24.9: Key Terms

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24.9: Key Terms

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Glossary Entries

Word(s)	Definition	Image	Caption	Link	Source
absorptive state	also called the fed state; the metabolic state occurring during the first few hours after ingesting food in which the body is digesting food and absorbing the nutrients
acetyl coenzyme A (acetyl CoA)	starting molecule of the Krebs cycle
anabolic hormones	hormones that stimulate the synthesis of new, larger molecules
anabolic reactions	reactions that build smaller molecules into larger molecules
ATP synthase	protein pore complex that creates ATP
basal metabolic rate (BMR)	amount of energy expended by the body at rest
beta (β)-hydroxybutyrate	primary ketone body produced in the body
beta (β)-oxidation	fatty acid oxidation
bile salts	salts that are released from the liver in response to lipid ingestion and surround the insoluble triglycerides to aid in their conversion to monoglycerides and free fatty acids
biosynthesis reactions	reactions that create new molecules, also called anabolic reactions
body mass index (BMI)	relative amount of body weight compared to the overall height; a BMI ranging from 18–24.9 is considered normal weight, 25–29.9 is considered overweight, and greater than 30 is considered obese
calorie	amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C
catabolic hormones	hormones that stimulate the breakdown of larger molecules
catabolic reactions	reactions that break down larger molecules into their constituent parts
cellular respiration	production of ATP from glucose oxidation via glycolysis, the Krebs cycle, and oxidative phosphorylation
cholecystokinin (CCK)	hormone that stimulates the release of pancreatic lipase and the contraction of the gallbladder to release bile salts
chylomicrons	vesicles containing cholesterol and triglycerides that transport lipids out of the intestinal cells and into the lymphatic and circulatory systems
chymotrypsin	pancreatic enzyme that digests protein
chymotrypsinogen	proenzyme that is activated by trypsin into chymotrypsin
citric acid cycle	also called the Krebs cycle or the tricarboxylic acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
conduction	transfer of heat through physical contact
convection	transfer of heat between the skin and air or water
elastase	pancreatic enzyme that digests protein
electron transport chain (ETC)	ATP production pathway in which electrons are passed through a series of oxidation-reduction reactions that forms water and produces a proton gradient
energy-consuming phase	first phase of glycolysis, in which two molecules of ATP are necessary to start the reaction
energy-yielding phase	second phase of glycolysis, during which energy is produced
enterokinase	enzyme located in the wall of the small intestine that activates trypsin
evaporation	transfer of heat that occurs when water changes from a liquid to a gas
FADH2	high-energy molecule needed for glycolysis
fatty acid oxidation	breakdown of fatty acids into smaller chain fatty acids and acetyl CoA
flavin adenine dinucleotide (FAD)	coenzyme used to produce FADH2
glucokinase	cellular enzyme, found in the liver, which converts glucose into glucose-6-phosphate upon uptake into the cell
gluconeogenesis	process of glucose synthesis from pyruvate or other molecules
glucose-6-phosphate	phosphorylated glucose produced in the first step of glycolysis
glycogen	form that glucose assumes when it is stored
glycolysis	series of metabolic reactions that breaks down glucose into pyruvate and produces ATP
hexokinase	cellular enzyme, found in most tissues, that converts glucose into glucose-6-phosphate upon uptake into the cell
hydroxymethylglutaryl CoA (HMG CoA)	molecule created in the first step of the creation of ketone bodies from acetyl CoA
inactive proenzymes	forms in which proteases are stored and released to prevent the inappropriate digestion of the native proteins of the stomach, pancreas, and small intestine
insulin	hormone secreted by the pancreas that stimulates the uptake of glucose into the cells
ketone bodies	alternative source of energy when glucose is limited, created when too much acetyl CoA is created during fatty acid oxidation
Krebs cycle	also called the citric acid cycle or the tricarboxylic acid cycle, converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
lipogenesis	synthesis of lipids that occurs in the liver or adipose tissues
lipolysis	breakdown of triglycerides into glycerol and fatty acids
metabolic rate	amount of energy consumed minus the amount of energy expended by the body
metabolism	sum of all catabolic and anabolic reactions that take place in the body
minerals	inorganic compounds required by the body to ensure proper function of the body
monoglyceride molecules	lipid consisting of a single fatty acid chain attached to a glycerol backbone
monosaccharide	smallest, monomeric sugar molecule
NADH	high-energy molecule needed for glycolysis
nicotinamide adenine dinucleotide (NAD)	coenzyme used to produce NADH
oxidation	loss of an electron
oxidation-reduction reaction	(also, redox reaction) pair of reactions in which an electron is passed from one molecule to another, oxidizing one and reducing the other
oxidative phosphorylation	process that converts high-energy NADH and FADH2 into ATP
pancreatic lipases	enzymes released from the pancreas that digest lipids in the diet
pepsin	enzyme that begins to break down proteins in the stomach
polysaccharides	complex carbohydrates made up of many monosaccharides
postabsorptive state	also called the fasting state; the metabolic state occurring after digestion when food is no longer the body’s source of energy and it must rely on stored glycogen
proteolysis	process of breaking proteins into smaller peptides
pyruvate	three-carbon end product of glycolysis and starting material that is converted into acetyl CoA that enters the Krebs cycle
radiation	transfer of heat via infrared waves
reduction	gaining of an electron
salivary amylase	digestive enzyme that is found in the saliva and begins the digestion of carbohydrates in the mouth
secretin	hormone released in the small intestine to aid in digestion
sodium bicarbonate	anion released into the small intestine to neutralize the pH of the food from the stomach
terminal electron acceptor	oxygen, the recipient of the free hydrogen at the end of the electron transport chain
thermoneutral	external temperature at which the body does not expend any energy for thermoregulation, about 84 °F
thermoregulation	process of regulating the temperature of the body
transamination	transfer of an amine group from one molecule to another as a way to turn nitrogen waste into ammonia so that it can enter the urea cycle
tricarboxylic acid cycle (TCA)	also called the Krebs cycle or the citric acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
triglycerides	lipids, or fats, consisting of three fatty acid chains attached to a glycerol backbone
trypsin	pancreatic enzyme that activates chymotrypsin and digests protein
trypsinogen	proenzyme form of trypsin
urea cycle	process that converts potentially toxic nitrogen waste into urea that can be eliminated through the kidneys
vitamins	organic compounds required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth

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