food chem Flashcards
num nums
(not a definition)
heat of neutralisation
energy released (kJ or J) when a neutralisation reaction occurs
what state is glucose in aerobic cellular respiration
aqueous
(important/handy to know)
enthralpy of aerobic cellular respiration?
-2860kJ/mol
enthralpy of anaerobic cellular respiration in animals
-120kJ/mol
enthralpy of anaerobic celluar respiration in yeast
-69kJ/mol
(not a definition)
what is a bomb calorimetry used for?
measure the heat of combustion of chemical reactions that involve **gaseous ** reactants or products
how to calculate molar mass of polysaccaride
[(Mr of # of glucose molecules) x number of glucose molecules]
-
[(number of glucose molecules minus 1) x Mr of water]
(theres a minus in the middle
how is combustion started in the reaction chamber of a bomb calorimetry reaction
reaction chamber is wired to an electrical circuit so that in the prescence of sufficient oxygen, contents can be electrically ignited
where is glcyogen stored
liver and muscle cells
what is a solution calorimetry used for
calculate energy transfered in a chemical reaction using a polystyrene cup
limitations of solution calorimetry
- polystyrene adsorbs some heat tf change in temperature will be slightly lower than it should be
- cannot measure energy content of food as combustion cannot occur in an aqueous solutions
suggestions to address limitations of solution calorimetry
- place lid on polystyrene cup to prevent the release of energy
- repeat the experiment 3-5 times to ensure reliability
random errors that arise with calorimeters
- not all food/substance is combusted -> lower energy content calculated
- incomplete combustion occured -> less nrg being released per amount of food combusted -> lower nrg content calculated
systematic errors that arise with calorimeters
- poorly insulated calorimeters -> nrg content cant be determined accurately
- calorimeer was calibrated incorrectly (ie if CF= lower than it should be -> nrg content would be lower than it should be and vice versa)
- measurements used to calibrate calorimeter (v, i, t) where measured incorrectly -> inaccurate rng calculation
functions of carbohydrates
- source of energy
- way of storing energy
- structural material (in plants)
(known as saccharides due to their sweet taste)
what elements are carbohydrates composed of
carbon, hydrogen, oxygen
list the
core monosaccarides
glucose
fructose
galactose
how is glucose formed
formed by plants through process of photosynthesis
how are disaccharides and polysaccharides formed
through condensation (polymerisation) reaction which forms a ether or glycosidic link
glycosidic is only when glucose/fructose/galactose molecules are joined
what are the different disaccharides and whcih combination of molecules are they formed from
maltose (glucose + glucose)
sucrose (glucose + fructose)
lactose (glucose + galactose)
ensure that in your equations, write out each individual molecule
even if there are 2 glucose produced/reacted
what is starch used for
energy storage in plants
what is starch made from and what are the 2 main forms of starch
made from the condensation polymerisation of alpha glucose
two forms= amylose and amylopectin
differences between amylose and amylopectin
- amylose = linear polymer w/a amylopectin = branched with occasional crosslinks
- amylopectin is easier to break down due to less efficient packing -> less attraction bw -OH groups -> weaker H bonds bw glucose molecules -> more soluble
what is glycogen used for
energy storage in humans and animals
how is glycogen formed
glycogen is formed from condensation polymerisation of alpha-glucose molecules, creating a highly branched structure
how to differentiate bw glycogen and amylopectin diagrams
amylopectin will have a straight chain in which cross links will branch off of w/a glycogen is sparatically branched
function of cellulose
structural material found in plants
how is cellulose formed
made from polymerisation of beta- glucose molecules joined together by glycosidic bonds which forms a tightly packed structure (which contributes to its strength as a plant fibre
special ft about cellulose that contributes to its sturcture
glucose molecules are arranged whereby adjacent molecules are inverted
explain why celluloe is difficult to break down
its large consistent linear structure allows for strong H bonds to form bw molecules -> strong and insoluble tf difficult to break down
giving an example, explain why artificial sweeteners are used in low nrg/low sugar food products
artifical sweeteners such as aspartame provide a similar amount of nrg per gram to many common sugars, however are significantly sweeter.
this means that far less of a of the artificial sweetener can be used to ‘sweeten’ which reduces the overall energy provided.
