2.4 - the chemistry of cooking Flashcards
what are examples of parts of the human body that proteins make up?
- muscle
- skin
- hair
what are proteins needed in our diet for?
growth and repair of tissue
what are two biological examples of what proteins are responsible for?
- enzymes
- haemoglobin
protiens are natural…
polymers
what are proteins made up of?
amino acids
what is the amino group?
NH2
what is the carboxyl group?
COOH
what is the name for amino acids which must be obtained through the diet?
essential amino acids
how are proteins made?
when amino acids join together through the removal of a molecule of water in a condensation reaction
how are protein molecules broken down during digestion?
through a hydrolysis reaction
where does the hydrolysis reaction take place when breaking down a protein?
at the peptide link
what is the peptide link?
draw this
OCNH
what does the peptide link form when broken?
- amino group
- carboxyl group
how can proteins be broken down in the labratory?
protein molecules can be hydrolysed in the labratory using a suitable enzyme
what is an example of an enzyme which breaks down protein and which conditions is it most active in?
- pepsin
- acidic conditions
what functional group do aldehydes have and what does this look like?
draw this
- carbonyl group
- CHO
- aldehyde names end in ‘al’
what functional group do ketones have and what does this look like?
draw this
- carbonyl functional group which is attached to a carbon which is not at the beginning of the molecule
- ketones have names ending in ‘one’
what is the general formula for the aldehydes?
CNH2nO
what is the general formula for the ketones?
CnH2nO
what is organic oxidation?
adding oxygen atoms or removing hydrogen atoms from a molecule
can aldehydes be oxidised?
aldehydes can undergo mild oxidation
can ketones be oxidised?
ketones cannot be oxidised
what are the three oxidising agents used to distinguish between aldehydes and ketones?
- acidified potassium dichromate
- fehling’s solution
- tollen’s reagent
what is the colour change of acidified potassium dichromate when an aldehyde is present?
orange to green
what is the colour change of fehling’s solution when an aldehyde is present?
blue to orange/red
what is the colour change of tollen’s reagent when an aldehyde is present?
colourless to silver mirror
why is a water bath used to heat aldehydes and ketones?
as aldehydes and ketones are flammable
what are aldehydes oxidised to?
carboxylic acid
the properties of flavour molecules are affected by what three factors?
- volatility
- solubility
- effect of heat on molecules
what is volatility?
how easily molecules vaporise (become gaseous)
what does volatility depend on?
- the type of van der waal’s attractions present
- the size of the molecule
- molecules with a formula mass below 300g are likely to be volatile
- the weaker the intermolecular forces the more volatile a substance will be
- boiling points are an indication of the strength of intermolecular forces and therefore compounds with low boiling points will be more volatile
how should asparagus be cooked to retain its flavour?
in oil or butter
what should polar flavour molecules be cooked in and why?
- oil or butter
- because polar flavour molecules will be soluble in water since polar substances dissolve in polar solvents
what should non-polar flavour molecules be cooked in and why?
- water
- because non-polar flavour molecules will dissolve in non-polar solvents such as oil
what is the term for when a protein loses its shape?
denatured
what is the specific shape of enzymes held together by?
hydrogen bonds
