Nutrition Biochemistry Flashcards
List the pancreatic digestive enzymes
zymogens
-trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidases
active enzymes
-a-amylase, lipases, colipase, phospholipases, cholesterol esters, RNAase, DNAase
ions
-HCO3
What controls pancreatic enzyme secretion at each stage of digestion?
cephalic: ACh
gastric: ACh, gastrin
intestinal: CCK, secretin
What is pancreatic section of HCO3- controlled by?
ACh
Secretin
What enzymes are needed for the digestion of fat?
lipase, phospholipase, cholesterol esterases
Where and how are fat’s absorbed?
via micelles in the duodenum and jejunum
How are fats transported in the blood once they’re absorbed?
chylomicrons
VLDL
How does an endopeptidase work?
cleaves in the center of proteins & peptides
How does an exopeptidase work?
cleave from N or C terminal end of peptide and proteins
-carboxypeptiases, aminopeptidases
How are amino acids absorbed?
AA transporters
-tripeptidase and dipeptidase on epithelial cells break down into individual AAs for absorption
What enzymes are needed for the digestion of carbohydrates?
a-amylase
Di and trisaccharidases
How and where are carbohydrates absorbed?
via SGLT1 & GLUT 5 receptors in the duodenum and jejunum
What are the symptoms of lactase deficiency?
loss of function w/age
bloating and diarrhea due to bacterial degradation of lactose
How much of the world population is lactase deficient?
75%
What are the essential amino acids?
arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
What are the essential fatty acids?
linoleic acid, linolenic acid
What are the calorie densities for the major nutrient groups?
(in kcal/g)
carbs: 4
proteins: 4
fat: 9
alcohol: 7
What percentages of each nutrient makes up dietary goals?
45-65 carbs
10-35 protein
20-35 fat
Where are the 2 protein storing compartments?
somatic protein-skeletal muscle stores
visceral protein-visceral organ stores
What is marasmus?
severe reduction in caloric intake >60% body wt reduction depletion of somatic protein compartment albumin normal growth retardation anemia immunodeficiency
What is kwashiorkor?
more severe than marasmus
protein deprivation greater than caloric deprivation
can be due to malabsoprtion or chronic protein loss
loss of visceral protein stores
hypoalbuminemia
sparing muscle mass
What populations does protein malnutrition occur in in the US?
chronically ill, hospitalized, cachectic cancer patients, AIDS
What are complications from protein energy malnutrition?
infeciton
impaired wound healing
sepsis
death after surgery
What is obesity?
excessive body weight (BMI >30)
overweight BMI 25-29.9
What are medical complication of obesity?
metabolic syndrome/type 2 diabetes cardiovascular morbidity cholelithiasis cancers pulmonary embolus/DVT obstructive sleep apnea hypoventilation syndorme osteoarthritis steatosis
How many people in the US are obese?
> 20%
What are the water soluble vitamins?
Bvitamins
-thiamne (B1), Riboflavin (B2), Niacin (B3), Pantothenic acid, biotin, folate (B9), B12, B6 (pyridoxine, pyridoxal, pyridoxamine)
Vitamin C
What are the fat soluble vitamins?
A (retinol, carotenes)
D (cholecalciferol)
E (tocopherois)
K (phlloquinones)
Features of Thiamine/Vitamin B1
absorbed in the duodenum and jejunum
non-toxic
excess is excreted, stores depleted in 14 days
active form is thiamine pyrophosphate
What are the functions of B1/thiamine?
cofactor for pyruvate dehydrogenase
cofactor in pentose phosphate pathway
maintains neural membranes and normal nerve conduction
What are sources of thiamine?
pork, whole grains, fortified breads and cereals, legumes and nuts
Features of thiamine/B1 deficiency?
extremely common in alcoholics
polyneuropathy “dry beriberi”
dilated cardiomyopathy “wet beriberi”
wernicke korsakoff syndrome
How is thiamine B1 deficiency treated?
banana bag
oral supplementation
What is wernicke-korsakoff syndrome?
aka wernicke encephalopathy
reversible, opthalmoplegia, confustion/disorientation, nystagmus, ataxi
has a chronic stage-korsakoff syndrome
What is korsakoff syndrome?
irreversible/chronic stage of wernicke-korsakoff syndrome
memory disturbances, confabulation
perivenricular and mammilary body hemorrhage/necrosis
Features of pantothenic acid/Vitamin B5?
absorbed in the duodenum
excess excreted, very little stored
active form is coenzyme A
-acyl carrier protein function, for fatty acid synthesis
Sources of pantohenic acid/B5?
wide spread in food
esp: whole grains, meats, fish, poultry
What is vit B5/pantothenic acid deficiency/Toxicity frequency?
