NTR 401 exam 2

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