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Chapter 13 Nutrition Notes
Nutrition (BIOL 256)
Community College of Baltimore County
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Water soluble vitamins
- Essential organic substances needed in small amounts of normal function, growth, and maintenance of tissues
- Thiamin, Riboflavin, Niacin, Patothenic acid, and Biotin are important for energy metabolism
- Vitamin B-6, folate, and vitamin B-12 are important for amino acid metabolism and red blood cell synthesis
- Vitamin C participates in the synthesis of numerous compounds including collagen and cholin is required for nervous system function and aids amino acid and lipid metabolism
Are WSV's stored in small amounts? Answer: Yes
WSV's toxicity and UL
- WSV's toxicity tends to be low because they are removed by the kidneys and excreted in the urine
- Retention of B-vitamin and C-vitamin is greater in foods that are prepared by steaming, stir-frying, and microwaving (Destroyed during cooking)
- Upper level intakes have been set for only 4 vitamins and choline
- Vitamin content can be decreased by exposure to heat, light, air, and alkaline substances
Coenzymes: Role of B vitamins
- All B-vitamins form coenzymes; small organic molecules that are a type of cofactor
Cofactor Coenzymes
- Metals are cofactors
- Cofactors combine with inactive enzymes (called apoenzymes to form active enzymes called holoenzymes) that are able to catalyze specific reasons
B Vitamins in energy metabolism
All 8 B-vitamins participate in energy metabolism; some also have other roles within cells
B-vitamins in energy metabolism, the need for many of them increases somewhat with higher amounts of physical activity
B-vitamins present as vitamins and or coenzymes, both of which are sometimes bound to protein
Digestion frees B-vitamins from coenzymes or protein
Free vitamins are the main form absorbed in the SI (50-90% are absorbed)
Once inside, the coenzyme forms of the vitamins are re-synthesized
B-vitamins and Epigenetics
- Epigenetics is the study of heritable changes to gene expression that are not due to changes in the underlying DNA sequence
- One mechanism is DNA methylation, 1 of the bases in DNA
- The B-vitamins along with choline, are key components in forming methyl (Too little or too much methylation are thought to cause some disease processes)
Enrichment and fortification of grains
- Grains are important sources of many B-vitamins, minerals, and fiber
- When grains are milled, nutrients, milling leads to a loss of vitamins, minerals, and fiber
- 4 B-vitamins-- Thiamin, Riboflavin, Niacin, and Folic acid, and mineral iron are added to cereal and grains
Disease beriber
- Disease beriber were known in Asian countries where polished white rice was the main food
- Cause extreme weakness, paralysis, and fatigue often died within several months
Thiamin
- Vitamin B-
- Central carbon attached to a 6 member, nitrogen-containing ring and a 5-member sulfur- containing ring
- 2 phosphate groups added to form this vitamin's coenzyme, thiamin pyrophospate (TPP), also thiamin diphosphate (TDP)
- The chemical bond between each ring and the central carbon in thiamin is easily broken by heat and vitamin can no longer function in the body (Destroyed by Akaline conditions)
Thiamin in foods and Needs
- Pork products, whole grains, ready to eat cereals, enriched grains
fluorescence 2. Contains 3 linked 6-membered rings with a sugar alcohol attached to the middle ring
Riboflavin in Foods
- 1/4 is from milk products
- Rest comes from coffee, tea, nonalcoholic beverages, meat, and bakery products
Absorption, Transportation, Storage, & Excretion of Riboflavin
- HCL releases riboflavin from its bound forms
- 60-65% of free riboflavin is absorbed, primarly via active transport or facilitated diffusion in the SI
- In blood, its transported by protein carriers
- Riboflavin is converted to its coenzyme forms in most tissues, but this occurs mainly in the SI, liver, heart, and kidneys
- Excreted via urine
Functions of Riboflavin
- FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide)
- Have oxidation and reduction functions
- FAD is oxidized form of the coenzyme
- When it is reduced, FADH2 is the result
Energy Metabolism
- In the citric acid cycle, the oxidation of succinate to fumorate the FAD-containing enzyme succinate dehydrogenase (Riboflavin is required in this citric acid cycle)
- The FADH2 formed in this reactions donate hydrogen to the electron chain
- Glucose---> Pyruvate--->Acetyle-CoA--->
- Succinate----> Fumaragte
Activation of Other B-vitamins
- Formation of niacin from the amino acid tryptophan requires FAD
- Active vitamin B-6 coenzyme requires FMN
- FAD is required for the synthesis of the folate matobolite 5-methyl-tetrahydrofolate
Antioxidant Function
- The synthesis of the antioxidant compound glutathione depends on the FAD containing enzyme gluthathione reductase
Riboflavin Deficiency
- Ariboflavinos: Condition resulting from a lack of riboflavin