deficiency-very rare
toxicity-excess excreted, no symptoms
Features of riboflavin/B2 function?
absorbed in the duodenum and jejunum mostly exreted active forms (FMN & FAD) functions as an electron carrier (complex dehydrogenases, citric acid cycle to electron transport chain)
Sources of riboflavin/Vit B2?
milk, milk products, eggs, meat, fish and whole grains, fortified breads and cereals, nuts and legumes
What are the symptoms or B2/riboflavin deficiency?
rare except in alcoholics
cheilosis (scaling and fissures at the corners of the mouth)
angular stomatitis (inflammation at the corner of the mouth)
glossitis (inflammation of the tongue-bald tongue)
dermatitis
Features of vitamin B3/niacin
absorbed in the duodenum and jejunum
excreted, not stored
active forms: NADH/NAD+, NADPH/NADP+
What is the function of NADH?
generated during degradation of carbohydrates, fats, amino acids and nucleic acids
carries electrons from the citric acid cycle to the electron transport chain
What is the function of NADPH?
generated by glucose-6-phosphate dehydrogenase in the pentose phosphate shunt
used in synthesis reactions for carbohydrates, fats, amino acids and nucleic acids
What are sorces of B3/niacin?
meat, fish, milk, eggs, whole grains, fortified cereal and breads, nuts legumes
What are the symptoms of niacin/vit B3 deficiency?
pellagra
uncommon except in alcoholics and impovershed
dermatitis (sun exposed skin), diarrhea, dementia
Niacin/B3 toxicity symptoms?
flushing
gastric irritation
rashes
Biotin/B7 features?
absorbed in duodenum and jejunum
active form: biotin bound to carboxylase
most excreted, not stored
What is the function of B7/Biotin?
carboxylase cofactor
-pyrubate carboxylase
acetyle CoA carboxylase
What are sources of B7/Biotin?
liver, milk, eggs, fish, peanuts, chocolate, nuts, whole grains, legumes
synthesized by intestinal bacteria
What are symptoms of biotin/B7 deficiency?
rare, usually in elderly
can occur by binding biotin to avidin in raw egg whites
biotinidase deficiency-inability to convert dietary derived biocytin to free biotin
porr growth, neuro disorders in infants
dermatitis and hair loss in adults/kids
B7 toxicity?
no, excreted
Features of pyridoxine/B6?
absorbed in the jejunum and ileum small amount stored, most excreted active form: pyridoxal phosphate coenzyme involved in -aminoacids degradation/conversion to other important molecules -glycogen degradation -porphyrin synthesis
Pyridoxine/B6 sources?
beans, nuts, legumes, meats, eggs, fish, whole grains, fortified grains & cereals
Symptoms of B6/pyridoxine deficiency?
cheilosis angular stomatitis glossitis (bald tongue) dermatitis peripheral neuropathy microcytic hypochromic anemia confusion and irritability
causes of B6/pyridoxine deficiency?
alcoholics and kidney failture pts
causes by isoniazid for tuberculosis
Symptoms of B6/pyridoxine toxicity?
peripheral sensory neuropathy
What are the hematopoeitic vitamins?
folate/B9
Cobalamin/B12
What are features of folate/B9?
absorbed in the duodenum, jejunum and ileum
most excreted, small amount stored
active form: tetrahydrofolate
carrier of 1 carbon units for: purine synthesis, dTMP synthesis, conversion of homocysteine to methionine for S-adenosylmethionine synthesis
Sources fo folate/b9?
beans, legumes, citrus fruits, dark green leafy vegetables, whole grains, fortified grains, cereals, meat
Causes of folate/b9 deficiency?
inadequate intake
associated w/antifolate tx (methotrexate, 5FU)
prevent w/ supplementation
Symptoms of folate/B9 deficiency?
megaloblastic anemia
leukopenia
fetal neural tube defects (spina bifida occulta–> anencephaly)
glossitis
What are some features of cobalamin/vit b12?
absorbed w/intrinsic factor in ileum
stored in liver (stores last ~2 years)
active form is cobalamin
What is the function of b12/cobalamin?
methionin synthase &
methyl malonyl coenzyme A mutatse rxns
myelination
Sources of B12/cobalamin?
meat, shellfish, fish, eggs, milk, cheese, yogurt
What are causes of B12 deficiency?
impaired absoprtion (IF def, ileal resection) decreased intake tapeworm
What are the symptoms of B12 deficiency?
megaloblastic (perniciuos) anemia
neural tube defects
subacute combined neural degeneration (sensory ataxia, parasthesias, spastic paraparesis)
What vitamines have antioxidant and post-translational modication functions?
