Nutrition, Diet and Body Weight Flashcards
Define metabolism
Metabolism is the set of processes which derive energy and raw materials from food and use them to support repair, growth and activity of the tissues of the body to sustain life
What is the difference between anabolism and catabolism
- Anabolic pathways - use energy and raw materials to make larger molecules for growth and maintenance
- Catabolic pathways - break down larger molecules to release energy in terms of reducing power (release H)
Explain the functions of metabolism
○ Oxidative pathways - convert food into energy
○ Fuel storage and mobilisation pathways - allow fuel to be stored when not needed such as through glycogen
○ Biosynthetic pathways - produce basic building blocks for cells
○ Detoxification pathways - remove toxins
Define energy
Energy is the capacity to do work
Explain why the body needs energy
○ Biosynthetic work (anabolism) - synthesis of cellular components
○ Transport work
§ Maintenance of ion gradients
§ Nutrient uptake
○ Mechanical work - muscle contraction
○ Electrical work - nervous impulse conduction
○ Osmotic work - kidney
Explain the biological role of ATP
• Gamma phosphate in ATP contains chemical bond energy to drive cellular processes
○ ATP is not stored, only molecules that can be broken down to produce ATP, including glycogen and fat
○ Energy released in exergonic reactions used to drive ADP + P -> ATP
Explain the biological role of creatine
• Creatine phosphate - when ATP levels are high, ‘phosphate bond energy’ may be stored in phosphocreatine
○ Creatine + ATP Phosphocreatine + ADP (via creatine kinase enzyme)
○ Creatine phosphate provides immediate energy - energy rich molecules in muscle
○ Creatine kinase (enzyme) a marker for myocardial infarction
§ CK is released from cardiac myocytes when damaged in myocardial infarction
§ Appears in blood after a few hours
○ Creatinine is the breakdown product of creatine and phosphocreatine
§ Produced by a spontaneous reaction at a constant rate unless muscle is wasting
§ Excreted via kidneys
Outline how creatinine is used as biological marker
§ Produced by a spontaneous reaction at a constant rate unless muscle is wasting
§ Excreted via kidneys
§ Creatinine excretion power 24h is proportional to muscle mass of the individual
□ Provides a measure of muscle mass
§ Creatinine concentration in urine is a marker of urine dilution
□ Can be used to estimate true urinary loss of many substances
Describe the structure and categories of carbohydrates
○ Contain aldehyde, ketone and multiple OH groups
○ Monosaccharides - single sugar units (3-9 C-atoms)
§ Glucose, fructose, galactose
○ Disaccharides - (2-3 units)
§ Maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose + galactose)
○ Oligosaccharide - (3-12 units)
§ Dextrins - from digestion of starch using amylase
○ Polysaccharides - (10-1000’s units)
§ Starch, glycogen, cellulose - all glucose monosaccharide monomers
§ Cellulose cannot be broken in humans as we don’t contain enzymes to break ß-1,4-glycosidic bonds between glucose
What are essential amino acids and list them
○ 9 ‘essential amino acids’ cannot be synthesised and must be obtained from diet
○ Isoleucine, lysine, threonine, histidine, leucine, methionine, phenylalanine, tryptophan, valine
If Learnt This Huge List May Prove Truly Valuable
What are examples of essential fatty acids
Linolenic and linoleic acids
Describe the structure of lipids within the body
Lipid composed of triacylglycerols (3 fatty acids esterified to one glycerol)
○ Saturated fatty acids contain no double bonds
○ Trans fats synthesised industrially to give favourable characteristics such as increased shelf life
Explain the biological role of minerals
○ Electrolytes establish ion gradients across membranes & maintain water balance
§ Sodium, potassium, chloride
○ Calcium and phosphorus essential for structure (bones and teeth)
○ Calcium also very important signalling molecule
○ Enzyme cofactors (iron, magnesium, cobalt, copper, zinc, molybdenum)
List the fat soluble vitamins and its associated deficiency diseases
