithelium
bile salts from the liver emulsify lipids so they have a large SA so are more easily hydrolysed by lipases
products from lipid hydrolysis can form micelles with bile salts
these can travel to the ileum and are broken down in contact with epithelium, these products can diffuse straight into epithelium
How are amino acids and monosaccharides absorbed into bloodstream
co-transport
Na+ ions move with the molecule into the epithelium by co transport from the lumen to the epithelium
Na+ ions in epithelium are actively transported into the blood via a Na-K pump to ensure a favourable concentration gradient of sodium between lumen and epithelium
substance then moves via facilitated diffusion from epithelium into blood
