Therapeutics > Macronutrition (unit 3) > Flashcards

Macronutrition (unit 3) Flashcards

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1
Q

Carbohydrates (role?)

A

Roles: major energy source (4cal/g)
- used to generate many metabolic intermediates
- excess carbohydrates converted to -> glycogen & triacylglycerol

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2
Q

Types of Carbohydrates

A

1) Simple Carbs
- sugars
- fruits/veggies/milk
monosaccharides -> single sugar molecules (glucose, fructose, galactose)
disaccharides -> 2 sugar molecules combined (sucrose, lactose, maltose)
2) Complex Carbs
- polysaccharides
- many monosaccharides linked together in chains
- glycogen in animals, starch and fiber in plants

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3
Q

Monoaccharides

A

1) Glucose (dextrose)
- most important carb fuel for the body
- frequently referred to as sugar
- rarely occurs as a monosaccharide in food, part of a disaccharide or starch
2) Fructose
- found in fruits/veggies, more than half the sugar in honey
- does not cause as great a rise in blood glucose as other sugars, but causes an increase in blood lipids
- dramatic increase in use of high fructose corn syrup has been suggested to be related in the increased incidence of diabetes and obesity

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4
Q

Digestion of Carbs

A

alpha- amylase
- hydrolyzes starch & glycogen to maltose & maltotriose
- exists in saliva & pancreatic juice
- enzymes on the luminal surface of small intestine
Maltase (alpha-glycosides): maltose + maltotriose -> glucose
Sucrase: sucrose -> glucose + fructose
Lactase: lactose -> glucose + galactose
lactose intolerance occurs when lactase is not produced enough
*ONLY monosaccharides are absorbed in the body

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5
Q

Bacterial Contribution

A

indigestible carbs?
- converted to monosaccharides by bacterial enzymes
- metabolized anaerobically by bacteria
- resulting in production of short chain fatty acids (lactase, H2, CH4, CO2)
Raffinose: oligosaccharide in leguminous seeds (bean + peas), cannot be hydrolyzed by human enzymes

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6
Q

Glycemic Index

A
  • Measure of how quickly individual foods will raise blood glucose level
  • defined as the ratio of the area of the blood glucose response curve to that of glucose
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7
Q

Dietary Fibers (3)

A

1) Cellulose + Hemicellulos
- unrefined cereals, bran, whole wheat
- insoluble
- increase stool bulk and decrease intestinal transit time
2) Lignin
- woody parts of veggies
- insoluble
- binds cholesterol + carcinogens
3) Pectin
- fruits
- soluble
- decreases rate of sugar uptake and decreases serum cholesterol

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8
Q

Lipids

A
  • efficient energy source (9 cal/g)
  • provides satiety
  • adds flavor + aroma to diet
  • carrier for fat-soluble vitamins
  • triacylglycerol is >90% of dietary fat
  • phospholipids, cholesterol, cholesterol esters, fatty acids are <10% of dietary fat
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9
Q

Essential Fatty Acids

A

1) Omega 3
- alpha-linolenic acid in veggie oils
- EPA & DHA in fish oils
2) Omega 6
- linoleic acid in corn oil
- arachidonic acid in meat & fish

  • used to synthesize eicosanoids in the body
  • deficiency is rare in US, needs to be added to artificial infant formula
  • ratio of O3 to O6 in the diet is important in regulating processes like BP, blood clotting, and immune functions
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10
Q

Trans Fatty Acids

A
  • most found in nature have cis double bond
  • hydrogenation process converts unsaturated FA to saturated FA produces trans FA
  • hydrogenated or partially hydrogenated veggie oils are primary ingredient in margarine or shortening
  • higher melting point than same FA in cis configuration
    raise cholesterol levels & increase risk of heart disease
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11
Q

Digestion of Lipids

A
  • fats need to be solubilized for digestion
  • dispersion of lipid phase into small droplets, done by bile acids
    Gastric + pancreatic lipases: hydrolyze triacylglycerol to FA + monoacylglycerol, produced FA act as surfactants
    Esterase: hydrolyzes monoacylglycerol + cholesterol ester
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12
Q

