topic one Flashcards
what is a monomer
small units that can form polymers
what is a polymer
large complex molecules made from monomers
what is a condensation reaction
joins 2 molecules and involves the release of a water molecule
what is a hydrolysis reaction
breaks a chemical bond between 2 molecules and involves the use of a water molecule
3 examples of monosaccharides (carbohydrates)
glucose, fructose, galactose
what type of bond does a condensation reaction between 2 monosaccharides form
glycosidic bond
what is maltose made from
glucose + glucose
what is sucrose made from
glucose + fructose
what is lactose made from
glucose + galactose
what type of glucose do starch and glycogen use
alpha glucose
what type of glucose does cellulose use
beta glucose
structure and function of starch
helical structure makes it compact = good for storage
insoluble, doesn’t affect water potential = good for storage
- long and branched chain
structure and function of glycogen
helix makes it compact = good for storage
insoluble, doesn’t affect water potential = good for storage
branched means glucose can be released quick for respiration
structure and function of cellulose
hydrogen bonds ensure microfibrils are strong, gives strength to cell wall = prevents cell from bursting when water enters by osmosis
- long and unbranched
test for protein
add water and shake, then add 3/4 drops of biuret
positive result = lilac
test for reducing sugar
add water and equal amount of benedict’s, heat for 5 mins
positive result = brick red
test for non reducing sugar
carry out reducing sugars test (get negative result) take second sample and add water, add dilute HCl and heat for 5 min. add sodium carbonate to neutralise, then re test by adding benedict’s and heating
positive result = lots of colour change, brick red in end
test for starch
one/two drops of iodine
positive result = blue black
test for lipids
add ethanol and shake, then make a new test tube that contains just water and pour first tube into that
positive result = milky emulsion
how does a triglyceride form
condensation reaction between of 1 molecule of glycerol 3 molecules of fatty acids
what bond forms between a fatty acid and glycerol
ester bond
what is the difference between saturated and unsaturated fats
saturated = no carbon-carbon double bond
monounsaturated = 1 carbon-carbon double bond
polyunsaturated = many carbon-carbon double bonds
what is a phospholipid made from
2 fatty acids, 1 glycerol and 1 phosphate
triglyceride structure and properties
- insoluble, good for storage because it doesn’t affect osmosis in cells
- low mass: energy = good for storage
fatty acid tail contains a lot of energy, used as energy storage molecules
phospholipid structure and properties
- forms bi-layer within cell surface membrane
- hydrophilic head/hydrophobic tail form a double layer with heads facing out towards water on either side
-centre of bi layer is hydrophobic, so water-soluble substances cant pass easily - membrane acts as a barrier
monomer of proteins
amino acids
how are dipeptides AND polypeptides formed
- dipeptide = formed when 2 amino acids are joined together
- polypeptide = formed when more than 2 amino acids are joined
proteins are made up of one or more polypeptides
amino acid structure (drawing)
H H O
I I II
N - C - C
I I I
H H H
general structure of an amino acid
carboxyl group, amino group, R group, hydrogen atoms
their R group is what makes them different
what reaction links amino acids
condensation
what are the bonds between amino acids called
peptide bonds
what reaction happens when di/polypeptides are broken down
hydrolysis
primary protein structure
the sequence of amino acids in the polypeptide chain
secondary protein structure
- hydrogen bonds form between the amino acids in the chain
- this makes it coil into an alpha helix or a beat pleated sheet
tertiary protein structure
- the coil/folded chain is coiled/folded further
-more hydrogen and ionic bonds form between different parts in the chain
-disulfide bridges also form when two molecules of the amino acid cysteine come close together
quaternary protein structure
- the way polypeptide chains are assembled
- proteins made from more than 1 polypeptide chain, the quaternary structure is the proteins final 3D structure
globular proteins example
- haemoglobin
- enzymes
what are globular proteins for
metabolism, transport
globular proteins structure and function
- hydrophilic r group on the surface makes them soluble in water
fibrous proteins example
- keratin
- collagen
what are fibrous proteins for
structure
fibrous proteins structure and function
polypeptide chains lay parallel with cross links make them strong
what are enzymes
globular proteins which act as biological catalysts that speed up chemical reactions without being altered themselves or used up
suffix for most enzymes & which are excluded
- most end in ‘ase’
- pepsin and trypsin excluded
difference between the lock & key model and the induced fit model
