Option B: Human Biochemistry
Study Guide
B1: Energy
q = mc Δ T
q = energy evolved (Joules)
m = mass of water (grams)
c = specific heat capacity of water (4.18 Jg-1K-1)
ΔT = temperature change in water (Kelvin)
Remember:
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You must use the mass, specific heat and temperature change of the water!
If it asks for kJ, divide your final answer by 1000.
If the question asks for the answer in kJ per gram, divide by the number of grams of food substance.
Example:
A 0.78g sample of a food substance was combusted in a bomb calorimeter and raised the temperature of 105.10
g of water from 15.4°C to 30.6°C. Calculate the energy value of the food in kJ g-1.
Temperature rise in water = 30.6 – 15.4 = 15.2°C or 15.2 K
Specific heat capacity of water = 4.18 Jg-1K-1
q = mc Δ T
q = (105.10 g) (4.18 Jg-1K-1) (15.2 K)
q = 6677.63 J per 0.78 g of sample heated
The energy value =
6677.63 J
=
0.78 g
8561.1 J g-1 or 8.56 kJ g-1
**If a question asks for an answer in J mol -1, multiply the answer in J g-1 by the molar mass ( g mol -1)
B2: Proteins
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Be able to draw the general formula of amino acids.
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Amino acids are:
o Crystalline compounds with high melting
points
o Are soluble in water. When dissolved in
water they
form zwitterions. This is the result of an internal acid-base reaction between the
carboxylic acid group and the amino group.
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The pH of a solution determines the net charge that an amino acid will carry.
o Low pH: (+) charge
o High pH: (-) charge
o The pH at which an amino acid is neutral is the isoelectric point.
Example:
Individual 2-amino acids have different structures depending on the pH of the solution they are
dissolved in. The structures of serine and cysteine are given in Table 19 of the Data Booklet.
(a) Deduce the structure of serine in:
(i) a solution with a pH of 2.
(Low pH(below isoelectric point) = positive charge)
(ii) a solution with a pH of 12.
(High pH(above isoelectric point) = negative charge)
(b) Deduce the structure of serine at the isoelectric point.
At isoelectric point = zwitterion

Amino acids link together through condensation reactions:
o In a condensation reaction, a molecule of water is eliminated and two amino acids link
together to form a peptide bond.
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Structure of proteins
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o Primary – The number and sequence of amino acids in a polypeptide chain.
 Determined by DNA sequence
 Bonding:
 Covalent peptide bonds between amino acids.
o Secondary – The folding of the poly peptide chain into two structures: alpha-helix and betapleated sheet.
 Bonding:
 Hydrogen bonds between C=O of one amino acid and N-H of another amino
acid.
o Tertiary – Further twisting, coiling and folding of the polypeptide chain as a result of
interactions between side chains.
 Bonding:
 Hydrogen bonds between C=O of one amino acid and N-H of another amino
acid.
 Van der Waals forces between nonpolar side chains
 Disulfide bonds between two S atoms in two cysteines.
 Ionic bonding between charged groups
o Quaternary – Some proteins are comprised of more than one polypeptide chain. These
chains being held together is known as quaternary structure.
 Bonding:
 Hydrogen bonds between C=O of one amino acid and N-H of another amino
acid.
 Van der Waals forces between nonpolar side chains
 Disulfide bonds between two S atoms in two cysteines.
 Ionic bonding between charged groups
Functions of proteins:
o Structural – keratin
o Enzymes – lactase
o Hormones – insulin
o Transport – hemoglobin
B3: Carbohydrates
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Functions of carbohydrates:
 Energy Source
 Energy Storage
 Important for Other Molecules
Types of carbohydrates
 Monosaccharide – simple sugars
 Disaccharide – two simple sugars linked together through condensation
 Polysaccharide – multiple simple sugars linked together through condensation
Structural features
 All monosaccharides have a carbonyl group (C=O) and at least two hydroxyls (OH).
 All monosaccharides have the empirical formula CH2O.
Be able to draw straight chain and ring structures for glucose and fructose.
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Know the difference between alpha-glucose and beta-glucose
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Monosaccharides undergo condensation reactions
 Disaccharides
 Formed by linking two monosaccharides together in a condensation reaction.
 Held together by glycosidic linkage.
 When 2 alpha-glucose molecules undergo condensation, a disaccharide called maltose
is formed. (Because carbons 1 and 4 are linked, it is called an alpha-1,4- glycosidic bond)
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Polysaccharides
 Polysaccharides are formed by multiple condensation reactions leading to a long chain
of monosaccharide units.
