Gaseos exchange, digestion and absorbtion Flashcards
what cells line the wall of the alveoli
flattened epithelial cells
what cells line the wall of the blood capillaries
endothelial cells
how do we breath in (inspiration)
1) the external intercostal muscles contract, pulling the ribs upwards and outwards whilst the internal intercostal muscles relax
2) the diaphragm muscles contract which pulls the diaphragm down so it flattens
3) both these actions increase the volume of the thoracic cavity
4) the pressure inside the lungs decreases below atmospheric pressure and air enters the lungs down a concentration gradient
is breathing in / inspiration an active or passive process
active as it involves muscle contraction
how do we breath out (expiration)
1) the external intercostal muscles relax
2) the diaphragm muscles relax and the diaphragm moves upwards to its dome shape
3) these actions decrease the volume of the thoracic cavity
4) the pressure increases above thoracic pressure and air is forced out the lungs
5) elastic recoil of the lung tissue helps to force air out the lungs during breathing out
5) the internal intercostal muscles may contract moving the ribcage inwards and downwards
what happens when we exhale strongly
the internal intercostal muscles contract pulling the ribcage inwards and downwards, forcing air out the lungs
the external intercostal muscles relax
^ antagonistic muscles
unicellular organisms have a large or small surface area : volume ratio
and what does this mean
large
this means exchange of gasses can occur directly across the cell membrane
large organisms have a low surface area : volume ratio what does this mean
they require specialised gas exchange organs
are insects active and require a high oxygen demand
yes
what are insects covered with
what does this mean
a protective exoskeleton made of the polysaccharide chitin
this means gasses such as co2 and o2 cant pass easily through the exoskeleton
what’s on the surface of insects exoskeleton
small openings called spiracles
what do spirscles allow
the diffusion of co2 and o2 into the body of the insect
what do spiracles lead to
lead into a network of tubes called trachea which are relatively large (1mm)
what are the walls of tracheae reinforced with
they are reinforced with spirals of chitin which keeps the tracheae open during pressure fluctuations or when an insect moves
what extends from the tracheae
very fine tubes called tracheoles
each tracheole is a single cell that has extended to form a hollow tube
a huge number of them extend down the insects body in between cells
unlike tracheae they are not supported by spirals of chitin
why is there a short diffusion distance between tracheoles and cells
what does this allow
because the tracheoles are very narrow in diameter and are extremely close to cells
this allows the oxygen in the air of the tracheoles to diffuse rapidly into the cells
this oxygen is needed for aerobic respiration which produces co2
the co2 can also rapidly diffuse back into the air of the tracheoles
is there a huge number of tracheoles
yes which provides a very large surface area for gas exchange
this allows insects to maintain a rapid rate of aerobic respiration
what are the ends of tracheoles filled with and what happens to it during intense activity
the ends of the tracheoles are filled with tracheole fluid
during intense activity the cells around the tracheoles undergo anaerobic respiration which produces lactic acid. this reduces the water potential in the cells. this causes the water in the tracheol fluid to move in to the cells via osmosis
this reduces the volume of tracheol fluid , drawing air into the tracheoles
this also means more tracheole surface is available for the diffusion of co2 and o2
in many insects is gas exchange a passive or active process
passive
o2 down a conc gradient from high conc in external air to tracheoles
co2 from high conc of tracheoles to low conc in air
why is the small size of insects useful
reduces the diffusion distance
how is water loss in insects controlled
valves around spiracles which can close when oxygen is not needed as much
in large / very active insects what is done to increase the rate of diffusion
the muscles in the insect may contract which will compress the tracheae forcing air out of it
when the muscles relax the tracheae springs back into shape
fresh oxygen rich air is drawn into the tracheae, increasing the rate of diffusion
why do fish need specialised exchange system
there are large and active organisms
they have low surface area to volume ratio
they are covered in scales so diffusion cannot occur
there’s a lower concentration of oxygen in water than in air
what is the flap of tissue behind the head of the fish
what’s inside it
the opercolum
the opercolum cavity which has gill arches,gill filaments and gill lamellae inside it
how does water enter the fish
oxygen rich water enters via the mouth
it passes through the gill lamellae and oxygen diffuses from water out of the epithelial cells of the gills and past the endothelial cells of the capillaries into the blood stream
finally water passes out through the operculum opening
what are the structure of gills
gills consist of 4 pairs gill arches
extending from these gill arches are a large number of gill filaments
gill filaments are covered with numerous gill lamellae
where does gas exchange take place in fish
gill lamellae
^ water flows between gill filaments
name the adaptations in the fish for gas exchange
1) a large surface area due to the large number of gill filaments and the gill lamellae which cover them
2) a short diffusion pathway as the blood and water are separated by a thin barrier consisting mainly of 2 cell layer
(epithelial layer of the gill lamellae)
and
(endothelial layer of the blood capillaries)
3) the circulatory system (which consists of a large network of blood capillaries) ensures a continuous flow of blood through the respiratory surface(lamellae) to absorb o2 and remove co2 to maintain a high diffusion gradient for gaseous exchange
4) ventilation system provides a continuous flow of water over the gills bringing more o2 and removing co2 maintaining a high diffusion gradient for gas exchange
5) the counter current system!!!! ( blood and water flowing in opposite directions ) which ensures water has a higher o2 concentration than blood so that a high diffusion gradient is maintain along the whole length of the lamellae
explain counter current exchange system in fish
water flows over the gills in the opposite direction to the flow of blood in the capillaries
counter current flow ensures equilibrium is not reached
this ensures a concentration gradient is maintained across the entire length of the gill lamallae
what is pulmonary ventilation ?