A - Xerophthalmia (fail to produce tears)
D - Rickets
E - Neurologic abnormalities
K - Defective blood clotting
State the associated deficiency diseases of some water soluble vitamins
B1 - Beriberi B12 - anaemia B6 - anaemia C - survy Folate - anaemia Niacin (B3) - pellagra
State the role of dietary fibre
○ Found in cereal foods - cellulose, lignin, pectins, gums
○ Cannot be broken down by human digestive enzymes but essential for normal functioning of GI tract
§ Humans do not produce enzymes to break beta-1,4 glycosidic linkages in cellulose
○ Low fibre intake associated with constipation and bowel cancer
○ High fibre diet shows to reduce cholesterol and risk of diabetes
§ Cholesterol produces bile salts but fibre suppresses bile salts and excretes it so it cannot be recycled
Give the equation for daily expenditure value
○ Daily energy expenditure = basal metabolic rate + diet induced thermogenesis (energy required to process food) + physical activity level
How can the components of daily expenditure value be estimated
§ For individuals who are not obese, BMR = 100 x weight in kg
§ Physical activity level = BMR + (30% to 100% of BMR) depending on level of exercise
§ Diet induced thermogenesis ~10% of energy content of ingested food
What are dietary reference values
• Dietary reference values are a series of estimates of the amount of energy and nutrients needed by different groups of healthy UK population
State the amount of energy obtained from carbohydrates, fats, alcohol and protein
Fat - 37 kJ/g
Carbohydrates - 17 kJ/g
Protein - 17 kJ/g
Alcohol - 29 kJ/g
List the essential components of the human diet
Protein, Fat, Carbohydrates, Minerals, Vitamins, Dietary fibre, Water
Define obesity
- Obesity is the excessive fat accumulation in adipose tissue which impairs health
- Usually measured using body mass index > 30
Give the BMI equation
• BMI = weight/height^2
○ Units are kg/m^2
Interpret BMI values
<18.5 = underweight 18.5 - 24.9 = desired weight 25 - 29.9 = overweight 30 - 34.9 = obese >35 = severely obese
What are the consequences of malnourishment
○ Longer hospital stays
○ Respond less well to treatment
○ 3 times more likely to develop complications after surgery
○ Higher mortality rates
Describe appearance of marasmus
• Marasmus - protein energy malnutrition most commonly seen in children under 5
○ Looks emaciated with signs of muscle wasting, loss of body fat, no oedema
○ Hair is thin and dry, diarrhoea common, anaemia
Describe appearance and pathophysiology of kwashiokor
Young child displaced from breastfeeding and fed a diet with some carbohydrate but low protein
○ Apathetic, lethargic, anorexic
○ Oedema, hepatomegaly, ascites (fluid in peritoneal cavity)
○ Low serum albumin (not enough amino acids to make), anaemia
○ Decrease plasma oncotic pressure - increase flow of fluid into interstitium = oedema
Explain the roles of redox reactions and H-carrier molecules in metabolism
• Chemical bond energy of fuel molecules is released by oxidation reactions
• All oxidation reactions accompanied by a reduction reaction
○ Reducing power is converted to energy currency (ATP) by oxidative phosphorylation
• H-carrier molecules - when fuel molecules are oxidised, electrons and protons are transferred to carrier molecules
○ Eg. Oxidised form: NAD, reduced form: NADH + H+
○ Can be converted to oxidised form for energy
Explain the roles of high- and low-energy signals in the regulation of metabolism
• When ATP concentration is high, anabolic pathways are activated and most molecules are in reduced form
○ Other high energy signals are NADH, NADPH, FAD2H
• When ATP concentration is low and ADP and AMP is high, catabolic pathways are activated
○ Adenylate kinase (myokinase): 2ADP -> ATP + AMP (AMP = low energy signal)
• When supply exceeds demand, energy is most often stored in the form of polymer macromolecules of fuel molecules
○ Eg. Glycogen, triglyceride
• Cell types that need to increase metabolic activity very quickly (skeletal muscles) need a reserve of high energy stores that can be used immediately (creating phosphate)
