2.4 - nutrition

• Absorption


  The movement of useful substances into the bloodstream
• Amylase

  An enzyme found in saliva and pancreatic juice that hydrolyses starch to maltose
• Anus


  The opening at the far end of the gut that controls egestion
• Assimilation


  The synthesis of biological compounds from absorbed simpler molecules
• Autotrophic


  Describes an organism that produces its own food. Autotrophs manufacture complex organic compounds from simpler inorganic molecules such as water and carbon dioxide. There are two types of autotrophic organisms: photoautotrophic and chemoautotrophic.
• Bile


  A fluid produced by the liver that is stored in the gall bladder and secreted, via the bile duct, into the duodenum. It consists of bile salts and an alkaline fluid that neutralises stomach acid, providing an ideal pH for lipase.
• Bile salts


  A component of bile that emulsifies lipid globules, increasing the surface area for lipase action
• Buccal cavity


  The oral cavity through which food enters the body. Mechanical digestion and chemical digestion of starch takes place here.
• Carnassials


  Modified pre-molars and molars, found in carnivores, with sharpened edges for shearing flesh
• Carnivores


  Animals that prey on and eat other animals. They have many adaptations to a high protein diet including a short gut, powerful jaw muscles and specialised dentition.
• Chemical digestion


  A type of digestion that involves breaking down large, insoluble molecules into smaller, soluble molecules using enzymes
• Chemoautotrophic


  Describes an organism which obtains its nutrition through inorganic molecules, such as sulfur, in the absence of light
• Colon


  The long, coiled organ (known as the large intestine) that is the final section of the digestive system. It reabsorbs water and minerals from the waste material.
• Diastema


  A gap between the incisors and premolars in a herbivore that separates fresh grass from the cud and enables the manipulation of food by the tongue
• Digestion


  The processes by which large, insoluble molecules are broken down into smaller, soluble molecules that can be absorbed across cell membranes
• Duodenum


  The first section of the small intestine where proteins and lipids are hydrolysed
• Ectoparasites


  Parasites that live on the host e.g. Pediculus
• Egestion


  The removal of undigested waste material from the body
• Endoparasites


  Parasites that live in the host e.g. Taenia
• Endopeptidases


  Enzymes found in gastric and pancreatic juices that hydrolyse non-terminal peptide bonds within a protein to form smaller peptides e.g. pepsin, trypsin
• Enterokinase


  An enzyme secreted by cells of the duodenum that converts inactive trypsinogen into active trypsin
• Epithelium


  A single layer of cells that line the gut wall
• Exopeptidases


  Enzymes produced in the pancreas and secreted into the duodenum that hydrolyse the terminal peptide bonds of a protein to form dipeptides and amino acids
• Gastric glands


  Glands of the stomach that secrete endopeptidases, hydrochloric acid and an alkaline mucus
• Gut


  A long, hollow, muscular tube where digestion and absorption takes place
• Herbivores


  Animals that eat plants. They have many adaptations to a high protein diet including a long gut, loose articulation of the lower jaw and specialised dentition for grinding tough plant material.
• Heterotrophic


  Describes an organism that cannot produce its own food. It obtains energy by feeding on organic compounds produced by other organisms.
• Holozoic


  Describes a heterotrophic organism that internally digests food substances. Holozoic nutrition involves ingestion, digestion, absorption, assimilation and egestion.
• Ileum


  The second section of the small intestine that serves as the main site of absorption of the products of digestion
• Ingestion


  The process by which organisms take food into their bodies
• Intestinal glands


  Glands in the wall of the duodenum that secrete digestive enzymes and alkaline fluid
• Intracellular digestion


  A type of digestion that takes place in the cytoplasm of unicellular organisms such as Amoeba
• Lactase


  An enzyme located on the epithelial cell membranes of the small intestine that hydrolyses lactose to glucose and galactose
• Lacteals


  Lymphatic vessels that absorb fatty acids and glycerol from the small intestine
• Lipase


  An enzyme found in pancreatic juice that hydrolyses triglycerides to fatty acids and glycerol
• Liver


  An organ that secretes bile into the small intestine via the gall bladder and bile duct
• Maltase


  An enzyme located on the epithelial cell membranes of the small intestine that hydrolyses maltose to α-glucose
• Mechanical digestion


  A type of digestion that involves physically breaking down food material into smaller pieces. This increases the total surface area for chemical digestion.
• Microvilli


  Protrusions of the epithelial cell membrane that provide a large surface area for absorption in the ileum
• Mucosa


  The mucous membrane lining the gut wall. It contains glands that secrete digestive enzymes, mucus, and an acid or alkaline liquid that provides an optimum pH.