Download Glossary Protein

Glossary
Protein
acidosis above-normal acidity in the blood and body fluids.
acids compounds that release hydrogen ions in a solution.
acute PEM protein-energy malnutrition caused by recent severe food restriction; characterized
in children by thinness for height (wasting).
alkalosis above-normal alkalinity (base) in the blood and body fluids.
amino acid pool the supply of amino acids derived from either food proteins or body proteins
that collect in the cells and circulating blood and stand ready to be incorporated in proteins
and other compounds or used for energy.
amino acids building blocks of proteins. Each contains an amino group, an acid group, a
hydrogen atom, and a distinctive side group, all attached to a central carbon atom.
antibodies large proteins of the blood and body fluids, produced by the immune system in
response to the invasion of the body by foreign molecules (usually proteins called antigens).
antigens substances that elicit the formation of antibodies or an inflammation reaction from the
immune system.
bases compounds that accept hydrogen ions in a solution.
branched-chain amino acids the essential amino acids leucine, isoleucine, and valine, which
are present in large amounts in skeletal muscle tissue; falsely promoted as fuel for exercising
muscles.
chronic PEM protein-energy malnutrition caused by long-term food deprivation; characterized
in children by short height for age (stunting).
collagen the protein from which connective tissues such as scars, tendons, ligaments, and the
foundations of bones and teeth are made.
complementary proteins two or more dietary proteins whose amino acid assortments
complement each other in such a way that the essential amino acids missing from one are
supplied by the other.
conditionally essential amino acid an amino acid that is normally nonessential, but must be
supplied by the diet in special circumstances when the need for it exceeds the body’s ability to
produce it.
deamination removal of the amino (NH2) group from a compound such as an amino acid.
denaturation the change in a protein’s shape and consequent loss of its function brought about
by heat, agitation, acid, base, alcohol, heavy metals, or other agents.
dipeptide two amino acids bonded together.
dysentery an infection of the digestive tract that causes diarrhea.
edema the swelling of body tissue caused by excessive amounts of fluid in the interstitial spaces;
seen in protein deficiency (among other conditions).
enzymes proteins that facilitate chemical reactions without being changed in the process;
protein catalysts.
essential amino acids amino acids that the body cannot synthesize in amounts sufficient to
meet physiological needs.
fluid balance maintenance of the proper types and amounts of fluid in each compartment of
the body fluids.
gene expression the process by which a cell converts the genetic code into RNA and protein.
hemoglobin the globular protein of the red blood cells that carries oxygen from the lungs to the
cells throughout the body.
high-quality proteins dietary proteins containing all the essential amino acids in relatively the
same amounts that human beings require. They may also contain nonessential amino acids.
immunity the body’s ability to defend itself against diseases.
kwashiorkor a form of PEM that results either from inadequate protein intake or, more
commonly, from infections.
limiting amino acid the essential amino acid found in the shortest supply relative to the amounts
needed for protein synthesis in the body.
marasmus a form of PEM that results from a severe deprivation, or impaired absorption, of
energy, protein, vitamins, and minerals.
matrix the basic substance that gives form to a developing structure; in the body, the formative
cells from which teeth and bones grow.
neurotransmitters chemicals that are released at the end of a nerve cell when a nerve impulse
arrives there. They diffuse across the gap to the next cell and alter the membrane of that
second cell to either inhibit or excite it.
nitrogen balance the amount of nitrogen consumed (N in) as compared with the amount of
nitrogen excreted (N out) in a given period of time.
nonessential amino acids amino acids that the body can synthesize.
pepsin a gastric enzyme that hydrolyzes protein.
peptidase a digestive enzyme that hydrolyzes peptide bonds.
peptide bond a bond that connects the acid end of one amino acid with the amino end of
another, forming a link in a protein chain.
polypeptide many (ten or more) amino acids bonded together.
proteases enzymes that hydrolyze protein.
protein digestibility a measure of the amount of amino acids absorbed from a given protein
intake.
protein turnover the degradation and synthesis of protein.
protein-energy malnutrition a deficiency of protein, energy, or both, including kwashiorkor,
marasmus, and instances in which they overlap.
proteins compounds composed of carbon, hydrogen, oxygen, and nitrogen atoms, arranged
into amino acids linked in a chain.
reference protein a standard against which to measure the quality of other proteins.
sickle-cell anemia a hereditary form of anemia characterized by abnormal sickle- or crescentshaped red blood cells.
tripeptide three amino acids bonded together.
whey protein a by-product of cheese production; falsely promoted as increasing muscle mass.
It is the watery part of milk that separates from the curds.
Metabolism of Energy Nutrients
acetyl CoA a 2-carbon compound (acetate, or acetic acid) to which a molecule of
CoA is attached.
adenosine triphosphate a common high-energy compound composed of a purine
(adenine), a sugar (ribose), and three phosphate groups.
aerobic requiring oxygen.
ammonia a compound with the chemical formula NH3; produced during the
deamination of amino acids.
anabolism reactions in which small molecules are put together to build larger ones.
anaerobic not requiring oxygen.
catabolism reactions in which large molecules are broken down to smaller ones.
