Transcript Prezentace aplikace PowerPoint

Animal nutrition – the need to feed
1) Homeostatic mechanisms manage an animal´s
energy budget
2) An animal´s diet must supply carbon skeletons and
essential nutrients
3) The main stages of food processing are ingestion,
digestion, absorption and elimination
4) Each organ of the mammalian digestive system has
specialized food-processing functions
5) Evolutionary adaptations of vertebrate digestive
systems are often associated with diet
All animals eat other
organisms
Animals obtain food by
different methods:
suspension feeders →
Herbivores
Carnivores
Omnivores
All consume prokaryotes
Animals obtain food by different methods:
bulk feeders ↓
Homeostatic mechanisms manage an animal´s energy budget
Glucose regulation is an excellent example of homeostasis
Inside cell: ATP
generation –
based on
oxidation of
energy-rich
molecules
Cells store
energy in form of
glycogen, fat
Ghrelin – triggers
feeling of hunger
x
insulin, leptin
(from fat tissue)
suppress appetite
Obesity can be useful, to overcome „hungry“ periods
Human’s energy
needs = 0.3 kg of
fat/day
Undernourshment
- own protein
used
Overnourishment
→ obesity
Important fat
depots →
An animal´s diet must supply carbon skeletons and
essential nutrients
Besides energy the food
has to contain:
• Carbon skeletons
• Amino acids
• Fatty acids
• Vitamins (C in primates)
• Minerals
Missing one or more
essential nutrients =
malnourishment
Penguins can use their
muscle protein as a
source of AA for new
feathers after molting
Animals require 20 AA
Most species can
synthesize about half
of these
8 AA are essential in
adults, + histidine in
infants
Essential fatty acids
Are only certain unsaturated fatty acids (with double bonds)
Deficiencies are rare
Vitamins
Required only small amount – 0.01 to 100 mg per day
13 vitamins essential to humans
Water-soluble vitamins generally function as coenzymes
Fat-soluble – part in visual pigments (A), calcium absorption
(D) etc.
Minerals
Simple inorganic nutrients for bones, hemoglobin, cofactors,
hormones, acid-base balance etc. - required 1-2500 mg/day
Excess could be harmful
The main stages of food processing are ingestion,
digestion, absorption and elimination
Polysaccharides => monosaccharides
Proteins => amino acids
Fats => glycerol and fatty acids
Nucleic acids => nucleotides
Macromolecules
too large
for cell
membrane
and
species
specific
Complete digestive tract
Each organ of the mammalian digestive system has
specialized food-processing functions
The stomach
Gastric juice
pH 2-3 (HCl)
→
unfolds =
denatures
proteins
Pepsin →
hydrolysis of
proteins
Cleaving into
smaller
polypeptides
The small intestine - enzymatic actions:
Most of enzymatic hydrolysis and absorption of nutrients occur there
How hormones help coordinate the secretion of digestive juices:
positive and negative feedback
Absorption of nutrients
In human – folds, villi and microvilli enhance absorption
surface up to 300 m2
Absorption of nutrients
Hepatic portal vein – direct
connection to liver
Vertebrates have an associated
network of vessels:
the lymphatic system – with
clear fluid lymph
Fatty acids and monoglycerids
enter epithelial cells →
chylomicrons
Evolutionary adaptations of
vertebrate digestive systems
are often associated with diet
Dental adaptations
Incisors, canines, premolars,
molars
A mammal´s dentition is generally
correlated with its diet
In particular, mammals have
specialized dentition that best enables
them to ingest their usual diet
Poisonous snakes (rattlesnakes) –
have fangs for injection of venom into
prey
Evolutionary adaptations of
vertebrate digestive
systems are often
associated with diet
Stomach and intestinal
adaptations
Herbivores generally have longer
alimentary canals than carnivores,
reflecting the longer time needed to
digest vegetation
In the hoatzin – large muscular
crop with symbiotic microorganisms
Evolutionary adaptations of vertebrate digestive systems
are often associated with diet - symbiotic adaptations
Many
herbivorous
animals have
fermentation
chambers
(rumen, cecum)
where symbiotic
microorganisms
digest cellulose
Rabbits, rodents
eat green feces