what is tidal volume?
what is ventilation/breathing rate?
what’s the equation for pulmonary ventilation
pulmonary ventilation = the total volume of air drawn into the lungs in 1 minute
tidal volume = the total volume of air drawn into the lungs in one breath
ventilation/ breathing rate = the total number of breaths per minute
pulmonary ventilation = tidal volume x ventilation/breathing rate
what is digestion
the process where large molecules are hydrolysed by enzymes to produce smaller soluble molecules
what does complete hydrolysis of carbohydrates result in
monosaccharides which are small soluble molecules which can be absorbed
explain the first stage of the digestion of carbohydrates
happens in the mouth:
the sight smell and taste of food stimulates the secretion of saliva from the salivary glands
saliva contains the enzyme salivary amylase
amylase hydrolyses STARCH into MALTOSE
only a small amount of starch is hydrolysed into maltose due to the short time food remains in the mouth . chewing breaks down food into smaller particles for a larger surface area so that hydrolysis by enzymes is more rapid
explain the 2nd stage of the digestion of carbohydrates
it happens in the small intestine
the pancreas releases pancreatic juice into the small intestine. pancreatic juice is an alkaline fluid which contains many enzymes including pancreatic amylase. this enzyme hydrolyses the remaining starch into the disaccharide maltose
the complete hydrolysis of starch into alpha glucose occurs in the ileum (end of the small intestine)
maltase and other disaccharidases are not released into the lumen of the ileum but form part of the cell surface membrane of the epithelial cells that line the ileum (they are referred to as membrane bound disaccharidases)
what are the disaccharidases that form part of the cell surface membrane of the epithelial cells that line the ileum
maltase -> hydrolyses maltose into 2 alpha glucose molecules
lactase -> hydrolyses lactose into glucose and galactose
sucrase-> hydrolyses sucrose into glucose and fructose
what are lipids hydrolysed into
lipids are hydrolysed into glycerol, fatty acids and monoglycerides (glycerol and one fatty acid) by the enzyme lipase
where is lipase secreted from and where to
lipase is secreted from the pancreas into the small intestine
what does lipase specifically hydrolyse
the ester bonds in triglycerides
how is the rate of hydrolysis of lipids increased and how
by bile salts
bile salts emulsify lipids into small droplets
this increases the surface area of the lipids which increases the rate of hydrolysis
where are bile salts found
in bile (an alkaline fluid) which is made in the liver and stored in the gall bladder
bile enters the small intestine via the bile duct
is emulsification and physical or chemical process
physical - there is no chemical breakdown
explain absorption of digested lipids
1) bite salts emulsify large droplets of lipids into smaller droplets. this increases the surface area for lipase to hydrolyse triglycerides
2) the products of lipid digestion (monoglycerides and fatty acids) combine with bile salts to form micelles
3) the micelles are necessary as it can transport the insoluble monoglycerides and fatty acids to surface of the epithelial cell in the ileum
4) the micelles break down next to the epithelial cell releasing the fatty acids and monoglycerides.
5) these non polar molecules can diffuse past the cell membrane of the epithelial cell
6) fatty acids, monoglycerides and glycerol recombine in the smooth endoplasmic reticulum to form triglycerides
7) they are packaged by proteins and phospholipids in the golgi body to form chylomicrons
8) chylomicrons are then absorbed into the lacteals in the villi which will eventually drain into the blood
explain absorption of digested lipids
1) bite salts emulsify large droplets of lipids into smaller droplets. this increases the surface area of the lip
adaptation of ileum to absorb
The ileum is adapted for absorption of digested products in the following ways.
• Large surface area due to its long length and the presence of villi (singular: villus) and microvilli (on the epithelial cells).
• Villi contain blood capillaries that absorb monosaccharides and amino acids maintaining a high diffusion gradient for further absorption.
The lacteals (lymph vessels) in the villi absorb digested lipids that also maintains a high diffusion gradient for further absorption.
The wall of each villus villi consists of a single layer of epithelial cells providing a short diffusion pathway for absorption.
• A large number of mitochondria are present to supply ATP. for active transport.
• There are carrier and channel proteins in the cell-surface membrane for absorption of specific molecules by active transport (carrier proteins) and facilitated diffusion (carrier & channel proteins).
