Transcript Lecture 7- 24 October 2013 Vitamins in metabolism and regulation

Lecture 7- 24 October 2013
Vitamins in metabolism and regulation
Most of this lecture taken from
Chapters 7,10,11 of Rolfes et al(Understanding
Normal and Clinical Nutrition
(Nutrition 2104/2105 text)
Outline of lecture 7
Vitamins
Definition of vitamins
Overview
Bioavailability
Precursors
Organic nature
Solubility
Water soluble vitamins
Fat soluble vitamins
Toxicity
Class exercise
Outline of lecture 7
Water Soluble vitamins
B vitamins and C
Found in what foods
Outline of lecture 7
B class-roles in metabolism and regulation of
metabolism
Thiamine
Riboflavin
Niacin
Biotin
Pantothenic acid
B6
folate
B12
Class exercise
Outline of lecture 7
Fat soluble vitamins
Found in what foods
Fat soluble vitamins class-roles in metabolism
and regulation of metabolism
A
D
E
K
Class exercise
More detailed comments
More Detailed Comments
Vitamins
Definition of vitamins-organic essential nutrients
required in tiny amounts to perform specific
functions that promote growth, reproduction and
maintenance of health and life.
-vita = life
-amine = containing nitrogen (first vitamins
discovered contained
nitrogen)
Vitamins
Overview
-two things attest to power of vitamins
absence- eg vitamin A –blindness
vitamin B3-niacin-dementia
presence-eg vitamin C prevents scurvy
vitamin E-appears to
protect against oxidation
component of
atherosclerosis
Vitamins
Overview
-differ from carbohydrates, lipids and proteins
-single units
-do not yield energy when broken downthey assist in energy yielding pathways
of carbohydrate, lipid and protein
metabolism
-daily dietary intake requirements are in
the microgram or milligram range
as opposed to gram range for
energy yielding nutrients
Vitamins
Bioavailability
-two factors-amount of vitamin in food
-amount absorbed and utilised
-efficiency of digestion and time of
transit through GI tract
-previous nutrient intake and nutrition
status
-other foods consumed at the same
time
-method of food preparation-raw,
cooked or processed
-source of nutrient-synthetic, fortified
or naturally occurring
Vitamins
Precursors
-also called provitamins
-provitamins-are metabolised to active form
-in measuring a person’s vitamin intake it is
important to count the active forms and
the potential of the precursors to be
converted to active forms
Vitamins
Organic nature
-this means they can be broken down
-eg-excessive heating destroys thiamin
-ultraviolet radiation-destroys
riboflavin
-oxygen- destroys vitamin C
-food processing-easily destroys
pantothenic acid
-B12-easily destroyed my microwave
cooking
-table 10-1
In Summary, p. 326
Vitamins
Solubility
-affects absorption, transport, storage, and
excretion by body
Vitamins
Solubility
Water soluble vitamins
-found in water portions of foods and
transported directly by blood
-no carriers are required for blood
transport
-stored in water portion of cells
-easy to excrete through kidney
Vitamins
Solubility
Fat soluble vitamins
-found in fat portions of foods and
transported first by lymph and
then by blood
-carriers are required for blood transport
-stored in body fat stores
-easier to keep stored in fat stores
rather than excrete-issue of toxicity
Vitamins
Toxicity
-water soluble-not likely to reach toxic levels
when consumed by supplements
-fat soluble-likely to reach toxic levels when
consumed by supplements
Class exercise
a) are all vitamin pre-cursors equally converted
to active form? Significance?
b) why the difference in likelihood of toxicity
between fat and water soluble vitamins?
c) how do you think fat soluble vitamins might
be transported in the blood?
