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nutrients
chemical substances found in foods that are necessary for human life and growth, maintenance, and repair body tissues
proteins, fats, carbs, vitamins, minerals, and water
essential nutrients (indispensible)
must be present in diet for growth, health, reproduction, & survival
deficiency can result in characteristic signs or even death
prevent growth failure
can demonstrate dose-response in deficiency condition when intake is below optimal
aren’t synthesized by the body in amounts that meet the needs for the critical function
conditionally essential
nutrients not ordinarily required in the diet but which must be supplied exogenously to specific populations that don’t synthesize them in adequate amounts
conditions include:
decline in plasma concentrations of nutrient in suboptimal range and chemical, structural, or functional appearance of abnormalities
dietary reference intakes (DRIs)
define appropriate nutrient intakes that prevent deficiencies
define intake levels that can begin to cause adverse or toxic effects
EAR, AI, UL, AMDR
used for planning and assessing diets of individuals and groups
recommended dietary allowance (RDA)
average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97-98%) of healthy individuals in a particular life stage and gender group
estimated average requirement (EAR)
the average daily nutrient intake level estimated to meet the requirements of half the healthy individuals in a particular life stage and gender group
can be used as a benchmark for assessing the nutrient intake of individuals and allows for calculation of the probability that a given intake will result in deficiency
adequate intake (AI)
the recommended average daily nutrient intake level based on observed or experimentally determined approximations of nutrient intake by groups of healthy people that are assumed to be adequate, used when an RDA can’t be determined
tolerable upper intake level (UL)
highest average daily nutrient intake level likely to pose no risk of adverse health effects to most individuals in the general population
as one increases intakes to levels above the ____ the potential risk of adverse effects may increase
acceptable macronutrient distribution range (AMDR)
intake range for an energy source (protein, fats, carbs) associated with reduced risk of chronic disease
*45-65% carbs, 10-35% protein, 20-35% fats
reference heights and weights
established for each age-gender population group
nutrient requirements for consumers can be dependent on body mass and can determine the EAR for an individual
calculated from mid point of ideal BMI
homeostasis
a self-regulating process by which a living organism can maintain internal stability while adjusting to changing external conditions; constancy of the internal environment in which cells live and survive
bone development
calcium, phosphorus, magnesium, vitamin D, fluoride
energy metabolism
thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, panthothenic acid, biotin, and choline
antioxidants
vitamin C, vitamin E, selenium, carotenoids (vitamin A)
electrolytes
water, potassium, sodium, chloride, sulfate
blood nutrient content
glucose, fatty acids, amino acids
gut
gastrin, CCK, secretin, GIP
adipose
leptin
GLP-1
at ileal brake
promotes insulin release (lowers blood glucose) and inhibits glucagon (raises blood glucose)
increases pancreatic B-cell growth
promotes weight loss and glucose control
gastrin
produced by antrum of stomach
stimulates gastric acid and pepsinogen secretion and gastric motility
role in proliferation of gastric mucosal cells
secretin
stimulates pancreatic bicarbonate secretion
promotes intestinal digestion by pancreatic enzymes
may also inhibit gastric emptying
CCK
responsible for post-pradial pancreatic enzyme secretion and gallbladder contraction
released in response to presence of fat or protein in small intestine
direct action of _____ on exocrine pancreas augment synthesis and release of amylase
once it reaches pancreas, it binds to acinar cells and stimulates secretion of zymogens
somatostatin
inhibitory effects on endogenous hormone release and on GI secretion
ghrelin
stimulates food intake by enhancing the hunger sensation and stimulates gastric emptying
leptin
a protein produced by fat cells (adipose) that is a hormone acting mainly in the regulation of appetite and fat storage
hunger
physiological state that causes food seeking behavior
appetite
desire or willingness to eat
satiation
reduction of hunger and termination of eating, generally marks the end of a meal
interplay of psychological, physiological, and metabolic event
satiety
physical feeling of fullness that allows us to stop eating for a while
decreases as nutrients from meal diminish
GI tract
function is to digest complex molecules in foods and absorb simple nutrients, including monosaccharides, monoacylglycerols, fatty acids, amino acids, vitamins, minerals, and water
serves as a barrier to the entry of bacteria into the body
contains specialized cells that secrete mucus, fluids, some digestive enzymes, intrinsic factor, and some peptide hormones
digestion
chemical breakdown of food by enzymes secreted into the lumen of the GI tract by glandular cells in mouth, chief cells in stomach, exocrine cells of pancreas, enzymes in brush border membrane, and cytoplasm of mucosal cells in small intestine
