3. BIOLOGICAL MOLECULES

3.2 Water

• 
• Caption: There are polar regions of negativity (oxygen) and positivity (hydrogen). The positive and negative regions react because opposites attract.Individual water molecules have covalent bonds.
• Properties
• Ice is less dense - it will float and trap air in to insulate and reduce heat loss
• Is a solvent - can dissolve solutes
• A transport medium - capillary action
• Stable temperature - high boiling point
• Cohesive - pond skater (molecules attracted to each other) and created surface tension

3.3 Carbohydrates

• Glucose
• Hexose monosaccharide - 6 carbons (C6H12O6)
• Alpha and beta glucose - The OH group on carbon 1. Beta OH group UP. Alpha OH group DOWN
• Hydrolysis - breaking bond using water
• Glycogen - animals
• Alpha glucose - 1-4 bonds + 1-6 bonds for branches
• Starch - plants
• Alpha glucose - Helical 1-4 + 1-6 glycosidic bonds
• Amylose + Amylopectin ( branched every 25 glucose molecules
• Cellulose
• Beta glucose - 1-4 bonds (straight chains reinforced by hydrogen bonds)
• Every other glucose is flipped - so glycosidic bonds can form (180)
• 
• Caption: A glycosidic bond between 2 alpha glucose. Joining glucose - Glycosidic bond - covalent bond. Condensation reaction - H20 is released

3.4 Testing for carbohydrates

3.5 Lipids

• Bond - ester (esterification)
• Glycerol uses
• Hormone production
• Buoyancy
• Thermal insulation
• Waterproofing
• Triglyceride - glycerol + 3 fatty acid tails
• Saturated - no double bond
• Monounsaturated - one double bond
• Polyunsaturated - two or more
• Mono + poly have kinks - harder to pack together (liquid)
• Phospholipid - 2 fatty acid tails + one phosphate head
• Identification - emulsion test

3.6 Structure of proteins

• 
• Caption: Condensation reaction. R group - 20 different things. Hydrolysis breaks peptide bond (water).
• Levels of protein structure:
• Primary structure - order of amino acids
• Secondary structure - aplha helix (loops) or beta pleated sheet (zig zag) from hydrogen bonds
• Tertiary structure - folding to final shape. Interactions: Hydrogen bonds, Ionic bonds, Hydrophobic + hydrophillic, Disulphide bridge
• Quarternary structure - 2+ proteins - subunits. Same interactions as tertiary structure but between different protein molecules

3.7 Types of proteins

• Globular protein e.g. insulin
• Hydrophobic core / hydrophillic R group on the outside making it soluble
• Specifically arranged
• Conjugated protein e.g. haemoglobin (pick up O2 and transport) - iron + catalase
• Protein with a non protein prosthetic group
• Globular
• Fibrous proteins e.g. keratin, elastin, collagen
• Insoluble - hydrophobic R group outside with a high proportion of amino acids
• Repeating structures
• Keratin
• Hair, nails, skin
• Many amino acids so strong disulphide bonds
• Flexible
• Sulphur in proteins
• Elastin
• Elastic fibres in blood vessels and alveoli
• Flexibility
• Quaternary protein - tropoelastin
• Collagen
• Connective tissue in skin, tendons, ligaments, nervous system
• Three polypeptides wound together
• flexible

3.8 Nucleic acids

3.9 DNA replication and the genetic code

• Semi-conservative replication
• Two new molecules of DNA is produced, each one consisting of one old strand of DNA and one new strand.
• Enzyme roles
• DNA helicase 'unzips' the double stranded helix and DNA polymerase catalyses the formation of phosphodiester bonds between the new strands nucleotides.
• 

3.10 Protein synthesis

• Transcription
• Translation

3.11 ATP

• 
• Caption: ATP is hydrolysed into ADP and a phosphate ion, releasing energy. ATP + H2O = ADP + P + energy (hydrolysis reaction and phosphorylation)
• ATP is an immediate energy store that is:
• Small - move easily between cells
• Water soluble - aqueous environment
• Has bonds between phosphates with energy - useful in cellular reactions and doesn't waste as heat
• Releases energy in small amounts - energy is not wasted as heat
• Easily regenerated - recharged with energy