CoA coenzyme A; the coenzyme derived from the B vitamin pantothenic acid and
central to energy metabolism.
coenzymes complex organic molecules that work with enzymes to facilitate the
enzymes’ activity.
Cori cycle the path from muscle glycogen to glucose to pyruvate to lactate (which
travels to the liver) to glucose (which can travel back to the muscle) to glycogen;
named after the scientist who elucidated this pathway.
coupled reactions pairs of chemical reactions in which some of the energy released
from the breakdown of one compound is used to create a bond in the formation of
another compound.
electron transport chain the final pathway in energy metabolism that transports
electrons from hydrogen to oxygen and captures the energy released in the bonds of
ATP.
fatty acid oxidation the metabolic breakdown of fatty acids to acetyl CoA; also called
beta oxidation.
fuel compounds that cells can use for energy.
glycolysis the metabolic breakdown of glucose to pyruvate.
keto acid an organic acid that contains a carbonyl group (C=O).
lactate a 3-carbon compound produced from pyruvate during anaerobic metabolism.
metabolism the sum total of all the chemical reactions that go on in living cells.
mitochondria the cellular organelles responsible for producing ATP; made of
membranes (lipid and protein) with enzymes mounted on them.
oxaloacetate a carbohydrate intermediate of the TCA cycle.
photosynthesis the process by which green plants use the sun’s energy to make
carbohydrates from carbon dioxide and water.
pyruvate a 3-carbon compound that plays a key role in energy metabolism.
transamination the transfer of an amino group from one amino acid to a keto acid,
producing a new nonessential amino acid and a new keto acid.
tricarboxylic acid cycle a series of metabolic reactions that break down molecules of
acetyl CoA to carbon dioxide and hydrogen atoms; also called the Kreb’s cycle after
the biochemist who elucidated its reactions.
urea the principal nitrogen-excretion product of protein metabolism. Two ammonia
fragments are combined with carbon dioxide to form this compound.
Energy Balance & Body Composition
adaptive thermogenesis adjustments in energy expenditure related to changes in
environment such as extreme cold and to physiological events such as overfeeding,
trauma, and changes in hormone status.
appetite the integrated response to the sight, smell, thought, or taste of food that
initiates or delays eating.
basal metabolic rate the rate of energy use for metabolism under specified conditions:
after a 12-hour fast and restful sleep, without any physical activity or emotional
excitement, and in a comfortable setting. It is usually expressed as kcalories per
kilogram body weight per hour.
basal metabolism the energy needed to maintain life when a body is at complete
digestive, physical, and emotional rest.
body composition the proportions of muscle, bone, fat, and other tissue that make up a
person’s total body weight.
body mass index an index of a person’s weight in relation to height; determined by
dividing the weight (in kilograms) by the square of the height (in meters).
bomb calorimeter an instrument that measures the heat energy released when foods
are burned, thus providing an estimate of the potential energy of the foods.
central obesity excess fat around the trunk of the body; also called abdominal fat or
upper-body fat.
diet-induced thermogenesis the sum of the TEF and any increase in the metabolic rate
due to overeating.
hunger the painful sensation caused by a lack of food that initiates food-seeking
behavior.
hypothalamus a brain center that controls activities such as maintenance of water
balance, regulation of body temperature, and control of appetite.
inflammation an immunological response to cellular injury characterized by an increase
in white blood cells.
insulin resistance the condition in which a normal amount of insulin produces a
subnormal effect in muscle, adipose, and liver cells, resulting in an elevated fasting
glucose; a metabolic consequence of obesity that precedes type 2 diabetes.
intra-abdominal fat fat stored within the abdominal cavity in association with the
internal abdominal organs, as opposed to the fat stored directly under the skin
(subcutaneous fat).
lean body mass the body minus its fat content.
neuropeptide Y a chemical produced in the brain that stimulates appetite, diminishes
energy expenditure, and increases fat storage.
obese overweight with adverse health effects; BMI 30 or higher.
overweight body weight above some standard of acceptable weight that is usually
defined in relation to height (such as BMI); BMI 25 to 29.9.
resting metabolic rate similar to the basal metabolic rate (BMR), a measure of the
energy use of a person at rest in a comfortable setting, but with less stringent criteria for
recent food intake and physical activity.
satiating having the power to suppress hunger and inhibit eating.
satiation the feeling of satisfaction and fullness that occurs during a meal and halts
eating.
satiety the feeling of fullness and satisfaction that occurs after a meal and inhibits
eating until the next meal.
thermic effect of food an estimation of the energy required to process food (digest,
absorb, transport, metabolize, and store ingested nutrients); also called the specific
dynamic effect (SDE) of food or the specific dynamic activity (SDA) of food.
thermogenesis the generation of heat; used in physiology and nutrition studies as an
index of how much energy the body is expending.
underweight body weight below some standard of acceptable weight that is usually
defined in relation to height (such as BMI); BMI below 18.5.
waist circumference an anthropometric measurement used to assess a person’s
abdominal fat.