Chapter 17: Nutrition & Metabolism Flashcards
metabolism
all chemical reactions that occur in the body
catabolism
breakdown of organic molecules that releases energy for synthesizing ATP or other high-energy compoundsonly captures about 40% of the released energy; the rest escapes as heattend to process carbohydrates first, then lipids; amino acids are a last resort and seldom broken down
anabolism
synthesis of new organic molecules through the formation of new chemical bondsrequires more amino acids than lipids and relatively few carbohydrates
metabolic turnover
continuous removal and replacement of cellular structures
four primary reasons for cellular anabolism
•to perform structural maintenance/repairs•to support growth•to produce secretions•to build nutrient reserves
structural/functional/storage components
triglycerides, glycogen, proteins
nutrient pool
fatty acids, glucose, amino acids; source of organic molecules for both catabolism and anabolism
complete catabolism of glucose
produces 36 ATP, 34 of which are produced within the mitochondria
glycolysis
anaerobic process in which glucose is broken down into 2 molecules of pyruvic acid; 2 net ATP are producedrequires glucose, cytoplasmic enzymes, ATP/ADP, and NADfirst step of ATP production; takes place in cytosol
pyruvic acid
creating during glycolysis; accumulation leads to lactic acid buildupcan also be used to synthesize glucose
nicotinamide adenine dinucleotide (NAD)
a coenzyme that removes hydrogen atoms during glycolysis
coenzyme
organic molecules usually derived from vitamins that must be present for a given enzymatic reaction to occur
aerobic metabolism
cellular respiration; mitochondrial activity responsible for ATP productionwaste products are water and carbon dioxiderequires oxygen
anaerobic metabolism
does not require oxygenproduces lactic acid
2 mitochondrial pathways
TCA cycle and electron transport system
tricarboxylic acid (TCA) cycle
“citric acid cycle” or “Krebs cycle”reaction involving a molecule of pyruvic acid which takes place within mitochondria; primary function is to remove hydrogen atoms from organic molecules and transfer them to coenzymes in the electron transport system produces CO2 as waste product; only immediate benefit is formation of 1 GTP per cycle, which equates to 1 ATP per cycle (2 cycles per glucose = 2 ATP per glucose)
guanosine triphosphate (GTP)
high-energy compound created in Krebs cycle; readily converted into ATP
coenzyme A
CoAinvolved in reaction between NAD and pyruvic acid which yields CO2, NADH, and acetyl-CoA
acetyl-CoA
consists of two-carbon acetyl group bound to CoAcannot be used to make glucose because the reaction that removes the carbon dioxide molecule between pyruvic acid and acetyl-CoA cannot be reversedused in lipogenesis to make steroids and nearly all fatty acids
citric acid
produced by adding acetyl group to four-carbon molecule
acetyl group
CH₃CObinds to CoA to form acetyl-CoA and is transferred to a four-carbon molecule to create citric acid
flavine adenine dinucleotide (FAD)
coenzyme which transfers hydrogen ions from citric acid cycle to electron transport system
electron transport system (ETS)
embedded within the inner mitochondrial membrane; comprised of cytochromesdoes not produce ATP directly; merely creates necessary conditions for its productionleads to creation of 95% of cell’s ATP through chemiosmotic conversion of ADP
cytochromes
series of protein-pigment complexes that make up electron transport chain
coenzyme Q
transfers the electrons of hydrogen atoms generated by Krebs cycle to the first cytochrome of the ETS
matrix
Innermost compartment of the mitochondrion
intermembrane space
the fluid filled space between the inner and outer mitochondrial membranes; H+ ions are pumped here by ETS using energy from electron movement
ATP synthase
enzyme located in inner mitochondrial membrane; chemiosmosis of H+ ion passing through generates ATP
chemiosmosis
movement of ions down their electrochemical gradient across a semipermeable membranein metabolism: kinetic energy of H+ ion passing through ATP synthase is used to attach a phosphate group to ADP, forming ATP
lactic acid
created from accumulation of pyruvic acid produced during glycolysis (anaerobic metabolism)
