lesson 2

• Nutrient


  Any substance required for the growth and maintenance of an organism
• Types of organisms based on mode of nutrition


  • Autotrophs
  • Heterotrophs
• Autotrophs

  Organisms that produce their own food
• Heterotrophs


  Organisms that cannot make their own food and obtain their energy from other organisms
• Examples of autotrophs


  • Plants
  • Chemosynthetic bacteria
• Examples of heterotrophs


  • Animals
  • Fungi
• Nutrient requirements of plants


  • Water
  • Carbon dioxide
• Photosynthesis


  The process by which plants convert the energy from sunlight into chemical energy
• Essential nutrients or elements for plants

  • Macronutrients (C,H,O,N,K,Ca,Mg,P,S)
  • Micronutrients (Cl,Fe,B,Mn,Zn,Co,Mo)
• Routes for absorption of water and minerals across plant roots

  • Symplast route (passing through plasmodesmata)
  • Apoplast route (along cell walls)
• The water and minerals from the soil need to reach the conducting tissues of plants, specifically the xylem
• Root hairs


  • Slender extensions of specialized epidermal cells that greatly increase the surface area available for absorption
• Root nodules


  • Localized swellings in roots of certain plants where bacterial cells live symbiotically with the plant. The bacteria help the plant fix nitrogen, and in return, the bacteria are able to utilize some organic compounds provided by the plant.
• Mycorrhizae


  • Symbiotic interaction between a young root and a fungus. The fungus obtains sugars and nitrogen-containing compounds from root cells while the plant is able to get some scarce minerals that the fungus is better able to absorb from the soil.
• Nutritional adaptations by plants


  • Symbiosis of plants and soil microbes
  • Symbiosis of plants and fungi
  • Parasitism
  • Predation
• Calorie


  A unit of energy that indicates the amount of energy contained in food
• The greater the number of Calories in a quantity of food, the greater the energy content
• Calorie


  The amount of heat energy required to raise the temperature of 1 kg (2.2 lb) of water by 1°C
• Nutritional requirements of animals

  • Carbohydrates
  • Proteins
  • Fats
  • Essential nutrients
• Carbohydrates


  Serve as a major energy source for the cells in the body, usually obtained from grains, cereals, breads, fruits, and vegetables, contain 4 Calories per gram
• Proteins


  Can 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, come from dairy products, poultry, fish, meat, and grains, contain 4 Calories per gram
• Fats


  Used to build cell membranes, steroid hormones, and other cellular structures, also used to insulate nervous tissue, and also serve as an energy source, obtained from oils, margarine, butter, fried foods, meat, and processed snack foods, contain about 9 Calories per gram
• Essential nutrients


  • Essential amino acids
  • Essential fatty acids
  • Vitamins
  • Trace elements or minerals
• Essential amino acids


  Needed for synthesis of proteins and enzymes, 8 could not be synthesized by humans (lysine, tryptophan, threonine, methionine, phenylalanine, leucine, isoleucine, and valine)
• Essential fatty acids


  Used for making special membrane lipids, an example is linoleic acid in humans
• Vitamins


  Organic molecules required in small amounts for normal metabolism, include fat-soluble vitamins A, D, E, K, and water-soluble vitamins B, B2, B3, B12, C
• Trace elements or minerals


  Inorganic nutrients needed by the body in minute amounts, form part of enzymes, body tissues, and body fluids, examples include iodine, cobalt, zinc, molybdenum, manganese, selenium
• Types of endocytosis


  • Phagocytosis
  • Pinocytosis
  • Receptor-mediated endocytosis
• Phagocytosis


  Engulfment of organic fragments or big particles, e.g. Pseudopod formation in Amoeba
• Pinocytosis


  Uptake of extracellular fluid by a cell using small vesicles derived from the plasma membrane
• Receptor-mediated endocytosis


  Relies on membrane receptor recognition of specific solutes which are then taken up by the cell via receptor-coated pits
• Types of animals based on feeding mechanisms

  • Substrate-feeders
  • Filter-feeders
  • Fluid-feeders
  • Bulk-feeders
• Substrate-feeders


  Animals that live in or on their food source, e.g. earthworms that feed through the soil where they live in, caterpillars that eat through the leaves where they live on
• Filter-feeders


  Many aquatic animals which draw in water and strain small organisms and food particles present in the medium, e.g. whales and coelenterates
• Fluid-feeders


  Suck fluids containing nutrients from a living host, e.g. mosquitoes, leeches, head lice, aphids
• 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, e.g. snakes, cats, man
• Types of digestive compartments in animals

  • Food vacuoles in unicellular organisms
  • Gastrovascular cavity or incomplete digestive system
  • Complete digestive system
• Food vacuoles in unicellular organisms

  Fuse with lysosomes that contain hydrolytic enzymes, e.g. food vacuole in a protozoan like Paramecium
• Gastrovascular cavity or incomplete digestive system


  Composed of a single opening through which food is taken in and where wastes are disposed of, a saclike body cavity, e.g. in the cnidarian Hydra and in flatworm Planaria
• 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), specialized organs in between that carry out transport, processing, and absorption of digested nutrients