Utilization of Lipids

A
  • chylomicron delivers lipid to peripheral tissues directly
  • muscle uses fat as energy source
  • excess fat is stored in adipose tissues
  • brain does NOT use fat as energy source
  • when starved, liver converts FA to ketone bodies, which are utilizes as energy source by the brain + muscle
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13
Q

Proteins

A
  • essential structural component
  • enzymes, hormones, plasma proteins, antibodies
    Excess amounts?
  • source of energy
  • glucogenic amino acids -> glucose
  • ketogenic amino acids -> keto acids + FA
  • eventually converted to triacylglycerol in adipose tissue
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14
Q

Nitrogen Balance

A

Negative:
- inadequate dietary intake of protein
- trauma or illness
Positive:
- net increase in body protein stores
- growing children, pregnant women, or adults recovering from illness

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15
Q

Essential Amino Acids

A
  • cannot be synthesized by the body or not enough (arginine, methionine, phenylalanine)
  • if not in diet, new proteins cannot be made without breaking down other body proteins -> negative nitrogen balance
  • mixed sources of protein necessary for vegetarian diet
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16
Q

Digestion of proteins

A

1) Gastric Digestion
- pH = <2
- low pH denatures proteins
- pepsins (stable + active acidic pH, aspartic protease)
2) Intestinal Digestion (peptidases in luminal surface
- brush border, luminal surface of epithelial cells
- rich in peptidases
- produces free amino acids & di/tripeptides
3) Intestinal Digestion (intracellular peptidases)
- amino acid & peptide transport systems
- intracellular hydrolysis of di/tripeptides
- practically only free amino acids are released to blood

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17
Q

Celiac Disease

A
  • celiac sprue
  • gluten intolerance (~2 million people)
  • autoimmune disorder in genetically predisposed individuals
  • caused by major proteins contained in wheat, rye, and barley
  • lining of small intestine gets inflamed and damaged (diarrhea, weight loss, malnutrition)
  • life long
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18
Q

Dietary Composition (avg consumption + energy content)

A

Av Consumption (male):
carbs -> 310 g
fat -> 94 g
protein -> 100 g
Energy Content:
carbs -> 4 cal/g
fat -> 9 cal/g
protein -> 4 cal/g
alcohol -> 7 cal/g

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19
Q

Energy Reserves of Humans

A
  • excess energy is stored mostly as fat in adipose tissue
  • glycogen in liver maintains blood glucose levels
  • glycogen in muscle is used for exercise
  • protein is not preferred as energy reserve
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20
Q

Caloric Homeostasis

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A
  • constant availability of fuels in the blood
    glucose is carefully regulated
  • if glucose <1.5 mM (27 mg/dL), coma and death will shortly follow
    Hyperglycemia: dehydration, hyperglycemic coma, complications of diabetes
21
Q

Energy for Brain

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A

1) Glucose
- brain uses more than 20% of total energy
- 100-120 g of glucose per day (preferred fuel)
- uses 15-20% of total oxygen
- constant energy need (awake or asleep)
2) Membrane potential
- NA/K ATPase
3) No energy source
- no glycoegn storage, brain does not use fat
4) Adaptation to starvation
- ketone bodies made from acetyl-CoA in the liver

22
Q

Protein-Energy Malnutrition

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A
  • quite common in developing countries (infants + young children, reduced ability to fight off infection)
    Marasmus:
  • inadequate intake of both protein + energy
  • thin, waster appearance
  • small for their age
    Kwashiorkor:
  • inadequate intake of protein with adequate energy intake
  • mainly children 1-3 yo
  • deceptive plump appearance due to edema
23
Q

Estimated average requirement (EAR)

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A

amount of nutrient estimated to meet the need of 50% of the health individuals in an age & gender group

24
Q

Recommended dietary allowance (RDA)

