subject guide notes

B1.1.1—Chemical properties of a carbon atom allowing for the formation of diverse compounds upon which life is based

carbon atoms can form 4 covalent bonds, meaning it allows for the formation of a variety of diverse molecules

carbon-carbon bonds are strong & stable - long-chained carbon compounds provide the basic structure for many molecules

  • longer the carbon-carbon bond is = the stronger the molecule is (cuz more covalent bonds holding it together)


  • carbon-carbon bonds holding together this fatty acid

carbon can bind to other carbon atoms or non-metallic elements through single or double bonds


B1.1.2—Production of macromolecules by condensation reactions that link monomers to form a polymer

in order for macromolecules to be constructed, monomers undergo dehydration synthesis/condensation reactions

1,4 glycosidic bond is a type of covalent bond formed by this

polysaccharides are formed when 2 molecules undergo a dehydration synthesis

polypeptides are also formed when 2 amino acids undergo dehydration synthesis


B1.1.3—Digestion of polymers into monomers by hydrolysis reactions

body breaks down polysaccharides in order to gain the nutrients it needs

occurs through hydrolysis reactions


B1.1.4—Form and function of monosaccharides

are classified by the number of carbon atoms they contain

  • examples: glucose (know how to draw), galactose, ribose (know how to draw), and fructose



using glucose as an example

different isomers - alpha glucose & beta glucose

  • difference in orientation is important for the formation of polysaccharides

solubility - contains several -OH groups & the connection between O & Carbon-Hydrogen groups= polarity

  • important - can dissolve in water ( a polar substance) meaning it can dissolve in plasma, so it ensures that cell receives glucose for cellular respiration

stable molecule - cyclic molecule with the -OH groups located in axial regions of molecule

can be oxidised - glucose breaks down & loses electrons to oxygen, producing CO2 & H2O

  • energy released - used to generate ATP


B1.1.5—Polysaccharides as energy storage compounds

there are 2 types of starch in plants: amylase & amylopectin

starch is compact in structure due to coiling & branching during polymerisation

  • compactness = efficient storage in limited space

large molecular size = relatively insoluble = helps maintain osmotic balance

hydrolysis breaks down starch when glucose is needed


glycogen has a coiled structure due to branching pattern

  • allows for efficient storage & mobilisation of glucose when energy needed

composed of 1,4 glycosidic bonds & 1,6 glycosidic bonds

large molecular size = relatively insoluble = maintain osmotic balance in organisms

mainly stored in liver & muscle cells & hydrolysis reactions are used to break down glycogen in order to use the glucose for energy


B1.1.6—Structure of cellulose related to its function as a structural polysaccharide in plants

every other beta glucose molecule is inverted - allows cellulose to form a straight line

  • these long, unbranched chains can be grouped into bundles called microfibrils


B1.1.7—Role of glycoproteins in cell–cell recognition

can attach to specific amino acid residues in the protein or can form branched or linear chains that extend from protein’s surface

cell-cell recognition: function as marker’s on cell’s surface, allowing them to identify & interact

  • ex: immune cells identify foreign bodies cuz they hv different glycoproteins on their surface

receptors - allows cell to receive signals from other molecules

  • ex: insulin binds to glycoprotein receptors on surface of cells, triggering events that result in glucose uptake by the cell

ligands - glycoproteins bind to specific receptors on other cells to initiate signalling

structural support - contribute to structural integrity of cell


ABO blood system is based on the presence of specific glycoproteins on the RBC’s surface

  • these glycoproteins are called antigens - A & B antigens

  • the presence of these antigens decides the blood type

compatibility of blood types is also caused by these glycoproteins

  • for blood donations, if the glycoproteins in the recipient’s & donor’s blood dont match, then the immune system identifies the other glycoproteins as foreign bodies

    • clumping occurs, leading to organ failure or death


B1.1.8—Hydrophobic properties of lipids

are non-polar molecules that’re are often insoluble in aqueous solutions BUT can dissolve in non-polar solvents

*hydrophobic can be a misleading term - it’s not that lipids are repelled by water but rather they’re attracted more to non-polar substances


waxes - completely insoluble & hv high melting point (solid at room temp)


B1.1.9—Formation of triglycerides and phospholipids by condensation reactions

each fatty acid linked to glycerol through an ester bond (a type of condensation reaction)

*dont typically draw the entire fatty acid, but instead use R(subscript 1), R(subscript 2), etc, for each fatty acid


phospholipids consist of a glycerol attached to 2 fatty acids & a phosphate

  • phosphate is partly hydrophilic = phospholipid is partly hydrophobic & partly hydrophilic

  • is now polar


B1.1.10—Difference between saturated, monounsaturated and polyunsaturated fatty acids

classification of fatty acids based on number of double bonds in their hydrocarbon chains


saturated fatty acids - no double bonds between carbon atoms = straight linear chain

  • contain max amount of hydrogen atoms

  • forms solid at room temp cuz each carbon atom is bound to 4 atoms, meaning it can tightly pack together

  • allows it to store energy


unsaturated fatty acids - hv one or more double bonds = limits the amount of hydrogen

  • double bond causes kink in the fatty acid chain

    • kink causes fatty acid to be liquid at room temp, as it cant be compact

  • lipids with high proportion of unsaturated fatty acids are oils

  • can be either monounsaturated or polyunsaturated


monounsaturated fats: hv one double bond in hydrocarbon chain

  • liquid at room temp due to the kink

polyunsaturated fats: hv 2 or more double bonds

  • even harder for the fatty acid to be compact due to the kinks = liquid at room temp


there are also 2 isomers of unsaturated fatty acids: cis-fatty acids & trans-fatty acids


plants store fats & oils (primarily as unsat.fatty acids) as an energy source in their seeds

  • germinating seeds utilize the energy to grow until it’s capable of photosynthesis

endotherms need constant energy source to help them create heat

  • fats are stored in adipocytes, & can be broken down into ATP to be used to create heat


B1.1.11—Triglycerides in adipose tissues for energy storage and thermal insulation

triglycerides act as thermal insulators & help regulate body temps

  • ex; the blubber in whales is primarily composed of adipose tissue which contain large amounts of triglycerides. this helps insulate the whale

search google for properties of triglycerides that make them appropriate for long-term energy storage


B1.1.12—Formation of phospholipid bilayers as a consequence of the hydrophobic and hydrophilic regions

phosphate head is negatively charged & hydrophilic

the hydrocarbon chains that form the tails, are non-polar & hydrophobic

this means that phospholipids are amphipathic

this also causes the phospholipid bilayer


B1.1.13—Ability of non-polar steroids to pass through the phospholipid bilayer

steroids, such as cholesterol, are also important for the bilayer, as they provide it with flexibility & stability

steroids, such as testosterone & oestradiol, are important for signalling

are hydrophobic, allowing them to pass through the phospholipid bilayer