- Inflammation of throat, mouth, tongue, and cracking of tissue are corners of the mouth
Niacin
- Pellagra: Dermatitis, diarrhea, dementia, death (Deficiency disease of the B-vitamin niacin)
- Vitamin B-3: Nicotinic acid and nicotinamide (Used to synthesize the niacin coenzymes: (NAD+ and NADP+)
Niacin in foods
- Poultry, meat, and fish provide about 27%and 28% is from food with flours and grains
- Heat-stable
- RDA women 14 mg and 16 mg for men
- DV is 16 mg
- Nutrient x mg tryptophan/60 mg tryptophan/ mg nutrient
Absorption, Transportation, Storage, & Excretion of Niacin
- Absorbed from stomach and the SI by active transport and passive diffusion, so generally almost all niacin that is consumed is absorbed
- Less than 30% is absorbed due to being tightly bounded to protein
Functions of Niacin
NAD+ NADP+ are active participants in oxidation-reduction reactions
Function in at least 200 reactions in cellular metabolic pathways, especially those that produce ATP
NAD+ is required mainly for the catabolism for carbohydrates, proteins, and fats
Storage is minimal and excreted via urine
Functions of Panthothenic Acid
- CoA is essential for the formation of acetyl-CoA from breakdown of carbohydrates, protein, alcohol, and fat
- Acetyl-CoA molecules most often enter the citric acid cycle (Important biosynthetic building block used to build fatty acids, cholesterol, bile, acids, and horomones)
- Beta-oxidation of fatty acids also requires coenzyme A
- Coenzyme A, pantothenic acid also donates fatty acids to proteins in a process that can determine location and function
- ACP attaches to fatty acids and shuttles through the metabolic pathway that increases their chain length
- Glucose
- Fatty acids-----> Acetyl CoA<------ Amino Acids
- Alcohol
Panthothenic acid deficiency
- Headache, fatigue, impaired muscle coordination, burning hands and feet, and GI tract disturbances (Rare)
Biotin
- Vitamin B
- Biotin heals rashes and paralysis
- Coenzyme that participates in reactions known as carboxylations (Addition carboxyl group)
Sources of Biotin
- Whole grains, egg yolks, mushrooms, nuts, legumes
- We excrete more biotin than we consume
Absorption, Transportation, Storage, & Excretion of Biotin
In the SI, the enzyme biotinidase releases biotin from protein and lysine
Free biotin is absorbed in the SI via a sodium-dependent carrier
Stored in small amounts in muscles, liver, and brain
Excreted via urine and bile
Functions of Biotin
- Functions as a coenzyme for several carboxylase enzymes that add carbon dioxide to various compounds (Require carbohydrates, proteins, and fats)
Glucose
|
(Biotin is required here)Pyruvate
|
Acetyl-CoA
Oxalocetue
Citric Acid Cycle
ATP CO
Pyruvate------> Oxalocetate-------> Glucose
3 carbons ADP+Pi 4 carbons Citric acid cycle
Biotin Deficiency
- Genetic defect in infants
- Skin rash, hair loss, convulsions, low muscle, and impaired growth
Vitamin B-
- All amino acids require a vitamin B-6 coenzyme in their metabolism
- Family of 3 compounds: pyridoxal, pyridoxine, and pyridoxamine (Can be phosphroylated to become active B-6 coenzymes)
- Primary vitamin B-6 coenzyme is pyridoxal phosphate (PLP)
- B-6 is converted to PLP by adding a phosphate group (PO4) to its hydroxyl group
from tyrosine, and gamma-aminobutyric acid (GABA) from glutamic acid 3. Synthesis of histamine from amino acid histidine also vitamin B- 4. PLP participates in vitamin formation (Synthesis of B-vitamin niacin from amino acid tryptophan)
B-6 Deficiency
- Rare in North America, but about 10% have low vitamin B-6 blood concentration
- Symptoms are seborrheic dermatitis, microcytic hypochromic anemia, convulsions, depression, and confusion
- Women, older adults, Blacks, smokers, users of oral contraceptive agents, alcoholics, and those underweight or consume poor diets
Pharmological Use of Vitamin B-
- Supplements, carpal tunnel syndrome, PMS, and nausea
Folate
- Vitamin B
- Found in leafy green vegetable (Found in natural sources)
- Folic acid refers to synthetic form of vitamin found in supplements and fortified foods
- Has 3 parts: para-aminobenzoic acid (PABA) and 1+ molecules of the amino acid glutamic acid (glutamate) (1 glumate is present, and is designated folic acid (folate monoglutamate))
- Food has 90% of the folate molecules have 3+ gluytamates attached to the carboxyl group aka polyglutamates
Folate in Foods
- Liver (very high source), green leafy veggies, grains, legumes, nuts, avocados, and citrus fruits
- Mandatory fortification of enriched cereal grains with folic acid in the US
- Food processing and preparation can destroy up to 90% of the folate in food
- Folate is extremely susceptible to destruction by heat, oxidation, and UV light
Dietary folate equivalents (DFE)
RDA folate is expressed as dietary folate equivalents (DFE)
DFE reflect the differences of food folate and synthetic folic acid
1 DFE= 1 ug foodl folate= 0 ug folic acid taken with= 0 ug acid taken on an empty stomach
DFE= ug food folate + (ug folic acid x 1)
Daily value of 400 ug x 0.
