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Flashcards in Animal Nutrition Deck (45):
1

Nutrition

The process by which food is taken in, taken apart, and taken up

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3 things an animal's diet supplies

Chemical energy (produce ATP)
Organic building blocks (biosynthesis)
Essential nutrients

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Essential nutrients

Those materials that an animal's cells require but cannot synthesize

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4 classes of essential nutrients

Essential amino acids
Essential fatty acids
Vitamins
Minerals

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Amino acid requirements of animals

Animals require 20 amino acids, about half of which they can synthesize from molecules in their diet
Essential amino acids must be obtained from food in preassembled form

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Essential amino acids

Found in meat, cheese, and eggs
"Complete" proteins
Most plant proteins are incomplete

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Essential fatty acids

Animals can synthesize most of the fatty acids they need
Obtained from diet and include certain unsaturated fatty acids (alpha-linolenic acid: omega-3 fatty acid; linoleic acid: omega-6 fatty acid)
Deficiencies in these are rare

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Vitamins

Organic molecules required in diet in small amounts
13 are essential for humans
2 categories: fat-soluble (vitamins A, D, E, K) and water-soluble (B vitamins, vitamin C)

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Minerals

Simple inorganic nutrients
Usually required in small amounts
Important in bone/teeth development, water balance, nerve/muscle function, oxygen transport, and blood clotting
Ingesting large amounts can upset homeostatic balance

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Main stages of food processing

Ingestion
Digestion
Absorption
Elimination

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Ingestion

Act of eating

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Digestion

Process of breaking food down into molecules small enough to absorb

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Absorption

Uptake of nutrients by body cells

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Elimination

Passage of undigested material out of digestive system

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4 main feeding mechanisms

Suspension feeders
Substrate feeders
Fluid feeders
Bulk feeders

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Suspension feeders

Sift small food particles from water
Example: whale that eats using baleen

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Substrate feeders

Animals that live in or on their food source
Example: caterpillar living on and eating leaf

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Fluid feeders

Suck nutrient-rich fluid from a living host
Example: mosquito that sucks blood

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Bulk feeders

Eat relatively large pieces of food
Example: boa constrictor eating mouse

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Mechanical digestion

Breaking food down into pieces, increasing surface area for chemical digestion

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Chemical digestion

Break food down using acids

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Digestive compartments

Most animals process food in specialized compartments
Compartments reduce risk of an animal digesting its own cells and tissues

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Intracellular digestion

Food particles are engulfed by phagocytosis
Food vacuoles, containing food, fuse with lysosomes containing hydrolytic enzymes

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Extracellular digestion

Breakdown of food particles outside cells
Occurs in compartments that are continuous with the outside of the animal's body (ex- gastrovascular cavity)

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Alimentary canal

Digestive tube with 2 openings, a mouth, and an anus
Specialized regions that carry out digestion and absorption in a stepwise fashion

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Mammalian accessory glands

Salivary glands
Pancreas (releases HCO3-, a buffer)
Liver
Gallbladder

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Peristalsis

Pushes food along using alternating waves of contraction and relaxation in smooth muscle

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Sphincters

Valves that keep food material in its proper place in the digestive tract

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Order of mechanical digestion in humans

Takes place in oral cavity
Salivary glands deliver saliva to lubricate food
Teeth chew food into smaller particles that are exposed to salivary amylase (enzyme that breaks down glucose polymers) and mucus (viscous mixture of water, salt, cells, and glycoproteins) in saliva
Tongue shapes food into a bolus and provides help with swallowing
Pharynx (throat) is the junction that opens to both the esophagus and trachea
Swallowing causes epiglottis to block entry to trachea
Bolus of food is guided by larynx (upper part of respiratory tract) into esophagus, which conducts food down to stomach by peristalsis

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Digestion in stomach

Stomach stores food and secretes gastric juice to convert food to acid chyme
Mucus protects the stomach lining
Churning
Sphincters prevent chyme from entering esophagus and regulate its entry into the small intestine

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Gastric juice

Low pH (about 2)
Kills bacteria and denatures proteins
Made up of HCl and pepsin (protease: protein-digesting enzyme)

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Digestion in small intestine

Small intestine is largest section of alimentary canal
Duodenum (1st section): most digestion occurs
Jejunum (2nd section) and ileum (3rd section): mainly absorption of nutrients and water
Bile (made in liver and stored in gallbladder) aids in digestion and absorption of fats and destroys nonfunctional red blood cells
Absorption occurs across villi and microvilli, which are exposed to the intestinal lumen

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Hepatic portal vein

Carries nutrient-rich blood from the capillaries of the villi to the liver, and then to the heart

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Liver

Regulates distribution of nutrients throughout body
Detoxifies toxins (alcohol, drugs, etc.)

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Absorption in the large intestine

Colon is connected to small intestine
Colon recovers water and houses bacteria which live on unabsorbed organic material
Some bacteria produce vitamins
Feces, including undigested material and bacteria, become more solid as they move through the colon
Feces are stored in the rectum until they can be eliminated through the anus
2 sphincters between the rectum and anus control bowel movements

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Carbohydrate digestion

Oral cavity, pharynx, esophagus: salivary amylase breaks polysaccharides down into smaller polysaccharides or maltose; disaccharides aren't digested until small intestine
Small intestine (enzymes from pancreas): pancreatic amylases break smaller polysaccharides down into disaccharides
Small intestine (enzymes from epithelium): disaccharidases break disaccharides and maltose down into monosaccharides

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Protein digestion

Stomach: pepsin breaks proteins down into small polypeptides
Small intestine (enzymes from pancreas): pancreatic trypsin and chymotrypsin breaker small polypeptides into even smaller polypeptides and then pancreatic carboxypeptidase breaks these smaller polypeptides down into small peptides
Small intestine (enzymes from epithelium): dipeptidases, caryboxypeptidase, and aminopeptidase break small peptides down into amino acids

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Nucleic acid digestion

Small intestine (enzymes from pancreas): pancreatic nucleases break DNA and RNA down into nucleotides
Small intestine (enzymes from epithelium): nucleotidases break nucleotides down into nucleosides (nucleotides minus PO4) and then nucleosidases and phosphatases break nucleosides down into nitrogenous bases, sugars, and phosphates

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Fat digestion

Small intestine (enzymes from pancreas): pancreatic lipase breaks fat triglycerides down into glycerol, fatty acids, and monoglycerides

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Function of B vitamins

Coenzymes

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Function of vitamin C

Collagen synthesis and antioxidant

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Function of vitamin A

Comprise visual pigments
Maintenance of epithelial tissue

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Function of vitamin D

Absorption and use of calcium and phosphorus

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Function of vitamin E

Antioxidant
Helps prevent damage to cell membranes

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Function of vitamin K

Blood clotting