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A
  • two standard deviations above the EAR
  • sufficient to meet the need of nearly all (97-98%) healthy individuals in a group
25
Adequate Intake (AI)
- used when scientific evidence is inadequate to set an EAR - approximations of the average nutrient intake by a healthy population
26
Tolerable upper intake level (UL)
maximum level of daily intake of a nutrient without any health risk
27
Micronutrients (vitamins + minerals)
Vitamins: fat soluble -> A, D, E, K water soluble -> B & C Minerals: macro -> Ca, Mg trace -> iron, iodine, zinc, copper, chromium, selenium, manganese, molybdenum, fluoride, boron
28
Vitamin A
- retinol, retinal, retinoic acid - produced from cartenoids, organic pigments in plants - delta-cis-retinal reversibly associates with opsins and function as light sensor deficiency? may cause night blindness Retinoic Acid: functions as hormones, regulating cell growth & differentiation - cartenoids are effective antioxidants, may reduce risk of cancers - stored in liver as *retinol palmitate* Dietary sources: dark green + yellow veggies, liver, egg yolk, butter, whole milk Deficiency? rare but 40-60% of Americans consume less than 2/3 of RDA
29
Vitamin D
- function as steroid hormones maintaining calcium homeostasis - synthesized from an intermediate in cholesterol biosynthesis - produced photochemically in the skin - insufficient exposure to sunlight can cause deficiency (rickets in young children, osteomalacia in adults) Dietary sources: vitamin D milk, saltwater fish, liver, egg yolk
30
Vitamin E
- occurs in the diet as tocopherol + tocotrienols - naturally occurring antioxidants protecting unsaturated FA - accumulate in circulating lipoproteins, cellular membranes, and fat deposits - reduces risk of cv disease by preventing oxidation of LDL (atherogenic) Dietary sources: veggie oils rich in polyunsaturated FA Deficiency? RARE
31
Vitamin K
- required for post-translational modification of glutamic acid residues to gamma-carboyxglutamic acid residues (allows for proteins to bind Ca) - essential for BLOOD CLOTTING - several proteins involved in blood coagulation require gamma-carboyxglutamic acid residues for Ca binding (prothrombin) - essential for BONE MINERALIZATION - several proteins in bone require gamma-carboyxglutamic acid residues for binding to hydroxyapatite (osteocalcin) - in carboxylation rxn, Vitamin K -> inactive epoxide form - regeneration requires active form of vitamin K epoxide reductase
32
Vitamin K antagonist & dietary sources
Antagonist: Warfarin - anticoagulant - prevents thrombosis - inhibits vitamin K epoxide reductase Dietary Sources: 1 in green veggies, 2 is synthesizes by intestinal bacteria Deficiency? RARE
33
Thiamin (B1)
- rapidly converted to thiamin pyrophosphate & thiamin triphosphate Thiamin pyrophosphate: functions as a cofactor in enzymatic catalysis - thiazole ring forms a carbanion, a strong nucleophile (pyruvate -> acetyl CoA by pyruvate dehydrogenase) Thiamin Triphosphate: function in transmission of nerve impulse in peripheral nerve membranes Severe thamin deficiency? Beriberi - characterized by muscular atrophy & weakness - may occur in populations exclusively relying on polished rice for food or in alcoholics
34
Riboflavin (B2)
- precursor of cofactors used in many redox rxns (FAD/FMN) - rich in milk, meat, eggs, and cereal products - riboflavin deficiency is rare sx: angular cheilitis, glossitis, and scaly dermatitis - usually seen in chronic alcoholics
35
Niacin (B3)
- exists as nicotinic acid or niacinamide in diet - rich in meats, peanuts, and enriched cereals - converted to cofactors (NAD & NADP) - electron acceptors or hydrogen donors - essential in many redox rxns & cellular respiration - NAD is also used for ADP-ribosylation Severe deficiency? Pellagra - dermatitis, diarrhea, and dementia - rare; primarily seen in alcoholics, pts with severe malabsorption and elderly on very restricted diets
36
Pyridoxine (B6)
- exists as pyridoxine, pyridoxamine, & pyridoxal in diet - rich in meats, veggies, whole grain cereals - converted to a cofactor, pyridoxal phosphate - transamination rxns in amino acid metabolism - synthesis of NTs & sphingolipids Deficiency: mild -> irritability, nervousness, depression severe -> peripheral neuropathy & convulsions *Significant fraction of US consumes less than recommended intake**
