Studied by 12 people
polymer
molecule made from larger number of monomers joined together
monomer
smaller units from which larger molecules are made
condensation
reaction that joins two molecules together with the formation of a chemical bond and involves the elimination of water molecule
hydrolysis
reaction breaks a chemical bond between two molecules and involves the use of a water molecule
monomer of carbohydrates
monosaccharide
2 monomers of carbohydrates
disaccharide
more than 2 monomers of carbohydrates
polysaccharide
bond between two monosaccharides
glycosidic bond
maltose
alpha glucose + alpha glucose
reducing sugar, disaccharide
sucrose
alpha glucose + fructose
non-reducing sugar, disaccharide
lactose
beta glucose + galactose
reducing sugar, disaccharide
starch
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
glycogen
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
cellulose
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
test for reducing sugars
add Benedict’s solution and boil
positive = blue turns to brick-red precipitate
test for non-reducing sugars
add Benedict’s solution and boil
negative result, stays blue
add acid and boil, to hydrolyse poly/disaccharides into monosaccharides
add alkali, to neutralise solution
add Benedict’s solution and boil
positive result, blue turns brick-red
test for starch
add iodine
positive result = brown to blue-black
triglyceride
1 glycerol molecule bonded to 3 fatty acid molecules
hydrophobic
found in fats and oils
phospholipid
1 glycerol molecule bonded to 2 fatty acid molecules and 1 phosphate group
hydrophobic tail
hydrophilic head
structure of fatty acids
R-COOH
R = hydrocarbon chain
COOH = carboxyl group
bond between glycerol and fatty acids
ester bond
difference between saturated and unsaturated
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
test for lipids
emulsion test
ethanol then water and shake
positive = cloudy-white emulsion
monomer of proteins
amino acid
2 monomers of proteins
dipeptide
more than 2 monomers of proteins
polypeptide
bond between two amino acids
peptide bond
between carboxyl and amine groups
how many amino acids are there
20
primary structure
series of condensation reactions leads to a sequence of amino acids/polypeptide chain
determines shape and function of protein
secondary structure
many hydrogen bonds form between amine and carboxyl groups
either alpha helix or beta pleated sheets
tertiary structure
secondary structure is twisted to for 3D complex shape
hydrogen, disulphide, and ionic bonds form between R-groups of amino acids
quaternary structure
more than one polypeptide chain
and non-protein groups like carbon
test for proteins
add Biuret solution
positive = blue to purple
how enzymes work
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
lock and key hypothesis
one substrate fits into active site
active site does not change shape and is complementary
induced fit hypothesis
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
rate of enzyme activity: temperature
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
rate of enzyme activity: pH
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
rate of enzyme activity: substrate/enzyme concentration
more substrate/enzyme = faster rate
until no longer the limiting factor
competitive inhibitor
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
non-competitive inhibitor
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
enzyme practical: control tubes
milk and water
= indicate colour of absence of enzyme activity
milk and hydrochloric acid
= indicate colour of complete hydrolysis of sample
enzyme practical: why are test tubes placed in water bath of set temperature for 5 mins before enzyme is added
to equilibrate temperature
enzyme practical: rate of reaction equation
rate of reaction = 1 / mean time to turn completely colourless
monomer of nucleic acid (DNA/RNA)
nucleotide
bond between nucleotides
phosphodiester
between pentose sugar and phosphate group
nucleotide structure
phosphate group
pentose sugar (deoxyribose, ribose)
nitrogen-containing base
double-helix structure of DNA
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
how is DNA a stable molecule
2 strands with specific base pairing
large number of hydrogen bonds
helix shape, reduces molecular damage
strong sugar-phosphate backbone
specific base pairing
each base only pairs with one specific base/one complementary base pairing
adenine to thymine
cytosine to guanine
DNA replication
occurs through semi-conservative replication
DNA helicase breaks hydrogen bonds between DNA strands
DNA uncoils, exposing the bases, and both strands act as a template
free DNA nucleotides are attracted to and bind with exposed bases
bases bind through specific base pairing: adenine to thymine and cytosine to guanine
DNA polymerase joins adjacent nucleotides by condensation reactions
semi-conservative replication
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
scientists that discovered model of DNA and DNA replication
Watson and Crick
Rosalind Franklin
ATP structure
adenosine triphosphate consists of
adenine, nitrogen-containing base
ribose sugar
3 phosphate groups
ATP hydrolysis enzyme
ATP hydrolase
ATP → ADP + Pi
ATP resynthesis enzyme
ATP synthase
(during photosynthesis and respiration)
why a large amount of ATP is required
ATP cannot be stored/immediate source of energy
release small amounts of energy at a time
why ATP is a suitable source of energy
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
properties of water
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
examples of inorganic ions
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
Note 
Flashcard (24)