Topic 1: Biological Molecules

molecule made from larger number of monomers joined together

smaller units from which larger molecules are made

reaction that joins two molecules together with the formation of a chemical bond and involves the elimination of water molecule

reaction breaks a chemical bond between two molecules and involves the use of a water molecule

monosaccharide

disaccharide

polysaccharide

glycosidic bond

alpha glucose + alpha glucose

reducing sugar, disaccharide

alpha glucose + fructose

non-reducing sugar, disaccharide

beta glucose + galactose

reducing sugar, disaccharide

polysaccharide used for storage in plants, made from alpha glucose molecules

helical so compact, fit lots of energy in small area

insoluble so osmotically inactive

larger molecule so cannot cross cell-surface membrane

branched so can be hydrolysed quickly from multiple ends

polysaccharide used for storage in animal and bacteria, made from alpha glucose molecules

helical so compact, fit lots of energy in small area

insoluble so osmotically inactive

larger molecule so cannot cross cell-surface membrane

highly branched so can be hydrolysed quickly from multiple ends

polysaccharide used in the structure of cell walls in plants

long, straight, and unbranched chains of beta glucose that are rotated by 180° alternatively

joined by lots of hydrogen bonding

to provide rigidity and form (micro)fibrils

add Benedict’s solution and boil

positive = blue turns to brick-red precipitate

1. add Benedict’s solution and boil

2. negative result, stays blue

3. add acid and boil, to hydrolyse poly/disaccharides into monosaccharides

4. add alkali, to neutralise solution

5. add Benedict’s solution and boil

6. positive result, blue turns brick-red

add iodine

positive result = brown to blue-black

1 glycerol molecule bonded to 3 fatty acid molecules

hydrophobic

found in fats and oils

1 glycerol molecule bonded to 2 fatty acid molecules and 1 phosphate group

hydrophobic tail

hydrophilic head

R-COOH

R = hydrocarbon chain

COOH = carboxyl group

ester bond

saturated = R-group/fatty acid chain which there is no C=C bonds

unsaturated = contains at least one C=C bond in the R-group

emulsion test

ethanol then water and shake

positive = cloudy-white emulsion

amino acid

dipeptide

polypeptide

peptide bond

between carboxyl and amine groups

20

series of condensation reactions leads to a sequence of amino acids/polypeptide chain

determines shape and function of protein

many hydrogen bonds form between amine and carboxyl groups

either alpha helix or beta pleated sheets

secondary structure is twisted to for 3D complex shape

hydrogen, disulphide, and ionic bonds form between R-groups of amino acids

more than one polypeptide chain

and non-protein groups like carbon

add Biuret solution

positive = blue to purple

enzymes have an active site which is complementary to substrate

they bind to each other forming an enzyme-substrate complex

lowering the activation energy of the reaction, by distorting/bending the bonds of the substrate

products no longer fit the active site so it is released

enzyme remains unchanged

one substrate fits into active site

active site does not change shape and is complementary

active site is not initially complementary to substrate

the shape of active site then changes, so that it fits around the substrate

caused by the distorted bonds in the substrate, leading to a reaction

as temperature increases:

more kinetic energy, more frequent collisions, increase in enzyme-substrate complexes forming, rate increasing

temperature increases above optimum:

hydrogen bonds break, change in the 3D tertiary shape, change in shape of the active site, can no longer form enzyme-substrate complexes, enzymes denatures

pH changes from optimum:

(hydrogen/ionic) bonds are broken, 3D tertiary shape is altered, active site changes shape, can no longer form enzyme-substrate complexes, enzyme denatures

more substrate/enzyme = faster rate

until no longer the limiting factor

similar shape to the substrate so can bind to active

if it blocks the active site, fewer enzyme-substrate complexes form, lower rate of reaction

temporary and no overall damage to enzyme so reaches same final point at slower rate

to increase rate add more substrate

attaches to enzyme away from the active site, altering the 3D tertiary structure, changing the shape of the active site and can no longer form enzyme-substrate complexes

adding more substrate has no effect due to enzymes being permanently altered

milk and water

= indicate colour of absence of enzyme activity

milk and hydrochloric acid

= indicate colour of complete hydrolysis of sample

to equilibrate temperature

rate of reaction = 1 / mean time to turn completely colourless

nucleotide

phosphodiester

between pentose sugar and phosphate group

phosphate group

pentose sugar (deoxyribose, ribose)

nitrogen-containing base

DNA nucleotides join to form 2 polynucleotide strands

nucleotides join up between phosphate and pentose sugar, creating sugar-phosphate backbone

hydrogen bonds between 2 strands

2 strands with specific base pairing

large number of hydrogen bonds

helix shape, reduces molecular damage

strong sugar-phosphate backbone

each base only pairs with one specific base/one complementary base pairing

adenine to thymine

cytosine to guanine

1. occurs through semi-conservative replication

2. DNA helicase breaks hydrogen bonds between DNA strands

3. DNA uncoils, exposing the bases, and both strands act as a template

4. free DNA nucleotides are attracted to and bind with exposed bases

5. bases bind through specific base pairing: adenine to thymine and cytosine to guanine

6. DNA polymerase joins adjacent nucleotides by condensation reactions

new strand of DNA is built on each of the original 2 strands so that the new DNA molecules are identical to original

each of the two new molecules of DNA has one of the original strands and one new strands

Watson and Crick

Rosalind Franklin

adenosine triphosphate consists of

adenine, nitrogen-containing base

ribose sugar

3 phosphate groups

ATP hydrolase

ATP → ADP + Pi

ATP synthase

(during photosynthesis and respiration)

ATP cannot be stored/immediate source of energy

release small amounts of energy at a time

small amount of energy lost as heat

releases energy instantaneously, immediate source

phosphorylates other compounds, makes them more reactive

rapidly re-synthesised

is not lost/does not leave cell

metabolite in metabolic reactions like condensation and hydrolysis

solvent so reactions can occur, allowing transport of substances

high heat capacity so buffers changes in temperature

latent heat of vaporisation so provides cooling effect with loss of water through evaporation

cohesion so supports column of water in tube-like transport cells of plants and produces surface tension where water meets air

hydrogen ions related to pH

iron ions related to haemoglobin

sodium ions related to co-transport of glucose and amino acids

phosphate ions related to DNA, RNA, and ATP