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nutrient
any substance an animal needs but cannot synthesize or produce in its own body
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digestion
the process by which an animal mechanically and chemically breaks down its food to produce simple molecules that can be absorbed into the circulatory system
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6 nutrients that animals need:
- lipids
- carbohydrates
- proteins
- minerals
- vitamins
- water
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Calorie
the amount of energy needed to raise the temperature of one gram of water by one degree Celsius
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lipids include these three:
- fats; used primarily as a source of energy
- phospholipids
- cholesterol; used to make cell membranes and several hormones
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carbohydrates
- source of quick energy
- include simple sugars and polysaccharides
- animals store sugars as glycogen, a large branched chain of glucose molecules
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proteins
- provide amino acids for building new proteins
- dietary protein comes from meat, milk, eggs, corn and beans
- our bodies can synthesize certain amino acids but the eight essential amino acids must be supplied by our diet
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minerals
- elements that are required by the body
- needed for strong bones and teeth, muscle contraction, nerve functions, proper blood cell functions
- also act as parts of enzymes in certain body reactions
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vitamins
- play many roles in metabolism
- organic compounds that animals require in very small amounts
- the body cannot synthesize them
- water soluble or fat soluble
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water-soluble vitamins
- dissolve in water or blood plasma and are excreted by the kidney; therefore do not build up in the body
- C and B complex
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fat-soluble vitamins
- can accumulate in the body and be toxic if present in too high a concentration
- K, A, D, E
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water
- human body about 2/3 water
- principal component of saliva, blood, lymph, extracellular fluid, and cytoplasm within each cell
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all digestive systems must accomplish certain tasks (5)
- ingestion: food through mouth
- mechanical breakdown: food into small pieces
- chemical breakdown: enzymes convert large molecules into small ones
- absorption: transfer of small molecules across the gut to the blood and then to the cells
- elimination: indigestible materials are expelled
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three types of digestive systems:
- individual cells: in sponges; microscopic organisms are ingested by phagocytosis
- sac like: in jellyfish; both food and waste pass through a single opening
- tube: most animals
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pharynx
connects the mouth to the rest of the digestive sytem
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esophagus
conducts food to the somach
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stomach
- stores and breaks down food, mechanically and chemically
- protein digestion begins (denatured) - pepsine (chemical for protein breakdown)
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liver and gall bladder
liver stores glycogen and detoxifies many poisonous substances
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