Chapter 45, 46, 49: Nutrition, Digestion, and Absorption
• Nutrition – process of consuming, using food/nutrients
o Ingestion, digestion, absorption, elimination
• Nutrient – any substance consumed by an animal that is needed for survival, growth, development, tissue repair,
or reproduction
o All organisms require nutrients to survive
• Animals require
o 5 categories of organic nutrients
Carbohydrates, proteins, lipids, nucleic acids, vitamins
o Inorganic nutrients – water and minerals
• Nutritional demands
o Herbivores – only plants
o Carnivores – animal flesh/fluids
o Omnivores – plant and animal material
o Ingested organic macromolecules are used
To provide energy (ATP) and to make new molecules
• Essential nutrients
o Certain compounds cannot be synthesized from any ingested or stored precursor molecules (must be
obtained in diet)
o 4 groups
Essential amino acids
• 8 required by many animals – Isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, valine
• Cannot be synthesized or stored by animal’s cells
• Readily obtain in meat
• Most plants do not contain every essential amino acid in sufficient quality
Essential fatty acids
• Certain polyunsaturated fatty acids cannot be synthesized by animal cells
• Unsaturated fatty acids found primarily in plants
• Strict carnivore obtain them from fish or adipose tissue of birds/mammals
Vitamins
• Organic nutrients (coenzymes)
• Water-soluble vitamins – vitamin C (not stored)
• Vitamin A (fat-soluble vitamin) stored in adipose tissue
• Not all animals require the same vitamins
o Some cannot synthesize vitamin C
Minerals
• Inorganic ions
• Many required only in trace amounts
• Some minerals can be stored (iodine or calcium)
• Not all used at same rate or in the same way
o Copper vs. iron for oxygen transport
• Strategies for obtaining food – ways in which an animal obtains its food are related to its environment
o Suspension feeding – food particles in the water get trapped by cilia and are moved toward the mouth
Filter organic matter out of water
Bivalve molluscs, sea squirts, baleen whales
o Bulk feeding
Carnivores (generally do not chew food), herbivores (highly adapted for chewing), omnivores
, Eat food in large pieces
Carnivores divided into predators and scavengers
o Fluid feeding
Lick or suck fluid from plants or animals
Do not need teeth except to puncture an animal’s skin
Evolved independently in many types of animals
• Principles of digestion and absorption
o Intracellular digestion
Only in some very simple invertebrates (sponges and some single-celled organisms)
Uses phagocytosis to bring food particles directly into a cell
Cannot meet metabolic demands of active animal for long
No mechanism for storing food
o Extracellular digestion
Extracellular digestion
• Protects interior of cells from hydrolytic enzymes
• Can consume large food
• Cycle
o Food sources are trapped by tentacles and delivered via the mouth to the gastrovascular cavity
o Digestive enzymes are secreted into the cavity by the cells lining it – these enzymes break
down the food into usable nutrients and waste
o Nutrients are absorbed by phagocytosis in to the cells that line the cavity
o Undigested waste products are excreted via the mouth
Gastrovascular cavity
• Simple (one opening)
• Digestion and distribution
• Food particles eventually phagocytosed
• Hydrolytic enzymes
o Digestion is required to convert polymers into smaller units that can be absorbed across plasma membranes
o Hydrolyze the chemical bonds in carbohydrates, proteins, lipids, nucleic acids
o Some substances (like vitamins) do not require digestion and are absorbed intact
• Passive or active absorption
o Nutrients must be absorbed by the epithelial cells lining alimentary canal
o 3 ways
Passive diffusion
Facilitated diffusion
Active transport
o Alimentary canal cells use some nutrients for their own needs but most transported into blood for the rest of
the body
• Vertebrate digestive systems
o Alimentary canal or gastrointestinal (GI) tract
o Accessory structures
Tongue, teeth, salivary glands, liver, gallbladder, pancreas
o Not all vertebrates share identical features (some fish lack a stomach, birds lack a gallbladder)
o Functional regions
Anterior end functions primarily in ingestion
• Oral cavity, salivary glands, pharynx (throat), and esophagus
• Mouth – processing may be extensive (herbivores) or not (carnivores)