Also, aspartame doesn’t contain glucose (its a carb) therefore doesnt result in a rise in blood glucose levels
how is aspartame produced
condensatuion reaction bw:
- aspartic acid
- phenylalanine
- methanol
process of starch breakdown in humans
amylase in our saliva catalyses the breakdown of starch into maltose, which is then broken down into glucose in the prescence of maltase in he small intestines
why can’t humans digest cellulose
because humans lack the necessary enzyme (cellulose) to catalyse its breakdown
role of cellulose in the human diet
cellulose acts as dietary fibre, helping food pass in he body in bulk amounts therefore reduing the likelihood and risk of things like constipation and bowel cancers
what is a lactose intolerance and what effects on the body can it have
lack of a sufficient amount of lactase preventing the hrdrolysis of lactose at an efficient rate resulting in symptoms eg bloating and diarrhoea
what is the glycaemic index
a measure of how quickly glucose is released into the bloodstream
NO UNITS BC RELATIVE MEASUREMENT
purpose of calibration factor
reduces error in calculating the energy content bc it takes into account the nrg lost to surroundings by the combustion reaction
how are tryglycerides formed
through a condensation reaction (1 glycerol +3 fatty acids -> 1 tryglic + 3 waters)
general formula for fatty acids
n # of C=C bonds has:
C(k)H(2k-(2n-1))COOH
essential fatty acids/ amino acids
fatty acids/amino acids that the body cannot synthesize
where are essential fatty acids obtained from
omega-3 and omega-6 foods
what does the 3 and 6 after “omega” refer to?
the position of the first C=C from the methyl/omega end of the chain
How are trans-fats made?
hydrogenation occurs which partially saturates oils by adding H across a double bond (need pressure, nickel catalyst and 200C). In the process, most of the cis double bonds that dont become saturated are converted into trans double bonds
what is rancidity
notable deterioration in taste or smell
what is oxidative rancidity and what are its products
fats and oils breaking down in the prescence if O2 near C=C.
FOrms short chain aldehydes and ketones that cause an unpleasant smell
most common type is autoxidation
oxidative rancidity
when oxygen reacts near a carbon-carbon double bond in fatty acids
steps in autoxidation
INITIATION: formation of free radicals (empty bonds and are highly reactie -> speed up oxidation) through breaking bond in an unsaturated fatty acid in the presence of sunlight or a metal catylst
PROPAGATION: continued formation of free radicals
TERMINATION: two radicals combine (when reaction ends)
what vitamins can the human body synthesize
only Vitamin D
water soluble vitamins
vitamins with a higher proportion of OH groups that need regular intakes as they are stored in the blood and tf aren’t retained
are saturated or unsaturated fatty acids more likely to go rancid
because the more c=c bonds present, the greater reactivity, unsaturated fatty acids, which have one or more c=c bond are more likely to undergo oxidation and become rancid than saturated fatty acids (only single c-c bonds)
fat soluble vitamins
largely non-polar compounds that bond to and are soluble in non-polar lipids in body’s fatty tissue thus can be stored for much longer periods.
consuming too much -> accululate -> can be toxic
antioxidants
donate electrons from OH group to free radicals, interrupting the propagation of free randicals, delaying oxidation thus slowing the decay of food
(bold is the main def)
primary, secondary, tertiary, quaternary
P: sequence of amino acids joined together by peptide bonds
S: primary structure folded into alpha-helices, beta bleated sheets or randomly folded
T: 3D composure of a protein, consisting of folded secondary structures
Q: 2 or more polypeptides joined together
vitamins
organic compounds that the body requires on a regular basis in small amounts to allow the body to function properly
list the essential amino acids
(9)
Met
Val
Phe
His
Ile
Leu
Lys
Thr
Trp
think MVP HILL TT
bottom 2 of p14, top 4 of p15, top 2 Ts, bottom of p15
zwitterion
dipolar compound that is electrically neutral overall but contains a positively and negatively charged region
only 2 polar regions
how do amino acids react in basic conditions vs acidic conditions
basic: act as acid -> donate proton (all protons that can be donated inc from R group)
acid: act as base -> accept proton
bonding in secondary structure of amino acid
- covalent bond bw atoms
- H bond bw H attached to N in amide link and O attached to C in a non-adjacent amide link
bonding in tertiary structure
- covalent bonds
- dispersion forces
- dipole-dipole interatcions
- ionic interactions
- di-sulfide bridges
- hydrogen bonds
think CD DISH
If not used directly by the body
how are amino acids used
broken down in the liver in process deamination where NH2 is converted into ammonia.
