Molecules

SOLVENT PROPERTIES:

• Dipolar molecule - it has electronegative O ions and electropositive H ions
• THEREFORE - substances can be easily attracted to the molecule and dissolved into it as they will be attracted to one of the charged ions.
• Hydrogen bonds - collectively hydrogen bonds make a stable substance and so dissolving other molecule into it does not affect it.

HIGH SPECIFIC HEAT CAPACITY:

• Very high and much of the heat is used to break hydrogen bonds.
• This means water does not rapidly change temperature and so can sustain life because an organism would not have to keep adapting or using its own resources to cool down/warm up

HIGH LATENT HEAT OF VAPORIZATION:

• Hydrogen bonds attract water molecules together so vapour finds it hard to escape
• It requires a lot of energy for water to vapourize 

SOLVENT PROPERTIES:

• Allows water to be transport medium (e.g. removal of urea and ammonia in urine).

TRANSPIRATION STREAM:

• Water continuously able to move up xylem because of COHESION between water molecules and adhesion between water and walls of xylem.

MOLECULAR ABILITY:

• Hydrogen bonds weakness means water constantly moves -  necessary for osmosis.

METABOLIC FUNCTIONS:

• Water is used as a reagent in photosynthesis
• Water hydrolyses macromolecules
• Water is a medium for all biochemical reactions

TRANSPARENCY:

• Visible light can pass through so photosynthesis is possible in relatively shallow aquatic environments.

THERMOREGULATION:

• High specific heat capacity means bodies that are mainly water are stable so less likely to be damaged by environmental changes
• High latent heat of vaporization means body can be cooled with little water loss

MONOSACCHARIDE:

• Simple sugar - GF - (CH2O)n
• It is a monomer

DISACCHARIDE:

• 'double sugar' 
• formed by two monosaccharides by a glycosidic bond

GLUCOSE:

• six carbon atoms - HEXOSE SUGAR
• C6H12O6
• energy source
• highly soluble
• two forms : alpha and beta glucose 
• These are structural isomers - the difference is the position of the OH group on the first Carbon
• Glucose can bond to other sugars to make disaccharides and polysaccharides (starch and glycogen)
• Soluble so affects osmosis and water movement in cells
• lots of energy stored in the bonds
• can be broken down in aerobic respiration to produce ATP 

ALL MONOSACCHARIDES ARE REDUCING SUGARS

DISACCHARIDES:

• Formed when two monosaccharide molecules join together with a glycosidic bond
• The glycosidic bond forms between a hydroxyl (OH) group and another OH group on another molecule.

IT IS CALLED A 1,4 GLYCOSIDIC BOND

• Polymers made from monomers (monosaccharides)
• GF - C6H10O5
• Held together by 1,4 or 1,6 glycosidic bonds
• 1,6 = O - CH2 - C (last carbon)
• 1,4 is OH and OH

STARCH

 AMYLOSE  - 1,4 glycosidic - alpha glucose - unbranched - helical - compact -storage -               respiratory substrate.

AMYLOPECTIN  - 1,4 and 1,6 glycosidic - alpha - highly branched

• 1,4 and 1,6 glycosidic (lots)
• alpha glucose
• very branches (more than amylopectin) 
• more soluble than starch
• easily broken
• stored as granules in liver and muscles
• dense
• create energy for metabolic processes

• 1,4 glycosidic
• beta glucose
• every other molecule rotates 180 to make adjacent hydroxyl groups
• unbranched
• microfibrils
• hydrogen bonding
• for tensile strength in cell walls to prevent cell bursting when full of water
• structural support

• Insoluble in water
• Soluble in organic solvents
• contain hydrogen, carbon, oxygen
• Triglycerides are the most common form

TRIGLYCERIDES:

• Formed by esterification ( condensation ) - ESTER BOND
• Between 3 fatty acids and a glycerol

Fatty Acids:

• Carboxyl group (-COOH) and general formula CH3(CH2)nCOOH
• Separates from water

ESTERIFICATION:

• Each glycerol end (H part of OH) joins to HO of fatty acid = water

SATURATED:

• single bonds
• straight chains

UNSATURATED:

• kinked chain
• some double bonds
• cis and trans

• major component of cell membranes
• contain glycerol, fatty acids and a phosphate group with an alcohol group ('x')

- Phospholipids are amphiathic

• they have both hydrophillic and hydrophobic parts

What are proteins?

• diverse groups of large and complex polymer molecules
• made from chains of amino acids
• proteins are main components in body tissues
• catalysts
• 20 different amino acids
• General structure:

- Condensation reaction

- Peptide bond 

- Water released

- Reversible reaction

- Covalent bond

- Two amino acids = dipeptide

- A long chain = polypeptide

PRIMARY:

• sequence of different amino acids along a polysaccharide chain

SECONDARY:

• shape formed by amino acid chain as it bends and twists to form the most stable arrangement
• alpha helix 
• beta pleated sheet

TERTIARY:

• 3D form of the amino acid as the polypeptide chain folds and bends
• bonds: hydrogen, ionic and disulfide bridges
• hydrophobic - inside, hydrophillic - outside

• formed from parallel polypeptide chains held together by cross links
• long
• rope-like
• high tensile strength
• generally insoluble in water

COLLAGEN:

• fibrous, insoluble
• each molecule has 3 polypeptide chains wound round each other
• hydrogen bonds between chains

• spherical shape (tightly folded polypeptide chains)
• hydrophobic on inside and hydrophillic on outside
• soluble
• transport proteins

HAEMOGLOBIN:

• 4 polypeptide chains
• 2 alpha, 2 beta
• carries oxygen from lungs to tissues (oxyheamoglobin)
• each polypeptide has a haem prosthetic group which contains an iron ion

• ENZYMES ARE GLOBULAR PROTEINS