Nutrition, Digestion and Animal Diets

• Nutrition and Digestion are key processes for life

Nutrition vs. Digestion

• Nutrition focuses on the intake of nutrients
• Digestion is derived from the Latin term "digestio", from "dis" (apart) and "gerere" (to carry).
• Mechanical and chemical digestion are two types of digestion

Autotroph vs. Heterotroph

• Autotrophs are self-nourishing organisms, taking from the Greek words "auto" (self) and "trophe" (nourishing).
• Heterotrophs obtain nourishment from different sources, derived from Greek "heteros" (another or different) and "trophe" (nourishing).

Animal Diets

• Animal diets include herbivores
• Animal diets include carnivores
• Animal diets include omnivores
• Animal diets include insectivores
• Herbivores mainly consume plants or algae
• Carnivores mainly consume animals
• Omnivores regularly consume animals as well as plants or algae

Calories and Energy

• The energy value of food is measured in calories or Calories
• A calorie is the energy needed to raise the temperature of 1 gram of water by 1°C, from the Latin "calor" (heat)
• A calorie (with a small "c") is also called a gram calorie.
• A kilocalorie, also known as a Calorie or kilogram calorie (kcal), is equal to 1,000 calories

The Metabolic Fates of Nutrients in Heterotrophs

• Macronutrients and micronutrients perform metabolic functions

Macronutrients

• Macronutrients include carbohydrates
• Macronutrients include lipids
• Macronutrients include proteins

Micronutrients

• Vitamins are micronutrients, derived from Latin "vita" (life)
• Minerals are micronutrients
• Minerals can be macrominerals
• Minerals can be microminerals

Water-Soluble Vitamins

• Vitamin B1 (thiamine) is found in pork, legumes, peanuts, and whole grains.
• Deficiency in Vitamin B1 results in beriberi.
• Vitamin B2 (riboflavin) is in dairy products, meats, enriched grains, and vegetables
• Vitamin B6 (pyridoxine) is found in meats, vegetables, and whole grains
• Pantothenic acid is found in most foods, including meats, dairy products, and whole grains
• Folic acid (folacin) is found in green vegetables, oranges, nuts, legumes, and whole grains
• Vitamin B12 is in meats, eggs, and dairy products
• Biotin is in legumes, other vegetables, and meats
• Vitamin C (ascorbic acid) is found in fruits and vegetables (especially citrus fruits, broccoli, cabbage, tomatoes, and green peppers)

Fat-Soluble Vitamins

• Vitamin A is found in dark green and orange vegetables and fruits, and dairy products
• Vitamin D is found in dairy products and egg yolk; also made in human skin in the presence of sunlight
• Vitamin E (tocopherol) is found in vegetables, oils, nuts, and seeds
• Vitamin K is found in green vegetables and tea

Physiological Roles of Essential Minerals (Macrominerals)

• Minerals animals require in large amounts include Calcium (Ca)
• Calcium is a component of bone and teeth, essential for blood clotting, and needed for cellular function
• Chlorine (Cl) is the principal negative ion in extracellular fluid, crucial for acid-base and fluid balance, and is needed to produce stomach HCl
• Magnesium (Mg) is a component of many coenzymes and needed for neuron and muscle, as well as carbohydrate and protein metabolism.
• Potassium (K) is a major constituent of bones and blood plasma needed for energy metabolism.
• Phosphorus (P) is a major positive ion in cells needed for muscle contraction, neuron excitability, and is part of DNA, RNA, ATP and energy metabolism
• Sodium (Na) is the principal positive ion in extracellular fluid that is important in fluid balance, essential for conduction of action potentials and active transport.
• Sulfur (S) builds protein structure, detoxification reactions, and other metabolic activity

Physiological Roles of Trace Minerals (Microminerals)

• Cobalt (Co) is a component of Vitamin B12, essential for red blood cell production
• Copper (Cu) is essential for melanin and hemoglobin synthesis, and part of cytochromes
• Fluorine (F) is a component of bone and teeth, preventing tooth decay
• Iodine (I) forms thyroid hormones
• Iron (Fe) forms hemoglobin, myoglobin, enzymes, and cytochromes
• Manganese (Mn) activates many enzymes and is essential for urea formation and parts of the Krebs cycle
• Molybdenum (Mo) is a constituent of some enzymes
• Selenium (Se) is needed in fat metabolism
• Zinc (Zn) is a component of at least 70 enzymes

Digestion

• Extracellular digestion is the enzymatic breakdown of larger pieces of food into constituent molecules in a special organ or cavity
• Intracellular digestion involves taking in whole food particles directly from the environment via diffusion, active transport and/or endocytosis, breaking them down with enzymes to obtain nutrients

Four Stages of Food Processing

• Food processing involves ingestion
• Food processing involves digestion
• Food processing involves absorption
• Food processing involves elimination

Continuous vs. Discontinuous Feeders

• Continuous feeders constantly consume food
• Discontinuous feeders eat periodically

Suspension Feeder

• Lophocyte or collenocyte cells secrete collagen in the suspension feeder
• Pinacocyte cells form the outer covering, and may phagocytize large food particles
• Oocyte cells are egg cells
• Porocyte cells are cells that control water flow through ostia
• Amoebocyte cells deliver nutrients to cells and differentiate into other cell types
• Sclerocyte cells secrete silica spicules
• Choanocyte cells generate water current and filter food particles from water

Deposit Feeders

• Deposit feeders feed on particulate organic matter that settles at the bottom of an environment

Herbivory

• Herbivory comes from Latin "herba" (herb eat)

Predation

• Predation encompasses motile stalkers
• Predation encompasses lurking predators
• Predation encompasses sessile opportunists
• Predation encompasses grazing carnivores

Main Types of Digestive Compartments

• Gastrovascular cavities are present in Hydra
• Alimentary canals (digestive tracts) are present in Earthworms

Diversity in Digestive Structures: Invertebrates

• A cnidarian demonstrates a gastrovascular cavity as an incomplete digestive tract with just one opening, and food vacuoles
• A planarian exhibits a gastrovascular cavity that branches extensively, with only one opening; it sticks its muscular pharynx out and sucks in food
• A nematode demonstrates a complete digestive tract with a mouth, pharynx, and anus
• An insect exhibits an expanded region called a crop as a food storage organ

Mammalian Digestive System

• The mammalian digestive system starts with ingestion
• Peristalsis involves movement
• Segmentation involves separation
• Secretion involves extracting fluids
• Digestion is the break down of material
• Absorption involves taking in nutrients
• Defecation involves removal of unused materials

Accessory Organs

• Salivary glands provide saliva
• The liver processes blood and creates bile
• The gallbladder stores bile
• The pancreas creates enzymes

Alimentary Canal

• The mouth introduces food
• The tongue manipulates food
• The pharynx aids swallowing
• The esophagus transports food
• The stomach breaks down food
• The small intestine absorbs nutrients
• The colon of the large intestine reabsorbs water
• The appendix has no clear function
• The rectum holds waste material
• The anus expels waste