37
Biotin (B7)
- serves as cofactor for activation of carbon dioxide in carboxylase enzymes - covalently bound to lysine side chains in enzymes - rich in wide range of food sources Deficiency? RARE - may occur when raw egg white is consumes regularly, avidin in egg white forms a tight complex with biotin - pregnant women tend to have a high risk
38
Folic Acid (B9)
- converted to tetrahydrofolate - used in synthesis of amino acids + nucleotides - essential for DNA synthesis & cellular proliferation - rich in wide range of food sources Deficiency? inhibits DNA synthesis - produces abnormal RBCs (anemia) - increases risk of birth defects (neural tube defect) - common in alcoholics
39
Cobalamin (B12)
- contains Co in a coordination state of six - exists as complex with proteins - required for 2 rxns in humans (homocysteine -> methionine by methionine synthase, methylmalonyl-CoA -> succinyl-CoA by methylmalonyl-CoA mutase) - when insufficient, homocysteine & methylmalonic acid accumulate, which causes anemia & neurological damage Deficiency? rare except pts with severe malabsorption disease & long term vegetarians *taking metformin in higher doses for long periods may cause this*
40
Vitamin C /Ascorbic Acid
- functions as cofactor for several oxidases - required for hydroxylation of lysine & proline side chains, which is necessary for collagen stability - proper collagen stability is essential for maintenance of normal connective tissue, wound healing, and bone formation - nonenzymatic reducing agent aids in absorption of iron by reducing it to Fe in the stomach & protecting vitamins A, E, and some B from oxidation
41
Vitamin C deficiency
mild -> capillary fragility - easy bruising - decreased immunocompetence severe -> scurvy - decreased wound healing - osteoporosis - hemorrhaging - anemia - smokers require more vitamin C than nonsmoking adults - use of medadoses of vitamin C to prevent & cure common cold is controversial
42
Calcium
*most abundant mineral in the body* - makes bones - serves as second messenger - required for many enzymes - essential for blood coagulation & muscle contractility -maintenance of constant serum levels is VITAL - elaborate homeostatic control system exists, bones serve as a reservoir - Vit D is required for optimal utilization of Ca Dietary sources? dairy products, nuts, seeds, seaweed, beans
43
Calcium Deficiency
- sx resemble Vit A deficiency - may contribute to osteoporosis - achieving max bone density from age 10-35 is critical in reducing risk of osteoporosis later - proper calcium intake from diet & exercise maximizes bone density Mild deficiency? Muscle Cramps - significant portion of low income children & adult females do not consume enough
44
Iron
- component of heme, the cytochromes, and non-heme iron proteins - required for O2 transport, energy metabolism, cell proliferation, and immune defense - blood loss during menstruation increases need (twice the amount needed than men) - iron homeostasis is TIGHTLY REGULATED - essential for life but also extremely toxic - free iron generates free radicals, normally sequestered in the cell by ferritin & in blood by transferrin Deficiency? widespread in children + menstruating women - long term use of PPIs may interfere with iron absorption & lead to anemia (rare)
45
Iodine
- used for synthesis of thyroid hormones - best natural food sources is seafood - added to tablet salt Deficiency? Goiter -> enlargement of thyroid gland Cretinism -> severely stunted physical & mental growth
46
Zinc
- required for many metalloenzymes & zinc finger proteins - deficiency in children results in poor growth and impairment of sexual development - deficiency may cause poor wound healing, dermatitis, and impaired immune function - zinc intake may be marginal for many individuals
47
Copper
- required for many enzymes (lysyl oxidase) which is necessary for collagen cross linking - deficiency may cause anemia, bone mineralization, and blood vessel fragility
48
Selenium
- incorporates into ~25 selenoproteins in humans - selenoproteins contain selenocysteine residues, which are incorporated during translation - selenocystyl-tRNA binds to UGA codons in mRNA with a special sequence in 3-untranslated region Deficiency? RARE
Therapeutics
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