C, E, B-carotene (provitamin A)-antioxidant
C, K-post translational modication
What are some features of VitC/Ascorbate?
absorbed in the jejunum and ileum
excreted, not stored
active form is ascorbic acid (ascorbate)
What is the function of vitamin C?
Antioxidant-reduces ROS, oxidized vit E
Cofactor of enzymes that reduce metal ions
post translational modification of proteins-collagen
synthesis of neurotransmitters and hormones
What are sources of vitamin C/ascorbate?
ALL fruits and vegetbles
highest in citrus fruits, strawberries, green peppers, broccoli, green leafy vegetables, tomatoes and potatoes
What occurs with vitamin C deficiency?
scury
- easy bruising
- corkscrew hairs
- petechial hemorrhages
What occurs with vitamin C toxicity?
usefulness for high levels for colds controversial, slowly reduce high levels
What are some features of tocopherol/Vitamine E?
most active form: a-tocopherol
absorbed via micelles in duodenum and jejunum
distributed via chylomicrons
stored in adipose tissue, liver, muscle
What is the function of vitamin E/tocopherol?
antioxidant-scavenges free radicals
What are good sources of vitamin E?
vegetable oils, liver and eggs
What occurs wtih vitamin E deficiency?
irritability, edema, hemolytic anemia
uncommon except w/malabsorption syndromes, TPN and premature infants
Is there vitamin E toxicity?
no
What is a pharmacological use of vitamin E?
Alzheimer’s disease progression inhibitor
What are some features of vitamin K/phylloquinones?
absorbed from micelles in duodenum, jejunum and ileum
distributed via chylomicrons
stored in the liver
active form: K1
What are some functions of vitamin K/phylloquinones?
post translational modification-cofactor for vitamin K dependent gamma-carboxylase
-cpag factors II, VII, IX, X, proteins S, C, bone calcium binding proteins
modifeid GIa residue binds calcium and localizes coagulation proteins on activated platelets
What are good sources of vitamin K/phylloquinones?
green vegetables, spinach, kale, peas, cauliflower and cabbage
What are features of vitamin K/S deficiency?
rare except w/warfarin tx, malabsoprtion syndrome, broad spectrum Abx, lack of gut flora in neonates, chronic bleeding
sx: bleeding/defective clotting ( bruising, hematomas), hemorrhagic disease of the newborn
What are features of vitamin K/S toxicity?
shortened bleeding time
food as source no toxicity
What are some features of vitamin A/carotenes/retinoids?
absorbed via micelles in the duodenum and jejunum
distributed via chylomicrons
stored in liver stellate cells or as retinyl esters (retinol)
What are the functions of vitaminA?
Bcarotene-antioxidant, vit A precursor
retinol-major transport form
11-cis-Retinal (retinaldehyde)-vision
Retinoic acid (all-trans, 9-cis)-regulation of retinoid responsive gene expression (epithelial cell function, mucous cell function, immunity, reproduction)
How does 11-cis-retinal aid with vision?
binds to rhodopsin in rods and to the cone pigments in cones
difference in minding to the 3 cone pigments results in absorption of different wavelengths of light
light absorbed by 11-cis retinal bound to rhodopsin in the rods and to the cone pigments in the cones of the retina, light converts 11-cis-ratinal into all-trans retinal, the g coupled receptor, transducin, in the rod and cone membranes changes conformation and acrivates the G-protein leading to activation of a phosphodiesterase, cleavage of cGMP closes the cGMP coupled iron channel and sending a signal to the brain
What are good sources of vitamin A?
Bcarotene: green leafy vegetables, other intensely colored vegetables (carrots, sweet potatoes, red peppers) Retinyl Esters (RE): eggs, meat, dairy
What is the result of a vitamin A deficiency?
impaired vision-night blindness
squamous metaplasia (mucus cells, epithelial cells-xeropthalmia, xerosis, bitot’s spots [keratin debris], corneal ulceration, keratomalacia, follicular hyperkeratitis)
renal, urinary calculi
predispostion to pumonary infections and diarrhea
What occurs from vitamin A toxicity?
