Definitions and Background

• A bolus of food is a ball-like mixture of food and saliva that forms in the mouth during the process of chewing.
• Hydrolysis is the breaking of a chemical bond between two molecules by the addition of a water molecule.
• Digestion: breaking down to smaller molecules, small enough for absorption.
• Absorption: passage of the digested nutrients through the mucous membrane into the blood and lymph
• Peristaltic waves are contractions of the circular muscle of the intestinal wall.
• Enzymes are sometimes secreted in pre-cursor forms. A pre-cursor enzyme is an enzyme that is not fully active.
• A microbiome is the community of microorganisms that live within a stomach.
• Mastication is the act of chewing or grinding food.
• Complex carbohydrates are made up of many monosaccharides joined together.
• A VFA ratio is is the ratio of volatile fatty acids within the food.
• A volatile fatty acid is a fatty acid that can be readily changed from one form to another.
• Microvilli in the small intestine increase the surface area for absorption. They are small brush-like structures made of epithelial cells.
• Passive absorption is when nutrients are absorbed from the GI tract into the bloodstream and uses no energy.
• Active absorption is when nutrients are absorbed from the GI tract into the bloodstream while using energy.
• Facilitative transport is where carriers transport molecules down the concentration gradient.
• Pinocytosis: the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.
• Oligopeptides are peptides with 3-10 amino acids.
• Foregut fermentation occurs in the rumen of ruminants and is anaerobic fermentation, meaning it does not require oxygen.
• Hindgut fermentation occurs in the caecum or colon of monogastric animals, and is anaerobic meaning no oxygen is required.
• A ruminant has four chambers in their stomach named the rumen, reticulum, omasum, and abomasum.
• A monogastric animal has a one-chambered stomach.
• Metabolism: fate of digested and absorbed nutrients.
• Catabolic reactions are reactions that break down molecules into smaller molecules.
• Anabolic reactions are reactions that build up molecules from simpler ones.
• The absorptive state is the period shortly following a meal, when nutrients are being absorbed from gastrointestinal tract.
• The postabsorptive state is the period during which there is no net absorption.
• Insulin is a hormone which lowers the blood glucose levels on an animal.
• Glycogen is a form of stored glucose which is used to increase the blood glucose level of an animal.
• Essential amino acids are not produced by the body and must be obtained from the diet.
• Non-essential amino acids are produced by the body.
• The non-glucogenic metabolic pathway is the anabolic absorption pathway that does not produce glucose.
• The gluconeogenesis metabolic pathway is the anabolic absorption pathway which creates glucose.
• Triglycerides are a type of lipid that is a mixture of three fatty acids and one glycerol.
• Lipoproteins are a mixture of cholesterol and fatty acids.
• Chylomicrons are the largest lipoproteins and are transported from the liver to the small intestine.
• Very low density lipoproteins (VLDLs) are transported to the liver and are broken down into cholesterol and bile salts.
• Lipase action is the act of breaking down lipids into fatty acids and glycerol.
• Cholesterol is a lipid that is found in the cell membrane.
• Glycogenolysis is the breakdown of glycogen into glucose.
• Adipose tissues are found in the body and are made up of fat cells.