Option B SL
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Essential ideas
  • Metabolic reactions involve a complex interplay between many different components in highly controlled environments.
  • Proteins are the most diverse of the biopolymers responsible for metabolism and structural integrity of living organisms.
  • Lipids are a broad group of biomolecules that are largely non-polar and therefore insoluble in water.
  • Carbohydrates are oxygen-rich biomolecules, which play a central role in metabolic reactions of energy transfer.
  • Vitamins are organic micronutrients with diverse functions that must be obtained from the diet.
  • Our increasing knowledge of biochemistry has led to several environmental problems, while also helping to solve others.
B.1 Introduction to biochemistry 
Understandings:
The diverse functions of biological molecules depend on their structures and shapes.
Metabolic reactions take place in highly controlled aqueous environments.
Reactions of breakdown are called catabolism and reactions of synthesis are called anabolism.
B.1 Photosynthesis and respiration 
Understandings:
Photosynthesis is the synthesis of energy-rich molecules from carbon dioxide and water using light energy.
Respiration is a complex set of metabolic processes providing energy for cells.
Applications and skills:
The use of summary equations of photosynthesis and respiration to explain the potential balancing of oxygen and carbon dioxide in the atmosphere.
B.1 Hydrolysis and condensation reactions 
Understandings:
Biopolymers form by condensation reactions and are broken down by hydrolysis reactions.
B.2 Introduction to proteins 
This video is a quick introduction to proteins. 
B.2 Amino acids - structure and bonding 
Understandings:
Proteins are polymers of 2-amino acids, joined by amide links (also known as peptide bonds).
B.2 Acid-base properties of amino acids 
Understandings: 
Amino acids are amphoteric and can exist as zwitterions, cations and anions
B.2 Isoelectric point of amino acids 
Applications and skills:
Application of the relationships between charge, pH and isoelectric point for amino acids and proteins.
B.2 Structure of proteins 
Understandings:
Protein structures are diverse and are described at the primary, secondary, tertiary and quaternary levels.
Applications and skills:
Description of the four levels of protein structure, including the origin and types of bonds and interactions involved.
Please note in the tertiary structure, the peptide bond is between the NH2 and COOH groups in the side chains. 
B.2 Fibrous and globular proteins 
Guidance:
Reference should be made to alpha helix and beta pleated sheet, and to fibrous and globular proteins with examples of each.

Globular proteins are folded such that their tertiary structure consists of the polar, or hydrophilic, amino acids arranged on the outside and the nonpolar, or hydrophobic, amino acids on the inside of the three-dimensional shape. This arrangement is responsible for the solubility of globular proteins in water.
B.2 Analysis of proteins (chromatography) 
Understandings:
Chromatography  separation is based on different physical and chemical principles.
Applications and skills:
Explanation of the processes of paper chromatography  and gel electrophoresis in amino acid and protein separation and identification.
Guidance:
In paper chromatography  the use of Rf values and locating agents should be covered.
B.2 Calculating retention factor (Rf) values
Guidance:
In paper chromatography  the use of Rf values and locating agents should be covered.
B.2 Analysis of proteins (gel electrophoresis) 
Applications and skills:
Explanation of the processes of paper chromatography and gel electrophoresis in amino acid and protein separation and identification.
Not mentioned in the video but the rate of ion migration depends on the charge on the ion and the molar mass of the ion - small more highly charged ions migrate to the electrodes faster. 
B.2 Enzymes 
Understandings:
Most enzymes are proteins that act as catalysts by binding specifically to a substrate at the active site.

 
B.2 Factors that affect enzyme activity 
Understandings:
As enzyme activity depends on the conformation, it is sensitive to changes in temperature and pH and the presence of heavy metal ions.
Applications and skills:
Deduction and interpretation of graphs of enzyme   activity involving changes in substrate concentration, pH and  temperature.
B.2 Effect of pH on enzyme activity 
This video covers the effect of pH on enzyme activity in more detail.
B.2 Enzyme activity and substrate concentration 
Applications and skills:
Deduction and interpretation of graphs of enzyme activity involving changes in substrate concentration, pH and temperature.
B.3 Introduction to lipids 
This video is a quick introduction to the three types of lipids and their functions. 
Understandings:
Lipids act as structural components of cell membranes, in energy storage, thermal and electrical insulation, as transporters of lipid soluble vitamins and as hormones.
B.3 Fatty acids 
Understandings: 
Fatty acids can be saturated, monounsaturated  or polyunsaturated.
Applications and skills:
Prediction of the relative melting points of fats and oils from their structures.
Guidance:
The structures of some fatty acids are given in the data booklet in section 34.
Specific named examples of fats and oils do not have to be learned.
The structural differences between cis- and trans-fats are not required.
B.3 Triglycerides 
Understandings: 
Triglycerides are produced by condensation of glycerol with three fatty acids and contain ester links.
Applications and skills:
Deduction of the structural formulas of reactants and products in condensation and hydrolysis reactions between glycerol and fatty acids and/or phosphate.
Prediction of the relative melting points of fats and oils from their structures.
B.3 Phospholipids 
Understandings:
Phospholipids are derivatives of triglycerides.
Lipids (phospholipids) act as structural components of cell membranes.
Note that the products of the hydrolysis of a phospholipid can also be a salt of the fatty acids.  
B.3 Steroids 
Understandings:
Steroids have a characteristic fused ring structure, known as a steroidal backbone.
Applications and skills:
Discussion of the  use and abuse of steroids.