• Saliva – begins initial processing of food
• Nutrition – process of consuming, using food/nutrients
o Ingestion, digestion, absorption, elimination
• Nutrient – any substance consumed by an animal that is needed for survival, growth, development, tissue repair,
or reproduction
o All organisms require nutrients to survive
• Animals require
o 5 categories of organic nutrients
Carbohydrates, proteins, lipids, nucleic acids, vitamins
o Inorganic nutrients – water and minerals
• Nutritional demands
o Herbivores – only plants
o Carnivores – animal flesh/fluids
o Omnivores – plant and animal material
o Ingested organic macromolecules are used
To provide energy (ATP) and to make new molecules
• Essential nutrients
o Certain compounds cannot be synthesized from any ingested or stored precursor molecules (must be
obtained in diet)
o 4 groups
Essential amino acids
• 8 required by many animals – Isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, valine
• Cannot be synthesized or stored by animal’s cells
• Readily obtain in meat
• Most plants do not contain every essential amino acid in sufficient quality
Essential fatty acids
• Certain polyunsaturated fatty acids cannot be synthesized by animal cells
• Unsaturated fatty acids found primarily in plants
• Strict carnivore obtain them from fish or adipose tissue of birds/mammals
Vitamins
• Organic nutrients (coenzymes)
• Water-soluble vitamins – vitamin C (not stored)
• Vitamin A (fat-soluble vitamin) stored in adipose tissue
• Not all animals require the same vitamins
o Some cannot synthesize vitamin C
Minerals
• Inorganic ions
• Many required only in trace amounts
• Some minerals can be stored (iodine or calcium)
• Not all used at same rate or in the same way
o Copper vs. iron for oxygen transport
• Strategies for obtaining food – ways in which an animal obtains its food are related to its environment
o Suspension feeding – food particles in the water get trapped by cilia and are moved toward the mouth
Filter organic matter out of water
Bivalve molluscs, sea squirts, baleen whales
o Bulk feeding
Carnivores (generally do not chew food), herbivores (highly adapted for chewing), omnivores
, Eat food in large pieces
Carnivores divided into predators and scavengers
o Fluid feeding
Lick or suck fluid from plants or animals
Do not need teeth except to puncture an animal’s skin
Evolved independently in many types of animals
• Principles of digestion and absorption
o Intracellular digestion
Only in some very simple invertebrates (sponges and some single-celled organisms)
Uses phagocytosis to bring food particles directly into a cell
Cannot meet metabolic demands of active animal for long
No mechanism for storing food
o Extracellular digestion
Extracellular digestion
• Protects interior of cells from hydrolytic enzymes
• Can consume large food
• Cycle
o Food sources are trapped by tentacles and delivered via the mouth to the gastrovascular cavity
o Digestive enzymes are secreted into the cavity by the cells lining it – these enzymes break
down the food into usable nutrients and waste
o Nutrients are absorbed by phagocytosis in to the cells that line the cavity
o Undigested waste products are excreted via the mouth
Gastrovascular cavity
• Simple (one opening)
• Digestion and distribution
• Food particles eventually phagocytosed
• Hydrolytic enzymes
o Digestion is required to convert polymers into smaller units that can be absorbed across plasma membranes
o Hydrolyze the chemical bonds in carbohydrates, proteins, lipids, nucleic acids
o Some substances (like vitamins) do not require digestion and are absorbed intact
• Passive or active absorption
o Nutrients must be absorbed by the epithelial cells lining alimentary canal
o 3 ways
Passive diffusion
Facilitated diffusion
Active transport
o Alimentary canal cells use some nutrients for their own needs but most transported into blood for the rest of
the body
• Vertebrate digestive systems
o Alimentary canal or gastrointestinal (GI) tract
o Accessory structures
Tongue, teeth, salivary glands, liver, gallbladder, pancreas
o Not all vertebrates share identical features (some fish lack a stomach, birds lack a gallbladder)
o Functional regions
Anterior end functions primarily in ingestion
• Oral cavity, salivary glands, pharynx (throat), and esophagus
• Mouth – processing may be extensive (herbivores) or not (carnivores)
• Saliva – begins initial processing of food