Water Soluble vitamins
B vitamins and C
Found in what foods
Thiamine-whole grains
Riboflavin-milk products or whole grains
Niacin-meat, eggs, fish, poultry, whole grains
Biotin-widespread in foods, organ meats, egg
yolks, soybeans, fish, whole grains,
GI bacteria
Water Soluble vitamins
B vitamins and C
Found in what foods
Pantothenic acid-widespread in foods, organ
meats, broccoli, whole grains
B6-meat, fish, poultry, legumes, fortified
cereals
folate-fortified grains, leafy green vegetables,
legumes
B12-animal products, fortified cereals
B class-roles in metabolism and regulation of
metabolism
Thiamine-part of thiamine pyrophosphate
(TPP)-a coenzyme-small organic
molecule that associates closely
with certain enzymes
-TPP removes carbon from
pyruvate to make acetyl
CoA
TPP participates in Krebs cycle
B class-roles in metabolism and regulation of
metabolism
Riboflavin-part of co-enzymes FMN(flavin
mononucleotide) and FAD(flavin
adenine dinucleotide) (used in
energy metabolism)
-used in energy metabolism
B class-roles in metabolism and regulation of
metabolism
Niacin-part of co-enzymes NAD(nicotinamide
adenine dinucleotide) and NADP(its
phosphate form)-used in
energy metabolism
Biotin-part of coenzyme used in energy
metabolism, fat synthesis, amino acid
metabolism and glycogen synthesis
Pantothenic acid-part of co-enzyme A-used in
energy metabolism
B class-roles in metabolism and regulation of
metabolism
B6-part of coenzymes PLP(pyroxidal phosphate)
and PMP(pyridoxamine phosphate) used in
amino acid and fatty acid metabolism;
helps convert tryptophan to niacin and
serotonin
folate-part of THF(tetrahydrofolate) and
DHF(dihydrofolate) used in DNA
synthesis
B class-roles in metabolism and regulation of
metabolism
B12-part of coenzymes methylcobalamin and
deoxyadenosylcobalamin used in new cells
synthesis(THF metabolism)
-reforms folate coenzyme
-assists in catabolism of some fatty acids and
amino acids
-figure 10-13
Fig. 10-13, p. 347
file:///E:/Media/Animations/chapter10/Coenzyme_
Action/0709.html
E:\Media\Animations\chapter10\Metabolic_Pathwa
ys\1013.html
B VITAMINS
REGULATION OF METABOLISM
IS BY DEGREE OF PRESENCE OF
CORRECT FORM OF VITAMIN
Vitamin C- found in what foods –
-citrus fruits, cabbage type vegetables,
dark green vegetables(bell peppers and
broccoli), cantaloupe, strawberries, lettuce,
tomatoes, potatoes, papaya, mangoes
Vitamin C-functions
-collagen synthesis
-forms scar tissue(collagen)
-forms collagen matrix for bone growth
-antioxidant (toxic doses-prooxidant)
-thyroxin synthesis
-amino acid metabolism(conversion of
tryptophan to serotonin and
norepinephrine)
-helps in absorption of iron
Vitamin C-regulation of metabolism
REGULATION OF METABOLISM
IS BY DEGREE OF PRESENCE OF
CORRECT FORM OF VITAMIN
Class exercise
Explain the connections between source
and function of each of the
water soluble vitamins
Fat soluble vitamins
Found in what foods
A- retinol-fortified milk, cheese, cream, eggs,
liver
-Beta-carotene-spinach, dark leafy greens,
broccoli, apricots, cantaloupe,
carrots, sweet potato
D-sunlight, fortified milk, butter, cereals; veal,
fish
E-polyunsaturated plant oils, leafy green
vegetables, liver, yolks
K-gi bacteria synthesis, leafy green vegetables,
cabbage type vegetables, milk
Fat soluble vitamins class-roles in metabolism
and regulation of metabolism
A -retinol-protein synthesis
-rhodopsin synthesis
-not antioxidant(lipids)
-Beta-carotene-antioxidant
D-regulates bone mineral metabolism,
primarily calcium
E-antioxidant of lipids(fatty acids)
K-activates blood clotting proteins
FAT SOLUBLE VITAMINS
REGULATION OF METABOLISM
IS BY DEGREE OF PRESENCE OF
CORRECT FORM OF VITAMIN
Class exercise
Explain the connections between source
and function of each of the
fat soluble vitamins