Cellular & Molecular Bioscience- Micronutrients - Vitamins Flashcards
Macronutrients
LARGE amounts (>grams/day)
Micronutrients
SMALL amounts (mg - μg/day)
Do not yield energy
MACRO-NUTRIENT - Principal component of the body
How much of daily intake
55-65% of the body weight (25% in bones – 75% in the brain)
It does NOT provide energy
What are the roles of water?
Needed for nearly all the cellular reactions
SOLVENT -It moves nutrients and waste within/between cells/tissues/organs
Maintain the body temperature – Thermoregulation
Moisten tissues (in the eyes, nose and mouth) and lubricate joints
Protect your spinal cord and other sensitive tissues
Dispose of through urination, perspiration, and bowel movements
Water balance
balance between water intake and output (loss)
Water Output
The minimum obligatory water excretion is about 500 mL
Above this amount, excretion adjusts to balance intake
Water Balance Disorders
Dehydration(hypohydration) :
Mild (< 5% body weight) - dry skin and mouth, tiredness, lack of concentration
Moderate (5-10%)
Severe (>10%) - seizures, kidney failure and even death
Overhydration
Excessive water intake that affects the electrolyte concentrations and could result in electrolyte imbalance. Urine production is significantly increased
Water intoxication
In rare cases, usually kidney disorders, drinking excessive amounts of water can lead to intoxication - hyponatraemia (due to low levels of sodium in the blood)
Does essential micro- nutrient provide energy?
no
What are the roles of electrolytes?
- many serve as electrolytes
- regulate fluid balance, blood pH and are critical for nerve and muscle function (action potential, neuromuscular junction, cell signalling)
Classification of minerals
MAJOR minerals
>100mg required per day
Sodium, Potassium, Chloride, Calcium, etc
TRACE minerals
<100mg required per day
iron, copper, zinc, selenium, fluoride etc.
What are enzymes?
proteins - act as biological catalysts to speed up specific enzymatic reactions by reducing activation energy
Cofactors activate
enzymes
Essential ions>
activator ions - loosely bound
metal ions for metalloenzymes - tightly bound
Coenzymes >
Cosubstrates - loosely bound
Prosthetic groups - tightly bound
HOLOENZYME
A complete catalytically-active enzyme together with its cofactor
APOENZYME
The protein part of the enzyme on its own without its cofactor
Essential MICRO-NUTRIENT
They must be provided by the diet (small amount)
Some essential vitamins are synthesised from dietary precursors
Do NOT provide energy
Roles of vitamins
Essential for metabolic processes
Assist enzymes as coenzymes
Act as individual units
What are the 2 classes of vitamins
WATER soluble
Excess excreted via kidney by urine
Increased risk of deficiency
Decreased risk of toxicity (excessive intake)
Vitamins B and vitamin C
LIPID soluble
Excess stored in the body (usually in liver)
Decreased risk of deficiency
Increased risk of toxicity
Vitamins A, D, E & K
Water soluble Vitamins – B group vitamins
Serve as coenzymes to Assist enzymes (to release energy)
But they do not directly provide the body with fuel
May have overlapping functions
Named in order of discovery, B4, B8, B10, B11 no longer classified as vitamins as it was found that they are produced by the body
Some can be synthesised by bacteria of the intestinal flora (Mutualism)
Vitamin B1 - Thiamine
roles
Part of the coenzyme TPP (thiamin pyrophosphate)
To activate many enzymes (holoenzymes) involved in:
Carbohydrates catabolism (e.g. pyruvate oxidation into acetyl-CoA – lecture 6)
Neuronal action potential conduction & neuro-muscular transmission
sources?
(whole grains, legumes, pork as the richest source, fruits, and yeast)
Vitamin B1 – Thiamine – deficiencies
Malnourished – inadequate intake
Prevalent in diets largely based on white rice (low content of B1)
Alcohol impairs thiamine absorption
Athletes and pregnant women with high carbohydrate catabolism
Beriberi - Prolonged thiamine deficiency, affecting different organ systems
Dry beriberi – affects nervous system (paralysis, peripheral neuritis)
Wet beriberi – affect cardiovascular system (cardiac failure, characteristic oedema)
Wernicke–Korsakoff syndrome - severe form of dry beriberi (mental confusion, jerky eye movements, memory loss)
no risk of toxicity
Vitamin B2 - Riboflavin
roles
part of the coenzymes FMN (flavin mononucleotide) and FAD (Flavin adenine dinucleotide)
FAD assists enzymes involved in energy metabolism
FAD is an electron carrier/acceptor during the citric acid cycle
sources?
Dairy products, eggs, green vegetables and almonds
Vitamin B2 Deficiency
Only common in developing countries
Symptoms - inflammation of the mouth, lips, and GI tract (stomatitis)
no risk of toxicity
Vitamin B3 – Niacin
roles
Part of the coenzyme NAD (Nicotinamide adenine dinucleotide) and NADP (Nicotinamide adenine dinucleotide phosphate)
Both act as coenzymes of enzymes involved in oxidorectuctase metabolic reactions (NAD - catabolic and NADP - anabolic)
NAD is an electron carrier during glycolysis and citric acid cycle NAD++ H+ + 2e- ⇄ NADH
sources?
