50.Nutrition, Digestion, and Absorption

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  • Created on: 26-05-21 16:40
Define a Kilocalorie (kcal)
The amount of heat required to raise the temperature of 1 gram of water by 1ºC. Physiologists commonly use the kilocalorie (kcal) as a unit of measure (1 kcal = 1,000 calories). Nutritionists also use the kilocalorie, but refer to it as the Calorie (Cal,
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Define a Heterotroph
An organism that requires preformed organic molecules as food. (Contrast with autotroph.)
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Define an Autotroph
An organism that is capable of living exclusively on inorganic materials, water, and some energy source such as sunlight (photoautotrophs) or chemically reduced matter (see chemoautotrophs). (Contrast with heterotroph.)
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Define an Energy Budget
A quantitative description of all paths of energy exchange between an animal and its environment.
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Define Carbon Skeleton
The chains or rings of carbon atoms that form the structural basis of organic molecules. Other atoms or functional groups are attached to the carbon atoms.
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Define an essential amino acid
Amino acids that an animal cannot synthesize for itself and must obtain from its food.
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Define a complementary diet
A mixture of foods that supplies all essential nutrients.
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Define an Essential Fatty Acid
Fatty acids that an animal cannot synthesize for itself and must obtain from its food.
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Define a Macronutrient
In plants, a mineral element required in concentrations of at least 1 milligram per gram of plant dry matter; in animals, a mineral element required in large amounts. (Contrast with micronutrient.)
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Define a Micronutrient
In plants, a mineral element required in concentrations of less than 100 micrograms per gram of plant dry matter; in animals, a mineral element required in concentrations of less than 100 micrograms per day. (Contrast with macronutrient.)
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Define an Malnutrition
A condition caused by lack of any essential nutrient.
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Define a Deficiency Disease
A condition (e.g., scurvy and beriberi) caused by chronic lack of any essential nutrient.
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Define a Saprobe
An organism (usually a bacterium or fungus) that obtains its carbon and energy by absorbing nutrients from dead organic matter. Also called a saprotroph.
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Define a Detritivores/Decompser
An organism that obtains its energy from the dead bodies or waste products (detritus) of other organisms, releasing nutrients and energy. (Contrast with carnivore, herbivore, omnivore.)
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Define a Predator
An organism that kills and/or consumes individuals (or parts of individuals) of another species (its prey).
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Define a FIlter Feeder
An organism that feeds on organisms much smaller than itself that are suspended in water or air by means of a straining device. Also called suspension feeder.
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Define a Fluid Feeder
An animal that feeds on fluids it extracts from the bodies of other organisms; examples include nectar-feeding birds and bloodsucking insects.
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Define an Enamel
The hard material, composed primarily of calcium phosphate, that covers the tooth.
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Define a Dentine
The layer of dense bony material beneath the enamel of the tooth.
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Define a Gastrovascular Cavity
Serving for both digestion (gastro) and circulation (vascular); in particular, the central cavity of the body of jellyfish and other cnidarians.
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Define a Gastrointestinal System/Gut
An animal’s digestive tract.
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Define an Anus
An opening through which solid digestive wastes are expelled, located at the posterior end of a tubular gut.
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Define a Mandible
A crushing part of arthropod mouth parts, in mammals, the lower jaw bone, in birds the upper or lower part of the beak.
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Define a Radula
A rasplike structure used for scraping food particles off a surface.
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Define a Gizzard
The second of two stomachlike organs in birds, other reptiles, earthworms, and various insects, that grinds up food, sometimes with the aid of fragments of stone. (See also crop.)
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Define a stomach
An organ that physically (and sometimes enzymatically) breaks down food, preparing it for digestion in the midgut.
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Define a crop
A simple food storage sac, the first of two stomachlike organs in many animals (including reptiles, earthworms, and various insects). (See also gizzard.)
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Define an Intestine
The portion of the gut following the stomach, in which most digestion and absorption occurs.
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Define a Rectum
The terminal portion of the gut, ending at the anus.
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Define Villi
Hairlike projections from a membrane; for example, from many gut walls.
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Define a Microvilli
Projections of epithelial cells, such as the cells lining the small intestine, that increase their surface area.
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Define a Protease
Digestive enzymes that break the bonds between adjacent amino acids in proteins.
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Define a Carbohydrase
Digestive enzymes that hydrolyze carbohydrates.
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Define a Peptidase
Digestive enzymes that break down peptides.
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Define a Lipase
Digestive enzymes that break down fats.
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Define a Nuclease
Digestive enzymes that break down nucleic acids.
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Define a Microbiota
The diverse communities of bacteria that live on or within the body.
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Define a Microbiome
The diverse community of bacteria that lives on or within the body of an organism and is essential to bodily function.
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Define Mucosa
The first layer of the gut that lines the luminal surface.
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Define Lumen
The open cavity inside any tubular organ or structure, such as the gut or a renal tubule.
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Define Submucosa
The tissue layer just under the epithelial lining of the lumen of the digestive tract.
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Define an Enteric Nervous System
The nerve nets in the submucosa and between the smooth muscle layers of the vertebrate gut.
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Define Peritoneum
The mesodermal lining of the body cavity in coelomate animals.
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Define Esophagus
That part of the gut between the pharynx and the stomach.
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Define Epiglottis
The flap of tissue that covers the entrance of the larynx to prevent food and liquid from entering the trachea.
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Define Peristalisis
Wavelike muscular contractions proceeding along a tubular organ, propelling the contents along the tube.
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Define a Sphincter
A ring of muscle that can close an orifice, for example, at the anus.
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Define a Gastric pit
Deep infoldings in the walls of the stomach lined with secretory cells.
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Define a Parietal Cell
