6. Exchange Flashcards
Name three components of the tracheal system in insects?
spiracles, trachea, tracheoles
Name two components of the gas exchange system in gills of a fish?
gill filaments, lamelle
By what principle do fish exchange gases in their gills?
counter current mechanism
define dicotyledonous?
a plant in which the seed has two embryonic leaves
name three components of the leaves of dicotyledonous plants involved in gas exchange?
stomata, guard cells, mesophyll cells
how do xerophytic plants limit water loss?
waxy cuticle hairy leaves curled shape sunken stomata in pits reduced SA:vol ratio of leaves
how do insects balance the need for gas exchange with the need to limit water loss?
in dry conditions spiracles close to limit water loss
what reaction occurs in which larger molecules are broken down into smaller ones?
hydrolysis
why must molecules be made smaller to allow digestion?
to allow them to pass through cell membranes
what two enzymes break down carbohydrates?
amylase and membrane bound dissacharidases
which enzyme breaks down lipids?
lipases
explain how bile salts aid with the digestion of lipids?
bile salts emulsify lipids into micelles.
This increases surface area for lipases to act upon
which three enzymes break down proteins?
endopeptidases
exopeptidases
depeptidises
How do endopeptidases carry out their function?
endopeptidases attack anywhere along polypeptide chain, apart from the ends.
how do exopeptidases carry out their function?
attack ends of polypeptide chain
how do depeptidises carry out their function?
break down dipeptides into single amino acids.
where in mammals does absorption occur?
illeum
what mechanism permits absorption of amino acids and monosaccharides?
co-transport
state the equation for cardiac output?
heart rate x stroke volume
what is digestion?
physical breakdown and chemical digestion
what type of digestion does salivary amylase aid?
hydrolysis of starch to maltose
where is salivary amylase produced?
produced by the salivary glands
what feature allows salivary amylase to maintain a neutral PH?
contains mineral salts
what type of digestion does pancreatic amylase aid?`
hydrolysis of starch to maltose
where is pancreatic amylase produced?
produced by the pancreas
what feature allows pancreatic amylase to maintain a neutral PH?
alkaline salts
what type of digestion does maltase aid?
hydrolysis of maltose to alpha glucose
where is maltase produced?
produced by the epithelial lining of the ileum.
where can maltase be found?
in the cell surface membrane of epithelial cells in the ileum
what type of digestion does sucrase aid?
hydrolysis of sucrose to glucose and fructose
where is sucrase produced?
produced by the epithelial lining of the ileum of the small intestine
where can sucrase be found?
in the cell surface membrane of epithelial cells in the ileum
what type of digestion does lactase aid?
hydrolysis of of lactose to glucose and galactose
where is lactase produced?
produced by the epithelial lining of the ileum.
where can lactase be found?
in the cell surface membrane of epithelial cells in the ileum
what type of digestion does lipase aid?
hydrolysis of lipids (triglycerides) to fatty acids and monoglycerides
How does the hydrolysis of lipids with the enzyme lipase occur?
Bile salts from the liver split lipids into tiny droplets (micelles)
This emulsification increases the surface area to speed up lipid hydrolysis in ileum.
what type of digestion do endopeptidases aid? how?
hydrolysis of peptide bonds between amino acids in central region of protein
acts in central region of protein to make smaller peptide molecules
Where are endopeptidases produced? and by what?