Meat, poultry, fish, and nuts
Vitamin B3 – Niacin – deficiencies
body can make this vitamin from the tryptophan (essential a.a)
needs are met AFTER protein synthesis
Vitamin B3 Deficiency
In diets based on maize (low content of niacin and tryptophan)
Chronic alcoholics also at risk
Pellagra - characterised (3Ds) - name
Dermatitis
Diarrhoea
Dementia
Vitamin B3 toxicity
large dose of nicotinic acid (supplements / food)
Skin flushes, liver damage
Vitamin B5 – Pantothenic acid
roles
part of the coenzyme A, which acts as a coenzyme of enzymes crucial to many metabolic pathway, such as:
Enzyme converting pyruvate into acetyl-CoA
Fatty acids activation (in fatty acyl CoA) to enter the β-oxidation cycle
sources?
widespread in foods
What are the three forms of Vitamin B6? ROLES
converted to the coenzyme PLP (pyridoxal phosphate), of many enzymes of numerous reactions (>100), e.g.:
In tryptophan metabolism (link to vitamin B3 synthesis)
Synthesis of neurotransmitters, haem, nucleic acids
Urea metabolism
sources?
Meats, fish, poultry, potatoes and other starchy vegetables
And intestinal normal flora release vitamin B6
Rare deficiencies B6 vitamin
Alcohol contributes to the destruction of vitamin B6
Neurological, anaemia, inflammation
Toxicity - cause nerve degeneration
Vitamin B7 - Biotin
roles
It is a coenzyme itself
Critical to assist enzymes of the citric acid cycle and other
sources?
Widespread in natural foods
Also, vitamin B7 id produced by bacteria in the GI
B7 - Deficiencies rarely occur
Risk for people who eat large amount of raw eggs, as a protein in egg white seizes biotin and reduces its absorption
symptoms include skin rash, hair loss, and neurological impairment
Vitamin B9 – Folic acid / folate
roles
Converted to coenzyme THF (tetrahydrofolate) of enzymes: involved in the biosynthesis of nitrogenous bases (DNA/RNA), amino acids and the embryonic development of spinal cord
sources?
Dark green and leafy vegetables, legumes, fruits, nuts
B9 DEFICIENCY - pregnant women and people with cancer are at risk
Some anti-cancer drugs (e.g. methotrexate) interfere with folic acid synthesis
To support baby’s development, folic acid supplement in pregnancy (first 12 w)
Effects -
In pregnancy - low birth weight, premature birth and neural tube defects (spina bifida)
Also, megaloblastic anaemia (larger RBCs) due to faulty erythrocyte multiplication and maturation
Vitamin B12 – cobalamin
Roles
Converted to 2 active forms -coenzymes of enzymes involved:
Production of THF coenzyme from folic acid (vitamin B9)
Regulation of cell replication and nerve activity
sources?
Foods of animal origin (meat, fish, poultry, shellfish)
Deficiency B12 (some are consequences of reduced Vitamin B9)
Megaloblastic anaemia,
gastrointestinal (diarrhoea, loss of bladder control)
neurological symptoms (seizures, degeneration of spinal cord)
Vitamin C – ascorbic acid
roles
coenzyme of enzymes involved in: the synthesis of collagen (connective tissue of bones, teeth, tendons), carnitine (fatty acids transporter), steroids, etc
Potent antioxidant to neutralise free radicals
sources?
Citrus fruits/juices, tomatoes, potatoes, other vegetables
Vitamin C Deficiency (rare in developed countries)
Scurvy - swollen gums, bruising, haemorrhage, bone fracture, loose teeth, poor wound healing and anaemia
Toxicity - GI distress after very large dose
Vitamin A – Retinol / retinal / retinoic acid
ROLES
does NOT form a coenzyme
Three forms (retinol, retinal, retinoic acid). Stored in the liver
Promoting vision (major role in eyesight)
Participating in protein synthesis and cell differentiation,
Supporting reproduction and regulating growth
sources?
(Retinol): fortified milk, fish, liver
(carotenoids): broccoli, spinach, orange fruits, carrots
Vitamin A deficiencies
Night blindness - Blindness after the sun goes down due to corneal damage
Failure to adapt vision after changes of lights (flash of bright light at night or after dark)
Xerophthalmia - Corneal damage. Total blindness
Keratinisation - dry/ hyperkeratotic skin, skin infection
Toxicity oF VIT A
large dose of supplements
Skin rush, hair loss, liver and bone abnormalities
Toxicity in pregnancy can lead to birth defects
Vitamin D – calciferol
It comes in two major forms. Vitamin D2 and D3
Sunlight UVB induces the synthesis of pre-vitamin D3 > PMP-202
ROLES
Regulate calcium in the blood (mineralization of bones)
Regulates the keratinocyte turnover in the skin
sources?
Synthesized in the uncovered skin with the help of sunlight (UVB)
Diet: fortified milk, liver, fatty fish (salmon, sardines)
Vit D - deficiency
rickets (children)- distortion of the long bones of the legs, pelvis, spine
osteomalacia (adults) - leading to bone softening and osteoporosis
Toxicity - Vit D
Hypercalcaemia - calcium deposits in organs (e.g. kidneys, liver, heart), anorexia, insomnia, abnormal bone formation
Vitamin E – calciferol
Roles
Act as an antioxidant against free radical species
Involved in smooth muscle growth and the maintenance of nerves
Sources?
(degraded by heat) - Vegetable oils, nuts, seeds, whole grains
Vit E deficiency
Usually due to malabsorption of fat rather than lack of dietary intake
Symptoms include nerve damage and anaemia
Toxcicity in vit E
Augments the effects of anticlotting drugs
Vitamin K – calciferol
There are three forms of Vitamin K (K1, K2, K3) - Roles
Acts as a coenzyme to assist the formation of coagulation factors
participates in the metabolism of bone proteins, osteocalcin
Sources of Vit K
Green leafy vegetables, broccoli, brussels sprouts, and cabbage
Vit. K2 - Produced by bacteria of the gut flora
Vt k - deficiency
Rare
Liver damage (e.g. alcoholics) or newborns with sterile intestines (no gut flora)
anaemia, bruising and bleeding at the mucosal membranes (e.g. gums, nose)
no toxicity known. not stored in great quantities in liver.
