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Lecture 11

BIO270H1 Lecture Notes - Lecture 11: Enteropeptidase, Amylase, Abomasum

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Chris Garside

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Lecture 11 (December 2, 2015): Digestion and Energy Metabolism
Ionic and Osmotic Regulation Continued:
There are two different types of primitive analogs of the nephron
Evolved to remove excess fresh water
Use this vacuole to pump fresh water out of the body
Cap cell (flame cell maybe)
Cilia produce a current down the protoephridium
Fluids are released out the cells
There can be reabsorption and secretion
Not as evolved and not as many cell types as the nephron
There are perforations in cap cell, so that the current made by the flagella
are a sort of filter
More evolved than protonephridium
More cell types available
Also have a bladder that can store primary urine until it can be released
Does not have a cap cell
Has a nephrostone
oOpen to the body cavity and collects solutions from the
body cavity, it does not filter
Longer in organisms that live in or near fresh water
Malpighian tubules
oInsect kidney
oUrine is formed by secretion, not by filtration
Secretion of cations through principle cells and anions through satellite
oSodium/potassium ATPase have no role
oProton ATPase drives the secretion of fluids and ions into the Malpighian tubules
oThere is no innervation of these tubules so they must be controlled hormonally
oThree groups of hormones that control it
Stimulate cation transport at basolateral and apical membrane
Stimulate the proton ATPase, stimulating secretion or production
of primary urine
Stimulate chloride transport across the cell
Salt glands

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oLizards that live by the sea drink seawater have salt glands
oBirds also have slat glands that can secrete salt solution three times more
concentrated than their blood plasma and they net gain a lot of fresh water
oCountercurrent organization
Blood is flowing counter current to the secretory tubules into which the
sodium chloride is being pumped
Important because as secretion is being initially produced, it comes into
contact with a rather low amount of sodium chloride, but as it moves, it
encounters a higher and higher concentration of it, so current maintains
Rectal gland
oBasolateral sodium potassium ATPase and cotransporter
oSodium is pumped out, sodium chloride passes in , potassium escapes
oLeaky tissue
oElectrical gradient drives the movement of sodium paracellularly
oConstantly have pressure of ions diffusing into tissues
oRate of salt excretion is regulated by hormones
oIncrease of salt turns on the effect of ANP which stimulates the release of
vasoactive intestinal peptide which activates pkA, which stimulates chloride
channels, moves to apical membrane, and stimulates production of hypertonic
sodium chloride solutions
oNeed extra renal tissues to augment processes
Primary roles of digestion
oMechanical breakdown
Movement of food throughout the gastrointestinal tract
Purpose of digestion
oProvide building blocks
Monomers, precursors to build tissues
Assimilation: nutrients are broken down, absorbed, and converted into usable forms
oHow to feed
Sense where food is using chemoreceptors, light, sound
Once sensed, you have to be able to capture it, so many organisms have
special structures to do that
Talons, claws
Mechanical digestion

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Bird beaks
Chemical processing
Absorb material into the body
Most digestion takes place outside the body
Indigestible material is released through the anus
All processes require energy or building blocks
Diet must provide energy source
Energy content has to match demands of the animal
Energy demands increase a lot when you’re growing or reproducing
oOrganism needs more food
Most organisms have to deal with imbalances unless they’re constantly eating
oSo organisms store fuels in things like macromolecules
oEach macromolecule has an energy amount, determined by burning the molecule
Organisms have to balance the amounts and types of food they take in
oWhether fat or carbohydrate
Gross energy = chemical energy
oCannot enzymatically breakdown and absorb all of the gross energy
oMuch of this energy is indigestible
Digestible energy
oSome are unmetabolizable which is lost in urine
Metabolizable energy
oSpecific dynamic action (SDA)
Energy lost through the increase in metabolic rate during digestion
There is a cost for metabolizing and digesting
Net energy = energy actually available to animals through assimilation
Essential nutrients (must intake in diet, cannot produce ourselves) and unessential
nutrients (can produce using enzymes from precursors)
Blood clotting, vision, coenzymes
Fat soluble or water soluble
You can take as many water soluble vitamins as you want but fat
soluble vitamins are stored in fat cells
James Lind, the doctor in the British Navy
Food supplies weren’t good
Lots of death on the ships because he thought they weren’t
provided with enough fresh fruits and vegetables
He set up the first ever controlled clinical trial
Took 12 men who had scurvy (vitamin C deficiency)
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