IB DP2 ChemistryOption B:

Human BiochemistryWhat compounds are living organisms built from?

Option B: Human Biochemistry

B1 Energy (0.5 hour)B.1.1 Calculate the energy value of a food from enthalpy of combustion data.

B2 Proteins (3 hours)B.2.1 Draw the general formula of 2-aminoacids.B.2.2 Describe the characteristic propertiesof 2-amino acidsB.2.3 Describe the condensation reaction of2-amino acids to form polypeptides.B.2.4 Describe and explain the primary,secondary (α-helix and β-pleated sheets), tertiary and quaternary structure of proteins.B.2.5 Explain how proteins can be analysed by chromatography and electrophoresis.B.2.6 List the major functions of proteins in the body.

B3 Carbohydrates (3 hours)B.3.1 Describe the structural features of monosaccharides.B.3.2 Draw the straight-chain and ring structural formulas of glucose and fructose.B.3.3 Describe the condensation of monosaccharides to form disaccharides and polysaccharides.B.3.4 List the major functions of carbohydrates in the human body.B.3.5 Compare the structural properties of starch and cellulose, and explain why humans can digest starch but not cellulose.B.3.6 State what is meant by the term dietary fibre.B.3.7 Describe the importance of a diet high in dietary fibre.

B4 Lipids (3.5 hours)B.4.1 Compare the composition of the three types of lipids found in the human body.B.4.2 Outline the difference between HDL and LDL cholesterol and outline its importance.

B.4.3 Describe the difference in structure between saturated and unsaturated fatty acids.B.4.4 Compare the structures of the two essential fatty acids linoleic (omega–6 fatty acid) and linolenic (omega–3 fatty acid) and state their importance.B.4.5 Define the term iodine number and calculate the number of C=C double bonds in an unsaturated fat/oil using addition reactions.B.4.6 Describe the condensation of glycerol and three fatty acid molecules to make a triglyceride.B.4.7 Describe the enzyme-catalysed hydrolysis of triglycerides during digestion.B.4.8 Explain the higher energy value of fats as compared to carbohydrates.B.4.9 Describe the important roles of lipids in the body and the negative effects that they can have on health.

B5 Micronutrients and macronutrients (2 hours)B.5.1 Outline the difference between micronutrients and macronutrients.2 Micronutrients are substances required in very small amounts (mg or μg) and that mainly function as a co-factor of enzymes (<0.005% body weight).B.5.2 Compare the structures of retinol (vitamin A), calciferol (vitamin D) and ascorbic acid (vitamin C).B.5.3 Deduce whether a vitamin is water- or fat-soluble from its structure.B.5.4 Discuss the causes and effects of nutrient deficiencies in different countries and suggest solutions.

B6 Hormones (3 hours)B.6.1 Outline the production and function of hormones in the body.B.6.2 Compare the structures of cholesterol and the sex hormones.B.6.3 Describe the mode of action of oral contraceptives.

Image: http://en.wikipedia.org/wiki/Human_body

What are the chemical constituents of food?

Image: http://en.wikipedia.org/wiki/File:Salami_sandwich.jpg

Food builds the bodies of living organisms

Nutrients: food components for growth, energy and replacement.

WaterMacronutrients Proteins built from amino acids Carbohydrates LipidsMicronutrients Vitamins Minerals

Energy in food

Energy density of foods

Food componentEnergy density

kJ/g kcal/gFat 37 9Proteins 17 4Carbohydrates 17 4Organic acids 13 3Fiber 8 2Ethanol  29 7

Too much or too little?Caloric starvation: Weakness, anaemia, muscle wasting.....Excessive foood: Fat storage, diabetes, cardiovascular diseases.

Energy: Young active male: 14700kJ (~3500 Cal) Young active female: 8400 kJ (~2000 Cal) At rest: ~60%

MetabolismCatabolism: breaks down organic matter and harvests energy by way of cellular respirationAnabolism: uses energy to construct components of cells such as proteins and nucleic acids

Image: http://en.wikipedia.org/wiki/File:ATP-3D-vdW.png

Energy units (Joules, but…) 1 Calorie = 1000 calories = 1 kcal 1 Cal: increases 1kg H2O by 1oC

1 cal: increases 1g H2O by 1oC

1 Cal = 4.18 kJ 1 cal = 4.18 J

Calorimeter- burns food to heat water

Images: http://www.chem.ufl.edu/~itl/2045/lectures/lec_9.html, http://www.azosensors.com/equipment-details.aspx?EquipID=285

 

Example:15.0 g of apple raises the temperature of 200g water by 45.3oC.Heat capacity of the container: = 85JoC-1

Calculate the energy released by the apple and the energy density of the apple.

