Nutrient Procurement and Processing - Animals

Animal Nutrition

1. The concept of calories from food.
    A Calorie is a unit of energy that indicates the amount of energy contained in food. It specifically refers to the amount of heat energy required to raise the temperature of 1 kg (2.2 lb.) of water by 1oC (1.8oF). The greater the number of Calories in a quantity of food, the greater energy it contains (Johnson and Raven, 1996).

2. The nutritional requirements of animals:
    I. Carbohydrates – serve as a major energy source for the cells in the body. These are usually obtained from grains, cereals, breads, fruits, and vegetables. On average, carbohydrates contain 4 Calories per gram.
    II. Proteins – can also be used as an energy source but the body mainly uses these as building materials for cell structures and as enzymes, hormones, parts of muscles, and bones. Proteins come from dairy products, poultry, fish, meat, and grains. Like carbohydrates, proteins also contain 4 Calories per gram.
    III. Fats – are used to build cell membranes, steroid hormones, and other cellular structures; also used to insulate nervous tissue, and also serve as an energy source. Fats also contain certain fat- soluble vitamins that are important for good health. Fats are obtained from oils, margarine, butter, fried foods, meat, and processed snack foods. They contain a higher amount of energy per gram than carbohydrates or proteins, about 9 Calories per gram.
    IV. Essential Nutrients – include substances that animals can only get from the foods they eat because they could not be synthesized inside the body. These include:
        A. Essential amino acids – needed for synthesis of proteins and enzymes; among the 20 amino acids, eight could not be synthesized by humans: lysine, tryptophan, threonine, methionine, phenylalanine, leucine, isoleucine and valine.
        B. Essential fatty acids – used for making special membrane lipids; an example is linoleic acid in humans.
        C. Vitamins – organic molecules required in small amounts for normal metabolism; examples include fat-soluble Vitamins A, D, E, K, and water-soluble Vitamins B, B2, B3, B12, C.
        D. Trace Elements or Minerals – inorganic nutrients needed by the body in minute amounts; these form part of enzymes, body tissues, and body fluids; examples include: iodine, cobalt, zinc, molybdenum, manganese, selenium.

3. Food uptake in cells via the three types of endocytosis:
     I. phagocytosis – engulfment of organic fragments or big particles, eg. pseudopod formation in Amoeba.
     II. pinocytosis – uptake of extracellular fluid by a cell using small vesicles derived from the plasma membrane.
     III. receptor-mediated endocytosis – this relies on membrane receptor recognition of specific solutes which are then taken up by the cell via receptor-coated pits.

4. Cite the different types of animals based on feeding mechanisms:
     I. substrate-feeders – animals that live in or on their food source. Examples: earthworms that feed through the soil where they live in; caterpillars that eat through the leaves where they live on.
     II. filter-feeders – include many aquatic animals which draw in water and strain small organisms and food particles present in the medium. Examples: whales and coelenterates
     III. fluid-feeders – suck fluids containing nutrients from a living host. Examples: mosquitoes, leeches, head lice, aphids
     IV. bulk-feeders – eat relatively large chunks of food and have adaptations like jaws, teeth, tentacles, claws, pincers, etc. that help in securing the food and tearing it to pieces. Examples: snakes, cats, man

5. The different kinds of digestive compartments in animals:
     I. Food vacuoles in unicellular organisms – these fuse with lysosomes that contain hydrolytic enzymes. Example: food vacuole in a protozoa like Paramecium
     II. Gastrovascular cavity or incomplete digestive system – composed of a single opening through which food is taken in and where wastes are disposed of; it is a saclike body cavity. Examples: in the cnidarian Hydra and in flatworm Planaria
     III. Complete digestive system – essentially like a tube with an opening at one end for taking in food (mouth) and an opening at the other end where unabsorbed waste materials are eliminated (anus). In between the mouth and anus, are specialized organs that carry out transport, processing, and absorption of digested nutrients.

6. The accessory organs for digestion in a complete digestive system:
     I. liver – secretes bile for emulsifying fats
     II. gallbladder – stores bile produced by the liver
     III. pancreas – secretes enzymes that break down all major food molecules; secretes buffers against HCl from the stomach; secretes the hormone insulin for control of glucose metabolism

Nutrient Procurement and Processing Quiz 1