BIOL1131 Lecture Notes - Lecture 5: Abomasum, Omasum, Trachea
7 Jun 2018
School
Course
Professor
Digestion
• The composition of a typical animal is
o 70% H2O
o 18% fat
o 8% protein
o 0.4% carbohydrate
o 1.6% calcium
o 0.96% phosphorus
o 0.21% potassium
o 0.16% sulphur
o 0.09% sodium
o 0.05% magnesium
o 0.03% chlorine
o 0.006 % iron
o < 0.005% cobalt
o < 0.005% copper
• Animals require biomaterials and energy to survive
o Water is essential to animal life
▪ Liquid water is the universal solvent for life on earth
▪ Cryptobiosis or hidden life
• Anhydrobiosis: absence of water
• Osmobiosis: high solute concentration
• Cryobiosis: frozen water
• Anoxybiosis: lack of oxygen
o Energy is required in the form of biomolecules (animals) or light
(plants)
o Certain specific organic biochemical are required by animals
o Many chemical elements are required by animals
• Animal nutrition energy
o Energy can be acquired in 3 ways
▪ Chemitrophs
• Obtain energy and nutrients from inorganic
chemicals
• Most use symbiotic organisms (bacteria) that are
able to synthesise organic materials from simple
characteristics
• E.g. pogonophoran worms have chemitrophic
bacteria within their body that produce much of the
worm’s food from sea-vent chemicals
▪ Autotrophs
• These animals obtain some or all of their energy and
nutrients by photosynthesis from sunlight
• Symbiotic organisms (bacteria, protozoans or
plants) often synthesise the organic materials
▪ Heterotrophs
• Gain their energy by consuming organic material;
• Herbivore consume plant material
find more resources at oneclass.com
find more resources at oneclass.com
• Carnivores consume animal material
• Insectivores are carnivores that consume insect
material
• Omnivores consume plant and animal material
• A few specialized heterotrophs (saprozoic animals)
obtain organic chemicals by absorption across the
body surface
• Organic nutrients
o Carbohydrates
o Proteins
o Lipids
o Nucleic acids
o Vitamins
▪ Organic compounds that are essential for normal
physiological functioning but are required in only trace
amounts
o Minerals
▪ There are many required minerals
▪ The more abundant minerals in the body are calcium and
phosphorus (bone), potassium, sodium and chlorine (body
fluid ions) and magnesium
▪ Trace elements make up >0.01% of the body
1. Iron
2. Cobalt
3. Nickel
4. Copper
5. Zinc
6. Vanadium
7. Chromium
8. Manganese
9. Molybdenum
10. Silicon
11. Tin
12. Arsenic
13. Selenium
14. Fluorine
15. Iodine
• Herbivores often do not obtain their required nutrients from their diet
and so crave salt
• Animals can assimilate nutrients into their body in three ways
o Trans-epithelial absorption: some animals absorb nutrients across
their body surface
o Intracellular digestion: large food particles are absorbed into the
cell by phagocytosis (solid particles) or pinocytosis (liquids)
• Extracellular digestion: a specialized digestive tract (gut) provides
ingestion and digestion of food particles much larger than individual cells;
the small products of digestion are absorbed into the gut cells
• Intracellular digestion: unicellular organisms
find more resources at oneclass.com
find more resources at oneclass.com
o Food items (smaller than the cell) are absorbed into the cell
through
▪ Phagocytosis (solid particles)
▪ Pinocytosis (liquids)
o Digestion occurs in the vacuole to protect the rest of the cell from
the digestive enzymes
• Extracellular digestion: multicellular organisms
o Uses a specialized digestive tract or gut
o Food is digested into it’s subunits monosaccharides, amino acids,
free fatty acids) by gut enzymes
▪ Then absorbed by gut wall
o Some animals, e.g. worms, have an incomplete gut; simply a mouth
to anus tube known as a gut tube
▪ These then can have regional specialized areas in more
complex animals, mouth → crop or stomach → gizzard or
stomach → large intestine → rectum and anus
• Digestion
o Some are very hard to digest
▪ Keratin: digested using keratinase
▪ Collagen: some fly maggots secrete collagenase to digest it
▪ Spider silk: digested using silkase by spiders & some
animals
▪ Chitin: some insectivores produce chitinase
o As are some lipids, especially waxes, which are common in marine
food chains; so many marine organisms have a wax-ase enzyme for
digesting it
o Plant carbohydrates like cellulose are impossible for normal
animal enzymes to digest
▪ Cellulose is a polymer of D-glucose units linked by β
−,4−glycosidic linkages, which animal enzymes generally
cannot break
o Omnivores have a longer and larger intestine than carnivores
▪ Also have some fermentation of plant material in a more-
developed caecum
o Plant material has a <50-70% digestibility, makes it hard for
herbivores
▪ Requires a more complicated, specialized digestive system
• E.g. ruminants & pseudo-ruminants
▪ Often have symbionts that provide cellulose digestion and
ciliate, ciliate bacteria, flagellate & fungal sporangia
▪ Need a fermentation vat (stomach or caecum or hind gut)
• Microbial growth
• Stable temperature
• Water and nutrients via saliva & digestive secretions
▪ Long digestive tract to slow movement of food so it has
adequate time to digest
▪ Stomach is 4 chambered & is where gastric fermentation
occurs
• Rumen
find more resources at oneclass.com
find more resources at oneclass.com