induced fit model suggests that the substrate and active site aren’t perfectly complementary at first, and the active site has to slightly change shape to bind to the substrate
whereas the lock and key model suggests the active site and substrate are always perfectly complementary
factors that affect the rate of reaction
- pH
- temperature
- enzyme concentration
- substrate concentration
- presence of an inhibitor
how does optimum temperature affect rate
at optimum temperature, there is more kinetic energy and a higher frequency of collisions between active sites and substrates - therefore more enzyme substrate complexes formed
how does high or low temp affect rate
- if the temp is too low, it is too cold for enzymes to function, and therefore fewer particle collisions = slower rate of reaction
- if the temp is too high, the enzyme will be denatured, hydrogen bonds between amino acids break, and change the shape of the active site = loses function
how does enzyme concentration affect rate
increase in enzyme concentration will increase the rate until all active sites become saturated
what happens if the amount of substrate is limited
enzyme concentration will stop increasing
how does substrate concentration affect rate
increase in rate until all sites are saturated
how does pH affect rate
- above or below optimum, hydrogen/ionic bonds will break and alter the shape of the active site
- enzyme substrate complexes formed less easily
what is a competitive inhibitor
shape is similar to a substrate and can occupy the active site, may compete for AS with substrate
what is a non competitive inhibitor
the inhibitor attaches to a binding site which is not the active site, changes shape of enzyme. this means the active site can no longer attach to the substrate = loses function
what do DNA/RNA stand for
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
what are DNA and RNA polymers of
nucleotides
what are the components of DNA
- pentose sugar
- phosphate
- a nitrogen base (adenine, thymine, cytosine, guanine)
what forms the backbone of DNA
sugar + phosphate
structure of DNA
double helix with two polynucleotide chains held together
physical structure
structure of RNA
single strand, short polynucleotide chain
what holds the base pairs together
weak hydrogen bonds
how many bonds between A + T
2 hydrogen bonds
how many bonds between C + G
3 hydrogen bonds
which bases are purines and how many rings are the structures
- A + T
- 2 ring structures
what are C + T called and how many rings are the structures
- pyrimidine
- 1 ring structure
what is the bond between 2 nucleotides called
phosphodiester bond (condensation reaction)
components of RNA
- adenine
- cytosine
- guanine
- uracil
why does DNA need to replicate
growth and repair
what phase does DNA replication take place in
S phase
what is the difference between the conservative model and the semi-conservative model
- conservative model = parent and daughter DNA kept completely separate
- semi-conservative model = half its own DNA, half original parent DNA
what does ATP stand for
adenosine triphosphate
what is ATP made from
ribose, adenine and 3 phosphate groups
how is energy released from ATP
energy is released when ATP is hydrolysed to form ADP and inorganic phosphate group. this process is catalysed by ATP hydrolase.
where does the energy come from in ATP
the bonds between phosphate molecules.
what does the condensation of ADP and Pi produce
ATP, during respiration and photosynthesis
properties of ATP
- it is an immediate source of energy
- it isn’t stored in large quantities and can easily be reformed back into ADP
- it is used in many different ways, such as metabolic reactions, active transport and movement.
how is ATP re-synthesised
the condensation of ADP and Pi
this reaction is catalysed by using ATP synthase
why is water polar
one end of the molecule is more positive and the other end is more negative
how is water a metabolite
involved in condensation and hydrolysis, which are used in forming and breaking chemical bonds
how is water a solvent
it allows gases to diffuse, as well as enzymes and waste products; urea and ammonia
why does water have a high specific heat capacity
alot of energy is required to break the hydrogen bonds
why does water have a high latent heat of vaporisation
the hydrogen bonding means a lot of heat is required to evaporate one gram of water.
this means the evaporation of water provides a cooling effect with little water loss.
why is strong cohesion between water molecules beneficial
between molecules enables transport. it supports columns of water and results in surface tension at the water-air boundary
what do hydrogen ions do
determine pH of substances such as blood.
higher conc of hydrogen ions = lower pH
what are iron ions components of
these are a component of haemoglobin and carry oxygen in red blood cells.
what are sodium ions involved in
involved in co transport of glucose and amino acids
what are phosphate ions components of
DNA and RNA