Heat produced = heat absorbed by water + heat absorbed by calorimeter

Image: http://en.wikipedia.org/wiki/Apple

Micronutrients

Macronutrients and micronutrients Macronutrients- need in relatively large

amounts >0.0005% of body weight protein, fat, carbohydrates, minerals (na, Mg, K, Ca,

P, S, Cl)

Micronutrients vitamins and trace minerals

Vitamins- water or fat soluble Vitamin A (retinol) Vitamin C (ascorbic acid) Vitamin D (calciferol)

Malnutrition and deficiency diseases

Proteins

Proteins built from 2-amino acids

Zwitterion

Image: http://en.wikipedia.org/wiki/Zwitterion

Image: http://en.wikipedia.org/wiki/File:Amino_Acids.svg

…joined by peptide bonds in a primary structure

Image: http://en.wikipedia.org/wiki/Peptide_bond

Secondary and tertiary structures

Image: http://en.wikipedia.org/wiki/Secondary_structure#Secondary_structure

Chromatography

Image: http://glossary.periodni.com/glossary.php?en=paper+chromatography

Image: http://en.wikipedia.org/wiki/Planar_chromatography

PAGE Polyacrimide Gel Electrophoresis

Electrophoresis

Amino acid

pH of isoelectric point

Glutamic acid

3.2

Serine 5.7Histidine 7.6

Move faster to anode

Move faster to cathode

+

-

Carbohydrates

Functions in the human body provide energy store energy (as glycogen) precursors dietary fibre

Calculating empirical and molecular formulae

A substance has the composition by mass 40% carbon, 7% hydrogen and 53% oxygen.Calculate the empirical formula.Calculate the molecular formula of the molecule with a molecular mass of 180g/mol.

Saccharides- empirical formula CH2O

PentosesHexoses

Chiral molecule: alpha-D glucose or beta-D-glucose

Disaccharides

Glycosidic link forms by condensation reaction between monosaccharides

Image: http://en.wikipedia.org/wiki/Disaccharide

Polysaccharides- amylose and amylopectin

Image: http://en.wikipedia.org/wiki/Polysaccharide

Cellulose

hydrogen bond between layers

glycosidic bond

Image: http://en.wikipedia.org/wiki/Cellulose

Lipids

Lipids

large and diverse group

naturally occurring organic compounds

soluble in nonpolar organic solvents (e.g. ether, chloroform, acetone & benzene)

generally insoluble in water

Triglycerides Ester of three fatty acid

molecules and a glycerol molecule

Ester-group slightly polar but R-groups large and non-polar insoluble in water.

R normally even number of C, 16-20.

Examples: Stearic acid C17H35CO(OH),

saturated acid (only single bonds) solid(e.g. butter)

Oleic acid: C17H33CO(OH): unsaturated (some double bonds) oil

Example of an unsaturated fat triglyceride. Left part:glycerol, right part from top to bottom: palmitic acid, oleic acid,alpha-linolenic acid. C55H98O6 Image: http://en.wikipedia.org/wiki/Triglyceride

Phospholipids Fatty acid substituted by phosphor-

choline group and gives a lecithin structure.

More polar than triglycerides and build up the bilayer structure in cell membranes.

Also used as a source of choline.

Image:http://en.wikipedia.org/wiki/Phospholipid

Phospholipids

Image:http://en.wikipedia.org/wiki/Phospholipid

Steroids three 6-memberd rings + one 5-memberd ring are

steroid skeleton that is found in many different steroids (e.g. sex hormones) and vitamins (e.g. Vit-D)

Image: http://en.wikipedia.org/wiki/Steroid

Cholesterol produced mainly in the liver, found in the

bloodstream and body cells present in dairy products, meat and eggs. not water soluble so it must have transport help

in the blood from a protein.

