food & biomolecules Flashcards
aerobic respiration equation /oxidation of glucose
glucose + 6O2 -> 6CO2 + 6H2O
anaerobic respiration equation
glucose -> 2ethanol + 2CO2
to find energy content of food
multiply percentage of component eg 35% carbs, by available energy (16)
add together and divide by 100
Bomb calorimetry
used to measure the heat of combustion of chemical reactions that involve gaseous reactants or products.The reaction chamber is surrounded by a vessel of water so that the heat energy that is transferred can be measured.
solution calorimetry
In a solution calorimeter, an insulated container holds a known volume of water in which a reaction in solution occurs, like the dissolution of a solid. If the temperature of the surrounding water increases, then it is an exothermic reaction as the reaction has released heat energy into the water. If the temperature of the surrounding water decreases, then it is an endothermic reaction as the reaction has absorbed heat energy from the water.
calibrating a Calorimeter
The calorimeter is calibrated by using an electric heater to release a known quantity of thermal energy and measuring the resultant rise in temperature. The thermal energy released when an electric current passes through the heater can be calculated using a formula
chemical Calibration of a Calorimeter
Bomb calorimeters can also be calibrated by chemical means by using a combustion reaction with a known ΔH.
Determine moles
Determine the energy
Calculate the CF
finding energy using chemical calorimetry
E = CF x temp change
Issues Arising With Calorimeters – Random Errors
Not all of the food/substance was combusted in the calorimeter = energy content lower than it should
There was incomplete combustion of the food in the calorimeter = energy content will be lower than it should be
The temperature recorded when the food was combusted was inaccurate = if the temperature change recorded was less than the actual temperature change then the result would be lower than actual
Issues Arising With Calorimeters – Systematic Errors
The calorimeter was calibrated incorrectly = the energy content will be higher/lower depending upon how the calibration factor was determined because E = CF x T. if the CF is lower than it should be then the energy content will be lower than it should be, if the CF is higher than it should be then the energy content will be higher than it should be.
The measurements used to calibrate the calorimeter where measured incorrectly – this will affect the energy calculation in E = VIt eg The amps used in the calibration was inaccurate
sucrose is made of
glucose and fructose
maltose is made of
glucose and glucose
lactose is made of
glucose and galactose
building up of monosaccharides reaction type
condensation
breaking down of di/polysaccharides reaction type
hydrolysis
mr of a polysaccharide formula
162n+18 (n is number of molecules)
polysaccharides containing alpha glucose
starch & glycogen
polysaccharide containing beta glucose
cellulose
starch
energy storage for plants
amylose & amylopectin
amylose & amylopectin relative GI
amylose more closely packed
amylopectin less close due to crosslinks
amylopectin has higher GI
glycogen
energy storage for humans and animals
alpha glucose
highly branched
cellulose
structural material in plants
tightly packed
strength as plant fibre
strong h-bonds between molecules
insoluble
difficult to break down
saturated fatty acid general formula
CnH2n+1COOH
monounsaturated fatty acid general formula
1x C =C double bond
CnH2n-1COOH