 
B.3 Cholesterol 
Applications and skills:
Discussion of the impact of of dietary high- density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol.
B.3 Hydrolysis of lipids 
Understandings:
Hydrolysis of triglycerides and phospholipids can occur using enzymes or in alkaline or acidic conditions.
Applications and skills:
Deduction of the structural formulas of reactants and products in condensation and hydrolysis reactions between glycerol and fatty acids and/or phosphate.
B.3 Rancidity of fats and oils  
Applications and skills:
Comparison of the processes of hydrolytic and oxidative rancidity in fats with respect to the site of reactivity in the molecules and the conditions that favour the reaction.
B.3 Iodine number 
Applications and skills:
Application of the concept of iodine number to determine the unsaturation of a fat.

 Link to worksheet
B.3 Energy in carbohydrates and lipids 
Understandings:
Fats are more reduced than carbohydrates and so yield more energy when oxidized.
Applications and skills:
Comparison of carbohydrates and lipids as energy storage molecules with respect to their solubility and energy density.
B.4 Monosaccharides 
Understandings:
Carbohydrates have the general formula Cx(H2O)y.
Haworth projections represent the cyclic structures of monosaccharides.
Monosaccharides  contain either an aldehyde group (aldose) or a ketone group (ketose) and several –OH groups.
Straight chain forms of sugars cyclize in solution to form ring structures containing an ether linkage.
B.4 Disaccharides 
Understandings:
Carbohydrates have the general formula Cx(H2O)y.
Glycosidic bonds form between monosaccharides  forming disaccharides.
Applications and skills:
Deduction of the structural formulas of disaccharides from given monosaccharides.


 
B.4 Polysaccharides
Understandings:
Glycosidic bonds form between monosaccharides  forming disaccharides and polysaccharides.
Carbohydrates are used as energy sources and energy reserves.
B.5 Vitamins 
Understandings:
Vitamins are organic micronutrients which (mostly) cannot be synthesized by the body but must be obtained from suitable food sources.
The solubility (water or fat) of a vitamin can be predicted from its structure.
Most vitamins are sensitive to heat.
Vitamin deficiencies in the diet cause particular diseases and affect millions of people worldwide.
Applications and skills:
Comparison of the structures of vitamins A, C and D.
Guidance:
The structures of vitamins A, C and D are provided in the data booklet section 35.
Specific food sources of vitamins or names of deficiency diseases do not have to be learned.
B.5 Vitamin deficiencies 
Understandings:
Vitamin deficiencies in the diet cause particular diseases and affect millions of people worldwide.
Applications and skills:
Discussion of the causes and effects of vitamin deficiencies in different countries and suggestion of solutions.
Guidance:
Specific food sources of vitamins or names of deficiency diseases do not have to be learned.
B.6 Xenobiotics 
Understandings:
Xenobiotics refer to chemicals that are found in an organism that are not normally present there.
Applications and skills:
Discussion of the increasing problem of xenobiotics such as antibiotics in sewage treatment plants.
B.6 Biomagnification 
Understandings:
Biomagnification  is the increase in concentration of a substance in a food chain.
Applications and skills:
Description of an example of biomagnification, including the chemical source of the substance. Examples could include heavy metals or pesticides.
B.6 Biodegradability 
Understandings:
Biodegradable/compostable plastics can be consumed or broken down by bacteria or other living organisms.
Applications and skills:
Description of the role of starch in biodegradable plastics.
B.6 Host-guest chemistry 
Understandings:
Host–guest chemistry involves the creation of synthetic host molecules that mimic some of the actions performed by enzymes in cells, by selectively binding to specific guest species, such as toxic materials in the environment.
Applications and skills:
Application of host–guest chemistry to the removal of a specific pollutant in the environment.
Guidance:
The emphasis in explanations of host–guest chemistry should be on non- covalent bonding within the supramolecule.