Key Terms Chapter 24: Metabolism and Nutrition

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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 FADH₂into 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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