15-17 Flashcards
What is the fundamental problem of animal nutrient acquisition?
How to get small organic molecules containing carbon, nitrogen and sulphur
What are autotrophs, name 2 examples
Organisms that can fix inorganic substances into organic
- plants
- some bacteria
What are heterotrophs?
Organisms which cannot fix inorganic carbon and nitrogen and so rely on autotrophs
- to eat/digest
- symbiosis with fixer - like some hydra symbiont with green alga
What are the 6 main categories of molecules that animals need to acquire?
- Carbohydrates
- Fats
- Amino Acids
- Minerals
- Vitamins
- Roughage
Why do animals need carbohydrate? where do they get it?
- energy
- carbon skeletons of other organic molecules
from - sugars and starches from milk, fruits, seeds and plant storage organs
- basically none from meat or fish
Why do animals need fats, where do they get them?
- for energy, insulation, padding, build other molecules, cell membranes, myelin
- some essential fatty acids are needed
- fats and oils from cell membranes, adipose tissue, oily fish, milk
- some seeds and fruits give enough (avocado and nuts)
What are the mammalian energy sources?
2 main
- brain requires glucose
- cannot use fat
- most carbs into fat for storage and carbs cannot be retrieved from these stores and so need carbs in diet
Why do animals need amino acids, where do get them?
- constructing proteins and also emergency energy source
- needed for growth and reproduction
- maintenance (like hail and nails)
- digestive enzymes need to be made everyday
- cell lining intestines-half replaced in 4 days
- need some in diets as cannot make
- rest from other amino acids and glucose
- from proteins in seeds, milk, eggs and meat/fish
Why is only a little bit of protein needed in daily diet?
cell and protein breakdown gives some amino acids as recycled
- only that which is lost and the essential amino acids to be taken in
Why do animals need minerals? where do they get them?
inorganic cations and anions
- body fluids = Na, K, Cl, Mg, Ca, Phosphate
- crystalline bone = Ca, phosphate
- Thyroxine = Iodine
- Haemoglobin = Fe
- Enzymes cofactors = Mg, Zn, Cu (cytochromes)
Why do animals need vitamins? where do they get them?
organic molecules we require in small quantities but cannot synthesise
a nutrient can be a vitamin for one animal but not for others - Vit C for us and guinea pigs but not for other mammals
What is roughage
- why do we need it
- where do we get it from
- near-indigestible to animals
- cellulose and chitin
- our gut flora extract some nutrients
- without we would be constipated
What is digestion?
Simply it is hydrolysis of macromolecules into monomers that can be absorbed
Polysaccharides —>sugars
Proteins —> amino acids
Fats —> fatty acids and glycerol
How do intestinal parasites get food?
in host - bathed in monomer food already foraged and digested by host
What is intracellular digestion and how does it work?
- single-celled animals internalise particles of foodstuffs and digest them within cell
- Amoeba extends pseudopodia
- phagocytosis—>so in vesicle
- Lysosome with digestive enzymes fuse
- digested absorbed
- waste exocytosis
What is extracellular digestion?
- take food into an internal cavity which is not within a cell
- most have entrance (mouth) and exit (anus or cloaca)
- some ‘batch reactor’ hydra or pitcher plants where one entrance/exit
What are the 4 main sections of an extracellular digestive system (with tube)
- Headgut
- Foregut
- Midgut
- hindgut
What does the headgut do?
specialised for tearing/biting/sucking food
- maybe toxins/anticoagulants/ digestive enzymes
What does the foregut do?
stores food between meals and also grinds it —>through muscular action as most dont chew
What does the midgut do?
secretes digestive enzymes into a fluid slurry
- where most absorption occurs
- small nutrient molecules and water
What does the hindgut do?
resorbs last of water and nutrients
- prepare remains for evacuation through intestinal exit
- some have fermentation chambers here
What parts of nutrient acquisition require energy?
x 5
1) Chewing, squeezing, grinding and peristalsis
2) Synthesis of digestive enzymes
3) Secretion of enzymes, electrolytes
4) Absorption of digestive products
5) Foraging
How do we know what to eat?
1) highly nutritious and non-toxic
- mainly off taste and copying other animals
2 for nice tastes=higher conc to activate = mM to M scale
25 for bitter/nasty=smaller conc=μm to detect
What part of the brain monitors day-to-day weight and overall hunger?
Hypothalamus - Arcuate nucleus
- Leptin from adipose tissue
- Insulin
both enter hypothalamus