absorption
movement of nutrients, including water and electrolytes, across the mucosal cells into lamina propia, where they enter the blood or lymph
gallbladder
serves to store and concentrate bile
pancreas
insulin and glucagon
secretes digestive enzymes when hormonally stimulated
peptidases (protein), lipases (lipid), bicarbonate, amylase (CHO)
liver
role in bile acid synthesis and secretion
secretes bile acids stored in gallbladder
contraction of gallbladder under hormonal and nervous control
bile salts
detergents form micelles(help absorb lipid & fat soluble vitamins), which facilitate emulsification of dietary fat
enterohepatic recirculation
recirculation of bile salts between liver and small intestine
cholesterol is converted to bile acids, liver releases bile acids into bile duct system, colon reabsorbs secondary bile acids
(NOT a process: Cholesterol is extracted from VLDL by lipoprotein lipase)
mouth
process of chewing bolus of food into smaller particles and to incorporate saliva into food
salivary amylase, as alpha amylase, begins to break down starch (CHO → maltose)
saliva
digestion of nutrients
antibacterial activity
moistening of mouth to facilitate speech and swallowing
buffer
stomach
stores food, process the swallowed with acid, water, enzymes, and pressure
not an important absorptive organ, but water and lipid soluble substances can be absorbed
gastric motility and secretion are regulated by neural and hormonal mechanisms
gastric glands in _____ wall secret HCl, pepsin, and mucins
gastric juice
contains mucin, inorganic salts, hydrochloric acid (from parietal cells for protein denaturation), digestive enzymes or zymogens, intrinsic factor
stimulation of gastric secretions depends on neural, endocrine, and paracrine mechanisms
vagus nerve
neural stimulation of gastric acid secretion and gastric motility
parietal (oxyntic) cells
contain vesicles which fuse into canalicula upon stimulation
acid secretion from K+/H+
ATPase coupled to K+/Cl- cotransporter
chief cells
secrete pepsin in stomach
zymogens
inactive precursor digestive enzymes, protein that can become an active enzyme through proteolysis at a location outside the cells where it is synthesized
intrinsic factor
a glycoprotein required for B12 absorption
gastric glands
in stomach wall to secret HCl, pepsin, and mucins
small intestine
primary digestive and absorptive organ (duodenum, jejunum, ileum)
folds of mucosa, villi, and microvilli structure of luminal or brush border membrane of absorptive cells give it a large surface area
epithelial surface of each villus is covered by enterocytes
_______ motility rate dependent on exposure of nutrients to enzymes in lumen
mixing is achieved by presence of slow waves of contractions, followed by relaxation of different segments
enterocytes
absorptive cells that cover the epithelial surface of each villus
ileal brake
nutrients in ileum slow the emptying of chyme from the stomach as well as for reducing intestinal motility
portal vein
most of water-soluble nutrients (amino acids, monosaccharides, glycerol, short chain fatty acids, electrolytes, and water-soluble vitamins)
first passes through liver, where they can be utilized by hepatocytes or returned to venous circulation
lymph system
lipid-soluble substances
enter blood and go to heart first and then can be circulated via arterial blood supply
colon epithelium
has folds, no villi, and is lined mainly by goblet cells (secrete mucus) and fewer absorptive cels
villi
tiny, finger-like projections made up of cells that line the entire length of your small intestine
absorb nutrients from the food you eat and then shuttle them into your bloodstream so they can travel where they're needed
chylomicrons
major lipoprotein secreted after lipid rich meal, a small fat globule composed of protein and lipid
hepcidin
a peptide hormone produced in the liver that plays a crucial role in iron homeostasis
decreases the level of iron by reducing dietary absorption and inhibiting iron release from cellular storage
production increases when iron levels rise above the normal range
ferroportin
the only known iron exporter
plays an essential role in the export of iron from cells to blood
calbinin D
facilitate the vitamin D dependent movement of calcium through the cytosolic compartment of the intestinal or renal cell
also has a major role in different cell types in protecting against apoptotic cell death
metallothionein
protein that binds zinc (or copper) for storage in the intestinal epithelial cells and therefore slows the rate of Zn absorption is
monosaccharides
glucose, fructose, galactose
disaccharides
sucrose, lactose, maltose, trehalose
oligosaccharides
often broken down components of polysaccharides
polysaccharides
starches
sugar alcohols
sorbitol and mannitol
alpha amylase
begins digestion of CHO in lumen
unable to cleave
raffinose, stachyose, cellulose, B-glycans
glucoamylase
high specificity for the alpha (1→4) link of larger straight chain oligosaccharides
sucrase
high efficiency for the alpha (1→4) links of smallest glucosyl oligosaccharides, maltose, and maltotriose
isomaltase (a-dextrinase)
maximal and unique specificity for the alpha (1→6) link of a-dextrinse
sodium-glucose cotransporter 1(SGLT1)
