human nutrition Flashcards
factors affecting nutritional status
biological - genetic, phase of lifestyle
psychology -satiety, appetite, palatability of food
social - availability of food, cultural customs
energy expenditure
disease presence
importance of nutrition in health + disease
prevention, progression + management of disease
excess weight -> covid 19 complications
main class - carbohydrate
main energy source, some create long satiety for weight control, some are digested rapidly + stimulate craving
main class - fats
main energy source + storage, linked to heart disease
main class - proteins
provide cell structure
for cell functions, communication, signaling
‘last resort’ energy substrate
main class - essential fatty and amino acids
essentials - cannot be synthesized de novo + must be obtained through diet
fatty acids = linoleic acid and a-linoleic acid
amino acids - 10 PVT TIM HALL
main class - vitamin and minerals
purpose of nutrients
supply energy needed for body to perform work
provide building blocks for synthesis of other important molecules
support function of metabolic pathways
how is energy obtained from diet
food digested and absorbed -> products taken up by cells + oxidised to produce energy in ATP form
energy expenditure + influencing factors
sum of basal metabolic rate (energy needed for normal physiological functions when body is at rest), energy used in physical activity (most important changeable variable), thermic effect of food (during digestion, absorption, metabolism)
energy balance with weight gain / loss
subcutaneous fat, visceral fat, ectopic fat
obesity - high intake of high-calorie food / decrease in physical activity
losing weight - combination of diet + exercise + behaviour interventions
dietary reference intake values
EAR - 50% healthy indiv requirement
RDA - margin of safety ~97-98%
AI - estimation. of nutrient intake
UL - highest level of daily nutrient uptake with no adverse effects
MUST - malnutrition universal screening tool
BMI score -> weight loss score -> acute disease effect score -> overall risk of malnutrition -> management guidelines
nutritional assessments
anthropometric - bmi (limitation in athletes / limb deformed), waist-to-hip ratio, mid-arm circum
(easy to administer, cheap, quick but more analysis needed)
biochemical - blood, urine, farces
(objective + quantities but affected by med+diseases)
dietary data - food frequency questionnaires, direct analysis of food
classify vitamins and minerals
micronutrients - form prosthetic groups of enzymes / serve as cofactors, as hormones, as cell growth + proliferation + differentiation
fat-soluble vs water-soluble vitamins
fat: absorbed alongside dietary fats into lymph, transported by carrier protein + receptors, stored in liver / fat tissues
water: directly absorbed into blood, excess removed
vitamin A
as antioxidant, aura (retinal to produce rhodopsin), activation (gene expression, reproduction maintenance)
deficiency - night blindness, wound healing
excess - liver toxicity, birth defects
vitamin D
1,25-dihydroxyvitamin D is active form
for calcium uptake
deficiency - rickets in children, osteomalacia in adults
excess - deposition of Ca in organ
vitamin E
antioxidant
deficiency - haemolytic anaemia, neurological + neuromuscular dysfunctions, retinopathy
vitamin K
blood clotting, gamma-carboxylation of proteins
crushed by warfarins, cannot be found in infants
deficiency - bleeding + bruising, anaemic
vitamin B - energy-releasing 1,2,3,5,7
B1 thiamine - coenzyme in carb metabolism (with pyruvate to gen ATP), deficiency - beriberi
B2 riboflavin - for electron transfer, deficiency - skin lesions
B3 niacin - for electron transfer, defi- pellagra
B5 - component of coenzyme A
B7 - coenzyme in synthesis of fat, glycogen + amino acids defi- depression, muscle pain
vitamin B - haematopoeitic 9,12
B9 floic acid - one-C metabolism, coenzyme in nuclei acid + amino acid metabolism, defi- megaloblastic anaemia
B12 coenzyme for reaction, defi-anaemia
vitamin B6
coenzyme of various enzymes (in amino acid metabolism), deficiency - neurological symptoms + anaemia
Vitamin C
antioxidant - protest cells from ROS
reducing agent - keep iron reduced -> collagen stability
deficiency - scurvy ( collagen - defective connective tissues)
excess - renal oxalate stones
use off vitamin supplements
sodium, chloride, potassium
regulation - what stays and leaves, electrolytes + body fluids
sodium excess (hyponatremia) -> cerebral edema, hypernatremia -> dehydration
potassium deficiency + excess (hypokalemia + hyperkalemia) -> arrhythmia
chloride deficiency -> acid-base disturbance
calcium, phosphate, magnesium
regulated by 3 key hormones - calcitriol (kidneys), parathyroid hormone + calcitonin (pth gland)
ca deficiency - osteoporosis, arrhythmia, excess - kidney stones
phosphate excess- calcification of soft tissues
magnesium deficient - arrhythmia
iron
component of heme binding to o2 - found in haemoglonin, myoglobin + redox enzymes
non-heme: complexed to sulphur in proteins
needed for normal amount of haemoglobin + cytochromes + iron-sulphur complexes for o2 transport
defi- anaemia
zinc
found in 100 enzymes used in carb + energy metabolism, protein + nuclei acid synthesis
copper
remove superoxide, ROS
deficiency - anaemia
excess - liver cirrhosis
enzymes to facilitate biochemical reaction
cells perform chemical reactions continuously or accomplish operations -> millions of reactions per second
enzymes as catalysts
lower activation energy barrier
one enzyme catalyses one reaction
types of enzymes
oxidoreductases - transfer H + P atoms / electrons
transferase
hydrolyse
isomerise
lysase
ligases
specificity + location of enzyme reactions
active site - cleft, crevice formed by 1< regions of polypeptide chain
lock-and key model — amino acid arranged in comp 3d surface to recognise substrate + bound h-bond / e. a
induced-fit mode, — side chains of amino acid in active site reposition to interact with binded substrate
enzyme rate + substrate conc
bisubstrate enzymatic reaction
two substrate giving 2 products
different factors affecting enzyme reaction rate
substrate concentration - rate increases when conc increase, maximum rate achieved at high velocity
enzyme conc - rate increase linearly with conc
pH - diff optimum range for diff pH depending on location in body
temp - reaction fastest and optimum temp reached, high temp cause active site to lose its shape -> enzyme lose ability to catalyze reactions
types of enzyme activity regulation
by inhibitors - compounds bind reversibly to active site
(all products are reversible inhibitors of enzymes producing it)
by conformation change - affect active site
allosteric site activation + inhibition
covalent modification - phosphorylation
protein cleavage + break peptide bonds
change amt of enzyme
competitive vs non-competitive inhibition of enzyme activity
competitive - compete with substrate to bind with site + high sub conc can overcome inhibition
non-competitive - affect binding, high sub conc cannot over on inhibition
allosteric molecules for regulating enzyme
allosteric site = away from activity site ,bind to enzyme
activator - change distorted site to complem shape
inhibitor - change active site to distorted
much stronger effect on enzyme velocity, can be non-substrate/product, rapid effect
proteolytic cleavage for regulating enzyme
break peptide bonds between amino acids
enzymes become functional (eg regulate blood clotting + activate protease when attaching to injury site -> clots formed)
enzymes using multiple regulation
