Nutrition 1

• Cell activity


  Depends on sources of chemical energy in the diet
• Energy


  After conversion to ATP (Adenosine-5'-Triphosphate), powers DNA replication, cell division to vision and flight
• To meet demand for ATP


  Animals ingest and digest nutrients for use in cellular respiration and energy storage
• Nutrients


  • Carbohydrates
  • Proteins
  • Lipids
• Animal nutrition


  Process of food being taken in, taken apart and taken up
• What an animal must obtain to grow, maintain itself and reproduce

  • Source of organic carbon (e.g. sugar)
  • Source of organic nitrogen (e.g. amino acids from protein digestion)
• Complex carbohydrates (e.g. starch)


  Broken down and absorbed as monosaccharides (e.g. glucose)
• Essential nutrients


  Materials that an animal's cells require but cannot synthesize
• Some essential nutrients are essential for some types of animals but not others (e.g. Vitamin C is essential nutrient for humans, primates and some birds, but not other animals)
• Adequate diet


  Contains enough chemical energy, organic building blocks and essential nutrients
• Essential Nutrients


  • Essential Amino Acids
  • Essential Fatty Acids
  • Vitamins
  • Minerals
• Essential Amino Acids


  Animals require 20 amino acids to make proteins, most animals can synthesize about half (with dietary nitrogen), rest must be absorbed (i.e. essential amino acids)
• Humans need 8 essential amino acids, infants need 9 (+ histidine)
• Plant protein


  Incomplete (e.g. corn maize deficient in tryptophan and lysine; beans lack methionine)
• Essential Fatty Acids


  Fat consists of triglycerides = containing one glycerol molecule attached to three fatty acids, animals can synthesize most fatty acids except some unsaturated ones (i.e. one or more double bonds)
• Humans need linoleic acid (C18) to make membrane phospholipids, deficiencies are rare because seeds, grain and vegetables contain ample amounts
• Vitamins


  • Water-soluble vitamins (vitamin B1, vitamin B2, Niacin (vitamin B3), Pantothenic acid, Folic acid, vitamin B12, Biotin, vitamin C)
  • Fat-soluble vitamins (vitamin A, vitamin D, vitamin E, vitamin K)
• Vitamin C


  Source: fruit and vegetables (citrus fruits, broccoli, cabbage, tomatoes, green peppers), Function: used in collagen synthesis in bone cartilage and gums, Deficiency: causes Scurvy - degeneration of skin, teeth and blood vessels, Structure: form of ascorbic acid
• Vitamin D


  Source: dairy products, human skin + sunlight, Function: aids absorption and use of calcium and phosphorus, promotes bone growth, Deficiency: Rickets - bone deformities in children, bone softening in adults, Vitamin D2 (invertebrates), Vitamin D3 (vertebrates)
• Diets derived from maize monoculture cause maternal infanticides in the endangered European hamster due to a vitamin B3 deficiency
• About 40% of proteins are metalloproteins (i.e. containing metal), including iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), selenium (Se), molybdenum (Mo), cobalt (Co)
• Undernourishment


  Diet consistently supplies less chemical energy than body requires - body uses up fat + carbohydrate, then uses own protein for fuel, animal will eventually die
• Malnourishment


  From diet lacking one or more essential nutrients over a long period of time - leads to deformity and sometimes death, animals can change behaviour (e.g. spiders switch prey from protein-rich flies to carbohydrate-rich flies)
• Folic acid (B9) found to be specific vitamin to prevent neural tube defects, now widely used
• Iodine deficiency


  Essential element because thyroid hormones (T3 and T4) that regulate rate of metabolism both contain iodine, Goiter - low amount of T3 causes swelling of thyroid gland, Cretinism - mental deficiency (IQ reduced 10-15 points), Affects nearly 2 billion worldwide
• Types of feeders


  • Omnivores (ingest both plants and animals)
  • Herbivores (vegetarians)
  • Carnivores (eat other animals)
  • Opportunistic feeders (can eat other things if they have to)
• Main stages of food processing

  • Ingestion
  • Digestion
  • Absorption
  • Elimination
• Ingestion - Suspension Feeders


  Many aquatic animals sift small food particles from the water (e.g. humpback whale - comb like plates called baleen which strain small invertebrates from water, clams and oysters use their gills to trap tiny morsels as cilia sweep food particles to mouth in a film of mucus)
• Ingestion - Substrate Feeders


  Animals that live in or on their food source (e.g. leaf miner caterpillar (larva of a moth) eating through soft tissue of an oak leaf, leaving faeces trail behind, maggots (fly larvae) which burrow into animal carcasses)
• Ingestion - Fluid Feeders


  Suck nutrient-rich fluid from living host (e.g. mosquito pierces human skin with hollow, needle-like mouthparts and consumes blood, aphids feed on the phloem sap of plants)
• Ingestion - Bulk Feeders


  Most animals eat relatively large pieces of food, adaptations to kill prey or tear off pieces of meat or vegetation include tentacles, pincers, claws, fangs, jaws, teeth (e.g. African rock python ingesting a gazelle, snakes swallow prey whole)
• African rock python can spend TWO WEEKS digesting a gazelle
• Digestion


  Food broken down in small molecules that can be absorbed by passing across cell membranes and entering cells. Mechanical digestion (e.g. chewing) breaks food into smaller pieces, increasing surface area for chemical processes. Chemical digestion by enzymes breaks covalent bonds with the addition of water (i.e. enzymatic hydrolysis)
• Digestive compartments


  Evolutionary adaptation = food processed within specialised compartments, Intracellular digestion - hydrolysis of food within cellular organelles called food vacuoles, which fuse with lysosomes containing hydrolytic enzymes, Extracellular digestion - in most animals at least some of the breakdown of food occurs in compartments that are continuous with the outside environment
• Intracellular digestion - Phagocytosis


  Pseudopodia engulf a particle and package it into a vacuole
• Intracellular digestion - Pinocytosis


  Droplets of extracellular fluid are incorporated into the cell in small vesicles
• Paramecium sp. is an example of intracellular digestion in a heterotrophic protozoan
• Extracellular digestion


  Larger amounts of food can be processed than can be ingested by phagocytosis, Animals with simple body plans have digestive sacs with single openings - gastrovascular cavities, They function in both digestion and distribution of nutrients through the body
• The cnidarian Hydra sp. is a good example of extracellular digestion
• Complete digestive tracts


  Digestive tubes extending between two openings, a mouth and an anus, Evolutionary advantage = specialization, Tube organised into specialised regions that carry out digestion and absorption in a stepwise manner