gluconeogenesis
synthesis of glucose from noncarbohydrate (protein or lipid) precursor sourcesfatty acids and many amino acids cannot be used for gluconeogenesis because their breakdown produces acetyl-CoA
glycogen
used to store glucose in liver and skeletal muscle because it is insoluble and therefore does not affect cell’s tonicity
lipolysis
lipid catabolization; lipids are broken down into pieces that can be converted into pyruvic acid or channeled directly into the TCA cyclesproduces more ATP per carbon molecule than glycolysis, but it takes longer to access lipid reserves and it is limited by the availability of oxygen
triglyceride
lipid made of three fatty acid molecules and one glycerol molecule
beta-oxidation
catabolism of fatty acids in which enzymes break them into two-carbon fragments; these fragments then enter the TCA cycle or combine to form ketone bodiescell generates 144 ATP from breakdown of one 18-carbon fatty acid molecule
ketone bodies
short carbon chains made during lipid and amino acid catabolismmetabolized by body cells, who convert them into acetyl-CoAexample is acetone
ketosis
accumulation of high ketone body concentrations in body fluids as a result of increased production from protein and lipid catabolism
acetone
small ketone which can diffuse into alveoli and give the breath a distinct odor
lipogenesis
synthesis of lipidsglycerol is made from an intermediate 3-carbon product of glycolysis; synthesis of most other lipids begins with acetyl-CoAcan use almost any organic molecule because most lipids, amino acids, and carbohydrates can be converted to acetyl-CoA
essential fatty acids
must be consumed because the human body cannot manufacture themincludes linolic and linolenic acids
lipoproteins
lipid-protein complexes that contain large insoluble glycerides and cholesterol within an outer coating of phospholipids and proteins; make entire complex soluble and allow for transportation of lipids throughout the body classified by size and by their relative proportions of lipids and proteins chylomicrons, LDL, and HDL
chylomicrons
largest lipoproteins; 95% of their weight consists of triglycerides, which they transport from GI tract to bloodstream to be absorbed throughout the body
low-density lipoproteins (LDL)
“bad cholesterol” because it may end up in arterial plaquesformed in the liver and deliver cholesterol to peripheral tissues
high-density lipoproteins (HDL)
“good cholesterol” because it does not cause circulatory problemstransports excess cholesterol from peripheral tissues to the liver for storage or excretion in bilenormally formed in the liver
free fatty acids
lipids that can diffuse easily across cell membranes; major source is the breakdown of fat stored in adipose tissue (bind to albumin in bloodstream)
vitamin b6
pyridoxinecoenzyme required for removal of amino group; essential in the catabolism of amino acids
transamination
attaches the amino group of one amino acid to another carbon chain, creating a “new” amino acidenable a cell to make many of the amino acids needed for protein synthesis
deamination
prepares an amino acid for breakdown in the TCA cycle; removal of amino acid in a reaction that produces an ammonia molecule
urea
produced in liver from ammonia and carbon dioxide; is then excreted in urine
essential amino acids
10 total8 cannot be manufactured at all: isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, methionine2 can be manufactured but not in sufficient quantities: arginine and histidine
nonessential amino acids
can be synthesized on demand
protein deficiency diseases
when an individual does not consume adequate amounts of essential amino acidsexamples are marasmus and kwashiorkor
phenylketonuria (PKU)
cannot convert the amino acid phenylalanine into tyrosine; as a result, they cannot synthesize norepinephrine, epinephrine, and melanin
uric acid
during breakdown of RNA, adenine and guanine cannot be catabolized and instead undergo deamination and are excreted as uric acid
nitrogenous wastes
uric acid and urea (because they contain nitrogen atoms)
gout
caused by hyperuricemia (elevated uric acid in the blood)
basic food groups