transports glucose and galactose into enterocyte
aldohexose and Na+ cotransport protein; 2Na+ and 1 glucose or galactose into cell
facilitated glucose-fructose transporter 5 (GLUT5)
transport fructose into enterocyte, functions independently of Na+
glucose transporter 2 (GLUT2)
transports all 3 hexoses out of enterocyte into basolateral membrane by diffusion
lactase
an enzyme that catalyzes the hydrolysis of lactose to glucose and galactose
hypolactasia
the inability to fully digest lactose in dairy products; lactose intolerance, normal phenotype
secondary active transport
transporter that couples movement of one nutrient across a membrane against its concentration gradient to the simultaneous movement of a second molecule down an energetically greater concentration gradient
solute has first to react with the carrier (mediator/pump) to form a solute-carrier complex, which then diffuses through the membrane to finally release the solute
facilitated diffusion
nutrient moves through a channel or pore in a membrane in the direction of high to low concentration
primary active transport
nutrient can be moved against a concentration gradient because a transport enzyme hydrolyzes a high energy bond from ATP or a related molecule
ex. the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants, Na+/K+ pump
passive diffusion
doesn’t require energy to move substances across cell membrane, random motion of small molecules allows them enter and leave small spaces between other molecules
movement of H+, H2O, and CO2 through cell membrane
pinocytosis
a process by which the cell takes in the fluids along with dissolved small molecules
the cell membrane folds and creates small pockets and captures the cellular fluid and dissolved substances
paracellular pathway
movement from the intestinal lumen to interstitial space by passing through leaky junctions between neighboring enterocytes
dietary fiber
nondigestible soluble and insoluble CHOs (with three or more monomeric units) and lignin that are intrinsic and intact in plants
functional fiber
consists of isolated, non-digestible CHOs (with three or more monomeric units) that have beneficial physiological effects in humans
plant sterols
inhibits intestinal absorption of cholesterol through displacement of cholesterol from bile salt mixed micelles by _____ or inhibition of the rate of cholesterol esterification in intestinal mucosa
margarines, vegetable oil spreads, salad dressings
tannins
inhibit absorption of minerals, especially iron (not Zn and Cu)
potent antioxidants
bind and precipitate proteins
tea, wine, pomegranate, persimmon, nuts, legumes, chocolate, coffee
phytic acid (phytate)
binds Fe, Zn, Ca, Mg
antioxidant
reduced colon cancer (binds to Fe2+)
protective against osteoporosis
component of grains and legumes that chelates minerals in the diet and reduces their absorption
oxalic acid
calcium ___ precipitates in gut and mouth, causes kidneys stones if it precipitates in kidney
free _____ is absorbed
inhibits absorption
star fruit, black pepper, parsley, spinach, chard, beets, chocolate, most nuts and berries, beans, tea leaves
chitin
complex carb in shell of insects and animals, functional fiber
Kupffer cells
phagocytes in liver structure
renal cortex
outer layer of the kidney
reabsorption of water and solutes in equal proportions from filtered tubular fluid
renal medulla
inner part of kidney
helps regulate concentration of urine by filtering out water, salts, and acid
nephron
functional unit of the kidney consisting of the glomerulus, Bowman's capsule, proximal and distal tubules, and loop of Henley is called
loop of Henle
part of a kidney tubule which forms a long loop in the medulla of the kidney where water and salts are resorbed into the blood
collecting duct
water extracted from ___ ____ when ADH is present
collects urine and transports it to the pelvis through ureters where it is temporarily stored in the urinary bladder
antidiuretic hormone (vasopressin)
pituitary hormone that is chiefly responsible for regulating the amount of water that is excreted by the kidney in response to change in the osmotic pressure of the blood
renin angiotensin aldosterone
Low BP prompts kidneys to secrete renin
Renin converts angiotensinogen (inactive) to angiotensin I (active) which is then converted into angiotensin II by angiotensin-converting enzyme (ACE)
Angiotensin II stimulates the adrenal cortex to secrete aldosterone
Aldosterone increases kidney's absorption/retention of Na & fluid, increasing BP
atrial natriuretic peptide
regulates salt-water balance and BP by promoting renal sodium and water excretion and stimulating vasodilation
acid base balance
the body’s balance between acidity and alkalinity
process of regulating the pH, bicarbonate concentration, and partial pressure of carbon dioxide of bodily fluids
osteoblast
cells responsible for formation of bone
activated by vit D
secrete collagen, osteocalcin to make bone scaffold
mineralization requires action of vit K
osteoclast
cells in the bone that use HCl and proteases to dissolve bone matrix and mineral
breakdown bone in areas where bone isn’t needed
if free blood Ca2+ drops, PTH stimulates _____ to breakdown bone
osteocytes
regulate phosphate, secrete bone mineral causing mineralization, sense bone activity and stress