Produced in the stomach
By chief cells in gastric pits
what type of digestion do exopeptidases aid? how?
hydrolysis of peptide bonds on the terminal amino acids
duodenum acts on terminal amino acids of peptides to make dipeptides and single amino acids
where are exopeptidases produced?
produced by the pancreas
what type of digestion do dipeptidases aid? how?
hydrolysis of the peptide bonds in dipeptides
membrane bound enzymes in epithelial cells of ileum result in single amino acids
where can dipeptidases be found?
in the cell surface membrane of epithelial cells in the ileum
list the order in which air passes before entering the lungs.
pharynx , larynx , trachea
Gas exchange in single-cell organisms and insects, explain how and why they do it this way.
oxygen is absorbed by diffusion across their body surface which is covered by only a cell surface membrane. In the same way, co2 diffuses out.
these organisms are small and therefore have a large sa:vol ratio
How does an insect get oxygen into its cells at rest?
spiracles allow gasses to diffuse into the trachea, down the concentration gradient
air diffuses directly down through tracheoles into cells
tracheoles have some water at their base which the gases dissolve into and out of during exchange
constant respiration means concentration gradient for both co2 and oxygen are maintained
How does an insect get oxygen into its cells when more is required, e.g when exercising intensely
lactate lowers the water potential of cells
water moves into cells via osmosis
water in ends of tracheoles decreases in volume and draws o2 in.
this means diffusion can happen in a gas phase as opposed to liquid phase and therefore occurs at a greater rate
how does an insect get oxygen into its cells if it needs to conserve water/water loss
closes spiracles to prevent water loss through evaporation.
air sacs filled during rest periods act as an oxygen reserve and allows respiration to be maintained, some spiracles are opened to allow co2 out.
do insects have a circulatory system?
no
describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. details of breathing are not required
- trachea and bronchia and bronchioles
- down pressure gradient
- down diffusion gradient
- across alveolar epithelium
- across capillary endothelium
explain the absorption of triglycerides.
Bile salts emulsify the lipid droplets into micelles
Micelles come into contact with epithelial cells lining the villi of the ileum
Micelles break down, releasing monoglycerides and fatty acids
Monoglycerides and fatty acids diffuse into epithelial cells
Monoglycerides and fatty acids are transported to endoplasmic reticulum and recombined into triglycerides
Triglycerides associate with cholesterol and lipoproteins to form chylomicrons in endoplasmic reticulum and then in golgi apparatus
Chylomicrons move out of epithelial cells by exocytosis and enter lymphatic capillaries called lacteals in each villus
Chylomicrons then pass into the blood system where the triglycerides are hydrolysed by an enzymes from where they diffuse into cells.
explain how starch is digested to glucose.
saliva enters the mouth
saliva containing salivary amylase from salivary glands breaks down starch into maltose
food passes into stomach
stomach acid conditions denatures salivary amylase
food passes into small intestine
pancreatic juice containing pancreatic amylase hydrolyses any remaining starch to maltose
disaccharide bound carbohydrase called maltose found in epithelial lining of ileum
maltose causes hydrolysis of maltose to alpha-glucose
what features allow fish to perform sufficient gas exchange?
gill lamellae provide a large surface area
gills have a rich blood supply
counter current flow maintains a favourable concentration gradient for oxygen across entire gas exchange surface
In what order are a fish’s gills composed
gill –> gill filaments –> gill lamellae
explain the importance of the counter-current flow principle in fish
in order for efficient gas exchange to take place.
at all times a diffusion gradient exists across the entire width of the lamellae to enable oxygen to move from the water into the blood.
equilibrium is never reached and a diffusion gradient exists at all times allowing oxygen to move from the water into the blood.
volume of o2 is always higher than blood
what are the essential features of gas exchange surfaces?
large surface area to volume ratio very thin partially permeable movement of external medium movement of internal medium
Why is it essential for a gas exchange surface to have a large surface area to volume ratio?
the rate of gas exchange occurs at a faster rate because of the large surface area
Why is it essential for a gas exchange surface to be very thin?
short diffusion pathway
therefore gas exchange occurs at a faster rate
Why is it essential for a gas exchange surface to be partially permeable?
to allow selected molecules to diffuse easily
Why is it essential for a gas exchange surface to have an efficient movement of external medium?
to maintain a concentration gradient for diffusion to occur
Why is it essential for a gas exchange surface to have an efficient movement of internal medium?
to maintain a concentration gradient for diffusion to occur