•grains (6-11 servings)•vegetables (3-5 servings)•fruits (2-4 servings)•dairy (2-3 servings)•meats/beans/fish (2-3 servings)
incomplete proteins
deficient in one or more essential amino acidsmany plants contain adequate amounts of protein, but may be inadequate
complete proteins
contain all essential amino acids
vitamin B12
cobalamincoenzyme in nucleic acid metabolismobtained only from animal products, fortified cereals, or tofularge and must be bound to intrinsic factor in order to be absorbed
minerals
inorganic ions released through the dissociation of electrolytes, such as sodium chloridedetermine osmotic concentration of body fluids, play roles in physiological processes
B complex vitamins
grouped together only because they occur together in foods; typically found in meat/milkwater-solubledeficiencies typically result in CNS issues/developmental retardationnamed for the order in which they were discovered
phosphorus
used in high-energy compounds, nucleic acids, and bone matrix
magnesium
cofactor of enzymes, required for normal membrane function
iron
component of hemoglobin, myoglobin, cytochromes
zinc
cofactor of enzyme systems, notably carbonic anhydrase
copper
required as cofactor of hemoglobin synthesis
vitamin A
maintains epithelia; required for synthesis of visual pigmentsfound in leafy green and yellow vegetables, butter, milkdeficiency = night blindness, skin lesions
vitamin D
steroid-like compoundsrequired for normal bone growth, calcium/phosphorus absorptionsynthesized in skin when exposed to sunlightdeficiency = bone/muscle pain/weakness
vitamin E
tocopherolsprevents breakdown of vitamin A and fatty acidsfound in meat, milk, vegetables, nuts, wheatdeficiency = hyporeflexia, ataxia, anemia
vitamin K
essential for synthesis of prothrombinfound in vegetables and produced by intestinal bacteriadeficiency = increased bleeding
vitamin B1
thiaminedeficiency causes beriberi or Wernicke’s encephalopathy
beriberi
vitamin B1 (thiamine) deficiency due to the consumption of milled (polished) rice or chronic alcoholismaffects cardiovascular system (wet beriberi) and nervous system (dry beriberi)
Wernicke’s encephalopathy
vitamin B1 (thiamine) deficiency; causes vomiting, fever, ataxia, mental deteriorationthiamine will completely reverse symptoms
Korsakoff’s syndrome
continuation of Wernicke’s encephalopathy; includes retrograde amnesia and impaired ability to learnthiamine will only partially reverse the symptoms
vitamin C
coenzyme; delivers hydrogen ions; antioxidantfound in citrus fruitsdeficiency = scurvy
Cholecalciferol
vitamin D3
fat soluble vitamins
A, D, K, Ebecause fat-soluble vitamins can diffuse through cell membranes, your body contains a significant reserve of these
avitaminosis
vitamin deficiency diseasemore common in water-soluble vitamins
hypervitaminosis
too much of a vitamin; occurs when dietary intake exceeds the ability to store, utilize, or excrete a particular vitamin often involves one of the fat-soluble vitamins because their excess are retained and stored in the body rarely involves a water-soluble vitamin because they can easily be excreted via urine
vitamins
organic compounds that the body needs for proper metabolismmay be water-soluble or fat-soluble
water-soluble vitamins
B and C; usually components of coenzymesexchanged between digestive tract and bloodstream and excreted at kidneys5/9 are provided by gut bacteria
daily water intake
average 10 cups or 40 mL/kg body weightfor each 1° raise in temperature during a fever, body requires an additional 200 mL of waterfood = 48% of water intake; fluids = 40%; remainder is produced in mitochondria during electron transport
calorie
amount of energy needed to raise the temperature of 1g water by 1°C; kcal or Cal used instead (1kg water)breakdown of carbs = 4 Cal/gbreakdown of fats = 9 Cal/g
metabolic rate
sum of all the various anabolic and catabolic processes occurring in your body; average person has a basal metabolic rate (BMR) of ~70 Cal/hour (1680 Cal/day)
four processes of heat exchange
radiation, evaporation, convection, conduction
hypothalamus
contains heat-loss and heat-gain centers; body’s thermostat
hydrolysis
the chemical breakdown of a compound due to reaction with water
necrosis
tissue death
pyrexia
fever