 Held together by glycosidic linkages.
 All polysaccharides are insoluble which makes them ideal for energy storage. There are
3 types:
 Starch
o A polymer of alpha-glucose
o The main storage carbohydrate in plants
o Two forms of Starch
 Amylose
 Straight chain polymer between the 1,4 carbons of the αGlucose units (unbranched)
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Amylopectin
 Branched structure that has both α- 1,4 linkage and α- 1,6
linkage
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Cellulose
o Created with a unbranched chain β - Glucose units
o Beta - 1,4 linkage
o Forms microfibrils that give it a rigid structure (to support plant cell wall)
o Cannot be digested by humans.
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Glycogen
o Storage polysaccharide found in the muscle and liver of animals
o Similar structure to amylopectin (but with more 1-6 branches).
Digestion of polysaccharides
 Polysaccharides are insoluble and must be broken down into monosaccharides by hydrolysis.
 The human body can digest starch and glycogen, but NOT cellulose. (**Because we do not have
the enzyme to break beta-glycosidic bonds found in cellulose.)
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Dietary fibre are substances that cannot be digested:
 Cellulose is considered dietary fibre.
 Dietary fiber passes through the body without being changed or digested much.
 Aids the health of the large intestine by stimulating the production of mucous and
helping the other products of digestion to pass out of the body more easily.
 Prevents:
 Constipation
 Obesity
 Crohn's disease
 Hemorrhoids
 Diabetes mellitus
B4: Lipids
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Functions of lipids in the human body:
 Energy storage
 Structure
 Sex hormones
 Insulation
Compare fats to carbohydrates in terms of energy storage
 Fats have more carbon atoms per gram when weighed, which means they will release
about twice as much energy as carbohydrates
 Fats: 9 kilocalories/gram
 Carbohydrates: 4 kilocalories/gram
Three types of lipids found in the body (triglycerides, phospholipids & steroids)
 Type 1: Triglycerides (fats & oils)
 They are esters formed by condensation of glycerol and 3 fatty acids
 Fatty acids can have differing lenths of carbon chains (even number).
A triglyceride
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Fatty acids can be saturated or unsaturated.
Saturated
Unsaturated
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Essential fatty acids must be obtained in the diet
 Linoleic acid (omega-6-fatty acid)
 Linolenic acid (omega-3-fatty acid)
o The terms omega-3 and omega-6 refer to the position of the 1st double
bond.
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The degree of unsaturation may be determined by using Iodine
 It is known that C=C readily undergo addition by adding a halide.
 We use the Iodine Number which is the number of grams of iodine which reacts
with 100g of fat.
o The higher the number of double bonds per molecule, the larger the
amount of iodine can react.
Example:
Linoleic acid has the formula C18H32O2. Determine the iodine number of linolenic acid.
Solution:
The formula for linoleic acid can be written C17H31COOH. From this we can deduce that there are 2 double
bonds. Therefore 2 moles of I2 will react with 1 mole of linoleic acid.
Mr of linoleic acid = 280 g mol-1 and Mr for I2 = 254 g mol-1
280 g linoleic acid will react with 508 g I2
So 100 g reacts with 508 x 100 = 181 g
Iodine # is 181
280
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Condensation reactions form triglycerides
 Between 1 glycerol and 3 fatty acids
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Type 2: Phospholipids (make up phospholipid bilayer in cell membrane)
 Composed of two fatty acids, glycerol and a phosphate group.
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Type 3: Steroids (cholesterol & hormones)
 Lipids with a structure consisting of 4 fused rings.
 Cholesterol is one of the most important steroids. It is used in the synthesis of other
hormones including sex hormones.