One of three types of secretory cell found in the gastric pits of the stomach wall. Parietal cells produce hydrochloric acid (HCl), creating an acidic environment that destroys many of the harmful microorganisms ingested with food. (See chief cells.)
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Define a Chief Cell
One of three types of secretory cell found in the gastric pits of the stomach wall. Chief cells secrete the protein-digesting enzyme pepsin. (See parietal cells.)
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Define Autocatalysis
A positive feedback process in which an activated enzyme acts on other inactive molecules of the same enzyme to activate them.
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Define Chyme
Created in the stomach; a mixture of ingested food with the digestive juices secreted by the salivary glands and the stomach lining.
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Define a Small Intestine
The portion of the gut between the stomach and the colon; consists of the duodenum, the jejunum, and the ileum.
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Define a Duodenum
The beginning portion of the vertebrate small intestine. (See also ileum, jejunum.)
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Define a Jejunum
The middle division of the small intestine, where most absorption of nutrients occurs. (See also duodenum, ileum.)
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Define an Ileum
The final segment of the small intestine. (See also duodenum, jejunum.)
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Define Bile
A secretion of the liver made up of bile salts synthesized from cholesterol, various phospholipids, and bilirubin (the breakdown product of hemoglobin). Emulsifies fats in the small intestine.
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Define Gallbladder
In the human digestive system, an organ in which bile is stored.
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Define a Cholecystokinin (CCK)
A hormone produced and released by the lining of the duodenum when it is stimulated by undigested fats and proteins. It stimulates the gallbladder to release bile and slows stomach activity.
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Define a Micelle
A particle of lipid covered with bile salts that is produced in the duodenum and facilitates digestion and absorption of lipids.
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Define a Pancreas
A gland located near the stomach of vertebrates that secretes digestive enzymes into the small intestine and releases insulin into the bloodstream.
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Define Zymogens
The inactive precursor of a digestive enzyme; secreted into the lumen of the gut, where a protease cleaves it to form the active enzyme.
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Define Trypsin
A protein-digesting enzyme. Secreted by the pancreas in its inactive form (trypsinogen), it becomes active in the duodenum of the small intestine.
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Define solvent drag
Transport mechanism in which solutes move across a tissue layer through intercellular spaces by a flow of water (solvent).
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Define Chylomicrons
Particles of lipid coated with protein, produced in the gut from dietary fats and secreted into the extracellular fluids.
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Define a Lacteal
The smallest vessels of the lymphatic system.
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Define a Hepatic Portal Vein
The vein that begins in capillary beds in the gut and ends in capillary beds in the liver.
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Define a Colon
The portion of the gut between the small intestine and the anus. Also called the large intestine.
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Define a Ruminant
Herbivorous, cud-chewing mammals such as cows or sheep, characterized by a stomach that consists of four compartments: the rumen, reticulum, omasum, and abomasum.
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Define Rumen
The first of the four chambers of the ruminant stomach. Along with the reticulum, it is where food is partially digested with the assistance of gut bacteria.
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Define Reticulum
The second of the four chambers of the ruminant stomach. Along with the rumen, it is where food is partially digested with the assistance of gut bacteria.
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Define Omasum
The third of the four chambers of the stomach in ruminants; concentrates food by water absorption before it enters the true stomach (abomasum).
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Define Abomasum
The fourth of the four chambers of the stomach in ruminants; the true stomach.
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Define Cecum
A blind branch off the large intestine. In many nonruminant mammals, the cecum contains a colony of microorganisms that contribute to the digestion of food.
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Define Coprophagy
The consumption of feces.
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Define Appendix
A small blind-end sac that is attached to the initial segment of the colon.
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Define Secretin
A peptide hormone secreted by the upper region of the small intestine when acidic chyme is present. Stimulates the pancreatic duct to secrete bicarbonate ions.
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Define Absorptive
State in which food is in the gut and nutrients are being absorbed. (Contrast with postabsorptive state.)
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Define Postabsorptive State
State in which no food remains in the gut and thus no nutrients are being absorbed. (Contrast with absorptive state.)
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Define Lipoprotein
Lipids packaged inside a covering of protein so that they can be circulated in the blood.
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Define High-density lipoproteins (HDLs)
Lipoproteins that remove cholesterol from tissues and carry it to the liver; HDLs are the “good” lipoproteins associated with good cardiovascular health.
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Define Low-density lipoproteins (LDLs)
Lipoproteins that transport cholesterol around the body for use in biosynthesis and for storage; LDLs are the “bad” lipoproteins associated with a high risk of cardiovascular disease.
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Define Very low-density lipoproteins (VLDLs)
Lipoproteins that consist mainly of triglyceride fats, which they transport to fat cells in adipose tissues throughout the body; associated with excessive fat deposition and high risk for cardiovascular disease.
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Define Insulin
A hormone synthesized in islet cells of the pancreas that promotes the conversion of glucose into the storage material, glycogen.
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Define Glucagon
Hormone produced by alpha cells of the pancreatic islets of Langerhans. Glucagon stimulates the liver to break down glycogen and release glucose into the circulation.
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Define Arcuate Nucleus
A group of neurons in the hypothalamus that produce and secrete many neuroendocrines and are involved in regulation of appetite.
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Define Leptin
A hormone produced by fat cells that is believed to provide feedback information to the brain about the status of the body’s fat reserves.
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Define Ghrelin
A hormone produced and secreted by cells in the stomach that stimulates appetite.
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Card 2

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Define a Heterotroph

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An organism that requires preformed organic molecules as food. (Contrast with autotroph.)

Card 3

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Define an Autotroph

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Card 4

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Define an Energy Budget

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Card 5

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Define Carbon Skeleton

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