Folate needs
- RDA for adults is 400 ug/day for pregnant woman
- Average intake is 601 DFE (men) and 459 DFE (women)
Absorption, Transportation, Storage, & Excretion of Folate
- To be absorbed., folate polyglutamates must be broken (hydrolyzed) in the GI tract to the monoglutamate form
- Enzymes known as folate conjugases produced by absorptive cells, and remove the additional glutamates
- Monoglutamate form is then actively transported across the intestinal wall
- Large doses of folic acid absorbed by passive diffusion
- Synthetic folic acid consumed with food is nearly 100% bioavailable (Consumed with food absorption is reduced)
- Portal vein delivers the monoglutamate for of folate from the SI to liver (Folate is either stored in the liver or released into the blood for delivery for other tissues in the body)
- Once folate is transported into a cell it is converted to polygulamate form that traps folate in the cell
- Excreted in bile and reabsorbed by enterohepatic circulation (Alcohol interferes with this)
Functions of Folate
- Coenzymes are required for the synthesis and maintenance of new cells
- Function in 1-carbon transfer reactions in the body
- Folate coenzyme are formed from a central coenzyme form called tetrahydrofolic acid (THFA)
- Folate coenzyme are critical for DNA synthesis, DNA methylation, anand amino acid metabolism
DNA Synthesis
- Normal cell division requires adequate folate because THFA is required for the synthesis of DNA
- Folate coenzyme supplies the CH
- THFA is also needed for the synthesis of purines in DNA
Epigenetic Modification of DNA
Absorption, Transportation, Storage, & Excretion of Vitamin B-
Healthy adults absorb about 50% of B-
Mouth: Salivary glands produce R-protein
Stomach
a. HCL and pepsin release vitamin B-12 bound to protein in food
b. Free vitamin B-12 binds with R-protein
c. Parietal cells secrete intrinsic factor
- Small intestine
a. Trypsin from the pancrea releases R-protein from vitamin B-
b. Vitamin B-12 links with intrinsic factor
Illeum: Vitamin B-12 intrinsic factor complex is absorbed into blood and binds to transport protein transcobalamin
Liver: Vitamin B-12 is stored in the liver
Function of B-
- Required for 2 enzymatic reactions
- Formation of the amino acid methionine from amino acid homocysteine is catalyzed by the enzyme methionine synthase which requires B-12 coenzyme methylcobalmin
- Homocysteine accepts a methyl group from methylcobalamin, which form methionine
- Methionine in turn is the source of S-adensyl methionine (SAM) (Methyl donor)
- Methylation reactions are important for DNA and RNA regulation myelim regulation and the synthesis of many biochemical compounds
- Methionine synthesis
- Mutase requires another B-12 coenzyme (5-deoxyyadenoscylcobalamine) to metabolize fatty
B-12 Deficieny
- Cause neurological problems and elevated blood homocysteine
Choline
- Can be obtained from the diet and can be synthesized in cells
- Synthesis alone cannot meet requirements and low dietary intakes can cause liver and
muscle damage
Choline Foods
- Found in free choline or other compounds like phosphatidycholine
- Animal origin and large contributors are grains, nuts, veggies, and fruits
Absorption, Transportation, Storage, & Excretion of Choline
- Choline absorbed from the SI by way of transport proteins
- Oxidized to form compound betaine and both compounds are excreted in urine
- Liver takes up choline rapidly from blood delivered by the portal vein from the SI
- All tissues contain choline
Choline function
- Enable cell membranes to form and that promote normal nervous system and liver function
- No deficiency disease, but can cause liver and muscle damage
Vitamin C
- Humans rely on vitamin C in diets
- Aka ascorbic acid (As oxidative) in many processes in the dehysroasor human body primarily as an acid electron donor
Vitamin C foods
- Fruits and veggies (citrus fruits, peppers, and green veggies)
- 5 servings a day of fruits and veggies
Absorption, Transportation, Storage, & Excretion of Vitamin C
- Absorption of vitamin C occurs in the SI by active transport and facilitated diffusion
- Absorbed at (30-200 mg)
Chapter 13 Nutrition Notes
Course: Nutrition (BIOL 256)
University: Community College of Baltimore County
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