B carotene-non toxic, yellow skin due to fat depostion
Retinol-toxic at high levels (blurred vision, abd pain, peeling of skin, hair loss, headache, dizziness, vomiting, bone pain and deformities)
-extremely toxic at very high levels-death
Retinal-toxic at high levels esp to the retina
Retinoic acid-toxic at levels used to treat acne (teratogenic, peeling of skin)
What are some key features of VitaminD/Calciferols?
dietary-D3, animals; D2, plants
hormone-D2-sunlight
Active: 1,25 dihydrovitamin D (cholecalciferol)
absorbed via micelles in duodenum, jejunum and ileum
distributed via chylomicrons
stored in the liver
what is the function of vitamin D?
controls expression of vit D responsive genes
maintenance of normal calcium and phosphate plasma levels
controls cell cycle arrest, apoptosis, immune suppression, anti-inflammation, differentiation
What are good sources of vitamin D?
cheese, butter, margarine, fortified milk, fish, fortified cereal
What initiates synthesis of vitamin D from 7-dehydrocholesterol?
sunlight
What are predisposing conditions for vitmain D deficiency?
inadequate synthesis or dietary deficiency
decreased absorption
metabolic errors
end organ resistance
phosphate depletion
less severe deficiencies assoc w/thyroid changes, cancer, CV disease, cognitive impairment, parkinson disease
What occurs in kids & adults with vitamin D deficiency?
kids-ricket's -bowed legs, frontal bossing, pigeon breast adults-osteomalacia -soft, painful, bendable bones -osteoporosis -dowager's hump
What occurs in vitamin D toxicity?
diarrhea dermatitis headache nausea anorexia calcification of soft tissue kidney stones decalcification of bones
Which vitamin has a special purpose to help with vision?
vitamin A
Which vitamins affect gene expression?
vitmain A, vitamin D and other vitamins
Which vitamins are antioxidants?
vitamin C, viamin E and carotene (provitamin A)
Which vitamins do posttranslational modification?
vitamin K, vitamin C
Which vitamins are substrate carriers?
thiamine, pantothenic acid
Which vitamins are electron transfer molecules?
riboflavin, niacin
Which vitamins are substrate binding?
biotin, pyridoxine
Which viamins have a hematopoeitic effect?
folate, vitamin B12
What are some key features of iron?
absorbed in the 2+ form in the duodenum and ileum
stores w/ferritin and hemosiderin in the liver, spleen and bone marrow
What are good sources of iron?
meats, fish, shellfish, lentils, beans,seeds, tofu, spinach
What are functions of iron?
in heme
iron-sulfer complexes required for aconitase in citric acid cycle and electorn transport chian
enzyme co-factor
What occurs with iron deficiency?
hypochromic microcytic anemia/IDA glossitis angular stomatitis cheilosis impaired cognition and work capacity immune deficiency
What occurs with iron toxicity?
hemochromatosis-abnormal deposits in liver, pancrease, heart and skin
where is zinc absorbed?
absorbed in jejunum
What are good sources of zinc?
oysters/shellfish
meat
plants at lower levels
What are the functions of zinc?
component of metabolic enzymes (metalloproteases, oxidases)
gene expression-Zn finger proteins
spermatogenesis
skin maintenance and wound healing
What occurs w/zinc deficiency?
Rare
rash
anorexia
diarrhea
growth retardation
depressed wound healing and immune response
infertility due to inhibition of testosterone synthesis
What populations is zinc deficienc more common in?
pts w/ DM malabsoprtion syndromes/chronic diarrhea renal disease/dialysis IV feeding major burn patients inborn error of Zn absorption
What are key features of iodine?
absorbed in the stomach
found in salt water fish and shellfish, iodized salt
is a component of thyroid hormones
What occurs in iodine deficiency?
goiter
cretinism
myxedema
What is myxedema?
adults w/ dry skin, swelling of skin around nose and lips
mental deterioration
subnormal bsal metabolic rate
What occurs with iodine toxicity?
goiter
thyrotoxicosis
What are some key features of copper?
absorbed in the stomach and duodenum
found in liver, shellfish, chocolate, nuts and seeds
What are some functions of alzheimers?
oxidation reactions including electron transport-cytochrome C oxidase, tyrosinase
neurotransmitter regulation-dopamine B-oxidase
antioxidants-superoxide dismutase
collagen crosslinking enzymes-lysyl oxidase
development of vascular and skeleton structures and the CNS
What occurs in copper deficiency?
microcytic hypochromic anemia muscle weakness neurological defects abnormal collagen crosslinks leading to bleeding neutropenia
What occurs in copper toxicity?
usually genetic
neurological defects
corneal copper deposits
What are some key features of fluoride?
absorbed in the stomach
found in water and toothpaste
needed by teeth to prevent dental carries
What are symptoms of fluoride toxicity?
mottled tooth enamel
What are key features of selenium?
absorbed in the duodenum
found in plans grown in selenium containing soil, fish and shellfish
component of glutathione peroxidase, antioxidant w/vitaminE and regulates thyroid hormone action
What occurs in selenium deficiency?
myopathy
cardiomyopathy (kids)
What occurs in selenium toxicty?
hair and nail damage nad oss tooth decay neuropathy liver cirrhosis depression
