A&P 24: Nutrition, Metabolism, & Body Temperature Regulation Flashcards
ATP
the chemical energy form used by cells
Kilocalories (kcal) or C
the energy value of foods is measured in this unit
Nutrient
substance in food the body uses to promote normal growth, maintenance, and repair
Major nutrients
carbohydrates, lipids, and proteins; bulk of what we eat
Healthy Eating Pyramid
food pyramid put out in 1992 by Walter Willett; 6 major food groups, subdivides some further
MyPlate
food guide (2011) by USDA using a round dinner plate as a symbol; shows food categories in healthy proportions as sections on the plate
Essential nutrients
at least 45 & possibly 50 molecules cannot be made fast enough to meet the body’s needs, so our diet must provide them
Glucose
monosaccharide; THE carbohydrate molecule ultimately used as fuel by body cells to produce ATP
Complete proteins
proteins in eggs, milk, fish, and most meats; meet all the body’s amino acid requirements for tissue maintenance and growth
Nitrogen balance
homeostatic state in healthy adults in which the rate of protein synthesis equals the rate of protein breakdown and loss
Vitamins
potent organic compounds needed in minute amounts for growth and good health
Coenzymes
most vitamins function as ___, which act with an enzyme to accomplish a particular chemical task
Water-soluble vitamins
B-complex vitamins (except B12) and vitamin C; absorbed along with water from the GI tract
Fat-soluble vitamins
vitamins A, D, E, & K; bind to ingested lipids and are absorbed along with their digestion products; anything that interferes with fat absorption also interferes with the uptake of fat-soluble vitamins
Minerals
the body requires moderate amounts of 7 of these (calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium) and trace amounts of about a dozen others; make up about 4% of the body by weight, with calcium and phosphorus (as bone salts) accounting for 3/4 of this amount
Metabolism
collective term for a variety of biochemical reactions
Anabolism
general term for all reactions that build larger molecules or structures from smaller ones, such as bonding amino acids to build proteins
Catabolism
all processes that break down complex structures to simpler ones, like the hydrolysis of foods in the digestive tract
Cellular respiration
group of catabolic reactions in which food fuels, particularly glucose, are broken down in cells and some of the energy released is captured to form ATP
Phosphorylated
when an enzyme shifts its high-energy phosphate groups to other molecules; primes a molecule to change in a way that increases its activity, produces motion, or does work
Oxidation reactions
many of the reactions that take place within cells; gain of oxygen or the loss of a hydrogen
Oxidation-reduction (redox) reactions
whenever one substance loses electrons (is oxidized), another substance gains them (is reduced)
Dehydrogenases
enzymes that catalyze redox reactions in which hydrogen atoms are removed
Oxidases
enzymes catalyzing the transfer of oxygen
Nicotinamide adenine dinucleotide (NAD+)
important coenzyme of the oxidative pathways, based on niacin
Flavin adenine dinucleotide (FAD)
important coenzyme of the oxidative pathways, based on riboflavin
Substrate-level phosphorylation
occurs when high-energy phosphate groups are transferred directly from phosphorylated substrates (metabolic intermediates such as glyceraldehyde 3-phosphate) to ADP
Oxidative phosphorylation
complicated process; releases most of the energy that is eventually captured in ATP bonds during cellular respiration; carried out by electron transport proteins forming part of the inner mitochondrial membranes; chemiosmotic
Chemiosmotic processes
processes that couple the movement of substances across membranes to chemical reactions
Glycolysis
“sugar splitting”; occurs in the cytosol of cells; series of 10 chemical steps; converts glucose to 2 pyruvic acid molecules; all steps are reversible except the 1st
Pyruvic acid
final products of glycolysis = 2 molecules of this and 2 molecules of reduced NAD+ (NADH & H+)
Lactic acid
addition of 2 hydrogen atoms to pyruvic acid yields this
Aerobic pathways
when oxygen is again available, lactic acid is oxidized back to pyruvic acid and enters this pathway, and is completely oxidized to water and CO2
Krebs Cycle
stage of glucose oxidation after glycolysis; occurs in the mitochondrial matrix; fueled largely by pyruvic acid produced during glycolysis and by fatty acids resulting from fat breakdown
Transitional phase
converts pyruvic acid to acetyl coA; 3-step process: decarboxylation, oxidation, and formation of acetyl coA
Decarboxylation
one of pyruvic acid’s carbons is removed and released as carbon dioxide gas
Acetyl Coenzyme A (acetyl coA)
acetic acid is combined with coenzyme A to produce this reactive final product
Oxaloacetic acid
coenzyme A shuttles the 2-carbon acetic acid to an enzyme that condenses with this 4-carbon acid to produce the 6-carbon acid, citric acid
Citric acid
6-carbon acid produced from oxaloacetic acid
Citric Acid Cycle
because citric acid is the 1st substrate of the cycle, biochemists prefer to call the Krebs cycle this
Keto acids
As the Krebs cycle moves through its 8 successive steps, the atoms of citric acid are rearranged to produce different intermediate molecules, most called __ ___
Electron transport chain
aerobic process carrying out the final catabolic reactions that occur on the mitochondrial cristae
Flavins
proteins containing flavin mononucleotide (FMN) derived from the vitamin riboflavin
Cytochromes
brightly-colored iron-containing pigments
Respiratory enzyme complexes
neighboring carriers are clustered together to form 4 of these that are alternately reduced and oxidized as they pick up electrons and pass them on to the next complex in the sequence
