biological molecules

• small organic molecules 
• building blocks 
• hexose sugars C6H12O6 e.g glucose
• ring structures in water
• glucose, a form and B form
• main functions- 
• source of energy in respiration via breaking of carbon-hydrogen bonds to make ATP from ADP
• building blocks for larger molecules 

• two monosaccharide units linked with a glycosidic bond and the elimination of water this is a condensation reaction.
• a glucose + a glucose = maltose
• glucose+ fructose = sucrose
• glucose + galactose = lactose
• used for storage and transport

• benedicts reagent
• heat  
• reducing sugar present= blue>green>yellow>orange>red
• non reducing sugars need to be broken down to monosaccharides by heating with hydrochloric acid in order for test to work
• qualitative / semi quantitative test

• large complex molecules called polymers
• large numbers of monosaccharides linked with glycosidic bonds.

• glucose dissolves 
• converted into starch as it is insoluble
• compact 
• found in plant cells as grains
• a glucose molecules polymers
• amylose is linear and coils
• amylopectin is branched and fits inside
• known as glycogen in animals
• starch and glycogen is readily hydrolysed
• test: orange iodine turns black

• structural polysaccharide
• cell walls
• long parallel chains of B glucose cross linked by hydrogen bonds
• 60-70 molecules form bundles called microfibrils
• microfibrils bundle into fibres
• cell wall has several layers in different directions
• very strong but freely permeable

chitin

• insects
• glucosamine
• forms mucopolysaccharide
• glucose with N acetyl group 

• non polar
• insoluble in water
• triglycerides= 1 glycerol 3 fatty acids
• condensation reaction removes 3 moecules of water
• ester bonds

• differences in fats and oils come from variations in the fatty acids
• no carbon-carbon double bonds the fatty acid is saturated
• double bonds = unsaturated
• saturated fats contribute to heart disease
• animal lipids= saturated
• plant lipids= unsaturated (oils)
• insoluble in water but dissolve in organic solvents like alcohols

• plasma membranes
• energy reserves
• insulator against heat loss
• protection around delicate organs
• triglycerides can produce a lot of metabolic water 
• waterproofing 

phospholipids

• one of the fatty acid chains is replaced by phosphate 
• hydrophilic head, hydrophobic tail
• polar
• plasma membranes

• contain nitrogen
• large compounds made of amino acids
• 20 different types of amino acids
• shape of a protein is determined by specific sequence of amino acids in a chain
• amino acids have amino group -NH2 and carboxyl group -COOH but differing R groups
• amino group of one amino acid reacts with carboxyl group of another eliminating water 
• peptide bond is formed making a dipeptide
• proteins are very large molecules of many amino acids joined to make polypeptides

Primary

• the sequence of amino acids in a chain
• large number of combinations of the 20 amino acids
• differ in variety, numbers and order of amino acids

secondary

• the shape the polypeptide chain forms as a result of hydrogen bonding
• causes a 3D shape
• spiral a helix 
• B pleated sheet

tertiary

• the a helix of the secondary protein structure being folded and twisted to give a more complex, compact 3D shape
• maintained by disulphide, ionic, and hydrogen bonds
• globular proteins

quaternary

• a combination of two or more polypeptide chains in tertiary form
• large complex molecules e.g. haemoglobin

Fibrous Proteins

• structural functions
• polypeptides in parallel chains/sheets with  numerous cross linkages to form fibres
• insoluble in water, strong and tough
• 1 fibre = 3 polypeptide chains twisted like a rope linked by cross bridges
• keratin in hair, collagen in tendons

Globular Proteins

• enzymes, antibodies, plasma proteins, hormones
• compact and folded as spherical molecules 
• soluble in water

testing- biuret reagent, blue > purple

• aquatic habitat
• key elements in solution
• medium for metabolic reactions
• important in plants animals and cells
• 'stick' by forming hydrogen bonds
• hydrogen bonds affect its properties

• excellent solvent, water is slightly polar and attracts charged particles
• chemical reactions can take plac in solution
• can be transported
• oxygen is 2d-
• hydrogen is d+

density

• max density at 4oC
• when solid as ice it is less dense than water- floats 
• insulates water underneath
• reduces liklihood of whole bodies of water freezing completely
• organisms can survive beneath

transparency

• light can pass through, aquatic plants can photo synthesise

• high specific heat
• large amount of energy needed to raise the temperature of water
• hydrogen bonds restrict movement
• prevents large fluctuations in water temperature- keeps aquatic habitats stable
• enzymes can work
• high latent heat 
• great deal of heat energy needed to turn it from liquid to gas
• important in temperature control e.g. sweating

• water is polar with no overall charge
• oxygen is slightly negative hydrogen slightly positive
• 2 molecules close together their opposing charges attract
• forms a hydrogen bond
• individually hydrogen bonds are weak but there are many of them forming a lattice
• this sticking together is cohesion
• columns of water can be drawn up xylem in tall trees
• at ordinary temps, water has high surface tension
• cohesion between molecules produces surface tension 
• body of an insect can be supported on surface of pond

• micronutrient are needed in trace amounts
• macronutrients are needed in small amounts
• magnesium- chlorophyll in plants
• iron- haemoglobin in red blood cells
• Phosphate- making nucleotides and phospholipids
• calcium- bones