B5: Micronutrients and Macronutrients
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Compare micronutrients and macronutrients
 Micronutrients
 Found in relatively large amounts (>0.005% of body weight)
 Provides energy
 Ex. Na, Mg, K, Ca, P, S and Cl
 Macronutrients
 Found in small amounts (<0.005% of body weight)
 Acts as a co-factor of enzymes
 Ex. Fe,Cu, F, Zn, I, Se, Mn, Mo, Cr, Co and B
Compare retinol (vitamin A), calciferol (vitamin D), and ascorbic acid (vitamin C)
 Retinol
 Only 1 hydroxyl group
 Long polyalkene chain
 Carbon ring and chain are non-polar
 Overall non-polar – fat soluble
 Doesn’t dissolve in water
 Fat soluble
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Calciferol
 4 Hydrocarbon rings and alkane chain are non-polar
 Only 1 hydroxyl group
 Overall non-polar – fat soluble
 Stimulates uptake of calcium ions by cells
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Ascorbic acid
 4 hydroxyl groups
 Several OH groups enable oxygen bonds to form with water
 Ester bond within the ring
 Polar due to hydroxyl groups
o Easily dissolvable in water - water soluble
 Cofactor in some enzyme reactions
o Important in tissue regeneration after injury
o Helps give resistance to some diseases
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Fat soluble vs. water soluble
 Water soluble
 Excess of the vitamin will come out in urine
 Fat soluble
 Can cause sickness because it is stored in the body and not easily released
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Effects of nutrient deficiencies across the globe
 Anemia: iron deficiency
 Necessary in binding oxygen to RBCs
 Leads to hypoxia across the organ systems
 Symptoms: skin and eyes begin to yellow, low blood pressure and muscular
weakness, shortness of breath and dizziness
 Treatment: eat cereal flours and milk products fortified with iron
o Red meats, fish, poultry, lentils
o Some fruits contain iron: green beans, potatoes, spinach, etc.
 Goitre: iodine deficiency
 Iodine is necessary in thyroxine, which regulate basal metabolic rates
 Swelling of the thyroid gland
 Can lead to swelling of the neck
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Large goitres will result in difficulty with breathing and swallowing
Can lead to mental retardation in children
Treatment: seafood and some vegetables contain iodine
o Iodized salt is specifically made to prevent having an iodine deficiency
Xerophthalmia: Vitamin A deficiency
 The eye fails to produce tears
 Leads to a dry conjunctiva, and can lead to corneal ulceration, night blindness, or
blindness from corneal damage
 Treatment: Vitamin A is fat-soluble, fatty staples such as margarine can be
fortified
o Sweet potatoes, carrots, dark leafy greens, and some squashes
Pellagra: niacin (Vitamin B3) deficiency
 Niacin is a precursor to NADH and NADPH, which are essential in cell metabolism
 Four main indicators: diarrhea, dementia, dermatitis, and death
 Death occurs after 4-5 years if left untreated
Rickets: Vitamin D, magnesium, phosphorus, or calcium deficiency
 All are necessary for bone formation/maintenance
 Leads to bone fractures/deformity
 Bone pain/tenderness
 Skeletal deformities and dental problems
 Muscle weakness and growth disturbances
Scurvy: ascorbic acid deficiency
 Ascorbic acid is necessary to synthesize collagen
 Symptoms: dark-spotted skin, bleeding gums, lowered resistance to infection
 Can result in neuropathy or death
Kwashiorkor: protein deficiency
 Disease afflicting malnourished children
 Symptoms: swollen feet, enlarged abdomen, thinning hair, dermatitis
o Afflicted individuals cannot produce antibodies and can have lasting
impacts on physical and mental growth, and can lead to death
What are solutions to the problem?
 Add nutrients to their diets
 Can be done through genetic modification to foods
 Provide foods rich in vitamins and minerals
 Fortify staple foods with micronutrients
 Provide nutritional supplements in a variety of forms
 Educate about balanced diets and the importance of personal responsibility in
dietary choices
B6: Hormones
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Hormones are chemical messengers.
o hormones have a variety of structures including proteins, steroids, modified amino acids and
fatty acids.
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Steroid based hormones all have a common structure
o Sex hormones all belong to a family of organic compounds called steroids (lipids) and are
derived from cholesterol.
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Oral Contraceptive pills
• consists of estrogen and progesterone hormones
• the increase in the levels of these hormones
o prevents ovulation
o inhibits pituitary gland from producing LH and FSH
 stops the development of the uterine lining --> prevents the attachment of the egg to
the wall of the uterus
o thickens the mucus around the cervix preventing sperm from entering the uterus
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Uses and abuses of Steroids
• Female Hormones
o ex. estrogen, progesterone: hormone replacement therapy (HRT) for menopausal women,
contraceptive pill
• Male hormones (androgens)
o ex. testosterone: treatment of disorders of testes and breast cancer.
o These hormones are also known as anabolic steroids as they promote tissue growth especially
muscles.
o Increase weight in patients from weight loss
• Abuse
o Modified synthetic forms of anabolic steroids have been used by athletes to build body muscle
and increase endurance.
o There are serious medical and ethical issues.
B7: Enzymes
B8: Nucleic Acids
B9: Respiration