Electrochemical proton (H+) gradient
a gradient that has potential energy and the capacity to do work
ATP synthases
large enzyme-protein complexes (complex V); populate the inner mitochondrial membrane
Glycogenesis
process of high ATP levels “turning off” glycolysis and glucose molecules combining in long chains to form glycogen
Glycogenolysis
when blood glucose levels drop, glycogen lysis/splitting occurs
Gluconeogenesis
process of forming new glucose from noncarbohydrate molecules; occurs in the liver; takes place when dietary sources and glucose reserves have been used up and blood glucose levels are beginning to drop
Beta oxidation
initial phase of fatty acid oxidation; occurs in the mitochondria
Lipogenesis
triglyceride synthesis; occurs when cellular ATP and glucose levels are high
Lipolysis
breakdown of stored fats into glycerol and fatty acids; lipogenesis in reverse
Ketogenesis
process in which the liver converts acetyl coA molecules to ketone bodies (ketones)
Ketone bodies (ketones)
acetoacetic acid, B-hydroxybutyric acid, and acetone
Ammonia
NH3; in the liver, the amine group of glutamic acid is removed as this compound
Urea
main nitrogen-containing waste excreted in urine
Urea cycle
cycle that rids the body of NH3 produced during oxidative deamination and bloodborne NH3 produced by intestinal bacteria
Nutrient pools
stores of amino acids, carbs, and fats; body draws on these to meet its varying needs; interconvertible because the pathways are linked by key intermediates
Amino acid pool
body’s total supply of free amino acids
Carbohydrate & fat pools
fats & carbs are oxidized directly to produce cellular energy; excess fats & carbs can be stored as such
Hypoglycemic hormone
insulin is this type of hormone; lowers blood glucose levels
Glucose sparing
the increased use of noncarb fuel molecules (especially triglycerides) to conserve glucose
Glucagon
insulin antagonist
Hyperglycemic hormone
glucagon is this type of hormone; raises blood glucose levels
Cholesterol
structural basis of bile salts, steroid hormones, and vitamin D; major component of plasma membranes
Lipoproteins
small lipid-protein complexes; transports triglycerides and cholesterol to and from tissue cells (bound to them)
Very Low Density Lipoproteins (VLDLs)
lowest density of lipids
Low Density Lipoproteins (LDLs)
mid-density of lipids
High-Density Lipoproteins (HDLs)
greatest proportion of proteins
Trans fats
“healthy” oils that have been hardened by hydrogenation to make them more solid (margarines); have a worse effect on blood cholesterol levels than saturated fats do; spark a greater increase in LDLs and a greater reduction in HDLs, producing the unhealthiest ratio of total cholesterol to HDL
Energy intake
energy liberated during food oxidation
Energy output
energy immediately lost as heat (60%), used to do work (driven by ATP), and stored as fat or glycogen
Body mass index (BMI)
index of a person’s weight relative to height
Leptin
hormone that is a key component of the long-term controls of feeding behavior
Metabolic rate
body’s rate of energy output; total heat produced by all the chemical reactions and mechanical work of the body
Calorimeter
chamber with water circulating around it that absorbs heat liberated by the body; rise in water temp is directly related to the heat produced by the person’s body
Respirometer
indirect method; measures oxygen consumption, which is directly proportional to heat production; for each L of oxygen used, the body produces about 4.8 kcal of heat
Basal metabolic rate (BMR)
energy the body needs to perform only its most essential activities
Thyroxine
hormone produced by the thyroid gland; probably the most important hormonal factor in determining BMR; the “metabolic” hormone
Total Metabolic Rate (TMR)
rate of kilocalorie consumption needed to fuel all ongoing activities - involuntary and voluntary
Food-induced thermogenesis
food ingestion induces a rapid increase in TMR; greatest when proteins and alcohol are ingested
Core
organs within the skull and the thoracic and abdominal cavities; highest temp here
Shell
skin; lowest temp here
Radiation
loss of heat in the form of infrared waves (thermal energy)
Conduction
transfers heat from a warmer object to a cooler one when the 2 are in direct contact with each other
Convection
process that occurs because warm air expands and rises, and cool air, being denser, falls
Evaporation
mechanism by which the body loses heat; water evaporating because its molecules are absorbing heat from the environment and become energetic enough to escape as a gas
Heat of vaporization
heat absorbed by water during evaporation
Insensible water loss
unnoticeable water loss occurring from lungs, oral mucosa, and skin
Insensible heat loss
heat loss from lungs, oral mucosa, and skin; unnoticeable
Thermoregulatory centers
heat-loss center (anterior) and heat-promoting center of the brain
Peripheral thermoreceptors
the hypothalamus receives afferent input from these receptors in the shell (skin)
Central thermoreceptors
the hypothalamus receives afferent input from these receptors sensitive to blood temp located in the body core, including the anterior portion of the hypothalamus
Chemical (nonshivering) thermogenesis
cold stimulates the adrenal medulla to release epinephrine and norepinephrine in response to sympathetic nerve stimuli, elevating the metabolic rate and enhancing heat production; occurs in infants
Hyperthermia
elevated body temperature
Heat stroke
at a core temp of 105F, heat-control mechanisms are suspended, creating a vicious positive feedback cycle; skin becomes hot and dry and multiple organ damage becomes a distinct possibility, including brain damage
Hypothermia
low body temp resulting from prolonged exposure to cold