This ammonia is converted into urea and excreted or used for synthesis for other amino acids.
The remainder of the protein molecule (C, H, O) can be converted to glucose, fat or other a,a
why is ammonia converted to urea during deamination
ammonia is toxic if allowed to build up in the body w/a urea is harmless even in high conc
denaturing (of proteins)
loss of structure or functuion of a protein at extreme temp or pH
disrupt 2, 3 and 3 structure
why are enzymes crucial to the body
catalyse chemical reactions necessary to sustain life that would otherwise occur too slowly
lock and key model
dhape of substrate is perfectly complementary + specific to the shapen of the enzyme’s active site
induced fit
active site adjusts its shape slightly to allow substrate to bind (after subtrate detaches -> a.s returms to OG shape)
subtrate binding (coming near to as) -> as change
enzyme activity
the amount of substrate converted to product per unit time
how does increasing temp cause denaturation
-> increase kinetic NRG of polypeptide chain -> molecules vibrate so rapidly -> H bonds bw peptide links (2nd structure), interactions bw R groups (3rd structure) and arangement of protein subunits (4th structure) are disrupted
how does pH outside enzyme’s optimum cause denaturation
bc enzymes function within narrow pH limits, diff pH -> change in charge of side chains -> different interactions esp ionic interactions -> change in 3rd and 4th structure -> affect bonding bw enzyme + substrate
how does increases temperature affect enzyme activity
-> increase average kinetic NRG of particles + more collisions per unit time bw enzymes + substrate -> increase enzyme activity
why do enzymes only bind to one enantiomer
Bc active site is 3D and enantiomers are non-superimposable mirror image molecules that aren’t indentical in 3D, then the substrate has to complement the 3D shape of the active site tf enzymes can distinguish bw enantiomers
coenzymes
organic molecules that are carriers of groups of atoms and/or electrons, coenzymes temporarily bind to the a.s of an enzyme, changing its shape so the enzyme can bind with the substrate
can act as reductant/oxidant by donating/accepting e to enz-sub complex
role of vitamins
boost the immune system preventing disease, support normal growth and development, and help cells and organs do their jobs.
use of amino acids in bodies
- new proteins
- glucose
- energy
where does hydrolysis of proteins start
in the stomach
function of fats in the body
- insulation of the body
- store fat soluble vitamins
- organ protection
iodine number
number of grams of iodine that will react with 100g of lipid
vitamin
a substance that is essential to the human body to function properly but is needed in much smaller quantities than the three major food groups
describe the bonding found in primary sturucture of proteins
covalent bondss bw C and N in peptie links bw amino acids
descrobe the bonding found in secondary structures of proteins
hydrogen bonds bw the O (-c=o) and the H (-n-h) on different peptide groups in the alpha helix or beta pleated sheet.
how to use HPLC
- calibrate the HPLC under experimental conditions
- run a range of standards solutions for species you are investigating
- use standards to produce a calibration curve
why does only one optical isomer bind to an enzyme
- ability of coenzyme to attach to enzymes acitve site depends on coenzyme having a complimentary shape that allows it to bind to the original active site
- enzyme has a specific shape that only matches with one enantiomer
- different optical isomers have different spartial arrangements of atoms so don’t match with the enzmye
- arrangements of atoms allow for effective binding to surface of the enzymes -> not present in other opticalisomers