HDL and LDL HDL high density lipoprotein. 40-55% protein LDL low density lipoprotein. 20-25% protein  HDL “good cholesterol”: Prevents the build up of

cholesterol in the arteries. HDL can absorb more cholesterol and carry it away from the arteries.

LDL “bad cholesterol”: Higher cholesterol content can give deposition in arteries plaque, a hard thick substance narrowing of arteries cardiovascular diseases.

Saturated fats: only single bonds between the carbons in the fatty acid.

common in animal (mammalian) fat (except seals and whales), milk and butter

usually solid at room temperature because regular tetrahedral arrangement makes it possible to pack molecules close together so van der Waals forces are large

Image: http://en.wikipedia.org/wiki/Butter

Unsaturated fats: one or more double bonds

often found in vegetable oils. usually liquid at room temperature C=C makes it hard to pack chains close together

lower Van der Walls forces the greater the number of double bonds, the lower

m.p. Monounsaturated: only one double bond (e.g. olive

oil, rapeseed oil) Polyunsaturated: more than one double bond (e.g

fish oil)

Image:http://en.wikipedia.org/wiki/Oil

Linoleic and Linolenic acid Essential fatty acid, EFA: a fatty acid that our body cannot make and

therefore must be present in our food in order for a properly body function.

Linoleic acid with 18 carbon atoms. 2 double bonds. Omega-6 fatty acid the last C=C in the chain is 6 atoms away from the end of the chain; the CH3 group (the omega carbon). 

Linolenic acid with18 carbon atoms. 3 double bonds. Omega-3 fatty acid the last C=C is three atoms away from the methyl-group.

Linoleic and linolenic are essential fatty acids. Important precursors for hormone like chemicals as prostaglandin and leukotrienes.

Omega-3 is important for brain development during pregnancy. EFA good effect oncholesterol levels, good health, good circulation,

immune system, etc.

Iodine numberH2C=CH2 + I2 H2IC=CH2I addition Colourless coloured Colourless Titrate fat solution with iodine solution

measurement of the number of double bonds. 1 mol I2 1 mol double bonds Iodine number: number of grams iodine that adds

to 100g of fat. more double bonds greater iodine number.

Example: Calculate iodine number of linoleic acid.

1 Linoleic acid + 2 I2 tetraiodo-lionoleic acid

m 280 g 506 gM 280 g/mol 253 g/moln 1 mol 1:2 2 mol

Iodine number = mass of iodine × 100 mass of linoleic acid= 506/280×100= 181

Example: The iodine number of a fatty acid (Mr = 278g/mol) is 274. Calculate the number of C=C double bonds.

Hydrolysis of a fat: the reverse reaction from an esterification/condensation reaction.

1 Fat 1 glycerol + 3 fatty acids. catalysed be the enzyme Lipase. The reaction

goes step by step: triglyceride diglyceride monoglyceride

Fats and carbohydrates as energy sources Both fats and carbohydrates are used in nature as

energy source/storage. React with oxygen and release energy (oxidation-

an exothermic reaction). Carbohydrates contains more oxygen than fats

carbohydrates already more oxidised less energy available

Fats very rich in energy: ~double of carbohydrates

Positive role of lipids in the human body Energy storage Insulation and protection of organs Steroid hormones Structural component of cell membrane Omega-3 polyunsaturated fatty acids reduce the

risk of heart disease. Poly-unsaturated fats may lower levels of LDL

cholesterol

Negative effects of lipids include Increased risk of heart disease from elevated

levels of LDL cholesterol and trans fatty acids. The major source of LDL cholesterol is saturated fats, in particular lauric (C12), myristic (C14) and palmetic (C16) acids.

Obesity is a disease in which excess body fat has accumulated to such an extent that health may be negatively affected.

Hormones

Hormones produced in endocrine glands Adrenaline Thyroxine Sex hormones Insulin

Teaching notes

Links Biological molecules https://

www.khanacademy.org/partner-content/crash-course1/crash-course-biology/v/crash-course-biology-103

Zwitterion and gel electrophoresis https://www.khanacademy.org/science/mcat/biomolecules/amino-acids-and-proteins1/v/isoelectric-point-and-zwitterions